Many theists believe there is an objective morality to be discovered. However, since you can't uncover such a morality in the same way you can lift a stone and find a pill bug, empirical systems are not use for this process. Instead, many rely on various works that they give implicit trust to, except when the advice of such books goes against their innate beliefs. Hence, we see homosexuals barred from military service, but don't see single women non-virgins barred in such a fashion, much less executed for being a single non-virgin.
Some attempt a seemingly more sophisticated approach of creating a morality based upon a few accepted notions and creating a formal system to reflect it. That's when you see people like the Maverick Philosopher examining the details on what their basic positions entail when examined in detail. Below the fold, I'll go into why I think this helps to pinpoint the inherent lack of objectivity in this construction of a moral system.
I'm not really concerned with the particular argument that Dr. Vallicella is making in his post, rather, I want to highlight what happens when he finds his argument is inadequate. In particular, he doesn't like the breadth of the conclusion of the argument, so he proposes a new starting point. That is, in creating this supposedly objective moral position, he changed his starting point to get the conclusion that he felt was the right one.
Now, I have no objections to this activity per se. In fact, this is one of the better advantages of operating strictly within a formal system. If the starting positions lead you to a situation you can't use, changing the starting positions is to be expected. If you are tracking the movements of ships on the surface of the earth, you don't pretend that the surface of the earth matches Euclid's parallel postulate; instead you assume that no lines (aka great circles) are parallel and use a Riemannian geometry. It will have the tools you need to look at ship movements around a globe.
However, the process of choosing these starting positions is strictly based on the conclusions you want to derive. That makes the starting positions arbitrary, and those positions will be carefully chosen so the results conform to the desired outcome. So, far from getting some objective morality that can be applied to all, you get a tailored morality designed to support a specific set of positions. Some of these systems, like natural law, were debated for hundreds of years before they were codified, and even then still generate disagreements around the edges.
When people come up with another method of knowing things that can exhibit certainty, reality, and demonstrability, that method of know may indeed lead to an objective morality. Until that time, there will be no such creature. All the construction within formal systems will not be able alter the shaky foundation upon which they rest.
Tuesday, December 7, 2010
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«Oldest ‹Older 201 – 400 of 2208 Newer› Newest»That said, let's look at the implications of GR for a minute, eh? If GR says that even a solitary rotating body in the universe would still have inertial properties (a way to tell if it rotating, or not, without reference to any other body), doesn't it actually imply (contrary to claims often made about SR) that motion is "real" and can be detected without reference to other objects? And that therefore the claim that all motion is (absolutely and ontologically) relative is false? A limitation on our ability to hear sound waves of a certain frequency does not mean they don't exist. It just means we can't hear them. Why should our inherent cognitive and sensible limitations be the sole measure of what is "absolutely true??" Sounds kinda anthropocentric, don't it?
That what Newton would consider to be gravitational "forces" may, in very artificial and fanciful circumstances, be undetectable is irrelevant. Gravitational and inertial "forces" may be mathematically equivalent, but mathematical equivalence says nothing about reality.
An astronaut, in space, knows he is in free fall and that the gravitional influences of the earth keep him in an accerated state and that his ship is following a perpetually "circular" path around the earth. He does not suspect, and has no reason to suspect, that he is actually motionless in space far from the influence all gravitational effects. Even though he might have the same subjective sensations if he were in that state, he would be crazy to think he actually is floating motionless in space, far from earth or any other body.
Just because you can contrive circumstances (no windows, virtually dimensionless amount of space to work in, etc.) where he would not be able to detect which state of motion and position relative to large masses he is in, you cannot on that basis conclude that he "could be in either." The question is not about what you can detect. From a practical, as opposed to theoretical and mathematical, perspective, the two alternatives are not "equally valid."
For logical positivists, like Mach, Einstein, and others whose ideas used to be prevalent and influential (with some) what is "true" is what you can detect. However, that whole philosophical position utterly crumbled under it's own weight long ago.
Ya know, Eric, we had a virtually interminable discussion about relativity a while back. My recollection of that is that you would simply repeatedly assert that all motion is “relative” (you meant “relational,” not relative) in SR and GR, and that all frameworks are "equally valid, and that therefore no answers to questions of motion could be given. No amount of logic or instances of self-contraction could keep you from assuming and re-asserting this proposition, nor could seem to even think about the matter in any way that did not support your claim. You simply attempted to maintain the logical positivist position by fiat.
I probably pointed this same site out then, but think about it, eh?
“…relativity very quickly disappointed its early logical-positivist supporters when it became clear that it was not, and never had been, a relational theory of motion, in the sense of Leibniz, Berkeley, or Mach. Initially even Einstein was disturbed…Early in his career, Einstein was sympathetic to the idea of relationism, and entertained hopes of banishing absolute space from physics but, like Newton before him, he was forced to abandon this hope in order to produce a theory that satisfactorily represents our observations.
…spacetime in the theory of relativity cannot simply be regarded as the totality of the extrinsic relations between material objects (and non-gravitational fields), but is a primary physical entity of the theory, with its own absolute properties, most notably the metric with its related invariants, at each point…The absolute significance of spacetime in the theory of relativity was already obvious from trivial considerations of the special theory.”
http://www.mathpages.com/rr/s4-01/4-01.htm
You don’t have to be a physicist to see that neither SR nor GR can solve problems without an implicit assumption that motion is not strictly relational. This was one simple question which I posed for Colton to answer and to which I never got a response: “Do you believe that SR or GR can make predictions?”
As this author puts it: ”The twins paradox is a good illustration of why relativity cannot be a relational (and local) theory, because the relation between the twins is perfectly symmetrical…This becomes even more obvious in the context of general relativity, because we can then have multiple distinct geodesic paths between two given events, with different lapses of proper time…we have no choice but to simply assume a plausible absolute inertial background field, just as in Newtonian physics, in order to actually make predictions and solve problems.”
Think about it sometime, eh?
Something to consider with respect to theory formation:
The author quoted above says: "Early in his career, Einstein was sympathetic to the idea of relationism, and entertained hopes of banishing absolute space from physics but, like Newton before him, he was forced to abandon this hope in order to produce a theory that satisfactorily represents our observations."
To the extent that this suggests that Einstein retreated from his positivist position, and formulated his theory accordingly BECAUSE he realized that such a position was incompatible with his goals, it is inaccurate. As this same author also notes:
"...relativity and relationism are fundamentally incompatible principles. Admittedly, during the years when Einstein was developing general relativity – and even for several years thereafter – he tended to conflate the two.."
Einstein actually thought he had developed a relational theory, at first, and it was only after completing it that he realized he was mistaken. Later in life said he said that Mach's view was too restricive and that it would, if taken literally, prevent positive theories. He said that Mach seemed to think that scientific theories were "discovered" instead of "invented" (as Einstien properly insisted). Einstein, on more than one occasion, made it clear that theories are creative products of a "free mind" that makes choices about what to assume.
Kinda the same thing you were complaining about when you said: "So, far from getting some objective morality that can be applied to all, you get a tailored morality designed to support a specific set of positions." Einstein was certainly trying to resolve a nagging problem that Maxwell's equations generated, and "chose" to make assumptions that helped him do so. To this day, those assumptions have never been proved, and are simply assumed, even while acknowledging that the assumptions are not "dictated by the evidence."
Even if you have mountains of "evidence" to "prove" SR, the fact remains that those self-same "mountains" also "prove" LR, which rejects the fundamental axiom of SR (i.e., that the speed of light in a constant, universal absolute).
My first post in this thread said: "Relativity, evolutionary theory, cosmology, etc. all have the same "shaky foundation," for the same reasons, that you object to with respect to moral values."
Now, 200+ posts later, you are still claiming, as you always vaguely have, that the "evidence dictates the theory." If you ever realize that this is a mistaken impression, let me know. Then maybe we can actually "discuss" such things, rather than pretend that we are "opponents" and "advocates" on opposites sides of a polemical debate.
To clarify what I said about when referring to gravity and common descent:
1. The existence of gravity (in the sense that "apples fall") is a fact. "The" theory of gravity is not a fact.
2. The existence of evolution (the word Gould used--not "common descent"--in the sense that living species can "change" with time) is a fact. "The" theory of evolution is not a fact.
3. The doctrine of common descent is NOT "evolution"
Agreed.
nor is it a "theory" of evolution.
It is a central part of the Theory of Evolution.
4. The doctrine of common descent is NOT a fact (insofar as we know),
Except it is.
and it is far from "certain" (other than on a subjective level, for some faithful individuals). It is a hypothetical proposition.
No, it's as well-established as it could be, sans a time machine.
Your claim is that common descent is both a theory and a fact. I say it is neither, at least if those two terms are properly understood in the context used.
Considering you're not even sure that germ theory is a theory, I don't find your "proper" understanding particularly proper.
What I am saying is relatively straightforward. Let me rephrase it: To date, no one has found a fossil that anyone has plausibly claimed is an intermediary link, etc. Some implausible claims to that may have been made, but, if so, such claims are implausible.
Why are such claims implausible (as opposed to, for example, unevidenced or speculative)?
One Brow said: "Do [Do1 and Do11] have separate lineages back in generation A? My answer would be no."
I'm not sure what you even mean by "separate lineage" or what your point is here, Eric.
After using "separate lineages" all this time, suddenly you don't understand what the term means? I doubt that.
They are simple enough questions. Ao they have a separate lineage in generation A? Do they have a LUCA? My point is that D01 and D11 exhibit common descent without having a LUCA.
Is your chart supposed to show that all living species come from generation A (the zebras)? If so, then what came from A of the crocodiles? Nothing, in the case of this union?
It's not relevant to the example, but it you like, you can say that one group of D's gave rise to zebras and another to crocodiles.
If you're simply saying that a lineage is not "separate from" itself, what does that even mean and what does it tell you? A=A, sure. Does that mean that A(the zebra lineage) = B(the crocodile lineage)?
So, you're saying we don't have good evidence for the common descent of crocodiles and zebras? A separate question, but one hardly lacking in a variety of evidences.
At least keep your analogies in the ballpark, OK?
That was the ballpark you were asking me to play in.
Take two organisms extremely primitive organisms that have the same genetic code.
Hyp 1: The reason these two creatures have the same genetic code is because they both inherited it from another (extremely primitive) organism which had that code.
Does the same code in two different organisms provide "evidence for" the hypothesis? Well, yeah, in the sense that the evidence is not inconsistent with the hypothesis. Where did the extremely primitive ancestor get the code, though? How is that question even addressed?
Hyp 2. The reason these two creatures have the same genetic code is because they both came to be by virtue of inert chemicals combining in such a way as to result in an extremely primitive living creature. The laws of chemistry are such that when such cominations occur, they will also tend to result in similar chemical structures in the genetic code.
Except, we have no laws of chemistry that dictate the genetic code, at least of which I have heard. Some amino acids have a weak affinity for some of the compounds in the triplets that are associated with them, but it is not strong enough to make the genetic code universal. Further, the use of troplets is almost universal, even though there is no chemical reason there could not have been strings of four, five, etc. in coding units.
Did life arise independently in more than one location in time-space on earth? I think so. For example, some bacteria use different stop and start codons. However, what has happened since then has been a merging/disappearance of all these various sources until we have a unified life history. Separate starting points don't change the fact of common descent.
Darwinistic assumptions "start in the middle" and ignore questions about the "first cause."
Aboigenesis (how life arose from non-life) is a separate field.
Give me any (scientific) theory, in any subject, and there will be extremely brilliant people who disagree that it is beyond dispute, for well-articulated reasons.
Does the mere existence of dissenters mean the theory can not be so well-confirmed that it is ludicrous to withhold provisional concent, or is it possible some of these people withhold their consent for ludicrous reasons despite their brilliance and articulation?
For example, since some people deny the germ theory of disease, is that theory tenuous because of their denials?
I said: "I grant you that all evidence can be "interpreted" as being consistent with, for example, either SR or LR. So how is one a "fact" and the other simply the "false" claim of a crank?"
I read poorly, there. Of course I should have pointed out neither was a fact.
SR is not "the result of" GR. But suppose it were, then what? As experts who I cited to you in past seem to agree, GR fails as a theory of "relative motion," but does pretty well as a theory of gravity.
GR failed to show all motion was relative, but apparently because all motion is not relative. Giving an accurate model of motion is not "failure", even if that were the goal. GR is a very accurate theory of raletive moption for all types of motion that behave as if they are relative.
Within their domains (which is not "gravity") both SR and LR "lead to" the exact same place--the same predictions, the same results.
Agreed. The difference is that SR is a special case of GR, a very highly confirmed theory, while LR doesn't lead anywhere.
Here's a headstart for you, if you have any interest (the answer is given by a professor of physics/astronomy--there are many others who agree)
The answer you quoted is pretty much what I would have expected. There is no harm in choosing the CMB rest frame as teh rest frame of the universe, when it's convenient to do so. When you have a good reason for another inertial rest frame, you might as well use that.
Why would you think I'd disagree with that?
Along the same lines, reputable physicists have developed respectable theories which claim that an "ether" (as opposed to "dark matter") can explain some of the gravitational anomalies observed in many parts of the universe.
It will be interesting to see how those tests come out.
They are NOT "equally valid" in any real sense, even if they are so in an abstract philosophical sense. The Sun and all other objects in the universe do NOT orbit the earth, even though it is mathematically consistent to pretend they do. With respect to the sun, the earth really moves.
As long as you assume conservation of energy, that is the only conclusion that can be drawn. To have the sun circle the earth would require an enormous amount of acceleration.
One Brow said: "So, the choice of theories and interpretations were dictated by the evidence."
Utterly wrong. The evidence does NOT "dictate" any theory or interpretation, although it may preclude some otherwise imaginable theories.
That the evidence dictates theories is a misimpression that you seem incapable of overcoming.
I said, as you quoted, it dictated the "choice" of theories. Further, you followed that by acknowledging evidence can rule out theories (thus restricting the choice of theories. So, there's not as much disagreement there as you seem to think.
When, in other contexts, I talked about the possiblity of abiogensis creating multiple creatures, I did not mean, and did not imply, that every such creature would have to be of the exact same species as the other. Quite the contrary, actually.
I didn't make that assumption. Even if you see ten, or 20,000 different species at that point, it doesn't change that we are descendend from every one of the ten (or 20,000) who left descendants.
You seem to have assumed the opposite.
I'm not surprised you made that misinterpretation.
Einstien, ... a priori premises (e.g. that the speed of light in a vacuum is universally constant--as a matter of "fact," not just as measured) that forced him to abandon the pursuit of some his preferred goals, not the "evidence."
YOu think he chose the constancy of the speed of light as a starting point based upon a whim, as opposed to evidence?
One Brow said: I didn't make that assumption. Even if you see ten, or 20,000 different species at that point, it doesn't change that we are descendend from every one of the ten (or 20,000) who left descendants.
I said: "You seem to have assumed the opposite."
You responded: "I'm not surprised you made that misinterpretation."
Well, we're right back were we started. You will call ANYTHING "common descent" and then state that common descent is a "fact." As I said, within the context of evolutionary theory, "common descent" does NOT mean "descended from 20,000 separately created distinct species."
If everything qualifies as common descent, then it is not a "fact" it is a mere semantical tautology. It's like me saying "It is a FACT all bachelors are unmarried." It may be analytically "true," but it is NOT a postiori fact.
"YOu think he chose the constancy of the speed of light as a starting point based upon a whim, as opposed to evidence?"
As I said, facts will constrain the (reasonable) choice of theories, but not DICTATE them. Most all claims have some basis in facts which inspires them, even moral claims such as: "It is wrong to inflict severe unwarranted pain upon an innocent child."
You can agree or disagree with that premise (value statement), but the fact that "pain" is discomforting is one fact which provides a factual "basis" for it.
One Brow said: "Does the mere existence of dissenters mean the theory can not be so well-confirmed that it is ludicrous to withhold provisional concent, or is it possible some of these people withhold their consent for ludicrous reasons despite their brilliance and articulation?"
When I said "well-articulated reasons," I obviously meant non-"ludicrous" reasons. Scientific "proof" is not achieved by scientific consensus. You act at though it is. Just before relativity hit the fan, prominent physicists were declaring that there was nothing new to be discovered, that all principles of mechanics, etc. had been discovered, well-understood, and admitted by all. So what?
You idea seems to be that your idea of what "all scientists agree to" (whatever your idea of that happens to be) is so "factual" in nature as to make it perverse deny it. But the "we know all the main highlights, we're just clearing up the details" stance" pronounced by neo-darwinists in say 1960, or 1990, for that matter, make them look rather ludicrious, not those (many) who disagreed with them. Some theories, such as Neo-darwinism, are prima facie ludicrous to begin with. The fact that most students who have been dogmatically indoctrinated with those theories accept them as "fact" does not change that.
One Brow said: "GR is a very accurate theory of raletive moption for all types of motion that behave as if they are relative."
1. So is LR. "Relative motion" is not a modern creation. It was presupposed by Newton and goes back at least as far as Gallileo as a scientific premise.
2. Again, GR is NOT a theory of relative motion to begin with. It is a theory of gravity.
3. You repeated that GR "comes from" SR ("SR leads to GR"), but that is not the case at all. Nothing about SR implies GR, and Einstein worked 10 long years on that theory. He did not simply "deduce" it from SR.
I really don't want to rehash it all, but I'm still somewhat disappointed that, despite all the time invested, you could never understand what I was saying about SR in general and about the twin paradox in particular, so I will briefly restate my point there. But first, let me re-quote from the "mathpages" website:
"...relativity and relationism are fundamentally incompatible principles...The absolute significance of spacetime in the theory of relativity was already obvious from trivial considerations of the special theory. The twins paradox is a good illustration of why relativity cannot be a relational..."
This guy says it is "obvious," but I guess it isn't, seeing as how Einstien himself conflated a relational theory of motion with a relative theory of motion, even for many years after he formulated SR.
As I said, there is no logical inconsistency in the twin paradox. The only "paradox" is the obviously inconsistent claim that the motion of the twins is ALSO "relational." Except people don't say "relational," they say "relative." But when asked to explain, the articulate a relational position and claim it is quite consistent with SR. But, as this guy says: "...relativity and relationism are fundamentally incompatible principles."
Ya know, Eric, I don’t care much about common descent, one way or the other. I do, however, care what I readily accept as “fact.” It is widely acknowledged that there is a huge gap of about 100 million years in known history of life on this planet. The evidence shows little more than the existence of bacteria, at one point, and the existence of organisms representing virtually all modern phyla at a later point.
What happened in the meantime is speculation, or, if you’re so inclined, a matter known via dogmatic revelation from Darwin. That all those phyla came from a single common ancestor is simply not known as a “fact.” Even if all currently living things could be indubitably traced back to a predecessor in ONE of those phyla, that would not prove that those predecessors themselves came from one species of bacteria (or anything else). To even conclude that every representative of each of those phyla “came from” bacteria is just speculation, particularly in light of no proven way that could happen in that amount of time. Among other things, there is simply not enough evidence to rule out such hypotheses as a “new round” of abiogenesis which generated a lot of (non-bacterial) organisms under new conditions.
I’m not saying that it is impossible, or that it is an unreasonable “working hypothesis,” for everything later found to have “descended from” the same species of bacteria. I’m saying it aint a known fact. Such a claim is even more suspect in light of the strong evidence of HGT, which is not a matter of genetic material being acquired by “descent.”
A few quotes from a relatively recent article:
“Woese believes that along the way biologists were seduced into thinking they had found the final truth about all evolution. "Biology built up a facade of mathematics around the juxtaposition of Mendelian genetics with Darwinism. And as a result it neglected to study the most important problem in science - the nature of the evolutionary process."
Darwinian evolution simply cannot explain how such a code could arise. But horizontal gene transfer can, say Woese and Goldenfeld… For the researchers the conclusion is inescapable: the genetic code must have arisen in an earlier evolutionary phase dominated by horizontal gene transfer…
"Most of life - the microbial world - is still strongly taking advantage of horizontal gene transfer, but we also know, from studies in the past year, that multicellular organisms do this too," says Goldenfeld…
As more genomes are sequenced, ever more incongruous sequences of DNA are turning up. Comparisons of the genomes of various species including a frog, lizard, mouse and bushbaby, for example, indicate that one particular chunk of DNA found in each must have been acquired independently by horizontal gene transfer (Proceedings of the National Academy of Sciences, vol 105, p 17023). "The importance of this for evolution has yet to be seriously considered.”
http://www.dailygalaxy.com/my_weblog/2010/01/-is-dna-a-fossil-of-the-origin-of-life-worlds-two-leading-biologists-say-yes-as-cosmic-microwave-bac.html
[contintued in next post]
As I said before, I take any claim of universal common descent literally, and do not count just “some kinda connection to” a present or prior organism with respect to genetic structure as a matter of “ancestry” or descent. Those terms have definite biological meanings entailing vertical continuation from parent to offspring, not incidental contact with another organism while jackpotting around.
In practice, “common descent” is synonymous with Darwin’s speculation about lineal descent from a common ancestor. Again: “Comparisons of the genomes of various species including a frog, lizard, mouse and bushbaby, for example, indicate that one particular chunk of DNA found in each must have been acquired independently by horizontal gene transfer.” The similarities here are NOT being explained by resort to the concept of inheritance from an common ancestor. And again, "The importance of this for evolution has yet to be seriously considered.”
You have substituted “common descent” for Gould’s “evolution,” but they are not the same thing and evolution could have occurred largely by means apart from “descent with modification.”
I am willing to acknowledge that “evolution” in a generic sense is a “fact.” I can’t do that with respect to common descent, even if it is a “working hypothesis” worth exploring. Anyone who can has a radically different concept of what a “fact” is than I do.
aintntuhin said...
You will call ANYTHING "common descent"
Common descent is compatible with different starting points for life. It is not compatible with completely separate lineages. I do not refer to "anything" as common descent, in particular, completely separate lineages are not common descent.
I have offered before to use a different prhrase to represent the notion that there is not necesarily a LUCA, or even a single anmcestral population, but that nonetheless all life had the same heritage from very early on. Your response has been that you don't understand the concept. Your lack of understanding is no reason to mischaracterize me by saying I'll call anything common descent.
As I said, within the context of evolutionary theory, "common descent" does NOT mean "descended from 20,000 separately created distinct species."
Actually, as long as each form of life is descended from each of those 20,000, that's exactly what it is taken to mean today, in no small part due to the work of Woese et. al.
aintnuthin said...
When I said "well-articulated reasons," I obviously meant non-"ludicrous" reasons.
Ludicrous reasons can be well-articulated, is that was not obvious at all.
Just before relativity hit the fan, prominent physicists were declaring that there was nothing new to be discovered, that all principles of mechanics, etc. had been discovered, well-understood, and admitted by all. So what?
Considering there were many unanswered, and indeed paradoxical-at-the-time phenomena (such as black-body radiation and the ultraviolet catastrophe), their statements seem ludicrous.
But the "we know all the main highlights, we're just clearing up the details" stance" pronounced by neo-darwinists in say 1960, or 1990, for that matter, make them look rather ludicrious, not those (many) who disagreed with them.
Agred.
The fact that most students who have been dogmatically indoctrinated with those theories accept them as "fact" does not change that.
Not to mention being a category error.
1. So is LR. "Relative motion" is not a modern creation. It was presupposed by Newton and goes back at least as far as Gallileo as a scientific premise.
LR does not describe the relativeness of motion under linear acceleration (as opposed to rotational acceleration). In that regard, GR is superior as a theory of relative motion.
2. Again, GR is NOT a theory of relative motion to begin with. It is a theory of gravity.
It's both. It's a theory tying gravitiy to a type of relative motion.
3. You repeated that GR "comes from" SR ("SR leads to GR"), but that is not the case at all. Nothing about SR implies GR, and Einstein worked 10 long years on that theory. He did not simply "deduce" it from SR.
The basic assumptions of SR were incorporated into GR, along with additional assumptions. SR does not imply GR (it's the other way around), but SR starts you down the path toward GR in a way LR does not.
This guy says it is "obvious," but I guess it isn't,
What's obvious in hindsight can be confusing while the discoveries are underway.
As I said, there is no logical inconsistency in the twin paradox. The only "paradox" is the obviously inconsistent claim that the motion of the twins is ALSO "relational." Except people don't say "relational," they say "relative." But when asked to explain, the articulate a relational position and claim it is quite consistent with SR. But, as this guy says: "...relativity and relationism are fundamentally incompatible principles."
You can't use relational physics to describe the twin paradox, because the relational physics is symmetric and the twins experience is not. It shows the fundamental insufficiency of a relational framework.
What happened in the meantime is speculation, or, if you’re so inclined, a matter known via dogmatic revelation from Darwin.
I agree. Common descent does not depend upon having precise details for this period.
I’m not saying that it is impossible, or that it is an unreasonable “working hypothesis,” for everything later found to have “descended from” the same species of bacteria. I’m saying it aint a known fact.
I agree.
Such a claim is even more suspect in light of the strong evidence of HGT, which is not a matter of genetic material being acquired by “descent.”
HGT has radically changed what common descent can mean, no doubt.
As I said before, I take any claim of universal common descent literally, and do not count just “some kinda connection to” a present or prior organism with respect to genetic structure as a matter of “ancestry” or descent. Those terms have definite biological meanings entailing vertical continuation from parent to offspring, not incidental contact with another organism while jackpotting around.
So, come up with an acceptable term for pointing out that each of us is descended from the each member of the same group of organisms through this "jackpotting around", as opposed to the notion that some organisms have completely separate lineages where the "jackpotting" played no significant role.
In practice, “common descent” is synonymous with Darwin’s speculation about lineal descent from a common ancestor.
Was, not is.
I am willing to acknowledge that “evolution” in a generic sense is a “fact.” I can’t do that with respect to common descent, even if it is a “working hypothesis” worth exploring. Anyone who can has a radically different concept of what a “fact” is than I do.
Or perhaps just a different notion of common descent.
One Brow said: "You can't use relational physics to describe the twin paradox, because the relational physics is symmetric and the twins experience is not. It shows the fundamental insufficiency of a relational framework."
Well, absent the assertion (which you clung to) that the motion being described is strictly relational, there IS no "paradox." Just speak on one's twins journey, and one who is at rest (relative to the other twin).
The whole "problem" explicitly presupposes that one of the twin's is travelling, and the other isn't. OK, no problem.
The problem arises when some naive logical positivist insists that neither twin can properly be said to moving while ALSO claiming that the SR analysis is correct. That's the "paradox," if you want to call self-contradiction a paradox, anyway.
I said: "The problem arises when some naive logical positivist insists that neither twin can properly be said to moving while ALSO claiming that the SR analysis is correct. That's the "paradox," if you want to call self-contradiction a paradox, anyway."
Anyone who would make such a claim does NOT "understand relativity," regardless of how many routine mathematical calculations he may have performed in a relativistic context, and regardless of how many advanced degrees in physics he may have.
Unfortunately, people can accomplish such things while lacking the basical ability to (or habit of) recognize(ing) the implications of his own statements and assumptions and then checking for obvious inconsistencies.
There are people, for example, who "understand" chess. They can tell you the name of every chesspiece and accurately tell you how each piece can legally move. They can explain what the object of the game (checkmate) is, and how to recognize it when you see it. They can explain and demonstrate examples of basic tactical and strategical themes, such as pins, forks, control of open files, etc.
All the same they do not "understand" chess. Some of these very people will routinely, and frequently, put their queen of a spot where his opponent can immediately take it without loss, for example. Understanding nomenclature is not the same as understanding the game (subject).
Something more is required for that, and often an essential part of the "something more" is the type of understanding which is "philosophical" in nature. Some of that "something more" is simply the fundamental ability to examine the implications and likely consequences of your own statements or actions, independent of wishful thinking. Maybe you could some it up by saying the "something more" is the ability and willingness to think. Anybody can push wood. Not everyone can think
That last post may come across as some kinda harsh condemnation, insult, or attempt to gratutitously assert superiority, Eric, but I really didn't mean it that way (although I was deliberately chiding you).
I see it more like this, I spoze: If a person is "positive" that he is right, he may never understand any questions, evidence, or considerations that might be inconsistent with his position. Why? Because he knows he is right. It is therefore impossible for there to be any logic or evidence which undermines his position. At best there could be the superficial appearance of evidentiary/logical contradiction, but that appearance would have to be a false one. Why? Because he is right. No so-called "fact" could possibly contradict a "true fact." Such appearances can therefore be summarily dismissed without critical evaluation. You know they are false appearances from the git-go.
One Brow said: "LR does not describe the relativeness of motion under linear acceleration (as opposed to rotational acceleration). In that regard, GR is superior as a theory of relative motion."
1. LR "explains" motion under both linear and rotational acceleration, just as Newton's theory of gravity explained the motions of planets. GR adds the understanding that large masses also affect time (or, as I would put it, the rate of physical processes--just as temperature can affect such processes).
But you're right, LR does not described the "relativenss" of acceleration. But neither does GR, because it aint relative. As hard as Einstein (initally) tried to insist that acceleration is "relative," he failed. Two mathematically equivalent perspectives are not necessarily two physically equivalent perspectives. Acceleration is absolute. If the car I am driving in at 100 mph makes a sudden right turn, I will know it. You can suggest that my "tendency to continue to move in a straight line" is "really" nothing more than the sudden apperance of an indetectable gravitional force all you want--it aint credible.
There may be no readily apparent way to clearly detect which of two objects is moving if both are moving at a uniform velocity. But if there is acceleration present (which includes a change of direction as with rotational motion)the signs are there: bulging at the equator of globes, etc.
As I understand it, Einstien claimed that the type of uniform acceleration caused by gravity in a free fall cannot be felt or discerned because gravity acts on all parts of the body "equally." Not according to NASA, eh?:
"A human falling into a black hole will also experience tidal forces. In most cases these will be lethal! The difference in acceleration between the head and feet could be many thousands of Earth Gravities. A person would literally be pulled apart! Some physicists have termed this process spaghettification!"
http://spacemath.gsfc.nasa.gov/weekly/4Page33.pdf
Eric, you often act as those GR is a sancrosanct "fact" that cannot be discarded. It aint the case.
Jerome James Brainerd purports to have B.S. in Physics from the University of Notre Dame and a Ph.D. in Astronomy from Harvard University and claims to be "a professional astrophysicist who is working on theoretical problems in high-energy astrophysics." He observes that, in GR: "the effects of gravity appear through the definition of acceleration."
Definitions do not dictate reality...they, can, however, serve the purpose of establishing a priori axioms within a theoretical context.
With respect to GR, he notes that: "Our decision to incorporate gravity into our physics as a curvature of space and time only gets us half way to a theory of gravity. The other half of the problem—the link between matter and the curvature of space-time—must yet to be specified. And here we run into a problem...The only guide we have is the requirement that when the gravitational field is weak, the equations of general relativity must revert to the Newtonian equations of gravity. Ideally we would have measurements of strong gravitational fields to guide us, but such fields are only found in objects too distant to observe accurately. This lack of guidance allows an infinite number of solutions...[Einstein] chose the mathematically simplest equation that relates matter and energy to the curvature of space-time. But in truth, there is no reason why reality should conform to our desire for mathematical simplicity. The greatest uncertainty in the science of gravity is whether matter and energy couple to the curvature of space-time in the was hypothesized by Einstein."
http://www.astrophysicsspectator.com/topics/generalrelativity/
According to the summary of an article published in the peer-reviewed "Physics Essays:"
"Einstein's general relativity requires space and time distortions to explain the advance of the perihelion of Mercury. This requirement is unnecessary. We show here that this phenomenon can be fully explained using Newtonian physics and mass‐energy conservation, without any relativity principle. Without having to introduce any new physics, we arrive at the same equation as predicted by Einstein. Similar consequences have been obtained when studying other relevant phenomena."
http://physicsessays.org/resource/1/phesem/v12/i3/p468_s1?isAuthorized=no
The myth that "only" GR can resolve certain puzzles may be wrong, eh? Either way, it seems that the Lorentizian transformations, which Einstein borrowed and which are not exclusive to GR, play a major role in resolving some "mysteries" arising from classical Newtonian mechanics.
"Einstein was not satisfied with special relativity for very long. He felt strongly that the principle of relativity for uniform motion ought to be generalized to arbitrary motion...
The special-relativistic answer is the same, except that Newton's absolute space needs to be replaced by Minkowski's absolute space-time. Einstein found this answer unsatisfactory, because neither Newton's absolute space nor Minkowski's absolute space-time can be directly observed...Einstein failed to appreciate that special relativity had already solved what he himself identified as the problem of absolute motion...In special relativity, the situation of the two globes is not even symmetric at the purely descriptive level. Because of time dilation, one revolution of the other globe takes less time for an observer on the globe rotating in Minkowski space-time than it does for an observer on the other one. It therefore need not surprise us that the situation is not symmetric at the dynamic level either, that is, that only one globe bulges out."
http://science.jrank.org/pages/11027/Relativity-General-Relativity.html
"Einstein failed to appreciate that special relativity had already solved what he himself identified as the problem of absolute motion:" It was Al's PHILOSOPHICAL desires (compliance with of the logical positivist agenda of pure relationalism), not the physics of SR, which he decided were not satisfactorily fulfilled. So what extremes of "reasoning" did he go to in an attempt to satisfy a philosophical need? See next post.
"This extended relativity postulate, it turns out, is highly problematic. What it boils down to is that two observers accelerating with respect to one another can both claim to be at rest if they agree to disagree about whether a gravitational field is present or not....
As a second example, imagine two astronauts in rocket ships hovering side by side somewhere in outer space where the effects of gravity are negligible. One of the astronauts fires up the engines of her rocket ship. According to the other astronaut she accelerates, but she can, if she were so inclined, maintain that she is at rest in the gravitational field that suddenly came into being when her engines were switched on and that the other rocket ship and its crew are in free fall in this gravitational field. Einstein produced an account of the twin paradox along these lines as late as 1919."
http://science.jrank.org/pages/11027/Relativity-General-Relativity.html
This claim about the relativity of acceleration is rightfully rejected (or even ridiculed) by thinking people and by virtually all physicists today. "Imaginary" gravitational fields are NOT a part of physics. That does not keep them from being a part of PHILOSOPHY, of course. But the whimsical inclination of one obstinate observer to "agree" that one is/is not within the gravitational influence of the earth cannot establish any objective type of "relativity of acceleration."
The point? It was Einstein's adopted (but misplaced) philosophical leanings, NOT SR, which "led" him to spend 10 years working on GR. SR did not "lead to" GR. Logical positivism did, and even then it merely led him to mistaken conclusions and accompanied by fantastical claims about "reality."
So much for "scientific theory" being entirely free from philosophical inclinations, eh?
As pointed out by the mathpages guy, the revolving globes "problem" is the same "problem" raised by the twin "paradox, just in a different form. In order to claim that the twins age different, one must posit that one of them is (relatively) at rest. How can you tell one is at rest (or that one globe is spinning)? Because of one them is accelerating, and one isn't. Acceleration NOT relative.
Edit:
Meant: "But the whimsical REFUSAL [not "inclination"] of one obstinate observer to "agree"
"According to the other astronaut she accelerates, but she can, if she were so inclined, maintain that she is at rest in the gravitational field that suddenly came into being when her engines were switched on and that the other rocket ship and its crew are in free fall in this gravitational field. Einstein produced an account of the twin paradox along these lines as late as 1919."
Here Einstein does NOT resolve any paradox. There is, after all, no paradox to resolve to begin with. In fact, it is this type of undiscplined "argument" that creates the false appearance. The logical conclusion of Einstein's argument is that, yes, each twin really is younger than the other.
Of course this claim is contradictory to his own claim that a cat travelling off into space at high speed, and then returning, would be younger than his stay-at-home homies. So, in addition to making internally inconsistent claims, it is externally inconsistent (with respect to other claims made by Einstein).
All due to the absolute determination to "somehow" arrive at a philosophically-desired, and pre-selected, conclusion.
Edit: "In fact, it is this type of undiscplined "argument" that creates the false appearance [of a paradox]."
J.J. Brainerd said: "Ideally we would have measurements of strong gravitational fields to guide us, but such fields are only found in objects too distant to observe accurately. This lack of guidance allows an infinite number of solutions."
Going back to a prior discussion, if GR allows an "infinite number" of solutions to a particular question about (problem involving) gravity in strong fields, is it surprising that you can achieve a "particular" solution that you want by assigning values accordingly? What kind of solution or answer has any significance if it is just one of a infinite number that can be given? The "calculations" of GR with respect to such questions seems kinda malleable, don't they?
According to Marcuse, if certain sources (e.g., discovery institute, narth, fox news, whatever) give viewpoints that do not advance the socio-political agenda of the left-wing, then it is "repressive" to tolerate such viewpoints. Of course, the solution is that such "repression" must be corrected by refusing to tolerate opposing viewpoints (i.e., supressing them).
We ALL hate repressive bigotry, right?
Well, absent the assertion (which you clung to) that the motion being described is strictly relational, there IS no "paradox." Just speak on one's twins journey, and one who is at rest (relative to the other twin).
There's no mathematical paradox, but it runs counter to most people's expectations. We often call such things paradoxes even when they do not fit the term literally. Another good example would be the Banach-Tarski paradox.
That last post may come across as some kinda harsh condemnation, insult, or attempt to gratutitously assert superiority, Eric, but I really didn't mean it that way (although I was deliberately chiding you).
No worries.
I see it more like this, I spoze: If a person is "positive" that he is right, he may never understand any questions, evidence, or considerations that might be inconsistent with his position. Why? Because he knows he is right.
Of course, to accurately assess such a situation, it's important to make sure that questions, considerations, and evidence are not being fully incorporated into the position of the "positive" person, and reflected in their viewpoints.
One Brow said: "LR does not describe the relativeness of motion under linear acceleration (as opposed to rotational acceleration). In that regard, GR is superior as a theory of relative motion."
1. LR "explains" motion under both linear and rotational acceleration, just as Newton's theory of gravity explained the motions of planets. GR adds the understanding that large masses also affect time (or, as I would put it, the rate of physical processes--just as temperature can affect such processes).
Since you used "explain" and I used "does not described the relativeness of", I see no conflict between those statements.
But you're right, LR does not described the "relativenss" of acceleration. But neither does GR, because it aint relative. As hard as Einstein (initally) tried to insist that acceleration is "relative," he failed.
Linear acceleration can be described relativistically, rotational acceleration (even under constant speed) can not be so described. That's why I was careful to note "linear acceleration" above.
If the car I am driving in at 100 mph makes a sudden right turn, I will know it.
A sudden right turn would not be linear acceleration.
There may be no readily apparent way to clearly detect which of two objects is moving if both are moving at a uniform velocity. But if there is acceleration present (which includes a change of direction as with rotational motion)the signs are there: bulging at the equator of globes, etc.
Agreed.
As I understand it, Einstien claimed that the type of uniform acceleration caused by gravity in a free fall cannot be felt or discerned because gravity acts on all parts of the body "equally." Not according to NASA, eh?:
We currently can not generate gravitational fields that are truly equipotent in all locations within a given volume. I'm not willing to say such fields can never be generated. Are you?
Eric, you often act as those GR is a sancrosanct "fact" that cannot be discarded. It aint the case.
Actually, I'm fairly sure that GR will be discarded/replaced, much as Newton's Law of Gravity was. My understanding it that it suffers from point singularitites and is in conflict with certain aspects of quantum mechanics. That said, it's the very best thing we have right now and has been thoroughly tested.
According to the summary of an article published in the peer-reviewed "Physics Essays:"
"Einstein's general relativity requires space and time distortions to explain the advance of the perihelion of Mercury.
No one did, before relativity predicted it. So, in 1999 a physicist uses some ad hoc changes to match some past observations, and this means relativity is useless and space behaves as though it were flat? I beleive you are fond of comparisons to epicycles. When the same changes can be used to make predictions just as reliable as GRs regarding phenomena not yet observed, then it will be something interesting.
But the whimsical refusal of one obstinate observer to "agree" that one is/is not within the gravitational influence of the earth cannot establish any objective type of "relativity of acceleration."
It's the inability of the observer to to detect such a state experimentally in a uniform gravitational field that establishes such relativity.
The point? It was Einstein's adopted (but misplaced) philosophical leanings, NOT SR, which "led" him to spend 10 years working on GR. SR did not "lead to" GR. Logical positivism did, and even then it merely led him to mistaken conclusions and accompanied by fantastical claims about "reality."
Actually, it's both. To the degree that GR has a philosophical basis, that basis is the same as SR, plus an additional consideration about the inability to detect a difference between uniform gravitational fields and linear acceleration. The shrinking yeardsticks and slowing clocks of LR are not so easily changeable into GR.
The logical conclusion of Einstein's argument is that, yes, each twin really is younger than the other.
Except gravity affects time as well as movement, and in the graviational field, the twin subject to gravity would age faster. Einstein's version gives the same answer for the ages of the twins.
aintnuthin said...
J.J. Brainerd said: "Ideally we would have measurements of strong gravitational fields to guide us, but such fields are only found in objects too distant to observe accurately. This lack of guidance allows an infinite number of solutions."
Going back to a prior discussion, if GR allows an "infinite number" of solutions
GR was the simplest solution among an infinite number of solutions. He is not saying GR itself offers an infinite number of solutions. Read your quote again.
We ALL hate repressive bigotry, right?
I'm just as opposed to left-leaning groups that distort the truth (such as PETA) as I am to the right-leaning groups. How about you?
One Brow said: "It's the inability of the observer to to detect such a state experimentally in a uniform gravitational field that establishes such relativity."
In the context of physics, "relativity" is not a subjective thing, which simply depends on either (1) what a person wants to claim, without reason, or (2) what one can "detect." I can't detect ghosts, so ghosts are "relative," that the idea? If I hear a chain rattling and it "could" be a ghost instead of some known physical phenomenon causing it, then "rattling chains" are relative?
Gravity can be detected in any event, due to a number of things, such as tidal forces, the most obvious of which is the presence of a large mass.
We're talking about what you yourself called "a theory of relative motion," not pyschological phenomenological or cognitive studies. The article I cited explains the reason why acceleration is absolute as follows:
"Free fall in a gravitational field (1a) and hovering in outer space (2a) are both represented as motion along the straightest possible lines in what in general will be a curved space-time. Such lines are called geodesics. Resisting the pull of gravity (1b) and accelerating in outer space (2b) are both represented as motion along crooked lines, or nongeodesics. Since no change of perspective will transform a geodesic into a nongeodesic or vice versa, there is an absolute difference between (1a) and (1b) as well as between (2a) and (2b). Absolute acceleration survives in general relativity, as in special relativity, in the guise of an absolute distinction between geodesic and nongeodesic motion."
You still seem to have a very confused idea of what relativity even is. Perhaps you are confusing the supposed relevance of "detection" with the (relationalist) logical positivist philosophical doctrine which says that any supposed concept or thing which cannot be empirically detected is "fictitious," metaphysical, and "meaningless." But, as noted, relationalism is NOT relativity, and is in fact fundamentally opposed to it.
Gravity can be detected in any event, due to a number of things, such as tidal forces, the most obvious of which is the presence of a large mass. If it couldn't be detected, how could Einstein even make a distinction between places where gravitational fields are either weak or strong.
One Brow said: "Linear acceleration can be described relativistically, rotational acceleration (even under constant speed) can not be so described. That's why I was careful to note "linear acceleration" above."
There is no distinction to be made here between linear and rotational motion. As noted, a geodesic is the straightest possible line.
One Brow said: "GR was the simplest solution among an infinite number of solutions. He is not saying GR itself offers an infinite number of solutions. Read your quote again."
Heh, we can't even read the same article and see the same things, eh? I would just tell you to read it again. It seems clear to me that the the "lack of guidance" within GR allows infinite solutions, and that the greatest uncertainty in gravitational theory is not knowing how or if GR's hypotheses correspond to reality. He is talking only about GR, not about an infinite number of other potential theories.
One Brow said: "No one did, before relativity predicted it."
Wrong. The anomaly of mercury's precession was known, not "predicted," and Einstein knew the exact formula which was needed to make the math correspond with the known observations. It was dervied by a guy named Gerber in 1898:
http://hypergeometricaluniverse.blogspot.com/2008/10/precession-of-mercurys-perihelion.html
A more familiar source: "Paul Gerber (1898) even succeeded in deriving the correct formula for the Perihelion shift (which was identical to that formula later used by Einstein)."
http://en.wikipedia.org/wiki/Two-body_problem_in_general_relativity
One Brow said: "When the same changes can be used to make predictions just as reliable as GRs regarding phenomena not yet observed, then it will be something interesting."
The guy was using Newtowian mechanics. Believe it or not, Newtonian gravity and mechanics have made tons of (since verfied) predictions about new phenomena. A gravitational field is considered "strong" only when the escape velocity nears the speed of light, so, as a practical matter, GR basically reduces to newtonian gravity in all parts of our solar system and virtually every other place in the universe.
Even Einstein said that we cannot assume that GR would hold true in "strong" gravitational fields.
I said: "Heh, we can't even read the same article and see the same things, eh? I would just tell you to read it again."
OK, I'll retreat from this position. I did misread it the first time, it seems.
But at least part of the point remains, i.e., that we can't observe and measure strong gravitational fields adequately enough to "confirm" any of GR's assumptions about such fields and how matter interacts with spacetime.
That, however, wasn't the point that I was emphasizing in the post in question, so I concede my misreading.
Still, as noted, even Einstein had reservations about the universal application of his locally-based hypotheses.
One Brow said: "I'm just as opposed to left-leaning groups that distort the truth (such as PETA) as I am to the right-leaning groups. How about you?"
I'm opposed to anybody distorting truth anytime. That said, if I asked two different people to tell me 100 things they know about, say GR, I would hear totally different things from a person who accepted the tenets of GR than I would from a person who didn't. Every single one of the 100 (200 total) things I was told might be free from factual distortion, but there would nonetheless be totally DIFFERENT things. I don't mind hearing from both sides of an issue that can be viewed from different perspectives. I don't assume that one side is right, and the other wrong, or that one is lying and the other is telling the truth just because they don't agree with the view I may personally favor. I don't see a "conservative" outlook as being any more or less "true" than a "liberal" one. Just different perspectives, with differing values, that's all.
That said, I have found that partisan zealots, on either side, are quite fond of both factual distortion and demonization of their opponents.
In the case above it's more a matter of emphasis. The GR supporters will want to tell me things that they think support GR, and will NOT mention things that might cast doubt on that proposition. The GR opponent will do the same, in reverse.
There are, of course, people who look at both the positives and the negatives and hold who adhere to no definite conclusion, one way or the other. They will, of course, present a much more balanced view. They might mention 50 things that favor GR and 50 things that don't.
Tidal forces can cause massive bodies to disintegrate. GR says gravity is a "fictitious" force. In my mind, there is nothing "ficitious" about a force that can tear you apart. Call the force "curved space" if you want. It's still a purty powerful force.
Relativst (to astronaut): You can't tell if you are in free fall or just stationary in space, far from all gravitational masses.
Astronaut: Sure I can. I'm looking out the window, right now, and I see the earth and see that I'm circling it.
Relativist: Hold on, just a damn minute! Who the hell drew the curtain!?
Relativist draws curtain, then: Can you see the earth now?
Astronaut: No.
OK, then! You can't detect it! There is no possible way for you to detect it. I've proved my point. There is no way to know. It's all RELATIVE!
Astronaut: Did the earth disappear when you closed the curtain?
Relativist: Of course it did. It can't be there if you don't see it. It would be fictitious, metaphysical, and meaningless for you to assert that something which you can't now see exists. You have no empirical basis for making such a claim, or assuming such a thing.
Relativist: I'm purty clever, doncha think, Astro-baby!?
Astronaut: Sorry, but, no, I don't.
Astronaut: I'm feelin some very strong tidal forces in my body and I fear I am approaching a black hole. I don't want to end up spagettified. What can I do?
Relavist: Very simple. Close your eyes. If you can't see your feet bein ripped off your body, then your calves, then your thighs, etc., then it can't happen. Spagettification is strictly relative, ya see?
Astronaut: But what if I forget and open my eyes?
Relativist: You'll be fine. If there is any circumstance under which you can't see something, like when you close your eyes for second, then you make it so that you NEVER see it. It becomes relative, at the instant you close your eyes, and hence there is no way to say that spagettification can or cannot ever occur. Both views are equally valid. It's your choice, at that point. So just take the position in your mind that spagettification does NOT exist, and you'll be fully protected.
One Brow said: "Except gravity affects time as well as movement, and in the graviational field, the twin subject to gravity would age faster. Einstein's version gives the same answer for the ages of the twins."
This claim just proves, once again, that you have no conception of the significance of what the many experts I've quoted for you are saying.
SR says that the twin who is really moving (has undergone relative acceleration) is REALLY younger. To begin with, gravity does not make one who is closer to the source (mass) age faster, as you claim, but rather slower because his clock slows down, rather than speeds up. But it's basically irrelevant anyway if you're suggesting the two separate effects on time of acceleration motion, on the one hand, and gravitational time dilation on the other would just cancel each other out. They wouldn't. If by "same answer for the ages of the twins" you mean they would be the same age, that would be inconsistent with SR.
The only reason any meaningful calculations or predictions whatsover can be made by either SR or GR is because both establish ABSOLUTE spacetime, not "relative spacetime."
Newton had absolute space; Einstein has (in both GR and SR) absolute spacetime. His continuing attempts, as late as 1919, to fallaciously argue that motion was strictly relational were later abandoned by him because...well because they were fallacious, misleading, and mistaken.
In GR, a geodesic path is inertial (not accelerated) and a non-geodesic path is accelerated (all according his own definitions of those terms, of course). As has been pointed out: "Since no change of perspective will transform a geodesic into a nongeodesic or vice versa,...absolute acceleration survives in general relativity, as in special relativity, in the guise of an absolute distinction between geodesic and nongeodesic motion."
In GR Einstein saw fit to give the concepts of inertia and acceleration the EXACT OPPOSITE meaning that they have in SR and Newtonian mechanics.
In SR, I am in a non-accelerated (inertial, geodesic) state while sitting at my desk.
This exact same state is ACCELERATED (non-intertia, non-geodesic) in GR.
====
Likewise, in SR, I am in a accelerated (non-inertia, non-geodesic) state while in free fall, and
This exact same state is non-accelerated (inertial, geodesic) in GR.
In both of Einstein's "contrasting" examples, it is the accelerated twin (clock) which "really" slows down. Newton was always careful to remind his readers that an object was inertial if it was EITHER 1. at rest, or 2. Moving uniformly in a straight line. He did not simply say an inertial object was "at rest," which implies "non-moving."
But in his fallacious argument Einstein equivocates by using the SR definition of "at rest" in one case, and the GR defintion of "at rest" (which means the exact opposite) in the other. By use of this rhetorical trick, he tried to persuade his listeners (and himself, apparently) that the two cases were completely symmetrical (relational) when they are not, in EITHER theory (SR or GR).
I really don't expect you to understand either of those last two posts, because you never do. You seem determined to keep yourself convinced that GR is an accurate "theory of relative motion" in which (linear) acceleration is "relative." Why, I don't know.
One Brow said: "You can't use relational physics to describe the twin paradox, because the relational physics is symmetric and the twins experience is not. It shows the fundamental insufficiency of a relational framework."
Even though you said this (apparently because you trusted the source it came from) it was quickly obvious that you did not understand it. The reason that the two twins are NOT in symmetrical situations in SR is BECAUSE one of them undergoes an (ABSOLUTE) acceleration, and one doesn't.
Insofar as you repeatedly claim that GR "implies" SR, you should be able to readily discern that the twins are not symmetrical in GR either and that this is so for the same reason (absolute acceleration).
All this is true notwithstanding Einstien's fallacious "response to his critics" which tried to deny the asymmetry (which bothered him greatly due to his positivistic philosophical inclinations).
It is apparently because you know that Einstein conceded the failure of GR to establish symmetry with respect to rotational motion that you also concede that rotational acceleration (only, in your view) is absolute. But, as I have already said, the mathpages articles clearly point out that the two globes asymmetry is just a variation on the twins "paradox" question. In both cases, the question is "how do you KNOW which one is accelerating?"
In each case the answer is the same: Because each theory implicitly incorporates ABSOLUTE spacetime, which thereby provides the means of detecting absolute acceleration.
In GR, for example, it is clear that "curved spacetime" (gravity) is "caused" by (the proximity of) matter. It does not just appear willy-nilly.
Hence, in GR, you must have matter to have a "gravitational field." You won't have it without matter. Even in the abstract theory of GR, matter is both "real" and "detectable." Hence we all have a means of detecting and knowing if we are in a gravitational field. It is not "unknowable." Contriving special circumstances (like blinding a guy) where he can't "see" the matter present does not change the "detectablilty" of matter to those with the proper equipment in the appropriate circumstances (i.e., he is not confined to a "point," he has measuring instruments, etc.).
To argue otherwise is to go the total solipsistic route, where the only thing that exists, and hence the only criterion for "truth." is a subjective mind.
Berkeley, the articulate forerunner of Mach, was an EXTREME empiricist, who took empiricism to it's extreme conclusions. Like Mach and Einstein, he argued vehemently again Newton's notion of absolute space on the grounds that it couldn't be perceived.
The logical consequences, as Berkeley showed, of extreme empiricism turns out to be a form of radical solipsism. His maxim was "to be is to be percieved." A tree "existed" if, and ONLY IF, someone perceived it. If an observer was looking at a tree, it existed, but the minute he turned his head, the tree ceased to exist. Of course it came back into "existence" if the observer looked in it's direction again.
The upshot of empiricism, for Bishop Berkeley, who was a cleric, was proof that matter does not exist (only mind) and that God was required to produce the immaterial images we perceive.
Not really a philosophy that is amenable to modern physics, know what I'm sayin?
Berkeley had an acute intellect, made coherent points, and has not been dismissed by philosopers as a "crank" or a "kook."
George Berkeley has gone down in the handbooks as a great spokesman of British empiricism. He influenced many modern philosophers, especially David Hume. Berkeley’s “thought made possible the work of Hume and thus Kant," notes Alfred North Whitehead.
http://en.wikipedia.org/wiki/George_Berkeley
aintnuthin said...
In the context of physics, "relativity" is not a subjective thing, which simply depends on either (1) what a person wants to claim, without reason, or (2) what one can "detect."
Actually, it is based on very specific inabilities to detect. SR/LR both use the fundamental idea that an experimenter in whether a true intertial environment (another thing that doesn't exist in reality) can not, within that environment, detect whether they are in motion from within the environment. GR adds the notion of an experiementer being unable to distinguich a uniform gravity field and acceleration. These are foundation concepts to relativity.
I can't detect ghosts, so ghosts are "relative," that the idea?
Feel free to put out a theory of ghost relativity.
Gravity can be detected in any event, due to a number of things, such as tidal forces, the most obvious of which is the presence of a large mass.
A uniform field would not have tidal forces. Sure, we can't produce a uniform field, any more than we can produce a truly inertial environment (friction keeps interfering). That doesn't stop the theories from working.
The article I cited explains the reason why acceleration is absolute as follows:
"... Absolute acceleration survives in general relativity, as in special relativity, in the guise of an absolute distinction between geodesic and nongeodesic motion."
If you are using this interpretation of acceleration, that means that buildings, for example, are under constant acceleration simply because the groung does not let them fall (this would be even more true if the earth did not rotate, the deviation from a geodesic would be larger on a non-rotating planet). So yes, an experiementer can tell whether "something tends to fall" or not. What they can't tell (within their environment) is whether that tendency comes from propulsion or a uniform gravitic field.
Gravity can be detected in any event, due to a number of things, such as tidal forces, the most obvious of which is the presence of a large mass. If it couldn't be detected, how could Einstein even make a distinction between places where gravitational fields are either weak or strong.
By the amount of change in velocity produced.
There is no distinction to be made here between linear and rotational motion. As noted, a geodesic is the straightest possible line.
Let's see how well you understand this. I roll one ball on the ground which follows a Euclidean straight line, while I throw a second into the air, and it goes up and down for a combined five second. For those five seconds, which ball is following a geodesic?
Answer: the one thrown into the air. The ball on the ground is not following a geodesic. Now, if you want to call going up. slowing, changing direction, and falling a "straight line", I'm up for that. You think you can avoid getting confused?
One Brow said: "No one did, before relativity predicted it."
Wrong. The anomaly of mercury's precession was known, not "predicted,"
Thank you for the correction. This doesn't change the point that it took until 1999 to come up with a "Newtonian" solution, which is almost certainly not standard Newtonian gravity. Epicycles.
The guy was using Newtowian mechanics.
If classical Newtonian mechanics has been sufficient to explain the perihelion shift, no one would have been impressed by the ability of GR to do so, and it would have happened well before the 1930s.
..., as a practical matter, GR basically reduces to newtonian gravity in all parts of our solar system and virtually every other place in the universe.
That depends on the degree of accuracy you need, of course.
Even Einstein said that we cannot assume that GR would hold true in "strong" gravitational fields.
I agree. Until we experiement in such fields, we don't know one way or the other. Such experiments may indeed require fundamental complications to GR, making the new hypothesis/theory as much more complex than GR as GR is than Newton.
They might mention 50 things that favor GR and 50 things that don't.
Until we have an alternative to GR, the 50 things that don't favor it shouldn't keep us from using it.
Tidal forces can cause massive bodies to disintegrate. GR says gravity is a "fictitious" force.
??? Having widely varying geodesics between different parts of your body, to the point where the inertial differences generate enough force to rip you apart, isn't good enough?
To begin with, gravity does not make one who is closer to the source (mass) age faster, as you claim, but rather slower because his clock slows down, rather than speeds up.
Following the geodesic results in maximal time passage. If the ship twin interprets event as the non-ship twin freefalling in gravity while the ship prevents the free-fall of the ship-twin, holding him in place, the ship-twin is still leaving the geodesic, the non-ship twin is following the geodesic, and the non-ship twin ages more rapidly. The GR answer is the same as the SR answer.
... would just cancel each other out.
I see no reason for the size of the effects to equal.
In GR Einstein saw fit to give the concepts of inertia and acceleration the EXACT OPPOSITE meaning that they have in SR and Newtonian mechanics.
In SR, I am in a non-accelerated (inertial, geodesic) state while sitting at my desk.
This exact same state is ACCELERATED (non-intertia, non-geodesic) in GR.
Within a gravitational field, that your chair is preventing you from free-falling in, of course.
By use of this rhetorical trick, he tried to persuade his listeners (and himself, apparently) that the two cases were completely symmetrical (relational) when they are not, in EITHER theory (SR or GR).
No one is perfect. However, as you have taken pains to note, relative and relational are not the same.
I really don't expect you to understand either of those last two posts, because you never do. You seem determined to keep yourself convinced that GR is an accurate "theory of relative motion" in which (linear) acceleration is "relative." Why, I don't know.
If we are using the geodesic-is-a-line terminology, linear acceleration is an oxymoron.
Even though you said this (apparently because you trusted the source it came from) it was quickly obvious that you did not understand it. The reason that the two twins are NOT in symmetrical situations in SR is BECAUSE one of them undergoes an (ABSOLUTE) acceleration, and one doesn't.
SR does not have the machinery to treat acceleration relatively, so I agree with you.
Insofar as you repeatedly claim that GR "implies" SR, you should be able to readily discern that the twins are not symmetrical in GR either and that this is so for the same reason (absolute acceleration).
In the sense of leaving the geodesic (as opposed to changing positions), sure.
In each case the answer is the same: Because each theory implicitly incorporates ABSOLUTE spacetime, which thereby provides the means of detecting absolute acceleration.
You don't need an absolute spacetime to detect absolute acceleration, just an inertial spacetime.
To argue otherwise is to go the total solipsistic route, where the only thing that exists, and hence the only criterion for "truth." is a subjective mind.
You seem to be confusing the use of ideal conditions to simplify things for theory creation with claims ideal conditions exist. Sure, there is not truly uniform gravitational field, any more than there is a truly interial environment. The ideas are used to create simpler theories.
Not really a philosophy that is amenable to modern physics, know what I'm sayin?
It makes hash of uniformitarianism, so I'd say it's probably not compatible with any modern science. Interesting idea, though.
One Brow said: "LR does not describe the relativeness of motion under linear acceleration (as opposed to rotational acceleration). In that regard, GR is superior as a theory of relative motion."
I didn't use the term "linear," you did. I said "straightest POSSIBLE line," not "straight line."
Later you say: "Linear acceleration can be described relativistically, rotational acceleration (even under constant speed) can not be so described. That's why I was careful to note "linear acceleration" above."
So YOU were careful to use "linear," you say.
Now you say: Let's see how well you understand this...if you want to call going up. slowing, changing direction, and falling a "straight line", I'm up for that. You think you can avoid getting confused?"
Finally, you make this pronouncement: "If we are using the geodesic-is-a-line terminology, linear acceleration is an oxymoron."
If you were talking about GR (which you were) why did YOU use "linear acceleration?"
What DID you mean when you said: "...motion under linear acceleration (as opposed to rotational acceleration)."
Is there some correction to *my* understanding that is needed here?
I used your own term ("linear") because I knew what you were trying to say. I didn't try to make technical corrected to your chosen terminology. I used it so we could be "on the same page."
I didn't think we would have to quibble (or that I would be "corrected") about a term you introduced into the discussion. Go figure, eh?
One Brow said: "??? Having widely varying geodesics between different parts of your body, to the point where the inertial differences generate enough force to rip you apart, isn't good enough?"
Seein as how you use the concept of force ("generate enough force to rip you apart") it seems we agree. Why the multiple question marks?
I said: "Call the force "curved space" if you want. It's still a purty powerful force."
One Brow said: "Actually, it is based on very specific inabilities to detect. SR/LR both use the fundamental idea that an experimenter in whether a true intertial environment (another thing that doesn't exist in reality) can not, within that environment, detect whether they are in motion from within the environment. GR adds the notion of an experiementer being unable to distinguich a uniform gravity field and acceleration. These are foundation concepts to relativity."
Yes, I agree with this, in general. But it is the last two sentences which are both suspect and ambiguous in a confusion-causing way.
Elsewhere, you say: "If the ship twin interprets event as the non-ship twin freefalling in gravity..."
Notice the difference between standard relativity (whether Galliean or relativistic) and GR "relativity." Galliean relativity does NOT depend on how a particular individual happens to subjectively "interpret" the phenomena.
The equivalence principle is indeed a foundational concept in GR, but, then again, GR is a misnomer, as Einstien himself said. GR is a theory of gravity, not one of relative motion (insofar as it is successful, anyway). You have often used the term "relativity" to mean drastically different things, all while insisting that it is the "same" thing.
Gravitation and acceleration (resulting in an increased relative velocity) both affect time, BUT they do so in different ways and for DIFFERENT reasons. You have claimed that both effects are part of one consideration, which you ambiguously call "relativity."
It seems to me that many of the confusing (and internally inconsistent) claims you have made in the past result from (1) this conflation of relative velocity and gravitation, (2) a failure to distinguish relationalism from relativity, and (3) a desire to "prove" (or at least assert) that all motion is relational.
One Brow said: "GR adds the notion of an experiementer being unable to distinguich a uniform gravity field and acceleration."
You keep bringing up a "uniform" gravity field for reasons that I could not fathom. The more you refer to it, the more I think I see what you are trying to say.
As I understand you, a "uniform" field in an idealized one where the strength of gravity does NOT, as Newton claimed, vary with distance between the material bodies involved. At the same time, you seem to concede that such "uniform" fields do not exist in nature and that we have not been able to artificially "generate" one.
If you're relying on empirical observations, and if you believe GR is dependent on an idealized and non-existent "uniform" field, then why don't you reject GR in favor of a Newtonian conception (attraction between matter, as opposed to "curved space")? Newton's gravitation certainly corresponds to observation more closely than does a "uniform gravitational field."
This desire to insist that all motion is strictly relational in an ontological sense is reiterated even in the statement I said I "generally agreed with."
There you say: "SR/LR both use the fundamental idea that an experimenter in whether a true intertial environment (another thing that doesn't exist in reality)..."
Why the parenthetical claim about "reality?" Where does that fit in to either SR or GR? Both SR and GR implicitly presuppose that "inertial states" (whether called a geodesic or something else) "really" do exist.
You claim the theories are accurate, all while denying their fundamental presuppositions. What's up with that?
You seem to have two conflicting desires, to wit:
1. A desire to claim that modern scientific theories, as you interpret them, are dictated by the facts and are as close to fact as you can get, and
2. A desire to ceaselessly assert, as "true," a philosophical ontology which is also, to you, indubitable.
When these desires conflict, you start shifting ground, and keep going back and forth with respect to the assumptions you claim to be making.
As you know, we discussed these issues at great length before, and the continous shifting was quite evident. In one sentence, you would purport to concede (at least implicity) the premises underlying SR and GR. OK, fine, now we have at least agreed on the assumptions (whether true or false) we are going to make for the sake of discussion.
But then, in the next sentence, you would deny the validity of the very assumptions we had just agreed upon. It is impossible to logically or coherently discuss anything when this happens.
One Brow said: "This doesn't change the point that it took until 1999 to come up with a "Newtonian" solution, which is almost certainly not standard Newtonian gravity."
Two comments:
1. Well, the derivation no doubt incorporates Lorentz contractions, which were not a part of "classical" mechanics. But that's part of the point. GR is not the only theory which uses those transformation, and other theories do NOT resort to "curved space," as the "explanation."
2. This probably was pointed out back in the '20's, I just happened to refer to a recent article. No one, not even Einstein, claimed that LR did not make the same predictions and arrive at the same conclusions as SR. Both rely on the Fitzgerald-Lorentz transformations. That was not the difference that led one theory to become more prevalent in useage than the other (mathematical simplicity and "aesthetic" considerations were a big part of it).
One Brow said: "Epicycles." That "point" could be made against GR, too. As I noted:
1) The anomoly was there, for all to see, crying for an explanation. It was not predicted. In that sense, any explanation is "ad hoc."
2) Even the exact mathematical formula which "solved" the problem had been around when Einstien came out with GR. He just had to match the formula with the observed facts in some coherent manner. Kinda "ad hoc," know what I mean? Einstien just kept adjusting the field equations that he was developing via trial and error until he got a match.
I don't pretend to understand the mathematics underlying GR. To the extent the general concepts can be explained in non-mathematical terms, I think I have some understanding of it, but I certainly don't pretend to be any kinda expert on the "conceptual" aspects, either.
With that admission, it seems to me that a very important implication of GR is that gravity ALSO affects "time." In that sense, even if there were no others, GR presented some novel insights.
But, after those insights became known, other theories which explain them have developed. Neo-lorenztian "ether" (which is a local effect of gravitional mass), for example, is claimed to be a component of alternative theories which explain this phenomenon.
We were indirectly talking about the "Roche limit" a few posts back:
"The Roche limit sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction."
http://en.wikipedia.org/wiki/Roche_limit
A body "held together by its own gravity" is presumably "accelerated" at all times by the GR definition, just like a guy standing on earth. Even if it is "motionless" it is "accelerated," with an equilibrium pushing and pulling forces between the component atoms having been achieved so as to create the appearance of "stability." But how is such a "stability" reached? Why doesn't the thing just collapse into a black hole?
In the old (since discarded) "solar system" model of atomic structure, the relative distance between the nucleus and orbiting electrons were said to have been (proportionately) just as great as the actual solar system on a macroscopic scale.
In a sense, the solar system and the atom, might be thought of as being just like a chunk of meteor, held together as a single "stable entity" by gravitational attraction. But this "stable" entity can be ripped apart by tidal forces (evidently not present in your "uniform gravitational field," whatever that is).
But, as I understand it, sub-atomic particles are believed to have a "gravity-repulsion" mechanism. Einstein proposed just such a "gravity-repulsion" factor when he formulated (mathematically) the "cosmological constant." He later rejected this as the "biggest mistake of his life," but some modern scientists are reviving it. Dark matter is supposedly just such a "gravity-repulsion" device. Like I said, some respectable scientists have proposed an "ether" theory in lieu of the "dark matter" hypothesis.
Modern physicists refer to gravitation as one of the four fundamental "forces" (particle interactions) in the universe. I haven't seen "curved space" on that fundamental list, for some damn reason.
None of this is relevant to any particular point, but gravitation (GR) seems to fall apart at quantum levels, and many alternative hypotheses are being advanced, as you have noted.
Which is all the less reason to reject alternative theories as being posited only by "cranks," I figure. For the same reason, it may not be be wise to contemptuously dismiss the notion of an "ether" out of hand as preposterous, just because that is the popular thing to do and doing so makes you look "cool" to your homeys, eh?
Newton had the task of explaining why, if "universal gravitation" was true, the moon hadn't simply been pulled down to the earth long ago.
His answer, of course, was that the moon (originally) came under the earth's influence with a uniform, pre-existing inertial velocity, which it had never lost, and settled into orbit around the earth once the inertial velocity had reached an equilbrium with respect to mutual "gravitational attraction" between the two bodies.
Fortunately for the moon, it was not within the Roche limit and therefore did not disintegrate into a crapload of small-ass particles to form an orbiting "ring." Of course, in GR, gravity is not a "force." It can't be, by postulation, since all the "heavy-lifting" formerly ascribed to gravitation has now been fobbed off on space-time as a matter of mathematical formulation. With powers like that, I don't know why anyone would claim that absoute spacetime is not "observable," know what I'm sayin?
I didn't use the term "linear," you did. I said "straightest POSSIBLE line," not "straight line."
I was using the notion of a Euclidean straight line, not a geodesic. When your discussiing situations like the twin paradox, you typically simplify the situation to focus on a concept. So, you don't see discussions of planetary gravities, curves in space, or even the gravities generated by the twins themselves. In that discussion, Euclidean lines are the paths of geodesics.
Even then, a geodesic is not just a path in space, its a path at a specific rate of change in speed. If you follow an orbital path by going faster than a standard orbit ( using a rocket to keep yourself on that path would be one way), you are following the path of the geodesic, but you have left the geodesic itself.
Is there some correction to *my* understanding that is needed here?
We were using different notions of line, so I would say there needs to be a correction to our mutual terminology.
Seein as how you use the concept of force ("generate enough force to rip you apart") it seems we agree. Why the multiple question marks?
I'm not sure how "fictional" applies.
Notice the difference between standard relativity (whether Galliean or relativistic) and GR "relativity." Galliean relativity does NOT depend on how a particular individual happens to subjectively "interpret" the phenomena.
I'm not sure what you mean by "depend" here. GR gives the same answer to the twin's aging whether you assume the ship twin changes position by propulsion, or the non-ship twin changes position in free-fall. So the answer in GR does not depend on the interpretation. Meanwhile, in Galilean relativity you are free to assume any particular inertial environment is the rest frame, so the individual can interpret any frame to be the rest frame, just happens in GR. I'm unclear where you see a difference.
It seems to me that many of the confusing (and internally inconsistent) claims you have made in the past result from (1) this conflation of relative velocity and gravitation, (2) a failure to distinguish relationalism from relativity, and (3) a desire to "prove" (or at least assert) that all motion is relational.
The conflation is gravitation with a particular sort of acceleration (not all acceleration), we just had a discussion on the difference between relationalism and relativity, and I just asserted that realtionalism is obviously insufficient to explain the twin paradox. So, I find you list to be non-correspondent to me.
If you're relying on empirical observations, and if you believe GR is dependent on an idealized and non-existent "uniform" field, then why don't you reject GR in favor of a Newtonian conception (attraction between matter, as opposed to "curved space")? Newton's gravitation certainly corresponds to observation more closely than does a "uniform gravitational field."
1) GR doesn't need a macro-level uniform gravitational field to work. The concept is used as a starting point to explain a principle, just as the concept of an inertial rest frame is used for SR/LR.
2) Any gravitational field will be uniform within the level of measurement error in a small enough volume (though the volume may be very small), so we can approximate uniform gravitational fields at the micro-level.
Why the parenthetical claim about "reality?" Where does that fit in to either SR or GR? Both SR and GR implicitly presuppose that "inertial states" (whether called a geodesic or something else) "really" do exist.
They are used to simplfy relationships and explain the ideas behind them. They don't need to exist in reality, at least not above the micro-level, for the theories to be useful.
You claim the theories are accurate, all while denying their fundamental presuppositions. What's up with that?
It's part of the process of simplification and abstraction. Simplification and abstraction are used in the same way by classical mechanics as by GR.
You seem to have two conflicting desires, to wit:
1. A desire to claim that modern scientific theories, as you interpret them, are dictated by the facts and are as close to fact as you can get, and
Theories contain facts, but contain much more than facts, and I would never try to reduce a theory to the level of a mere fact.
2. A desire to ceaselessly assert, as "true," a philosophical ontology which is also, to you, indubitable.
Philosophical ontologies are formal systems, and can never be proven to represent reality. We can only hope to come close.
When these desires conflict, you start shifting ground, and keep going back and forth with respect to the assumptions you claim to be making.
Again, I do not find your sentence descriptive of me.
2. This probably was pointed out back in the '20's, I just happened to refer to a recent article. No one, not even Einstein, claimed that LR did not make the same predictions and arrive at the same conclusions as SR. Both rely on the Fitzgerald-Lorentz transformations. That was not the difference that led one theory to become more prevalent in useage than the other (mathematical simplicity and "aesthetic" considerations were a big part of it).
If it was pointed out in the 1920's, why would a magazine publish 70-year-old work as research? Neither of us has access to the article, so I don't see much point in further speculating. I suspect that the author has added some additional items besides the Lorentz transformations to classical mechanics (there are other articles in that magazine that specifically try to approximate GR by doing this), but I can't prove it. You seem convinced that there is nothing new being added, but you can't prove it. There we are.
Einstien just kept adjusting the field equations that he was developing via trial and error until he got a match.
I'm not sure that's true, but if it is, that's what he should have done (assuming Mercury was the first evidence used). You let the data guide the theory. Once the equations worked with Mecury, then you test on other phenomena to see if those precise values keep working. If they don't, you need to scrap the theory. In the case of GR, the chosen values kept working, so the theory was kept.
But, after those insights became known, other theories which explain them have developed. Neo-lorenztian "ether" (which is a local effect of gravitional mass), for example, is claimed to be a component of alternative theories which explain this phenomenon.
So, moving fast through the ether slows down clocks, but concentrating the ether speeds clocks up? That's an interesting pair of properties for the ether.
A body "held together by its own gravity" is presumably "accelerated" at all times by the GR definition, just like a guy standing on earth.
The body as a whole is not accelerated, but any small part of it which is not at the center of mass is accelerated. The sum of all the smaller accelerations (as vectors) will be zero.
Which is all the less reason to reject alternative theories as being posited only by "cranks," I figure.
GR will probably be superseded and discarded at some point. However, the theory that replaces it will have to look like GR in all the experiements done locally. Not every proposed replacement (as far as I know, none so far) can meet this test. Those that can't are crankish.
With powers like that, I don't know why anyone would claim that absoute spacetime is not "observable," know what I'm sayin?
Accelertion is still absolute, though, right? The Roche limit is about differing accelerations and their effect on physical integrity.
One Brow said: "…I just asserted that realtionalism is obviously insufficient to explain the twin paradox. So, I find you list to be non-correspondent to me."
Well, Eric, I have often suggested that you pay mere "lip service" to certain standards. I assume you know what I mean by that. You can say one thing and act (or think) in an entirely inconsistent manner.
It is not your isolated "assertions" that I am referring to. It is a combination of separate assertions that are then combined in an inconsistent way.
I can say, at one point, that "this ball is white," and in another instance I can say "this ball is black." There is no apparent inconsistency, unless and until it is discovered that "this ball" in both of my statements is intended to be the very same ball, at the same instant, viewed from the exact same perspective, under identical conditions, etc. For example:
I asked: "You claim the theories are accurate, all while denying their fundamental presuppositions. What's up with that?"
You responded: "It's part of the process of simplification and abstraction. Simplification and abstraction are used in the same way by classical mechanics as by GR."
This "response" is typical of the way you blow off your own inconsistencies. It does not address the underlying issue at all. It does not confront, or respond to, the question. It is merely a glib red herring/non sequitur which you use to dismiss and avoid the question. It satisfies you, and so you just go on about your business. It doesn't satisfy me (as an explanation).
Why the claim about “reality?” What is “real” with respect to a “true inertial environment?” You say it “doesn’t exist in reality.” Why not? What DOES exist in reality, then?
One Brow said: "Meanwhile, in Galilean relativity you are free to assume any particular inertial environment is the rest frame, so the individual can interpret any frame to be the rest frame, just happens in GR. I'm unclear where you see a difference."
In physics, the principle of relativity ultimately applies to the laws of physics, not an arbitrary and unwarranted assumption about "reality."
If I am on a (uniformly) moving ship, and hit a baseball with a bat with just enough force to accelerate it away from me at the rate of 100 mph, it will end up so many feet away (from me). Same if I'm not moving. The laws of physics are the same. It hasn't nothing to do with assuming (or not assuming) that I'm "really moving."
The principal of relativity does NOT say that I am freely entitled to claim that the ball is at rest and that I (and everything else in the environment) am simply forced away from the ball when I strike it. Nor do the laws of physics (as adjusted by the principle of relativity) allow me to assume that God, not the swing of the bat, moved the ball even though that is otherwise theoretically "possible."
The existence of other possibilities (that I can creatively imagine) do not make every law of physics "relative." The laws of physics do not depend on "my interpretation" of what is actually happening.
I can "imagine" that at the exact moment I hit the thruster, a cancelling gravitational field suddenly appeared, out of nowhere, all I want. There is no plausible reason to think that is the case, and more than there is for me to think my striking a ball moves everything else away from it. To say that I wouldn't be able to "know" if that is what actually happened doesn't make the movement of the ball "relative."
Put another way, the "laws of physics" do not allow for the possibility that gravitional fields will "suddenly" appear, ex nilio.
Likewise, the principle of relativity applies to moving "systems" not dimensionless points. If I have to resort to a "point" and call it a "system" or an "environment" to "prove" my claim, it is meaningless. It's simply like stating the obvious fact that a blind man can't see. That's true of course. But it doesn't mean what he can't see isn't there. It doesn't say ANYTHING about what is there, to be seen. It doesn't say anything about what is "observable" to those given the capacity to observe. The particular handicaps of a given individual do not change the "laws of physics."
You may recall that when Einstein responded to his critics, he also addressed the question of whether a rotating and flip-flopping railroad car was "really" at rest, while everything else in the universe was moving in unpredictable and chaotic ways relative to the stationary car.
I don't recall his exact words, but his response was to the effect that "of course it would be absurd to suppose that the car was motionless, but it is still theoretically (i.e. mathematically) possible to treat it that way."
Yeah, so what? To the logical positivists, it's a big "WHAT," just like it was for Berkeley. Why? Because they had a (ultimately self-contradictory) ontological notion of what was "real" and what was "fictitious, metaphysical, and meaningless." By their logic, the "laws of physics" are meaningless and fictitious, so why even consider them--they aren't "real."
But to others, who think there is something "meaningful" to be found in the laws of physics, there is a big difference between what is merely "theoretically and mathematically possibile" and that which is "physically" possible.
One Brow said: "GR gives the same answer to the twin's aging whether you assume the ship twin changes position by propulsion, or the non-ship twin changes position in free-fall."
Same "answer?" In what sense? I get the same answer (10) if I add 5 = 5 as I do if I add 2+3+4+1. Does that mean they are "equivalent." The same? Is one 5 megaton nuclear bomb and five rabbits the "same as" 2 cows, 3 atoms, 4 wounded ducks, and 1 "crank?"
In Einstein's contrast, each factual situation could be false, but let's ignore that possiblity. Let's also ignore the self-contradictory assumption that both are simultaneously true.
Now what? We are left with the inescapable conclusion one or the other is true, but not both.
Suppose I don't know which one is true. Does that change the "truth" of the proposition that either one, or the other, is true, but not both?
What does the state of my knowledge say about what actually is true? But let's go one step further. Suppose I do "know" that strong gravitational fields are not known to appear spontaneously and that, given the laws of physics, they cannot just magically appear out of thin air. Now I know which clock is being accelerated (however you wish to define that) and which one isn't.
Since the acceleration of one of two objects causes time (really, and not just "apparently") to pass at different rates for each (because the relative velocity between them will change), I can know which one "really" slows down.
If I say nothing can be known, and hence that nothing can be real, then GR and SR, and all their corresponding assumptions and predictions are not "real" either. But I can't have it both ways.
I can't say that there is (1) no way of knowing which one is accelerating and what is not known is fictitous, meaningless, and "impossible," on the one hand, and also simultaneously claim that (2) either SR or GR have even the slightest degree of reality, meaning, or possibility.
Take your pick. Once you do, stick with it, if that's your belief.
The "equivalence principle" was basically built into Newton's gravitatonal formula too.
If I swing a baseball bat at (1) a golf ball, then (2) a baseball, and then (3) a bowling ball, all with equal force, they will not all go the same distance. The SAME force will produce different effects on each, because their "masses" are different.
So, then, the question arises: If gravitation is a uniform "force," how can it produce the same effect on different masses? Well, it's (mathematically) simple, eh? The "force" of gravity is not uniform, in any absolute sense. It is proportional to the mass(es) involved.
NASA explains it this way:
"Galileo Galilei either dropped balls from the top of the Leaning Tower of Pisa or he rolled balls down slopes at home. Either way, the result was the same: Although the balls were made of different materials, they all reached bottom at the same time.
Today, this is known as "the equivalence principle." Gravity accelerates all objects equally regardless of their masses or the materials from which they are made. It's a cornerstone of modern physics."
http://science.nasa.gov/science-news/science-at-nasa/2007/18may_equivalenceprinciple/
And it all kinda makes intuitive sense too, when ya think about it.
Gravitational attraction is mutual. When the earth is "pulling" on a falling bowling ball, the bowling ball is simultaneously pulling the earth toward it. The net result is that the combined forces will pull the two together faster would happen if the bowling ball wasn't intensifying the acceleration. A golf ball is doing the same. But the golf ball, being less massive, does not attract itself to the earth with the same amount of force as a bowling ball, so it all equals out. A golf ball just aint got as much "power" as a bowling ball does.
aintnuthin said...
Well, Eric, I have often suggested that you pay mere "lip service" to certain standards.
I have often countered that this results from understanding things in different ways.
It is not your isolated "assertions" that I am referring to. It is a combination of separate assertions that are then combined in an inconsistent way.
They are not inconsistent. If you can't distinguish what I am saying from relational physics, that's unfortunate. Relativity is based upon certain, very specific sorts of inabilities to distinguish between particular phenomenon, none of which inabilities corresponds to relational physics.
It does not address the underlying issue at all.
I'll try to be more detailed, then. Let's look at the notion of conservation of mometum. You have two bodies, with masses m1 and m2, moving at velocities v11 and v21. After a collision, they bodies will be moving at velocities v12 and v22. Conservation of momentum says that m1*v11 + m2*v21 = m1*v12 + m2*v22. However, if you measure precisely enough, that never happens. Momentum will dissapate into friction before and after the collision, and into heat energy during the collision. The equation is a simplified version of what happens, used to make the math easy and demonstrate the theory in simple terms, not because it describes some real thing. Also, if you measure over a small enough time frame, mometum will appear to be conserved to within whatever degree of measurment error you can muster.
Now, let's look at the idea of a truly inertial environment. There is no such thing as truly empty space. Even in momentary vacuums, quantum fluctuations are constantly creating particle pairs. So any environment is going to have collisions with matter of some sort, inducing acceleration on the environment. SR/LR uses the notion of truly inertial environments to keep the math simple and to demonstrate the theory in simple terms, not because it describes some real thing. Also, if you measure over a small enought time period, any environment will seem inertial within whatever degree of measurement error you can muster.
Similarly, there are no truly uniform gravitational fields, and probably never will be (quantum fluctuations again). GR uses the notion of equating a specific type of acceleration with a uniform gravity field to keep the math simple and to demonstrate the theory in simple terms. Also, if you measure over a small enough volume, any gravity field will seem uniform to whatever degree of measurement error you can muster.
Your critique that, because GR speaks of uniform gravitational fields it is doing something unlike other sorts of physics, is unwarrented.
What DOES exist in reality, then?
Confounding factors and complications.
In physics, the principle of relativity ultimately applies to the laws of physics, not an arbitrary and unwarranted assumption about "reality."
Again, I am unclear where you see a difference.
The principal of relativity does NOT say that I am freely entitled to claim that the ball is at rest and that I (and everything else in the environment) am simply forced away from the ball when I strike it.
What is "freely entitled" supposed to mean here? The results of the equations come out the same either way, so you probably don't mean that.
To say that I wouldn't be able to "know" if that is what actually happened doesn't make the movement of the ball "relative."
Actually, if you replace "know" with "experimentally verify" exactly what being relative means. Of course, maybe that's the source of your problem. You do understand you can know things that you can't experiementally verify, right?
Put another way, the "laws of physics" do not allow for the possibility that gravitional fields will "suddenly" appear, ex nilio.
What about the laws of physics prevents that? Now, I agree that our current understanding of physics leads to no method to make gravitational fields suddenly appear. But "don't know how it could be done" is very different from "prevent it from happening".
Likewise, the principle of relativity applies to moving "systems" not dimensionless points.
Agreed.
But to others, who think there is something "meaningful" to be found in the laws of physics, there is a big difference between what is merely "theoretically and mathematically possibile" and that which is "physically" possible.
For someone who thinks I have a closed mind, you seem to be fond of saying certain things are not possible.
Same "answer?" In what sense?
In the sense that if you get the answer the ship twin ages x years and the non-ship twin ages y years in SR, then you get the answer the ship twin ages x years and the non-ship twin ages y years in GR.
In Einstein's contrast, each factual situation could be false, but let's ignore that possiblity. Let's also ignore the self-contradictory assumption that both are simultaneously true.
Coordinate systems are not true or false. They are more or less useful. While there are an infinite number of possible coordinate systems (all of which give the same answer regarding the aging of the twins), two of the more useful and simpler ones are those where we respectively assume each twin is stationary.
Suppose I do "know" that strong gravitational fields are not known to appear spontaneously and that, given the laws of physics, they cannot just magically appear out of thin air.
That means you are more likely to prefer one sort of coordinate system over the other.
I can't say that there is (1) no way of knowing which one is accelerating and what is not known is fictitous, meaningless, and "impossible," on the one hand, and also simultaneously claim that (2) either SR or GR have even the slightest degree of reality, meaning, or possibility.
Take your pick. Once you do, stick with it, if that's your belief.
Actually, what SR/GR says is that there is no way to experimentally verify which coordiate system is the most reflective of the underlying reality. It does not prevent you from using other notions, outside of relativity, to make such determinations. For example, you might use the conservation of energy.
So, I'll ignore your false dilemma.
But the golf ball, being less massive, does not attract itself to the earth with the same amount of force as a bowling ball, so it all equals out. A golf ball just aint got as much "power" as a bowling ball does.
In classical mechanics, the force of gravity is proportional to the mass of what it is acting upon. So, the force of gravity increases as mass increases, automatically. So, I think you've got it.
Eric, you continue to inflate and confuse some things:
1. The principle of relativity in physics vs. the "principle of relativity" as a philosophical proposition Two different things.
2. A mathmatical "answer" with a physical answer. Two different things.
3. A mathematical possibility with a practical possibility.
If your best answer is "anything's possible, so why not this?" best stay out of the realm of physics and head toward myticism and/or superstition.
Math is NOT physics. It is, at best, a tool of physics. Even many physicists seem to forget this sometimes.
One Brow said: "Coordinate systems are not true or false." Typical.
One Brow said: "What is "freely entitled" supposed to mean here? The results of the equations come out the same either way, so you probably don't mean that." Exactly. That's the LAST thing I would be talking about (equations) in this context. "The principle of relativity is the requirement that the equations describing the laws of physics have the same form in all admissible frames of reference."
"Special principle of relativity: If a system of coordinates K is chosen so that, in relation to it, physical laws hold good in their simplest form, the same laws hold good in relation to any other system of coordinates K' moving in uniform translation relatively to K.
– Albert Einstein: The Foundation of the General Theory of Relativity, Part A, §1"
(WIKI)
Neither Galleo's nor Einstein's principle of relativity addressed anything about what one could discern WITHIN a single environment. It was NOT about: "I can't tell which is moving, the ball, or everything else in the uniform. It only pertained to the laws of physics (as we know them) in two contrasting frames of reference. Can you see that? All of the "I can't tell which one is moving" crap is philosophy, not physics.
By "WITHIN" above, I mean two items both enclosed in the same system. The laws of physics (again, as we know them) will be the same on a (uniformly) moving ship the are on a stationary one. I can't tell if *I* am moving if I can't look out the window, but that's it. I don't have to guess which what is moving if I hit a ball. The laws of physics tell me I have applied a force to it and that it will therefore accelerate, not everything else in the universe, while the ball stays still.
Einstein freely intermixed his philosophical convictions with his statements on physics, and I guess many people now think, for that reason, that physics is philosophy and philosophy is physics. His "response" to his critics is about philosophy, which he kinda tried to pass off as "physics." Nice try, but....
Mach said that the copernican (heliocentric) and ptolemic (geocentric) systems were "equally valid." But he IMMEDIATELY followed this with the reminder that the world is only given ONCE (not twice--one for heliocentricity and one for geocentricity).
He meant "equally valid" mathematically but NOT as a matter of reality. They CANNOT both be true, even though both could be false. Mach knew that. The significance of this "equal mathematical validity," as a philosophical matter (ontology, epistemoloy, etc.) is an entirely different issue.
Throughout our discussions on relativity, you have consistently treated the philosophical position of Einstein (well, not really his position, but yours) as a inherent part of the physics. You treat it as "fact" (what else is new?). You act as though the "principle of relaivity" says x, y, or z as a matter of physics when it DOESN'T. It is your failure to distinguish philosophy from "the facts" that I have been addressing all this time, but you still can't see it.
Einstein never said, for example, that the ether doesn't exist (in fact, he later said an "ether" MUST exist). He never said that absolute space was "impossible," he merely said that we can't observe it. Following the logical positivism of Mach, he therefore concluded (as a philosophical matter) that it was "meaningless" to ask if there is empty space. This is strictly a philosophical position about what has "meaning" and that whole school of thought has since been repudiated and abandoned.
Can you even see the difference? Likewise, he tried to suggest that it was "meaningless" to ask which of two systems (a tumbling railway car versus the entire universe) was "really moving." All the while he was ignoring that SR implicitly presumed (as it HAD to in order to be of any use, mathematical or otherwise) that we CAN tell which of two objects is moving. You still can't see this.
I always find it ironic that some people claim that absolute space is a "taboo" concept because it can't be observed (itself a dubious proposition, given the CBR), while insisting that (absolute) spacetime is "real." Who has "observed" spacetime?
Likewise, it seems naive beyond belief that people will "explain" the twin paradox, and the difference between the twin's circumstances, at elaborate length, all of which explanation ASSUMES that the ship twin has REALLY acceleratd (without that presumption there is NO explanation), and, then, as soon as they are finished with their windy explanation INSIST that you can't tell which one is moving. Go figure, eh?
One Brow said: "They are not inconsistent. If you can't distinguish what I am saying from relational physics, that's unfortunate."
"Relational" physics says, like SR, that two observers travelling at different relative speeds will each see the other's clocks slowing down. SR makes this point too. So what's the difference?
Relational physics says there would not be (and could not be) any "real" age difference between the two, whatever their subjective perceptions might be. Relativity says that they will necessarily age differently, and that one is aging slower than the other, whatever their subjective perceptions might be.
You consistently try to claim that both are somehow true. Or, in the alternative, that you can't "know." Like, if the twin were accelerated, and never came back, you could not "know" if he were really aging slower. SR tells you that you WOULD know, whether he ever came back, or not.
You stances are hopelessly confused and conflated, and, as a result, you make hopelessly confused claims. Herbert Dingle was ultimately written off as a crank, because he could not consistently distinguish the implications of a relatvie theory from a relational one. Einstein himself did a lot to foment this type of confusion, unfortunately, by making conflicting statements in his attempt to convince himself that he had a relational (as opposed to relative) theory.
Einstien had (for a long while) a relationalist philosophy, and a relativistic physical theory. Like I said before, he promoted both. But his philosophy was NOT compatibile with his theory. Damn shame, eh?
I said:
""Relational" physics says, like SR, that two observers travelling at different relative speeds will each see the other's clocks slowing down. SR makes this point too. So what's the difference?
Relational physics says there would not be (and could not be) any "real" age difference between the two, whatever their subjective perceptions might be. Relativity says that they will necessarily age differently, and that one is aging slower than the other, whatever their subjective perceptions might be."
Their is a third type of philsophical "relativism" that is often thrown in here too, i.e., that the subjective perceptions are the things that are "true." In that view, each is younger than the other. That is clearly not a physical view, and no theory of physics propounds it, but you wouldn't know that by talking to some people. They think it's a physical theory.
So you can get constant shifting from (implied) (1)relationalism to (2)relativism to (3) subjectivism in statements made by undisciplined thinkers.
The appearances I see in the sky might be identical if either of the following was true:
1. I am motionless and the stars are slowly revolving around me, or
2. I am standing on a rotating earth and the stars are motionless.
So what? What is this supposed to prove about "reality?"
The appearances I see might be identical if:
1. An optical illusionist made it seem as if an elephant suddenly appeared out of nowhere, or
2. An elephant actually and really suddenly appeared out of nowhere.
So what? What is this supposed to prove about "reality?"
The appearances I see when skydiving would be the same if I was motionless and the earth was moving toward me. So what?
I am not asking this frivolously. What is the great significance of the fact that different sets of circumstance can look (or feel) like the same thing to me?
You tell me that you have written down a number between 1 and 100 and ask me to guess it.
I say "It could be anything."
But it can't be "anything." The number is 37, not 36, not 38, and not any other number between 1 and 100.
So what do I mean when I say "it could be anything?" I'm saying I don't "know" what it is, and that I have no way of knowing, that's all. The number is still 37 whether I personally know it, or have any way of knowing it, or not. How do my epistemological limitations determine, alter, influence, or in any way affect the number in question?
Suppose you give me a hint and say it is a two-digit number where the individual digits add up to 10. Because both 37 and 91 fit the bill, does that mean the "answer is the same," if I pick one instead of the other? Does it mean 37 is "equivalent to" 91?
Ya see what I'm gittin at? Somehow, I doubt it.
Coming back to this for a minute:
"Special principle of relativity: If a system of coordinates K is chosen so that, in relation to it, physical laws hold good in their simplest form, the same laws hold good in relation to any other system of coordinates K' moving in uniform translation relatively to K." (Einstein)
As I assume you know, the "in their simplest form" part just means, without having to resort to so-called "fictitious" forces of inertia, such as centripetal, centrifugal, and coriolis forces. I will need such fictitious forces to explain what I see (on another system) if I am accelerating relative to that system.
So, just to make sure the point is clear, if I hit a baseball with just the exact amount of force to go 303.76 feet before it stops, on earth, it will also go 303.76 feet (assuming it was hit at the exact same angle, and all other things being equal) on a 7-acre ship go 50 nauts at sea. It will not go any more or less distance for the person on the ship, and it will STAY 303.76 feet from the batter until a force acts on one of them. The laws of physics are the same, because the two systems are in "uniform translation" to use Al's words.
I can use simple transformations (Galliean, Lorentzian, whatever) to adjust between these two systems, again, without further resort to inertial forces.
THAT is the "principle of relativity" in physics. It is not a question about whether (or whether I can know) if the ball is staying still while everything else is pushed away from it by a distance of 303.76 feet. In physics, it is assumed that the ball is being accelerated, and that I know it is the ball (not everything else) that is being accelerated.
What is "really" accelerating, and/or how can I subjectively detect what is accelerating, are philosophical (not physics) questions. Al's own statement of the "special principle of relativity" says nothing about questions of if/how I can know "what" is "really moving." That aint a physics question.
Just to be clear, I'm deleting what I basically agree with your position, or don't really know enough to comment upon independently. Not that it isn't amusing to read you telling me how wrong I am and how I should understand this, while saying pretty close to exactly what I understand things to be. It's very amusing.
aintnuthin said...
It is your failure to distinguish philosophy from "the facts" that I have been addressing all this time, but you still can't see it.
Then, maybe you could find something to distinguish that I don't distinguish?
All the while he was ignoring that SR implicitly presumed (as it HAD to in order to be of any use, mathematical or otherwise) that we CAN tell which of two objects is moving. You still can't see this.
Since SR gives the same answer regardless of which of the two inertial objects is moving, why do you think is HAS to say one is moving to be useful.
Or, if you are discussing the twin paradox, SR identifies one of the twins as accelerating (changing inertial conditions). I agree with that.
Likewise, it seems naive beyond belief that people will "explain" the twin paradox, and the difference between the twin's circumstances, at elaborate length, all of which explanation ASSUMES that the ship twin has REALLY acceleratd (without that presumption there is NO explanation), and, then, as soon as they are finished with their windy explanation INSIST that you can't tell which one is moving. Go figure, eh?
Since we are using geodesic terminology, you can accelerate without moving.
By the way, who's been insisting there is no way to tell the difference? I've been saying all along there is a way to tell the difference, but that way is external to GR. YOu can know, but not from using only GR.
You consistently try to claim that both are somehow true. Or, in the alternative, that you can't "know." Like, if the twin were accelerated, and never came back, you could not "know" if he were really aging slower. SR tells you that you WOULD know, whether he ever came back, or not.
The determination of a real age difference requires the determination of a true rest frame, which can be used by SR once it has been determined. Determining that frame is external to SR. You can know, but not from using only SR.
The appearances I see in the sky might be identical if either of the following was true:
1. I am motionless and the stars are slowly revolving around me, or
2. I am standing on a rotating earth and the stars are motionless.
So what? What is this supposed to prove about "reality?"
The inability to distinguish them within a certain methodology tells you about that methodology and about the phenomena.
I am not asking this frivolously. What is the great significance of the fact that different sets of circumstance can look (or feel) like the same thing to me?
It's a good starting point for the discussion of what is inimical to motion and what is not.
..., if I hit a baseball with just the exact amount of force to go 303.76 feet before it stops, on earth, it will also go 303.76 feet (assuming it was hit at the exact same angle, and all other things being equal) on a 7-acre ship go 50 nauts at sea. ...
THAT is the "principle of relativity" in physics.
It's a good starting point for the discussion of what is inimical to motion and what is not.
What is "really" accelerating, and/or how can I subjectively detect what is accelerating, are philosophical (not physics) questions. Al's own statement of the "special principle of relativity" says nothing about questions of if/how I can know "what" is "really moving." That aint a physics question.
I think it is a physics question, but not a question GR or SR can answer.
One Brow said: "Actually, what SR/GR says is that there is no way to experimentally verify which coordiate system is the most reflective of the underlying reality." No, SR/GR does NOT say this. Some philosophers do, however.
"It does not prevent you from using other notions, outside of relativity, to make such determinations. For example, you might use the conservation of energy." Or you might just look out the window, eh? Is that an "experiment?" Heh, with respect to the equivalence principle, GR basically just "says" "If we blind you, then you won't be able to see." Like, who knew, eh? Even then it's not true. I can still "see" (distinguish gravity from floating in space "far away from all gravitational influences"), even if I don't look out the window.
One Brow asked: "Since SR gives the same answer regardless of which of the two inertial objects is moving, why do you think is HAS to say one is moving to be useful."
1. I used "moving" as shorthand for accelerated, since linear acceleration results in a higher relative velocity.
2. SR does NOT say the answer is the same regardless of which one is accelerating (moving). Jeez, you still don't get this?
One Brow said: "Since we are using geodesic terminology, you can accelerate without moving."
No, "we" are NOT using "geodesic terminology." Everybody and his brother knows that GR is NOT necessary to address the twin paradox, and the "solutions" are seldom given using that terminology. I get totally sick of the equivocation, and we've been through this dozen of times. "Acceleration" as used in SR, is basically the exact reverse of "acceleration as used in GR. It's like every time I say "black" you say I said "white." This "game" is not fun.
One Brow said: "The determination of a real age difference requires the determination of a true rest frame, which can be used by SR once it has been determined. Determining that frame is external to SR. You can know, but not from using only SR."
Wrong. A "true rest frame" is determined in SR just like it is determined in Newtonian mechanics. It is determined by abolute space and absolute time for Newton, and absolute "spacetime" for SR. We've already been through this. It was one thing Al and Mach hated about SR. Most others had (and have) no problem with it. As Al later noted, after finally abandoning Mach's logical positivism, you MUST have it, or something like it, to do physics. You don't have to have it to be Parmenides, of course. Then it's all very simple: "All appearance of motion and change is strictly an illusion."
I said: "SR does NOT say the answer is the same regardless of which one is accelerating (moving). Jeez, you still don't get this?"
Then I see that you do acknowledge it (which could be distinguished from "getting" it): One Brow said: "...if you are discussing the twin paradox, SR identifies one of the twins as accelerating (changing inertial conditions). I agree with that."
So think through the implications of your acknowledgment. If you did, you wouldn't say things like this in the next breath: "The determination of a real age difference requires the determination of a true rest frame ... Determining that frame is external to SR."
Let me ask you this, Eric...is there any "meaningful" difference in these two statements?:
1. The speed of light (in a vacuum) will always be MEASURED to be the same by any observer, regardless of the motion of either the observer or the source of the light, and
1. The speed of light is absolute. It is always 186,000 mps. Furthermore, nothing can ever exceed that speed.
One Brow said: "I think it is a physics question, but not a question GR or SR can answer."
Well, that's the problem, as I see it. You don't consistently distinguish philosophy from science, math from observation, etc.
This stance leads you to make "factual" assertions, in response to Feser, about the "reality" of the shape of the universe, and similar claims.
This whole commentary started with this observation (or "claim") on my part. You seem to think that conclusions based on theoretical scientific premises are "fact" and are "true," but want to deny that status to "moral" questions. You think that philosophy has nothing to do with science, and that all science is a product of known fact.
I will grant you that philosophical questions such as "how can we know which of two objects is moving" can have a bearing on how we interpret physics, but that does not make them "questions of physics." That said, a theorist's underlying philosophical assumptions and beliefs will invariably influence the type of axioms he starts with. So philosophy is not "irrelevant" to scientific theory, but it is still DIFFERENT from the theory itself.
Like any deductive system, physical theories must start with certain axioms and assumptions. After those are chosen, you don't (within the context of the theory) ever question them again. They cannot be questioned. They aren't the type of proposition which is even open to question (again, within the context of the given theory). Once Newton posits absolute space and absolute time, everything follows from there. A physical theory is then developed.
Needless to say, merely positing something (such as the absolute speed of light, or absolute space) does not make it "true" or "fact." All the more reason not to treat it as such, at least not on the grounds that it is a "scientific theory" that has some kind of special, exempt status that other formal, deductive systems don't enjoy.
Or you might just look out the window, eh? Is that an "experiment?"
Not of the type SR/GR refer to. I'm sure there are many ways to verify who is really accelerating outside of GR.
I can still "see" (distinguish gravity from floating in space "far away from all gravitational influences"), even if I don't look out the window.
Just like you can see the difference between accelerating in a rocket and floating in space, sure.
No, "we" are NOT using "geodesic terminology."
Make up your mind what terminology you want to use, please. I am as tired as you as talking about one thing and then another using the same word.
"Acceleration" as used in SR, is basically the exact reverse of "acceleration as used in GR.
It's quite possible to use the term to mean "change in velocity" in both GR and SR. Following a geodesic can result in that sort of acceleration, such as when you are orbiting or falling toward a mass. Can we agree to use it that way? When following a geodesic is relevant, we can call that "geodesic movement".
Wrong. A "true rest frame" is determined in SR just like it is determined in Newtonian mechanics. It is determined by abolute space and absolute time for Newton, and absolute "spacetime" for SR.
SR has no mechanism to determine a true rest frame.
So think through the implications of your acknowledgment. If you did, you wouldn't say things like this in the next breath: "The determination of a real age difference requires the determination of a true rest frame ... Determining that frame is external to SR."
You're taking a statment that referred to two inertial objects in different rest frames, and applying it to the twin paradox. If you have two inertial objects moving at .6c relative to each other, there is no way to determine which one is younger until you decide what the true rest frame is. Due to issues regarding the lack of simultaneity of observations, SR does not have a mechanism to determine which of the rest frames in the determining rest frame. In the twin paradox, there are two different timepoints where the spacelike and timelike difference in locations between the twins is negligible. That allows SR to make a comparison of two points where simultaneity of observations is not an issue, so SR can make a determination there.
Let me ask you this, Eric...is there any "meaningful" difference in these two statements?:
1. The speed of light (in a vacuum) will always be MEASURED to be the same by any observer, regardless of the motion of either the observer or the source of the light, and
1. The speed of light is absolute. It is always 186,000 mps. Furthermore, nothing can ever exceed that speed.
Well the second is false. The speed of light changes according the medium that carries it, IIRC. However, if you amend the second to include "in a vacuum", and also to say "nothing with mass", then the second is a derivation of the first (along with other observations), though still not identical.
Well, that's the problem, as I see it. You don't consistently distinguish philosophy from science, math from observation, etc.
I was unaware that principles such as the Conservation of Energy, the CMB, or "you might just look out the window, eh" were relegated to the domain of philosophy. Or, did you make another switch from bodies under acceleration to inertial bodies in the middle of a paragraph? YOur paragraph started out referring to acceleration.
Within GR, you can't tell which of the twins is accelerating (as in changing velocity). However, the creation of a massive graviational field creates enormous amounts of potential energy to be converted to kinetic energy. That creation ex nihilo violates the conservation of energy. Gr does not use the conservation of energy in its equations, but physicists certainly use it when interpreting GR.
This stance leads you to make "factual" assertions, in response to Feser, about the "reality" of the shape of the universe, and similar claims.
The universe behaves as if it has negative curvature. That's empirical, not philosophical.
This whole commentary started with this observation (or "claim") on my part. You seem to think that conclusions based on theoretical scientific premises are "fact" and are "true,"
Many conclusions are not fact. Are you mistakenly confusing that term with "so reliable that its perverse to withhold provisional consent"?
As for true, one of the themes of my blog is the different ideas and ways of determining truths each have their strengths and weakness, and that there is no perfect way to get truth.
but want to deny that status to "moral" questions.
I find the notion that morality might be the same type of truth as you get from science to be ludicrous, and notions that morals might be facts to be silly. On that, I'm friarly sure Dr. Feser would agree.
You think that philosophy has nothing to do with science, and that all science is a product of known fact.
The scientific method, and other starting positions such as uniformitarismism, are of course philosophical, and not sucject at all to scientific verification. The knowledge from science is a product of facts combined with other types of things (theories, experiements, predictions, etc.). When you tell me what I think, I usually get a good chuckle out of it.
Like any deductive system, physical theories ...
There's one of the main errors. Physical theories use the trappings of deductive (aka formal) systems to go from general notions to more specific notions, but they are not formal systems. For example, physical theories (and other scientific theories) are contantly subject to revision, and they can accomodate contradictory explanations for an event as both being plausible, something very few use formal theories can accomodate. YOu are thinking of scientific theories as if they are mathematical theories, but they are very different creations.
I'm not a physicist, and don't pretend to be, but there appear to be some interesting alternatives to GR and some ways to account for inertia in accordance with what Einstien called "mach's principle." Although it is far from clear that Mach himself intended, "mach's principle" as propounded by Einstien was (roughly) that "matter there (in the univere) affects (causes) inertia here."
As it turns out, "Dennis Sciama later showed that the reaction force produced by the combined gravity of all matter in the universe upon an accelerating object is mathematically equal to the object's inertia..." Here it is, mach's principle, so dear to Einstein, seemingly achieved. One problem, though:"...but this would only be a workable physical explanation if by some mechanism the gravitational effects operated instantaneously."
Curiously enough, Newton said that gravitional effects operate instantaneously. Maybe he was right. I guess the absolute speed limit was even more important to Al than his cherished mach's principle, all said and done, eh?
According to wiki, this Sciama guy did his PhD work under Paul Dirac and is considered to be "one of the fathers of modern cosmology." He went on to supervise guys like Hawking and other famous physicists and strongly influenced Roger Penrose, so he seems legit.
Among other things, Sciama "helped revitalize the classical relativistic alternative to general relativity known as Einstein-Cartan gravity." http://en.wikipedia.org/wiki/Dennis_William_Sciama
Hmm, what's this "classical relativistic alternative" to GR about, I wonder? Well, again, according to Wiki"
"Cartan's theory is particularly interesting both because it is a non-metric theory and because it is so old. The status of Cartan's theory is uncertain. Will (1981) claims that all non-metric theories are eliminated by Einstein's Equivalence Principle (EEP). Will (2001) tempers that by explaining experimental criteria for testing non-metric theories against EEP. Misner et al. (1973) claims that Cartan's theory is the only non-metric theory to survive all experimental tests up to that date and Turyshev (2006) lists Cartan's theory among the few that have survived all experimental tests up to that date."
http://en.wikipedia.org/wiki/Alternatives_to_general_relativity
Interestingly enough, it seems to solve some problems that GR creates:
"Within the scope of classical physics, general relativity has one flaw that stands out: it cannot model spin-orbit coupling (conversions between intrinsic angular momentum (spin) and orbital angular momentum). This flaw stands out because angular momentum is one of the two main conserved currents (along with momentum) arising from the basic symmetries of classical spacetime, so any master theory of classical physics should handle angular momentum well...Einstein-Cartan theory resolves the problems with spin angular momentum.
A mathematical proof has been published that general relativity plus a fluid of many tiny rotating black holes generate affine torsion that enters the field equations exactly as in the equations of Einstein–Cartan theory (Petti, 1986)...Adamowicz showed that general relativity plus a linearized classical model of matter with spin yields the same linearized equations for the time-time and space-space components of the metric as linearized Einstein–Cartan theory (Adamowicz 1975)."
http://en.wikipedia.org/wiki/Einstein-Cartan_theory
As I said, I'm no physicist, nor a mathematician but, from what I gather this is a non-metric theory, formulated in 1922, which does not rely on Riemannian geometry, but rather on a Euclidean type of "flat space" as used by Minkowski (combined with time).
I bring this to your attention mainly in response to your repeated claims that GR is the ONLY theory of gravity which solves all known problems and which is compatible with all known observations. This model goes way back to 1922.
One Brow said: "The universe behaves as if it has negative curvature. That's empirical..."
You don't know it, but this claim simply reinforces, rather than refutes, my claim about your failure to distinguish theory from observation, philosophy from physics, etc. You might want to take a look at this wiki entry: http://en.wikipedia.org/wiki/Philosophy_of_physics
One Brow said: "There's one of the main errors. Physical theories use the trappings of deductive (aka formal) systems to go from general notions to more specific notions, but they are not formal systems... YOu are thinking of scientific theories as if they are mathematical theories, but they are very different creations."
But you've aleady said: "The knowledge from science is a product of facts combined with other types of things (theories, experiements, predictions, etc.)."
There are different approaches to what can be called "science," and that concept may differ between the natural vs the social "sciences," but the fact remains that:
"In the 20th century, a hypothetico-deductive model[8] for scientific method was formulated...This model underlies the scientific revolution...Normally hypotheses have the form of a mathematical model."
http://en.wikipedia.org/wiki/Scientific_method
Scientific theories and mathematical theories are not, as you claim "very different creations." Newton, with his mechanics, no less that Euclid with his plane geometry, first introduced definitions, axioms (laws) and theorems and all conclusions of classical mechanics were deductively arrived from that starting point.
The scientific method relies on deduction, and you can't really "deduce" any conclusion whatsover without premises, in math or science.
The fact that abstract theories can be "tested" by observation does NOT change the nature of the theory, as you seem to think. Experiments designed to "test" deductions from abstract theories are NOT "part of the theory."
One Brow said: "When following a geodesic is relevant, we can call that "geodesic movement".
Sure, when it's relevant. SR was based entirely on the assumption (and acceptance) of Newton's definition of inertia (which relates acceleration to motion). "Geodesic deviation," etc., only comes into play with GR, a theory of gravity, not a theory of relative motion. No need to keep dragging "geodesic" notions into such discussions. They're not relevant.
One Brow said: "If you have two inertial objects moving at .6c relative to each other, there is no way to determine which one is younger until you decide what the true rest frame is. Due to issues regarding the lack of simultaneity of observations, SR does not have a mechanism to determine which of the rest frames in the determining rest frame."
I know what you're saying here, but you're missing the point. Again, there is the confusion about what we know with what is implied by SR. Even an orphan knows he had parents, even if he has no clue who they are. You can "know" your history, in a general sense, without necessarily knowing the specifics details.
In SR two different objects cannot be travelling at different speeds relative to each other without one of them have been relatively MORE accelerated in the (perhaps unknown) past than the other. It will be the clock on that "object" which "really" slows down, not the clock on the other. This conclusion is dictated by SR, with ultimate reference to "absolute spacetime."
Just to reinforce the point, YOU knowing, or YOU "deciding," which one you believe is "really younger" is totally irrelevant to the issue of which one IS really younger. The circumstance that I am in no position to "know" and cannot easily guess, what number (between 1 and 100) that you have written down does not in any affect the fact that you wrote down the number 37.
I'm probably over-doing it now, but the conflation of epistemological considerations with "fact" have come up so frequently and so regularly that I'm going to give one more illustration of the point:
With the twin question, we happen to "know" which twin was accelerated, and we know exactly how and when that acceleration happened. Good for us. Now we know which one SR says is "really younger."
But how about a passerby space traveller came across the scene later and saw that the earth maintained a different relative velocity than the travelling twin's spaceship? He wouldn't "know" which one is younger, eh? But that is NOT due to a lack of a standard in SR. It is merely due to his own ignorance, which ignorance cannot change the fact that SR says the travelling twin will be younger. Why? Because the travelling twin is travelling at a higher relative speed, whether the passerby knows it, or not.
One Brow said: "The universe behaves as if it has negative curvature. That's empirical..."
What would your response/comment be if I said: "Falling apples behave as if they (being composed of a fundamental element that is not wind, air, or fire and hence having "gravity," aka "heaviness") are seeking their natural place at lower levels. That's empirical..."
I composed these two claims, and asked you if you saw a meaningful difference:
"1. The speed of light (in a vacuum) will always be MEASURED to be the same by any observer, regardless of the motion of either the observer or the source of the light, and
1. The speed of light is absolute. It is always 186,000 mps. Furthermore, nothing can ever exceed that speed."
With a couple of qualifications (which I will grant you) you responded: "...the second is a derivation of the first (along with other observations), though still not identical."
What do you mean by "derivation?" Do you mean that IF you always measure light the same THEN is MUST be the case that the speed of light is absolute? That you must necessarily "derive" that conclusion from the "facts," that the idea?
One Brow asked: "Many conclusions are not fact. Are you mistakenly confusing that term with "so reliable that its perverse to withhold provisional consent"?"
I'm not confusing them, but, for the purpose of our discussions, yeah, let's just say I am treating them as though they were synonyms in some contexts (those contexts where "facts" depend on personal convictions). "Fact" is a lot easier to type out than that other long-ass phrase.
It appears that I omitted the source of this quote, from above: "Dennis Sciama later showed that the reaction force produced by the combined gravity of all matter in the universe upon an accelerating object is mathematically equal to the object's inertia [1], but this would only be a workable physical explanation if by some mechanism the gravitational effects operated instantaneously."
Here it is, if you're interested:
http://en.wikipedia.org/wiki/Inertia
I've already cited this site, but I think this (further edited by me) quote of Einstein to be found there is well-worth reflecting on:
"How does it happen that a properly endowed natural scientist comes to concern himself with epistemology?...So many people today - and even professional scientists - seem to me like somebody who has seen thousands of trees but has never seen a forest. A knowledge of the historic and philosophical background gives that kind of independence from prejudices of his generation from which most scientists are suffering...Concepts that have proven useful in ordering things easily achieve such an authority over us that we forget their earthly origins and accept them as unalterable givens. Thus they come to be stamped as 'necessities of thought,' 'a priori givens,' etc....
...it is by no means an idle game if we become practiced in analyzing the long-commonplace concepts...by this means, their all-too-great authority will be broken... This independence created by philosophical insight is - in my opinion - the mark of distinction between a mere artisan or specialist and a real seeker after truth."
http://en.wikipedia.org/wiki/Philosophy_of_physics
I've commented on the implication of this "operational definition" before, and it certainly seems to be utterly at odds with the foregoing sentiments of Einstein:
"Currently, the standard space interval, called a standard meter or simply meter, is defined as the distance traveled by light in a vacuum during a time interval of 1/299792458 of a second (exact). This definition coupled with the present definition of time (see above) makes our space-time to be Minkowski space and makes special relativity theory to be absolutely correct by definition." (same site)
Do you see why I say that? The "all-too-great authority" of "common prejudices," which become viewed as "a priori givens" could hardly be better illustrated than by definitions which suppose the absolute correctness of postulated (not proven or empirically demonstrated) axioms. What better way to entrench speculation and make it unassailable?
Of course, for those who Einstein refers to as "mere artisans and specialists," this is not only unobjectionable, but absolutely desirable.
“Expert (specialist): Someone who knows more and more about less and less until he knows absolutely everything about nothing.” (Nicholas Murray Butler)
Wiki said: "Currently, the standard space interval, called a standard meter or simply meter, is defined as the distance traveled by light in a vacuum during a time interval of 1/299792458 of a second (exact)."
Is there anyone who can't see the obvious circularity here? I can't know the speed an object is going unless I FIRST know the distance travelled and the time it took to traverse that distance. But here "distance" is being defined in terms of speed (of light), which presupposes that distance has already been defined and determined.
Here's an analogy. Let's say it's 600 miles between Chicago and New Orleans. If I tell you I made the trip in 10 hours, you will tell me I was averaging 60 mph. If I tell you I made the trip in 5 hours, you will tell me I was averaging 120 mph, etc. OK, fair enough.
But now, I tell you, apriori, that all travellers ALWAYS average exactly 60 mph when going from Chicago to New Orleans, and that you must always assume this. Now what?
If I make the trip in 10 hours, fine. But suppose I make the trip in 5 hours? What will you tell me now?
You will tell me that the distance between Chicago and New Orleans "shrunk" to only 300 miles while I was driving. Why? Because at 60 mph I will go 300 miles.
That would have to be the case, by virture of my apriori assumption, now. No longer is distance a necessary component of speed, but rather speed (which presupposes a known distance, if it is to be calculated) is a necessary component of (and therefore dictates) distance.
Does asserting that the distance between Chicago and New Orleans shrunk to 300 miles while I was driving make any sense, either logically or empirically? Is this not circular?
Let's say 10 cars leave Chicago at the same time, all headed for New Orleans. But they all drive at different speeds, one at 10 mph, one at 20 mph, and so on, and the "last" car is going 100 mph. Now what would we expect, and what can be empirically verified?
1. We would expect all of their odometers to have registered a distance of 600 miles if they are working properly, and they do.
2. We would expect each to arrive in New Orleans at a different time, and they do. One arrives 60 hours later, one 30 hours later, etc., with the "last" car arriving in 6 hours.
But that's all an illusion. Why? Because I TOLD you, they can't go 10 mph, or 100 mph. They ALL always go 60 mph. You would have to be stupid to think the could go any speed other than 60.
Here's what really happened, see? For the first car the distance between Chicago and New Orleans was 3600 miles, for the second the distance was 1800 miles, and so on, until, for the last car, the distance was 300 miles. Only distance can change, not speed.
Think I'm wrong? Well, guess what? tTere is nothing MATHEMATICALLY inconsistent with anything I said. Good luck trying to argue with cold, hard math, eh?
Edit: Should have said "...and so on, until, for the last car, the distance was 600 [not 300] miles."
Suppose 10 cars all leave Chicago at the same time and all arrive in New Orleans at the same time. Well, it would seem that now we know that, whatever the distance, they all travelled at the same speed. If one guy says his speedomoter told him he was going 10 mph and another says his told him 100 mph, we will simply say that at least one (perhaps both) has a miscalibrated speedometer.
If they're all going the same distance, at the same speed, they will arrive at the same time. But what do we say in case number 1 (above) when we KNOW they all travelled at the same speed, but arrive at different times?
If we don't want to mess with distance, we say: "Your watch is wrong, that's all. You say it took you 60 hours, but it really took you only 6 hours, see? You arrived at the same time, it just seems like you didn't because of your miserable time-keeping piece. Sure, one guy "seemed" to arrive earlier than you did. He ate dinner, went to Bourbon Street, got drunk, got laid, got up the next morning, went swimming, and so on, but the time difference is merely an illusion. You mistakenly "thought" you were still on the road, driving, while he did all that, but in truth you were already in New Orleans because you arrived at the same time, whether you know it, or not."
It all works out MATHEMATICALLY, I tellya!
Purty simple, actually.
Kinda interesting, eh?:
"This Absolute Space Theory (AST) has been extensively investigated by other researchers [9-12] who have highlighted the close agreement between such a theory and Special Relativity Theory (SRT) for nearly all predicted effects. Selleri in particular [9, 13] has shown that the SRT and AST are members of a complete set of
theories that differ only according to the clock-synchronization convention employed. This set is based on equivalent transformations that incorporate the experimental facts of the constancy of the twoway speed of light and clock retardation. Selleri [13] has shown that the entire set of theories makes the same predictions for several phenomena and used acceleration in an attempt to argue that the AST gives the best description of the physical world.
In order to more convincingly separate the theories, we note that the theories in the set make different light speed predictions. We therefore compare these different light speed predictions for light from Io a satellite of Jupiter detected on Earth with the light speed determined by direct calculation in the space time framework of these theories...
CONCLUSION...The AST wasthe only theory whose prediction was in agreement with the directly calculated relative light speed value ( ) 1− β 2 − c CAL = c v R corresponding to a clock synchronization parameter 0 1 e = . On this basis, the Absolute Space Theory with its preferred frame appears to be the best description of physical space and time."
http://redshift.vif.com/JournalFiles/V16NO3PDF/V16N3GIF.pdf
But, "best description of PHYSICAL space and time?" Why bring that up? What does "physical space and time" have to do with physics? The onliest real question should be what the best mathematical and metaphysical description is, I figure.
"Franco Selleri (b. Bologna, Italy 1936) is an Italian Theoretical Physicist and professor at Bari University. He received his Ph.D. cum laude from Bologna University in 1958, and has been a fellow of the Istituto Nazionale di Fisica Nucleare since 1959. He is a member of the New York Academy of Sciences and the Fondation Louis de Broglie, and has served on the Board of Directors of the Italian Physical Society. He has had numerous visiting professorships and fellowships, including CERN, Saclay, Cornell and Dubna. He is the recipient of a medal from Gdanskie Towarzystwo Naukowe (Poland). He has published more than 200 papers in particle physics, quantum theory, relativity and history and philosophy of physics. He is the author of numerous books and editor of numerous conference proceedings on topics relating to the foundations of physics. In 2009 he was elected Vice chairman to the Telesio Galilei Academy of Science and joined Francesco Fucilla's research and development team."
A list of his books (but not his 200+ papers), can be found here:
http://en.wikipedia.org/wiki/Franco_Selleri
One book of particular interest, relative to our discussions, is "Weak Relativity: The Physics of Space and Time Without Paradoxes (2009)
An online version of that book can be found here:
http://blog.hasslberger.com/docs/Selleri_Weak_Relativity.pdf
Anyone actually seeking to evaluate and compare the pros and cons of SR versus LR on an informed basis, rather than just preferring to authoritatively pronounce edicts, should find it interesting.
Sellari concedes that a "weak" principle of relativity still exists, which he summarizes as follows:
"Weak relativity, stating merely the impossibility to measure the absolute velocity of the Earth. This principle does not demand necessarily the validity of the Lorentz transformations and opens a logical space for new theories, such as the one based on the inertial transformations...Experimental evidence based on the clock paradox (§ 14) and on stellar aberration (§ 13) shows that absolute velocities exist in nature. The weak relativity principle accepts this, but maintains that they nevertheless remain
unmeasurable. (P 172).
He nonethless concludes that:
"In spite of this conclusion, with which I agree, I must insist that the statements made in the initial part of the present book are correct. The theory with the free e1 applied to the rotating platform and to the Sagnac effect shows that only e1= 0 gives a rationally acceptable formulation of the physics on the
disk. Similarly, only with e1= 0 one can obtain a reasonable description of aberration. The paradoxes of the special theory of relativity disappear if e1= 0. The growing evidence for the existence in nature of superluminal signals can easily be accommodated if e1 = 0, while it is incompatible with standard relativity due to the presence of a famous causal paradox. Therefore the best theory of the physics of space and time seems to be the one based on absolute simultaneity." (pp 172-73)
Another excerpt from the first page of that book that I find particularly interesting, inasmuch as it echoes much of what I have been saying here:
"Einstein’s 1905 philosophical standpoint was as follows:...“What really happens to the clock, which is it its true rate?” The relativistic answer is that this question does not make sense, and that the conclusions of all the different observers are equally valid.
The impact of Mach’s positivism was transmitted by the young Einstein. But around 1920 Einstein turned away from positivism because he realized with a shock some of its consequences...Popper witnessed Einstein’s radical change of opinion about Mach’s philosophy: “Einstein himself was for years a dogmatic positivist ... He later rejected this interpretation: he told me in 1950 that he regretted no mistake he ever made as much as this mistake.”
As Berkeley showed, the logical consequence of radical empiricism is utter subjectivism. Einstein (rightfully, in my view) did not agree with such consequences. But, as this author notes: "Einstein’s withdrawal came too late. “Physics had become a stronghold of subjectivist philosophy, and it has remained so ever since.” [Popper]."
One Brow said: "The universe behaves as if it has negative curvature. That's empirical..."
The point I am trying to make when addressing this quote is not really whether the claim is an accurate reflection of the current understanding, but even that seems suspect, which is not totally irrelevant to our discussion here (which includes the basis upon which you are ready to assert "fact").
"Within the Friedmann-Lemaître-Robertson-Walker (FLRW) model, the presently most popular shape of the Universe found to fit observational data according to cosmologists is the infinite flat model."
http://en.wikipedia.org/wiki/Shape_of_the_Universe#cite_note-0
"For practical purposes most cosmologists now use the Euclidean model of the universe."
http://books.google.com/books?id=KhTJZG-U3ssC&pg=PA161#v=onepage&q&f=false
Ronald R. Hatch wrote a book called "Escape from Einstien"
According to a reveiw by W. H. Cantrell:
"The author is one of the world's foremost experts on the Global Positioning System and a former president of the Institute of Navigation. His book discusses GPS satellite data that contradicts Einstein's relativity theories and proposes his own Modified Lorentz Ether Gauge Theory (MLET) as a replacement for Einstein's relativity. It agrees at first order with relativity but corrects for certain astronomical anomalies not explained by relativity theory."
http://www.amazon.com/Escape-Einstein-Ronald-R-Hatch/dp/0963211307
By the way, while doing a little browsing, I came across an accessible online version of the peer-reviewed article involving a classical explanation of the precession of Mercury's orbit. In the introduction it says:
"Using only classical mechanics, we obtain the same equation as predicted by Einstein’s General Relativity, without using any of the relativity principles. We have seen [1] that the advance of the perihelion is due to gravitational potential and kinetic energy, which modify the standard meter and the clock rate on Mercury. The physical change of length and the change of clock rate were demonstrated previously [1] . The only difference between the usual Newton’s physics and the results presented here is that, contrarily to Einstein, we fully take into account the principle of mass-energy conservation. This paper shows how to use the units existing on Mercury to derive the correct shape of the precessing elliptical orbit around the sun."
It concludes with these words:
"The cause of the advance of the perihelion of Mercury is now perfectly explained. We see that this demonstration has been done using Newton's physical laws instead of non-realistic mathematical models. This paper shows the beauty and the universality of Newton's laws in Galilean coordinates. Those laws are valid internally, everywhere inside all frames when we use proper values. We msut recall that the basic principle of mass-energy conservation has also been foreseen by Newton [3].
It has been reported that Einstein said: Since the mathematicians have invaded the theory of relativity, I do not understand it anymore [4]. It is the author's wish that the realistic physical explanations presented in this paper will never be drowned into the mathematics.
http://www.newtonphysics.on.ca/mercury/index.html
Guys like "Sharpshooter" from Jazzfanz struggle to get a bachelor's degree in "physical sciences" from some two-bit college and end up displaying their brilliance to the high school students they teach by conditioning them to sneer, scoff, and roll their eyes at the very mention of the word "ether." They also instill crude epistemological "truths" (which they themselves don't even understand) to those students, who thereafter parrot them, even if they can't really explain them.
And they reinforce each other's ignorance by denouncing anyone who exposes their lack of understanding. Such is "science" for many of it's adherents.
A = A. The distance from New York to San Francisco is the same as the distance from San Francisco to New York, right?
New Orleans is not in constant motion relative to Chicago, sliding all over the map depending on the speed of every particular motorist driving there from Chicago. Likewise, San Francisco is not moving relative to New York, even if both are moving relative to the Sun.
So why does light take more time to go from New York to San Francisco than it does to go from San Francisco to New York? I thought GR said that the speed of light is the same, REGARDLESS of the motion of either the source or the receiver. By the logic of the new definition of distance, there is more distance between New York and San Francisco than there is between San Francisco and New York. Zup wit dat?
Edit: I figure you understand the question, either way, but meant to say "By the logic of the new definition of distance, there is LESS [not more] distance between New York and San Francisco than there is between San Francisco and New York."
Another question: If there is now way to tell if the earth is moving, then how do we explain the fact the it takes less time for light to go around the world going west than it does going east? Isn't that one way to tell that the earth is "really" and not just "apparently" moving (foucalt pendulum being another way)? Are, as suggested by Mach and Einstein, the geocentric and heliocentric views truly "equally valid" as a PHYSICAL, as opposed to merely MATHEMATICAL, proposition?
What physical significance is there (and you always seem to suggest that there must be some "real" physical significance) to the suggestion that you can treat any frame as a "preferred" one and still get the same MATHEMATICAL results?
If you sent a light signal from New York, bounced it off a mirror in San Francisco, measured the elapsed time once it returned, and then divided by 2, would that give you the one way time between the two? I don't think so. Homey don't play dat.
As I have repeatedly stated, there is no internal contradiction in SR as it applies to the twin "paradox." That is because SR smuggles in absolute motion in absolute spacetime. The contradiction is external and arises only when one wants simultaneously accept that one twin ages less than the other and to ALSO claim that there is no absolute motion and that all frames of reference are "equally valid." Dingle was 100% correct in his arguments that both of these claims could not be true.
I don't care about the math, and don't need to resort to it to see the contradiction. However, since you want to rely on math, and purport to understand it, this discourse on the mathematical errors incorporated by these contradicatory assertions may be of interest to you:
"In his 1905 relativity paper Einstein did not derive the inverse Lorentz transformations. However, the equivalence of the equations x2+y2+z2=c2t2 and x’2+y’2+z’2=c2t’2 was essential to his derivation of the Lorentz transforms. These equations assert that the velocity of light is an invariant constant when measured in two different frames of reference which use the same standards of measurement. This proof of sufficiency showed that a sufficient condition for the deduction of the Lorentz transformation was the constancy of light velocity assumption. However, there was no proof of necessity. Here we have shown that the Lorentz transform implies that the coordinate measures in S and S’ are different when the above equations are imposed. Hence, the coordinate measure of c is the same in both frames but the measurement scales are not the same....It is clear that these results refute the version of Einstein relativity that appears in the traditional textbooks...
In his 1907 relativity paper, Einstein made a very clear statement regarding the reciprocal relation between frames S and S’. “In general, according to the principal of relativity each correct relation between “primed” (defined with respect to S’) and “unprimed” (defined with respect to S) quantities or between quantities of only one of these kinds yields again a correct relation if the unprimed symbols are replaced by the corresponding primed symbols, or vice versa, and if v is replaced by -v.” This assertion is the source of the paradoxes and inconsistencies. This statement is trivially true, when interpreted to mean a redefinition by renaming of coordinates, but it is false as shown above when applied to the derivation of the relation between reference frames...The problem is that the bijective requirement for the Lorentz transformations was never demonstrated mathematically. It was simply assumed to be valid without actually proving it. This turned out to be a mistake, because the transformations are not bijective inverses...
From this it is concluded that there are two different relativity postulates, or perhaps different interpretations applied to the same postulate. It appears that the postulate that denies the existence of an absolute rest frame is the cause of the problem, and dropping this assertion removes the inconsistencies and paradoxes....When we combine the two postulates as usually interpreted, we obtain the incorrect inverse Lorentz transform equations. These are derived from the equations x2+y2+z2=c2t2 and x’2+y’2+z’2=c2t’2, and make the reference frames S and S’ equivalent. This equivalence is the basis for asserting that no reference frame has the right to be considered as the absolute rest frame. However, these equations are really the same equation with the symbol names changed. To correct this error, new inverse Lorentz transformations were derived. These equations require the concept of an absolute rest frame.
[continued in next post]
"The fault lies in the way that the inverse Lorentz transforms are derived so that they apparently support the postulate that there is no absolute rest frame. But when derived this way the system of Lorentz transforms becomes inconsistent. This can be avoided by asserting one frame as reference, and then deriving inverse Lorentz transforms consistent with this hypothesis..."
http://www.mrelativity.net/Papers/18/Ricker2.htm
As a matter of technical nomenclature, I have no idea what "bijective inverses" means, but I still think I know what he is saying, conceptually. There is a lot of mathematical equivocation involved, and this is a result of Einstein's determination to treat his physical theory AS THOUGH it were consistent with his logical positivist philosophy, even though the two were fundamentally incompatible and mutually exclusive.
Does it make technical sense to you?
"This result shows that the Einstein light velocity postulate is inconsistent with the interpretation that Lorentz transforms change the scale of measurement to keep the coordinate measure of light velocity invariant. The inconsistency in the Lorentz and inverse Lorentz transforms occurs because light velocity in an absolute sense, i,e, that the same measurement scale is used in both frame S and S’, is inconsistent with the fact that the Lorentz transform changes the measurement scales. Hence the physical standards of measure in frames S and S’ are different. But Einstein relativity asserts that they are the same. Hence the contradictions and paradoxes. This is illustrated by the first and most basic paradox, the paradox that arises when we assert that the distance traveled by light is the same in frames S and S’. The light spheres do not represent the same distance in both cases, but only that when the coordinate measures of distance in S and S’ are compared, they are equal. Since the measurement standards for distance and time are not the same in both frames, there is no paradox."
Short version: "...the physical standards of measure in frames S and S’ are different. But Einstein relativity asserts that they are the same. Hence the contradictions and paradoxes."
Make sense to you?
Without the math, I take him to be saying that it is inconsistent to simultanously claim that (1) the tranformations serve to change the scale of measurment, while also claiming that (2)no transformation is needed to begin with because the speed of light is supposedly invariant from the get-go.
It's like saying the distances in the two frames are "the same" because they are "different." It's simply comparing apples to oranges and equivocating by calling different scales of measurement "the same." Einstein wanted to view them as "the same" so that they could be "equally valid." That way he could serve his philosophical "master" and claim that absolute motion had been abolished.
We've been through all of this before, with no progress, but I will return one more time to the "specific example" given in wiki for the twin paradox resolution. I'm hoping that this time you can see the problem with the textbook interpretation (i.e., Einstein's own) of the relationship between different inertial frames.
First wiki says:
"Consider a space ship traveling from Earth to the nearest star system outside of our solar system: a distance d = 4.45 light years away, at a speed v = 0.866c (i.e., 86.6 percent of the speed of light)." So the distance in question is 4.45 light years, here, OK.
Then it says:
"The ship's crew members also calculate the particulars of their trip from their perspective... In their rest frame the distance between the Earth and the star system is εd = 0.5d = 2.23 light years (length contraction), for both the outward and return journeys." OK, so now the distance is only 2.23 light years.
Math aside, does it make any PHYSICAL sense to say that the distance "really" changed for the ship crew the second they reached their cruising speed? That a star just suddenly jumped a distance of 2.23 light years, and did so JUST for them, but not for other observers?
No more so than saying the distance between Chicago and New Orleans "shrinks" from 600 miles to only 300 miles if I go 120 miles per hour instead of 60 miles per hour.
Despite the lack of (physical) sense to such a claim, you will hear physicists claiming that "space" contracts at higher speeds, as though space is a "thing" which constantly contorts itself to accomodate expectations of observers with mistaken premises. Only one (like Einstein) with an overpowering need to achieve a predetermined agenda could conceivably try to pass such absurdities off as "real." It is a marvel of human nature that such agenda-driven people are able to somehow convince themselves that it "all makes sense," somehow.
"The fundamental question regarding the speed of light is the following: Is the speed of light constant with respect to the observer (receiver) or is it constant with respect to the chosen inertial (isotropic light speed) ECI frame?...
...the Sagnac effect is not due to rotational motion. Contrary to Ashby’s claims, the Sagnac effect is caused by any motion of the observer or receiver relative to the chosen inertial frame...
The strong evidence is that the constancy of the speed of light is wrong. The speed of light is not always c relative to a moving observer (receiver). Instead, the speed of light is always c relative to the chosen inertial (isotropic light speed) frame."
http://www.worldnpa.org/pdf/abstracts/abstracts_3053.pdf
So the speed of light is only constant with respect to the inertial frame? Yeah, that's what the math guy was sayin above.
As these same authors note:
"The principle of the constancy of the speed of light asserts that in vacuum light always has a definite speed of propagation that is independent of the motion of the observer [1]. That is, no matter whether the observer is moving or at rest, and no matter how fast the observer is moving, 0.000001c or 0.999999c, the speed of light is always c. This assertion in fact is the most controversial part of Special Relativity. Relativistic physicists claim that people who refuse to accept the constancy of the speed of light simply cannot give up their common sense acquired through slow speed experiences."
This attitude is certainly typical. All through our discussions of SR you have consistently treated me as though I were a completely uninformed and naive child, in need of enlightment from someone who "really" understood. When you cannot detect your own logical inconsistencies then of course you must see anyone who points them out to you as being "illogical."
"...Newton objectivises space. Since he classes his absolute space together with real things, for him rotation relative to an absolute space is also something real. Newton might no less well have called his absolute space ``Ether''; what is essential is merely that besides observable objects, another thing, which is not perceptible, inust be looked upon as real, to enable acceleration or rotation to be looked upon as something real...
...the special theory of relativity does not compel us to deny ether...the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only wonld be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense." (Einstein, 1920)
http://www.tu-harburg.de/rzt/rzt/it/Ether.html
So, in other words, Newton could just as well have called "absolute space" ether, because something like it is necessary for SR, GR, or any other theory which intends to rely on any "possibility of existence for standards of space and time (measuring-rods and clocks)." Without it, neither rotation nor acceleration could be "looked upon as real."
Absolute space = ether = required for SR and GR, accordin to Al his own damn self, eh?
Of course, that was the Al who, after years of dogmatic positivism and years of trying to promote, justify, and realize positivistic goals, finally turned his back on positivism. No positivist would ever say: "... besides observable objects, another thing, which is not perceptible, must be looked upon as real..."
Two people, A and B, are separating in space at rate equal to .5c.
A and B are both "equally entitled" (whatever that means) to ASSUME they are "at rest," and hence, each insists upon receiving what he is entitled to, and ASSUMES he is at rest.
Can both assumptions be right? Of course not. If both assumptions are right, they could not possibly be separating in space, because they are both simply at rest and neither is in motion.
So one of them (if not both) is wrong. In fact, despite their subjective demands that their "rights" be respected, at least one of them is NOT at rest, regardless of what he subjectively "assumes." At least one is wrong in his assumptions.
It is only in this way that there can be a solution to the twin paradox, wherein both sides assumes that one (the earth twin) is at rest, and the other is moving.
To say that "both are right" in their assumptions leaves you, in Al's words in a spot where there is "no possibility of existence for standards of space and time."
So, put another way A and B are NOT "equally entitled" to assume they are at rest. At best only one (perhaps neither) is "entitled" to claim he is at rest. That's because objective reality, not subjective demands, determines whether A is "at rest" with respect to B, or vice versa. The two views (A at rest vs. B at rest) may be "equally valid" for choosing a framework within which to do mathematical calculations, but they CANNOT be "equally valid" as a matter of physics (i.e., physical, or "actual" validity).
I said: "Can both assumptions be right? Of course not. If both assumptions are right, they could not possibly be separating in space, because they are both simply at rest and neither is in motion."
Perhaps I spoke too fast. One could take the view that nothing ever moves and that the only reason the distance between them can increase or diminish is because the space between them either expands or contracts. That appears to the the "relativist" view, as expressed by many of it's proponents.
When I hit a baseball, neither the ball nor the batter moves, the "space" between them merely takes a sudden notion to up and expand itself. Yeah, that's the ticket!
The whole problem of logical circularity involving the relationship between time and distance in order to arrive at a determination of "speed" (which is a product of time and distance), is quite evident in this "explanation" of "simultaneity:"
"How can simultaneity, the notion of events ocurring at the same time at different places, be defined operationally?
"One way is illustrated in the diagram. Vermilion surrounds herself with a set of mirrors, equidistant from Vermilion. She sends out a flash of light, which reflects off the mirrors back to Vermilion. How does Vermilion know that the mirrors are all the same distance from her? Because the relected flash returns from the mirrors to Vermilion all at the same instant.
Vermilion asserts that the light flash must have hit all the mirrors simultaneously. Vermilion also asserts that the instant when the light hit the mirrors must have been the instant, as registered by her wristwatch, precisely half way between the moment she emitted the flash and the moment she received it back again. If it takes, say, 2 seconds between flash and receipt, then Vermilion concludes that the mirrors are 1 lightsecond away from her."
http://casa.colorado.edu/~ajsh/sr/simultaneous.html
Here "Vermillion" purports to "know" the distance "because the relected flash returns from the mirrors to Vermilion all at the same instant." Given this "knowledge," she begins to make "assertions" about the simultaneity of distant events and about the time of those events.
But why didn't Vermillion just measure out a distance of 1 lightsecond (or whatever) with a yardstick (or whatever) to detemine the distance? Again, one cannot calculate speed without knowing the distance. But here the distance is inferred from the "time of arrival." The inference is implicitly premised upon an assumed speed.
But if I throw a rubber baseball off two different brick walls with the same force in two directions, one against a 10 mph wind, and one with the wind, the two balls will bounce back and reach me at the same time ONLY IF the two brick walls are NOT equidistant from me. I have to know the distance before I can gauge the speed, not vice versa. If I want to know the distance to each brick wall, why don't I just get out a tape measure? "Speed" can tell me nothing new about distance, nothing that wasn't already known before I determined the speed. I can't know the speed until I know the distance.
Know what I'm sayin?
The very term "lightyear" attempts to define distance in terms of time and assumed speed. Let's say we are distance x from a star, and we conclude that that distance is 4 lightyears. This means that if we travelled at the speed of light, it would take us four years to get there.
Suppose we travel at .5C. Now it takes 8 years to get there. Is the "distance" now 8 lightyears? By definition, no, but if one fallaciously conflates the question of "how long it takes us to get there" (time) with the question of distance ("how far away is it") then, yeah, now, now it's 8 years away, instead of only 4. So what?
These days, athletes (and others) seem quite fond of saying "It is what it is." Completely contentless, but true in the sense that A = A. You can distort the units in which you measure the distance to a star (i.e., use a "yardstick" which is only 1 inch, and that will give you a different "reading" of distance than will a standard yardstick), but it cannot change the distance itself. As far as distance goes, "it is what it is," assuming the objects are at rest with respect to each other.
Well, unless you're a relativist, maybe.
The problem with SR is not the math. As far as I know the math is perfectly consistent.
But mulitple problems arise when it's supporters (Einstein included) attempt to verbalize the implications of the math. Verbally and conceptually, they will impute things as "necessarily implied" by the theory that are not implied at all (and may even be refuted by the relevant math). Often such statements are guided by philosophy, not by the math formulaes involved. That is one problem.
The other problem is, mathematically consistent or not, the implications sometimes make no physical sense whatsoever, unless maybe you are a solipsistic "idealist" like Berkeley. Mathematically, the theory is probably fine, and if you find it convenient to use it to calculate strictly mathematical consequences, OK. Same with geocentric astronomy, if you prefer to do you math calculations from that perspective. The problem comes in when it's supporters try to claim that it reflects "reality."
They have no more basis for such a claim than does a moralist who wants to say that abortion is wrong. Less actually, because, agree with it or not, the stance that abortion is "wrong" does not offend well-established notions of "reality."
The idea that Einstein arrived at his "constancy of light" postulate either (1) by necessary logic, given the data or (2) without heed to his philosophical leanings is, I think, clearly erroneous.
Eric, I've made, God only knows--maybe 30-40 straight posts in this thread over the past week or so with no response. For all intensive purposes, I've simply turned the thread into my own personal blog, ya might say.
But, even so, these posts were directed to you, and to points/posts you have made in the past. I understand that you have other things to do and may not have time to respond. I also understand that you may simply have no inclination to respond.
Either way is cool. If you never respond to any of this, that's fine. But, if you do respond I would ask that you try to understand and address the points I am making and, more importantly, address the questions I am asking (by direct question and by implication).
It will do little to promote any meaningful discussion if you merely breeze through these posts, selectively isolating particular sentences for the purpose of nit-picking, and ignoring the real issues and questions.
By the way, I made a post about Zeno, Protagoras and Socrates that apparently got filtered (which, I think, sheds some light on the underlying issues). There may be other posts which are missing, not sure.
I said: "The problem with SR is not the math. As far as I know the math is perfectly consistent."
This mathematician claims that there is a very subtle misinterpretation of the math used in SR that is made by people applying it, and he seems to make sense. His basic claim is it is easy to, and that people routinely do, confuse rates with measures and functions with equations. Often this make no real difference, but it can (and does in SR, he says). Listen to the podcast here, if you're interested:
http://www.relativitychallenge.com/archives/728#more-728
According to Einstein, at least, GR does NOT hold that c is constant. He says, for example: "according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [. . .] cannot claim any unlimited validity."
Although he uses the word "velocity" here, Carlip says interpreting Einstein to mean "speed" rather than literal "velocity" in this context is an interpretaton which "is perfectly valid and makes good physical sense."
Nonetheless Carlip goes on to say that "a more modern interpretation is that the speed of light is constant in general relativity." So now we have "modern interpretations," eh? Carlip discusses the SI defintion of a meter and notes that it is given as "exactly 299,792,458 m/s." As he notes, this makes the speed of light constant "by definition." So modern "interpretations" lead to new definition, it seems. Just another semantical way to appear to make the world conform to your "interpretations" in my view. As many have noted, using this defintion makes it IMPOSSIBLE to even "test" the validity of SR.
Carlip also asserts that: "... if velocities added vectorially as newtonian mechanics requires, the last 5 digits in the value of the speed of light now used in the SI definition of the metre would be meaningless." As I read this, he is saying that you could just stop at 299,8xx,xxx meters per second. Not really a big difference in the scale of things, is it?
Carlip also, as I have done above, notes the circularity and inherent problems involved in defining "speed" within the context of relativity when he says; "To determine speed (distance moved/time taken) you must first choose some standards of distance and time, and different choices can give different answers."
http://www.phys.ncku.edu.tw/mirrors/physicsfaq/Relativity/SpeedOfLight/speed_of_light.html
This is all just something I thought I would throw in based upon your claim that SR must be preferred to LR because GR assumes the same things SR does. No, it doesn't, not unless you reinterpret it in some way that suits you. According to Al (and many others) GR does NOT incorporate or presuppose a constant speed of light.
I said: "According to Al (and many others) GR does NOT incorporate or presuppose a constant speed of light."
According to Carlip, "In this passage [i.e., the one I quoted above], Einstein is not talking about a freely falling frame, but rather about a frame at rest relative to a source of gravity. In such a frame, the speed of light can differ from c..."
Like a person on earth, who is "at rest" relative to the "source of gravity" (earth), eh? In SR, light would be constant in this frame (at least it has always been treated as such, hence the Lorentz equations, etc.). Most of the experiments "confirming" the constant speed of light have been terrestial. But this appears to be inconsistent with GR, as interpreted by Einstein. GR "inconsistent" with SR? Zup wit dat?
But how can there be any "inconsistency?" Carlip goes on to assert that: "If general relativity is correct, then the constancy of the speed of light in inertial frames is a tautology from the geometry of spacetime."
The inconsistency seems to go away if you just look at the words. But the inconsistency is apparent once you understand the equivocal way in which the term "inertial" in being used in SR as contrasted with GR. As previously noted, the exact conditions which are treated as "inertial" in SR are treated as "accelerating" in GR, and vice versa. Despite the equivocation in language (using the exact same word to make two different things, such as black vs. white, "appear to be the same thing), and the false impressions that may thereby be generated, there is in fact an inconsistency, eh?
Somehow, I still doubt if you will ever see this. Your mind just doesn't seem to operate that way. I have always thought you had a strong tendency to believe that the words you choose to use, and the definition you chose to assign to those particular words, settled any questions about "truth" or "reality" for you.
In modern cosmolosgy, in order to avoid a violation of the "speed limit law" (which could get you fined, ya know?), they now say that objects which appear to be receding from us at speeds faster than light are not "really moving." Instead, they say, the objects are "motionless" and space is "expanding."
Once you take the position that two objects separating in space could be either (1) in motion, or (2) motionless, just depending on how you want to label it at the time, all possibility for any kind of objective standards is lost, as Al pointed out.
Similarly, once you take a linguistic position that opposites can be "the same" or "different" all depending on how you want to define them at the time, all possibility of meaningful discussion, all possibility of "logical laws," and all objective meaning of concepts disappears. All very convenient if you desire to assert and maintain self-contradictory things and maintain that both are "true," but....
I said: "Carlip goes on to assert that: "If general relativity is correct, then the constancy of the speed of light in inertial frames is a tautology from the geometry of spacetime."
Carlip is just talking in circles, and trying to give the impression that it is all consistent and "makes sense," and is a "fact" somehow. It is no coincidence that, he "proves" his point, in closing, by conspicuously claiming (as though it settles the issue) that: "Finally, we come to the conclusion that the speed of light is not only observed to be constant; in the light of well tested theories of physics, it does not even make any sense to say that it varies."
First of all, light is not "observed to be constant." The imputation of constancy is strictly a conclusion of theory, NOT "observation." Then he makes an appeal to what "makes sense." But the question remains: Makes sense" in what context? Given what "indubitable" assumptions and definitions?"
He says that the "geometry of spacetime" makes it tautological to say that the speed of light in inertial frames is constant. But this is wrong. Saying something is "tautologically true" is the equivalent of saying that it is true by definition. The "geometry of spacetime" does NOT give definitions, and does not form "tautologies." People (theorists) do. All thinking people agree that something that is tautologically true (true a priori) is contentless and insignificant as an empirical (true a postiori) matter.
Al himself denies a claim that you have made in the past (as I understood you), i.e., that, by clever manipulation and choice of a reference frame, a gravitional field can always simply be "transformed away." I don't find this claim (that a gravitational field can be transformed away by choice of co-ordinates) to be of any substantial significance to begin with, but I thought you might be interested in Al's pronouncement on the topic:
"... I must warn the reader against a misconception suggested by these considerations. A gravitational field exists for the man in the chest, despite the fact that there was no such field for the co-ordinate system first chosen. Now we might easily suppose that the existence of a gravitational field is always only an apparent one[more comments from me on this part later]. We might also think that, regardless of the kind of gravitational field which may be present, we could always choose another reference-body such that no gravitational field exists with reference to it...It is, for instance, impossible to choose a body of reference such that, as judged from it, the gravitational field of the earth (in its entirety) vanishes."
http://www.bartleby.com/173/20.html
In the prior post, Al claims that the "man in the chest" was in a gravitational field that exists "in fact." One perplexing aspect of this claim is that the "man in the chest" in this example was supposedly being constantly accelerated upward by virtue of "some being" cranking on a rope tied (externally) to his chest.
This would seem to be "artificial" not "real" gravitation, since no massive body is responsible for the acceleration. Furthermore, Al says he is "really" at rest:
"Relying on his knowledge of the gravitational field (as it was discussed in the preceding section), the man in the chest will thus come to the conclusion that he and the chest are in a gravitational field which is constant with regard to time. Of course he will be puzzled for a moment as to why the chest does not fall in this gravitational field. Just then, however, he discovers the hook in the middle of the lid of the chest and the rope which is attached to it, and he consequently comes to the conclusion that the chest is suspended at rest in the gravitational field."
Get the picture, so far? He wonders why the gravity is only pulling on him, and not the chest also. Then he sees the rope and concludes that "the chest is suspended at rest in the gravitational field."
So what does Al have to say about this man's conclusion? This:
"...we must rather admit that his mode of grasping the situation violates neither reason nor known mechanical laws. Even though it is being accelerated with respect to the “Galileian space” first considered, we can nevertheless regard the chest as being at rest."
Here Al once again reverts to subjectivism (what a man can "reasonably believe) as the standard for objecive reality. Notice that he doesn't limit it to the perspective of the man in the chest. He doesn't say "HE can nevertheless regard the chest as being at rest." On the contrary, he says WE can regard it as such, even though we know better. Another example follows in the next post.
He does the same thing we he tries to claim that acceleration cannot be distinguished from an inertial state (i.e., when he tries to claim that acceleration is "relative" rather than absolute). By “same thing” I mean that he tries to shift from imagination to “reality” as though the two cannot be distinguished.
He sees the problem, when he says:
"As long as it is moving uniformly, the occupant of the carriage is not sensible of its motion, and it is for this reason that he can un-reluctantly interpret the facts of the case as indicating that the carriage is at rest, but the embankment in motion. Moreover, according to the special principle of relativity, this interpretation is quite justified also from a physical point of view." [He should say "mathematical" point of view here, not "physical"].
"[But] if the motion of the carriage is now changed into a non-uniform motion, as for instance by a powerful application of the brakes, then the occupant of the carriage experiences a correspondingly powerful jerk forwards...and for this reason it would appear to be impossible that the same mechanical laws hold relatively to the non-uniformly moving carriage, as hold with reference to the carriage when at rest or in uniform motion. At all events it is clear that the Galileian law does not hold with respect to the non-uniformly moving carriage."
http://www.bartleby.com/173/18.html
So how does he resolve this evidently insurmountable problem with trying to treat acceleration as relative rather than absolute? The same way as always: by trying to make subjective imagination, speculation, ignorance, a substitute for "reality."
"But he is compelled by nobody to refer this jerk to a “real” acceleration (retardation) of the carriage. He might also interpret his experience thus: “My body of reference (the carriage) remains permanently at rest. With reference to it, however, there exists (during the period of application of the brakes) a gravitational field which is directed forwards and which is variable with respect to time. But he is compelled by nobody to refer this jerk to a “real” acceleration (retardation) of the carriage. He might also interpret his experience thus: “My body of reference (the carriage) remains permanently at rest. With reference to it, however, there exists (during the period of application of the brakes) a gravitational field which is directed forwards and which is variable with respect to time."
Because no one can "compel" this obstinate fool to refrain from imagining the appearance of a non-existent gravitational field, he has suddenly altered the way "we" should perceive reality? I don't think so. Homey don't play dat.
Unfortunately, even now, over a hundred years later, similarly loose-thinking subjectivists think their mode of apprehension has been legitimatized by Einstein, and that therefore such modes of thought and assertion need not be independently examined by them.
Einstein said: “My body of reference (the carriage) remains permanently at rest. With reference to it, however, there exists (during the period of application of the brakes) a gravitational field which is directed forwards and which is variable with respect to time."
Here there is not even any attempt to explain why the man, who speculated that he was suddenly in "gravitational free-fall" toward the front of the train would not temper his speculation with the knowledge that the train was not also being subjected to the "gravitational field." Nor, of course, is there any consideration of why a gravitational field might be "variable with respect to time." Is a massive body intermittenly appearing and disappearing, willy-nilly, that the idea?
This train-ridin guy aint real bright, eh? At least the guy in the chest had "reason" to believe what he did, even if we know he was being deceived and he didn't.
This submission by Al is supposed to convince me that the acceleration of the train is not actual, but merely relative? I kinda feel like my intelligence has just been insulted, know what I'm sayin?
Of course, for that matter, his claims are not credible even so far as uniform motion goes. As noted, in that context, Al says: "...he can un-reluctantly interpret the facts of the case as indicating that the carriage is at rest, but the embankment in motion. Moreover, according to the special principle of relativity, this interpretation is quite justified also from a physical point of view."
The "special principle of relativity" (which, again, deals with the operation of laws of physics) certainly does NOT "justify" from a "physical point of view" the claim that a guy on the train might imagine that all the trees, rocks, etc. on the embankment are moving (but not himself) while he watches them pass by. Not even a fool would begin to think that, let alone be "justified" in thinking it.
I said (about 10 posts up): "The problem with SR is not the math. As far as I know the math is perfectly consistent. But mulitple problems arise when it's supporters (Einstein included) attempt to verbalize the implications of the math. Verbally and conceptually, they will impute things as "necessarily implied" by the theory that are not implied at all (and may even be refuted by the relevant math). Often such statements are guided by philosophy, not by the math formulaes involved."
After saying that, I started trying to really understand what SR (or LR, for that matter) actually (and not just allegedly) implies, and to distinguish that from the multitude of claims (which are all over the lot) made about what SR (or LR, for that matter) implies. Among other things, I started looking at the design of the GPS again; the assumptions it makes, and the "conclusions" it (as a "system") reaches, the basis for those conclusions, etc. The more I thought about it, the harder it was for me to see any "real" difference between LR and GR.
People (depending on who you listen to) will tell you, as examples, that LR differs from SR in the following ways:
1. In SR the speed of light cannot be exceeded, but in LR in can be,
2. In SR "time" and "space" necessarily change, not rods and clocks, whereas LR implies that rods and clocks (but not time and space) change,
3. The transformations of SR are "derived" from the postulates in that theory whereas they come into being only as ad hoc hypotheses in LR,
4. In SR the transformations are "reciprocal," but in LR the transformation is only one way. In other words, in LR both observers will not see the other's rods and clocks to have slowed down/shortened, and
5. Space and time are fundamentally different in LR and SR.
I'm sure there are many other supposed differences. I have seen so many contradictory claims about what SR "implies" that I know that they cannot ALL be implied. Although you don't see much about it, claims about the "necessary" implications of LR are also contradictory (again, depending on who you "listen" to, if anyone at all).
[Continued in next post]
Recently I have seen a theoretical physicist argue, and purport to prove, that SR and LR are in fact IDENTICAL theories, in substance. He's not simply saying that they lead to identical empirical results. He's saying that there is no "choice" to be made between the two because they are the same (substantially, if not semantically) in EVERY respect. Among other things, he claims that (1) whatever one implies about the nature of time and space, the other also implies, for example (2)that whatever one implies about whether clocks "really" slow down, the other implies and (3)that whatever mathematical formulaes can be "derived" from the premises of one can also be derived from the other. This is course in addition to the "empirical results" identity--that whatever one predicts, the other will also predict. Again, there is no choice to make, he claims, because they are identical.
It follows (as he also claims) that neither (1) the existence/non-existence of an ether nor (2) the existence/non-existence of a "non-moving" frame is essential to, or implied by, either. It is, however, the misleading and improper introduction of such questions into the issues that give the (semantical only) appearance of a difference between the theories.
I certainly get the sense of what he is claiming, and why, but I can't say I have completely digested and critically analyzed his arguments. That said, at this point I find his arguments to be persuasive and would have to say I agree with him, based on my current understanding of his points.
If he is right, it appears that the arguments about the implications of SR vs LR are semantical, and, ultimately, philosophical. Each side takes a theory that is neutral and then illegitimately contorts it (by adding in unwarranted assumptions and, therefore conclusions) to conform to their philosophical preferences. Then the arguments begin about which (allegedly different) theory (philosophy, really) is "true."
Just another instance, in other words, where there is a failure to distinguish theory from fact and philosophy from theory. Part of this in due, I'm sure, to the desire to present one's individual philosophy as "fact."
Here is an informative philosophical analysis of (kinematical)frames of reference and (dynamic) "inertial frames of reference:
"Leibniz articulated a more general “equipollence of hypotheses”: in any system of interacting bodies, any hypothesis that any particular body is at rest is equivalent to any other. Therefore neither Copernicus' nor Ptolemy's view can be true—though one may be judged simpler than the other—because both are merely possible hypothetical interpretations of the same relative motions."
So Liebniz has a notion of what can be considered "true." Now what?
"...the notion of a dispute between “relativists” or “relationists” and “absolutists” or “substantivalists”, in the 17th century, is a drastic oversimplification. Newton, in his controversial Scholium on space, time, and motion, was not merely asserting that motion is absolute in the face of the mechanists' relativist view; he was arguing that a conception of absolute motion was already implicit in the views of his opponents—that it was implicit in their conception, which he largely shared, of physical cause and effect."
This is what I, and many others before me, have been trying to say. Even those who argue against an "absolute" preferred frame of reference themselves implicitly adopt one. Then they try to convince themselves that they have not done this. They themselves must implicitly have a notion of (and presumably some standard for discerning) "truth" in order to dismiss anything whatsoever as being "untrue."
http://plato.stanford.edu/entries/spacetime-iframes/
This consideration goes to the heart of most of the debates about the supposed "differences" between absolute vs. relative/relational motion, as I see it.
"For Leibniz and many others, this general equivalence was a matter of philosophical principle, founded in the metaphysical conviction that space itself is nothing more than an abstraction from the geometrical relations among bodies. In some form or other it was a widely shared tenet of the 17th-century “mechanical philosophy”. (Same article)
I find it ironic that Liebniz, the positivitic forerunner of Mach, Einstein, et al., considered space itself to be "nothing more than an abstraction." I tend to agree with this. The irony is that these days it is the supposed relationists, relativists, and empirical positivists who end up trying to claim that "space" is a physical thing which expands, contracts, etc. They end up trying to treat "time" (another abstract concept) in the same way. Go figure, eh?
A few questions, and a few possible answers (inconsistent with SR and LR, depending on the interpretation):
1. Why didn't (couldn't) the Michaelson-Morley experiment "detect" the motion of the earth relative to the sun (the speed of it's orbital path)?
Answer: For the same reason that we cannot detect that we are moving when we measure the speed of a baseball thrown i.e., it participates in the motion of the earth, just like we (and our atmosphere) do. This is nothing new, and there is nothing new or unique about light in this respect. We do not require that ALL speeds be uniform in order to conclude that the laws of physics are (with appropriate transformation) "the same" in all inertial frames. On the contrary NO speed, other than light, per Al, is deemed to be directly transferrable from on frame to another. It does appear, however, that light produced on earth does NOT share earth's rotational motion, hence the Sagnac effect (computed at c = v and/or c - v). Hence the GPS makes adjustments for "observers" travelling in easterly and westerly directions.
2. How can the (real and experimentally-confirmed) time dilation effects of "relative motion" occur if motions are "relational?"
They can't, and SR doesn't suggest that they do (in itself, that is, although many "interpreters" of SR claim otherwise). Here's why. The time dilation is NOT a function of the "merely relative" (relational) motion between two objects (observers). It is a function of the motion with respect to the "preferred frame" chosen only. This point is crucial. The "preferred frame" is the one is which the standards of measurement for length and distance (miles and hours, for example) are "at rest." In that sense, the preferred frame is the "absolute frame." SR itself alway incorporates such an "absolute" frame." "Absolute" here does NOT literally mean absolute, and Newton never claimed it did. The "absolute" frame in this context could itself be moving at a rate of 1000 miles per second with respect to something else. It is "absolute" only in the sense that, by definiton, one will be "at rest" if he is motionless with respect to it, and "accelerating" or ("accelerated" in the case of uniform motion) if he isn't. "Observers" or their state of motion with respect to each other, is irrelevant to the issue of time dilation. Again, it is only motion with respect to the preferred frame which is relevant.
Agree, or disagree, Eric?
Edit:
Meant to say; "The "preferred frame" is the one is which the standards of measurement for length and TIME [not "distance"] (miles and hours, for example) are "at rest."
I just edited a post (or perhaps two posts, depending on how this post appears) post which is now gone. It seems that if I make more than one post and some or all "disappear," it is my most recent post which remains displayed
aintnuthin,
I don't have time tonight, and probably not in the near future, to read through all of this. I got through a small amount at the beginning. I'm sure you have a lot more you feel like piling on, as well.
I may eventually bother to make a full, detailed reply. But frankly, when you make very basic errors like saying Einstein-Cartan theory doesn't use Riemannian manifolds, or when you rely on sources that say there is a discrepancy between GPS data and relativity, it's very discouraging to bother to try. So, I will probably wind up ceding this on volume, ignoring the majority of what you posted. If you care to repost four or five paragraphs that sum up what you are trying to say, I would be more likely to take the time to respond.
It's a shame, because you do make some good points as well, perhaps wihtout realizing what they really mean. You are absolutely correct that if the speed of light is variable, and we incorrectly treat it as being constant, that could arise in all sorts of possible mis-measurements, changing measurements, etc. So, all you need to do to disprove the concept is to show where these variable measurements are occuring. Do you have a list? Not that the lack of a list proves anything, it's still a valid point, and something to keep in mind as a potential refutation for relativity.
One Brow said: "I may eventually bother to make a full, detailed reply. But frankly, when you make very basic errors like saying Einstein-Cartan theory doesn't use Riemannian manifolds, or when you rely on sources that say there is a discrepancy between GPS data and relativity..."
1. It is said to be a "non-metric" theory, which means, from what they say, that it's not relying on "curved space," Riemannian manifolds, or not.
2. I didn't say there was a discrepancy between GPS data and relativity. Of course, Einstein's SR aint the onliest relativity, neither. In fact, he took his formulaes from Lorentz.
3. Al said SR didn't apply to rotating bodies, so getting Galliean transformations for light in that context doesn't "violate" SR (it was an inexplicable exclusion from the get-go). But why should that be an "exception?" Turns out, recent experiments appear to have demonstrated that the Sagnac effect occurs when light travels in a straight line too. Go figure, eh?
The main point was, and still remains, that scientific theory suffers from the same "flaws" as those you complained about in your original post. As I said before, I'm not really arguing for or against SR or GR. I'm just asking questions and pointing out some of the philosophical assumptions involved.
I figure you'll never read it, but if you do, keep the point in mind, eh, Eric?
A little elaboration on point 1:
"General relativity is fundamentally awkward in the way it handles how energy/momentum is exchanged between the gravitational field and everything else; teleparallel gravity is an alternative theory motivated in part by an attempt to remedy this theoretical flaw.
General relativity is awkward in the way it handles the coupling of spin to gravitation at the level of test particles; Einstein-Cartan gravitation is motivated in part by an attempt to remedy this flaw."
http://en.wikipedia.org/wiki/Classical_theories_of_gravitation
"Teleparallelism (also called distant parallelism and teleparallel gravity), was an attempt by Einstein to unify electromagnetism and gravity. The idea is to use a geometry with a pseudo-Riemannian metric of signature (3,1), vanishing curvature, and non-vanishing torsion, and to use tetrads, rather than the metric, as basic variables. Nowadays, people study teleparallelism purely as a theory of gravity[2][3] without trying to unify it with electromagnetism....Unlike GR, gravity is NOT due to the curvature of spacetime. It is due to the torsion."
http://en.wikipedia.org/wiki/Teleparallelism
"According to general relativity, curvature is used to geometrize spacetime. Teleparallelism, on the other hand, attributes gravitation to torsion, but in this case torsion accounts for gravitation not by geometrizing the interaction, but by acting as a force. As a consequence, there are no geodesics in the teleparallel equivalent of general relativity, but only force equations quite analogous to the Lorentz force equation of electrodynamics.5 We may then say that the gravitational interaction can be described in terms of curvature, as is usually done in general relativity, or alternatively in terms of torsion, in which case we have the so called teleparallel gravity."
http://arxiv.org/PS_cache/gr-qc/pdf/0501/0501017v1.pdf
aintnuthin said...
1. It is said to be a "non-metric" theory, which means, from what they say, that it's not relying on "curved space," Riemannian manifolds, or not.
Actually, non-metric spaces can still be curved. If it's non-metric, it's because the space does not have the topological properties of a metric space.
2. I didn't say there was a discrepancy between GPS data and relativity.
Nor did I say you made such a claim.
Turns out, recent experiments appear to have demonstrated that the Sagnac effect occurs when light travels in a straight line too. Go figure, eh?
You have a light beam travel in a different inertial path than the measuring apparatus, and that can happen.
http://arxiv.org/abs/gr-qc/0401005
The main point was, and still remains, that scientific theory suffers from the same "flaws" as those you complained about in your original post.
I disagree, again. Scientific theory uses the trapping of formal theories, but it is not a formal theory, and and has a different set of flaws than formal theories.
I figure you'll never read it, but if you do, keep the point in mind, eh, Eric?
I have not forgotten that is your main point. However, to be clear, in a formal system, "... the process of choosing these starting positions is strictly based on the conclusions you want to derive." In an empirical system, you are limited to starting points that result in agreement with the experimental data. This removes the flaw of having no "reality" to match the results to, but introduces the flaw of using inductive reasoning to determine reality. So, convincing me that the scientific theory has no reality to which it can be compared will be quite the challenge. diversions into alternatives for relativity and the like don't really come close to that.
A little elaboration on point 1:
Teleparallelism is an attempt to explain why space behaves as if it is curved by using the concept of torsion (that is, saying space is twisted rather than curved). A twist is not a curve, but I don't think the difference is sufficient to make your point.
These Arcos and Pereira guys (cited above) obviously know a crapload about gravity and the associated math. Read the article, if you're actually interested in gravity. I aint, really. That aint my point. Here's the point:
They say: "In this theory, instead of torsion, curvature is assumed to vanish. The corresponding underlying spacetime is, in this case, a Weitzenb¨ock spacetime. In spite of this fundamental difference, the two theories are found to yield equivalent descriptions of the gravitational interaction.4 This means that curvature and torsion are able to provide, each one, equivalent descriptions of the gravitational interaction."
"Equivalent" descriptions of gravity, eh? Relativists want to say that, for example, that gravity is "equivalent" to acceleration (it aint) and that geocentricism is "equivalent" to heliocentricism (it aint). They then insist that each one is "equally valid."
Here's my question: Why does "equivalence" mean "equally valid" to them, when it comes to espousing their values and preferences, but "equivalence" means cranky and misguided when it comes to any theory which doesn't favor their pet views?
LR is equivalent to SR. From the looks of it, many options are "equivalent" to GR, so why do you hand-wave them off with scorn?
I think people prefer what they were taught, and assume that what they are taught must right. Many potential theories of gravity and relativity of motion could have emerged triumphant in the '20's, some of which have seeming superiority over SR and GR. For historical reasons, they didn't. As I understand it, GR kinda just laid around, mainly because it didn't square with QM, until the '60's, at which time the cosmologists took a big interest in it because it seemed useful for their big bang theory.
One Brow said: "...space behaves as if it is curved..."
Easy to say, but what does it mean? Space is....what, exactly? If a high fly ball goes up, then comes down, all in a curve, is that space "behaving" like it's curved?
Do you even realize how theory-laden and assumption-ridden it is to make a statement like that? Space behaves as if it's curved?
One Brow said: "However, to be clear, in a formal system, "... the process of choosing these starting positions is strictly based on the conclusions you want to derive." In an empirical system, you are limited to starting points that result in agreement with the experimental data... So, convincing me that the scientific theory has no reality to which it can be compared will be quite the challenge."
Why do you think I'm trying to convince you of that? It seems we have entirely different ideas of what a "formal" system is.
Is math a formal system?
Is Euclidean geometry a formal system?
Can geometry be "compared to reality." What "conclusions" is geometry bound and determined to arrive at, ya figure?
Al wanted badly to fulfill "mach's principle" and he needed a closed, curved universe to accomplish it (which he didn't, but...). So he just made up a cosmological constant and, voila, the whole universe is curved. Look in a telescope long enough and you will see the back of your own head. Pretty imaginative, and pretty bold, to say what the entire universe is like.
aintnuthin said...
Here's my question: Why does "equivalence" mean "equally valid" to them,
It doesn't. By "equivalence", they usually refer to the Einstein Equivalence Principle, which discusses indistinguishability under certain conditions, not "equal validity", whatever that means.
LR is equivalent to SR.
LR uses the same equations as SR.
From the looks of it, many options are "equivalent" to GR, so why do you hand-wave them off with scorn?
You must remember the sentence, "And that leaves, as a likely valid alternative to GR, nothing [except possibly Cartan (1922), which may violate EEP]." It was on the the page you quoted. All of the other investigated theories have problems, and Cartan is simply an extension of GR.
I have no problem with Einstein-Cartan is someone wants to put that forward.
Easy to say, but what does it mean? Space is....what, exactly? If a high fly ball goes up, then comes down, all in a curve, is that space "behaving" like it's curved?
That's part of it. There's the bending of light around heavy objects, for example.
Why do you think I'm trying to convince you of that? It seems we have entirely different ideas of what a "formal" system is.
Is math a formal system?
Of course.
Is Euclidean geometry a formal system?
Definately.
Can geometry be "compared to reality."
Sure. Then again, "Axis & Allies" can be compared to WWII. Axis & Allies is still a formal system.
What "conclusions" is geometry bound and determined to arrive at, ya figure?
Pythagorean theorem, the usual area formulas, etc.
Al wanted badly to fulfill "mach's principle" and he needed a closed, curved universe to accomplish it ...
And then gave it up when it wasn't workable.
One Brow said: "Pythagorean theorem, the usual area formulas, etc."
Do ya think Euclid WANTED pi as part of the formula for the area of circles, etc.? I don't.
Just offhand, my idea of a "formal system" is one where the conclusions are dictated as a "matter of form," i.e. by necessary implication from the definitions and premises. Formal logic (as opposed to informal logic), for example, dictates that certain conclusions as "valid," as a matter of form, no matter how unsound they may be.
Same with GR. It's all math. The conclusions are dictated, like it or not, and Al definitely did NOT like some of those conclusions. But they just followed as a matter of logical deduction, like them or not. Logic can't tell you anything about reality, and you have to check for yourself to see if the premises are sound. Same with science. The expermental aspect of science checks for the "soundness" (but not the logic) of the theoretical implications.
The theory is formal (in most cases), especially in physics where most of it is strictly mathematical. Experiment does NOT make, alter, or modify the theory in any way, althought theorists might do so if the expermentals "disconfirm" the existent theory.
One Brow said: ""And that leaves, as a likely valid alternative to GR, nothing [except possibly Cartan (1922), which may violate EEP]." It was on the the page you quoted. All of the other investigated theories have problems..."
GR has problems, too. But either way, I didn't take one wiki article as having the final say on the matter. Read the article by the gravity experts, they say otherwise.
One brow said: "not "equal validity", whatever that means."
Mach, Al, you, Colton, and many others, have suggested that it is "equally valid" for each of two observers moving relative to each other to assume he is "at rest." It aint. That is merely a philosophical claim, not an empirical or scientific one. SR itself says they CAN'T both be at rest. Hence it can't be "equally valid" for each to assume he is, except in an abstract sense, for the purposes of doing calculations, maybe.
One Brow said: "That's part of it. There's the bending of light around heavy objects, for example."
Yeah, so? You didn't respond to this question, which was not strictly rhetorical:
I asked: "Do you even realize how theory-laden and assumption-ridden it is to make a statement like that? Space behaves as if it's curved?"
I said: "Mach, Al, you, Colton, and many others, have suggested that it is "equally valid" for each of two observers moving relative to each other to assume he is "at rest." It aint. That is merely a philosophical claim, not an empirical or scientific one."
Every time a physical prediction of SR is confirmed, the philosophical baggage which the relativists want to impute to it gets disconfirmed. That is because the two are fundamentally incompatible and incoherent, as Al himself eventually recognized.
Here's an example:
Suppose that an object is approaching me at the rate of about 350,000,000 mph (about half the speed of light). At the instant it is even with me, I send a light beam out in the same direction the object is heading in. One hour later, I see the light beam to be 700,000,000 miles from me and the object to be 350,000,000 from me, right?
But one hour later, the object also sees the light beam to be 700,000,000 miles ahead of him. It's the same light beam. It left from a known spot and has travelled whatever distance it has (whether that distance is 700,000,000 miles, 350,000,000 miles, one mile, or 10 billion miles, it's still the same distance)in the last hour.
From our perspective, the light beam has only moved 350,000,000 miles from the object in one hour, and hence he should see it as moving away from him at 1/2 the speed of light. But, because his measuring instruments have shrunk and because time runs slower for him, he MEASURES the speed to be c, not 1/2 c.
So, which is it, 700,000,000 miles in front of the traveller, or only 350,000,000 miles in front? The positivist answer is that the question is "meaningless." But that "answer" is what's meaningless. What SR is saying is that, in terms of earth's frame, the light is only 350,000,000 miles ahead of the object. That's why we have to explain why the (faster) moving object erroneously measures light to be travelling at c, when, in fact, it is only moving at 1/2 c by our standards.
Again, one of the twins will REALLY be younger. It is not just an illusion. This means lengths REALLY shortened and time REALLY slowed down for only one of the two objects. So it's legit to ask "which one REALLY slowed down, etc." and to determine which one only apparently (to the traveller who is deluded into thinking he is "at rest") slowed down, etc.
The guy with the warped instruments and time will meaure the time and distance (speed) differently, but the distance cannot simultaneously be BOTH 350,00,000 miles AND 700,000,000 miles in "reality."
Shortening my ruler will change the distance I measure from one end zone to the other on a football field, but it does not change the football field; only the ruler. The positivist wants to say that whatever I measure it to be is what it "is." Fraid not.
We all get fooled on occasion, but only a quintessential chump insists that he aint been played when he has been.
Do ya think Euclid WANTED pi as part of the formula for the area of circles, etc.? I don't.
The definition of pi is the ratio of the circumference of a circle to its diameter. I think Euclid did indeed want to include that in his work. However, it's possible you meant that Euclid did not want pi to be an transcendental number. I'm not aware that the Greeks of the time even conceived of transcendentals, they barely had a concept for irrational. I'm also not aware Euclid thought pi was irrational.
More to the point, I didn't claim that because you choose the axioms of a formal system to derive the results you want, that means you can always a set of results that perfectly match your desires.
Just offhand, my idea of a "formal system" is one where the conclusions are dictated as a "matter of form," i.e. by necessary implication from the definitions and premises. Formal logic (as opposed to informal logic), for example, dictates that certain conclusions as "valid," as a matter of form, no matter how unsound they may be.
That would be a limited version of what formal systems can be.
Same with GR. It's all math.
If you remove all the physics, the understanding, the need to conform to exsperimental results, you can leave a shell of GR that looks like a formal system, sure. But GR is not just a system on its own, it a part of physics that uses the form of a form system to develop empirical knowledge.
Logic can't tell you anything about reality, and you have to check for yourself to see if the premises are sound. Same with science. The expermental aspect of science checks for the "soundness" (but not the logic) of the theoretical implications.
If I understand you correctly, that seems like part of the process.
GR has problems, too.
But not in matching the experiemental data.
But either way, I didn't take one wiki article as having the final say on the matter. Read the article by the gravity experts, they say otherwise.
You can always find someone with expertise who nonetheless believes the moon is really made of cheese.
Mach, Al, you, Colton, and many others, have suggested that it is "equally valid" for each of two observers moving relative to each other to assume he is "at rest." It aint. That is merely a philosophical claim, not an empirical or scientific one.
I think you have that reversed. It is a very specific empirical claim about what you can determine from very specific sorts of empircal investigations, which investigations fit under the notion of science, but do not encompass science. Using other scientific standards, you can raise objection that dispute "equal validity" (still not sure what you precisely mean, so I'm going with EEP for now), and naturally you can use philosophical preferences to choose among different interpretations that are equivalent under the EEP.
One Brow said: "That's part of it. There's the bending of light around heavy objects, for example."
Yeah, so? You didn't respond to this question, which was not strictly rhetorical:
I asked: "Do you even realize how theory-laden and assumption-ridden it is to make a statement like that? Space behaves as if it's curved?"
That was the response. Think about it. Light has no rest mass we can measure, yet it bends around heavy objects. Why does a massless phenomenon react to gravity, unless gravity is changing the medium that it must pass through? There is nothing theory-laden or assumption-ridden in noting the effect of gravity on something without mass. Any furture theory of gravity will need to expain what light curves.
So, which is it, 700,000,000 miles in front of the traveller, or only 350,000,000 miles in front? The positivist answer is that the question is "meaningless." But that "answer" is what's meaningless.
Then don't use positivism.
What SR is saying is that, in terms of earth's frame, the light is only 350,000,000 miles ahead of the object. That's why we have to explain why the (faster) moving object erroneously measures light to be travelling at c, when, in fact, it is only moving at 1/2 c by our standards.
How do you prove that our measurements are accurate and theirs erroneoous? As I have said before, you need to step outside relativity to do that.
Again, one of the twins will REALLY be younger. It is not just an illusion.
Of course. The one that didn't accelerate is older.
The guy with the warped instruments and time will meaure the time and distance (speed) differently, but the distance cannot simultaneously be BOTH 350,00,000 miles AND 700,000,000 miles in "reality."
Whatever "reality" means for an arbitrary unit like "miles". You can't define that unit in such a way that both observers will give the same measurement.
Shortening my ruler will change the distance I measure from one end zone to the other on a football field, but it does not change the football field; only the ruler. The positivist wants to say that whatever I measure it to be is what it "is." Fraid not.
I would say that whatever you measure it to be is what it might as well be, regardless of what "is".
One Brow said: "Whatever "reality" means for an arbitrary unit like "miles". You can't define that unit in such a way that both observers will give the same measurement."
Sure ya can. Earth miles, that's all I mean. Meters can be converted to yards, kilometers to miles, etc. As you noted: "Of course. The one that didn't accelerate is older." Likewise, the one who didn't accelerate has the right lengths. His have NOT been shortened.
One Brow said: "I would say that whatever you measure it to be is what it might as well be, regardless of what "is".
Why would you say that? If I find out that I have laid out a football field with a defective yardstick that is only 34" long, I will change it even though I measured 94.44 yards to be 100 yards 3 times (originally) just to be sure. I will ignore my erroneous measument, not affirm and ratify it just because "that's what I measured."
I said: "GR has problems, too."
You responded: "But not in matching the experiemental data."
What data? Your personal selective data, that it? How about data from QM?
One Brow said: "Think about it. Light has no rest mass we can measure, yet it bends around heavy objects. Why does a massless phenomenon react to gravity, unless gravity is changing the medium that it must pass through? There is nothing theory-laden or assumption-ridden in noting the effect of gravity on something without mass."
1. You answered your own question, didn't you? You say a photon has no rest mass. So what? It's never at rest, so it always has mass.
2. Light has been slowed to a speed of 38 mph in extreme cold. What does that tell us about the way "space behaves?" Does anyone ever say that "space behaves" as if it is wet, when it's raining, or that "space behaves" as if it's cold when the temperature drops? Not that I've ever heard. Those features are never ascribed to space itself hauling off and "behaving" in ways it takes a notion to.
3. Are you suggesting that "space" has mass, since it is being bent by massive objects?
One Brow said: "You can always find someone with expertise who nonetheless believes the moon is really made of cheese."
Your typical way of dismissing and ignoring any issue you want to duck. Do you really think this kind of statement says anything of substance whatsoever?
One Brow said: "How do you prove that our measurements are accurate and theirs erroneoous? As I have said before, you need to step outside relativity to do that."
SR says the one who has accelerated with have it's lengths shortened. You don't have to "go outside relativy" for that. A zoologist can tell you exactly how to identify a box turtle, but he can't tell you if there's one in your backyard right now. So what?
One Brow said; "If I understand you correctly, that seems like part of the process."
What "process?" I have been trying to get you to recognize and respect the difference between experimental science and theoretical science.
Again, the rules of formal logic regarding validity will not change one iota if a given syllogism is either (1) patently unsound, or (2) indisputably sound. "Verification" or lack thereof, in no way affects the theory and it's implications. Two completely different things.
Let's say I have a moral "system" that says pleasure is the greatest good. As an illustration I say "eating strawberries is pleasurable, therefore eating strawberries is good."
You can go empirically test whether (for you) eating strawberries is pleasurable, so my system is completely subject to verification. Or is it? Strawberries are in fact irrelevant, per se, to my thesis, which is that pleasure is the greatest good. If you don't like strawberries, that just means they are "not good."
One Brow said: "But GR is not just a system on its own, it a part of physics that uses the form of a form system to develop empirical knowledge."
I find this statement to be virtually incoherent, Eric. Can you elaborate on what you mean and, perhaps, tell me how GR differs from Euclidean geometry in some important aspect that you're alluding to?
One Brow said: "How do you prove that our measurements are accurate and theirs erroneoous?"
In any number of a variety of ways, as we have previously discussed, but that's irrelevant to the point, anyway.
Suppose I flip a coin and cover it so you can't see it. Suppose it landed heads up, but you don't know it.
So what? Does your ignorance mean it's not "heads?" Does it mean it "could be tails?" It is what it is, whether you know it or not. Your personal state of enlightenment is not the standard for objective reality.
One Brow said: "Any furture theory of gravity will need to expain what light curves."
Einstein predicted curvature, but he did not attribute it to "curved space." He said it was due to variable light speed (light slows down in the presence of strong gravitational fields--which, by the way, is exactly what at least some of the neo-lorentzian relativity theories also say, as I understand them).
"...according to the general theory of relativity, the law of the constancy of the velocity of light in vacuum, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position." Albert Einstein (The General Theory of Relativity: Chapter 22)
See that? "A curvature of rays of light can only take place when the velocity of propagation of light varies with position."
I find this statement to be virtually incoherent, Eric. Can you elaborate on what you mean and, perhaps, tell me how GR differs from Euclidean geometry in some important aspect that you're alluding to?
Eucliead geometry, like much of mathematics, exists for its own sake as much as anything else.
I think that it is a relatively good approximation to truth — which is much too complicated to allow anything but approximations — that mathematical ideas originate in empirics. But, once they are conceived, the subject begins to live a peculiar life of its own and is ... governed by almost entirely aesthetical motivations. In other words, at a great distance from its empirical source, or after much "abstract" inbreeding, a mathematical subject is in danger of degeneration. Whenever this stage is reached the only remedy seems to me to be the rejuvenating return to the source: the reinjection of more or less directly empirical ideas.
A large part of mathematics which becomes useful developed with absolutely no desire to be useful, and in a situation where nobody could possibly know in what area it would become useful; and there were no general indications that it ever would be so. By and large it is uniformly true in mathematics that there is a time lapse between a mathematical discovery and the moment when it is useful; and that this lapse of time can be anything from 30 to 100 years, in some cases even more; and that the whole system seems to function without any direction, without any reference to usefulness, and without any desire to do things which are useful.
<a href="http://en.wikiquote.org/wiki/John_von_Neumann>John von Neumann</a>
Of course, there are no absolutes. Some mathematicians really care about pratical applicaitons for their work. But for most of the ones I've met, mathematics is studied for the beauty of mathematics. This meakes more sense when you consider the subject matter. Science (like physics) is a study of things you can measure, mathematics is a study of patterns, numbers, etc., things that have no extrinsic reality.
Sure ya can. Earth miles, that's all I mean.
The observer moving at .5 c will meausre his earth mile, you'll measure yours, and they will look different to each of you.
Why would you say that? If I find out that I have laid out a football field with a defective yardstick that is only 34" long,
The observer moving at .5 c does not have a defective yardstick, he has an ordinary yardstick.
What data? Your personal selective data, that it? How about data from QM?
What experimental data at the quantum level disputes GR? I'm aware that the theories, as currently structured, are not compatible. I'm not aware of any experimental data that verifies one over the other.
1. You answered your own question, didn't you? You say a photon has no rest mass. So what? It's never at rest, so it always has mass.
The attribution of mass to moving photon comes from the same relativity that says the space is curved.
2. Light has been slowed to a speed of 38 mph in extreme cold. What does that tell us about the way "space behaves?"
I think that would tell us more about how Bose-Einstein condensates behave.
3. Are you suggesting that "space" has mass, since it is being bent by massive objects?
No, I am suggesting it behaves as if the second is true, even thought the first is not.
Your typical way of dismissing and ignoring any issue you want to duck. Do you really think this kind of statement says anything of substance whatsoever?
Do really think "I found some guy with training who believes A, and even though 95% of the relevant scientific community says his reasoning is flawed, I think he's an expert" says anything substantial?
SR says the one who has accelerated with have it's lengths shortened. You don't have to "go outside relativy" for that.
Actually, you do. SR gives you differential time effects, but to apply them consistently to a non-inertial example, you need more than just vanilla SR, which does not incorporate acceleration.
What "process?" I have been trying to get you to recognize and respect the difference between experimental science and theoretical science.
There are people who specialize in the theoretical aspects of science, and those who specialize in the experiemental aspects of science. But it is all science. There is no "experimental science" that is separate from "theoretical science". It's all part of the same process.
Again, the rules of formal logic regarding validity will not change one iota if a given syllogism is either (1) patently unsound, or (2) indisputably sound. "Verification" or lack thereof, in no way affects the theory and it's implications. Two completely different things.
You are correct that this is a feature of theories in formal systems, and incorrect that this is how scientific theories operate.
Your personal state of enlightenment is not the standard for objective reality.
Of course not. Hence my use of "might as well be", as opposed to "is". I am unconcerned whatever the "true rest frame" is supposed to be. Let me know when it matters.
Einstein predicted curvature, but he did not attribute it to "curved space." He said it was due to variable light speed (light slows down in the presence of strong gravitational fields--which, by the way, is exactly what at least some of the neo-lorentzian relativity theories also say, as I understand them).
So, loght slows down more on one side of a photon than the other, making the photon change its path?
See that? "A curvature of rays of light can only take place when the velocity of propagation of light varies with position."
A curvature implies a change in direction as well as speed. Both types are changes in velocity.
One Brow said: "Do really think "I found some guy with training who believes A, and even though 95% of the relevant scientific community says his reasoning is flawed, I think he's an expert" says anything substantial?"
YOU'RE speaking for 95% of the scientific community? Did you even read the article? It was a peer-reviewed review of the existing literature with about 80 footnotes and a ton of math.
You're hopeless, Eric. You will simply believe what you want to believe and groundlessly dismiss anything and anyone who does't share your prejudices.
One Brow said: "The observer moving at .5 c will meausre his earth mile, you'll measure yours, and they will look different to each of you."
No, he won't measure an earth mile, he will measure his distorted 1/2 mile. But that aside, so what? That's what SR is about. It tells you who is WRONG in their measurments, and tells you how they should be corrected.
One Brow said: "The observer moving at .5 c will meausre his earth mile, you'll measure yours, and they will look different to each of you."
Back to the subjective "everyone is right, and all frames of reference are equally valid positon," eh? Who cares what it "looks like?" Why do you keep bringing this up? One is deluded. SR says one of the two is REALLY shortened, and one isn't. Don't you get that?
Edit: Didn't mean to quote your same words twice in the last post. Second quote should have been: "The observer moving at .5 c does not have a defective yardstick, he has an ordinary yardstick."
His yardstick is not "ordinary." It is shortened and therefore defective.
Von Neuman said: "But, once they are conceived, the subject begins to live a peculiar life of its own and is ... governed by almost entirely aesthetical motivations. In other words, at a great distance from its empirical source, or after much "abstract" inbreeding, a mathematical subject is in danger of degeneration. Whenever this stage is reached the only remedy seems to me to be the rejuvenating return to the source: the reinjection of more or less directly empirical ideas."
I suspect we read entirely different things into this. You probably think this distinguishes physics from mathmatics. I don't. I see the "life of it's own" in string theory and all kinds of theories of different dimensions and universerves, space "expanding" to avoid a speed faster than light, and all sorts of fanciful metaphysics brought on by an undisciplined interpretation of the math upon which GR (just for example) is based.
One Brow said:
3. Are you suggesting that "space" has mass, since it is being bent by massive objects?
No, I am suggesting it behaves as if the second is true, even thought the first is not.
Let me get this straight, OK? Space has no mass, but "behaves" as though it has mass, that right? Why can space do this, but not light?
Your argument was that space MUST be bent, because (you claimed) light has no mass--and, hence, presumably cannot be affected by gravity. But "space" can? How does that work, exactly?
One Brow said: "You are correct that this is a feature of theories in formal systems, and incorrect that this is how scientific theories operate."
How do they operate differently? I already asked to if you could point out an important difference between the way GR and Euclidean geometry operate. What's the difference?
One Brow said: "So, loght slows down more on one side of a photon than the other, making the photon change its path?"
I believe Al was addressing phenomena such as the Shapiro delay. We know the exact distance that a planet like Mars is from us, but when we bounce light off of it when we have to pass close to the sun to do it, there is a "delay" in the expected return time. Just another way of saying it slowed down.
Of course the "modern" interpretation is probably mostly along the line that "time slowed down," not the light. As if that makes any sense. Why would our time, on earth, slow down, just because we are observing an object with the sun between us?
There is a time delay, and Al properly saw the explanation as being that the speed of light diminished. Of course, since speed equals distance/time, you can arbitrarily (for mathematical purposes) play with either time or distance to get the answer you want. Like me saying all cars going from Chicago to New Orleans ALWAYS average 60 mph. If it's 600 miles, but a guy makes the trip in 5 hours, I simply say the distance "shrunk" to 300 miles for him while he was driving (because 5 hours at 60 mph will only take you 300 miles).
Nice little trick, even if it is completely non-sensical, eh?
One Brow said: "There is no "experimental science" that is separate from "theoretical science". It's all part of the same process."
Eric, you seem to have a unique ability to conflate and congomerate many disparate things so as to make them all "the same" (to you, that is). This comes in very handy for equivocation purposes, since you can readily present entirely different concepts as equivalent, i.e., use the same term to denote different things while (fallaciously) treating them as identical for "logical" purposes. It makes it very easy to logically prove virtually any proposition you want to advance if that is your idea of how logic works.
From the Encyclopedia Britannica:
"Empirical laws and scientific theories differ in several ways. In a law, reasonably clear observational rules are available for determining the meaning of each of its terms; thus, a law can be tested by carefully observing the things and properties referred to by these terms...
In the case of scientific theories, however, some of the terms commonly refer to things that are not observed. Thus, it is evident that theories are imaginative constructions of the human mind—the results of philosophical and aesthetic judgments as well as of observation—for they are only suggested by observational information rather than inductively generalized from it. Moreover, theories cannot ordinarily be tested and accepted on the same grounds as laws.
A theory may be characterized as a postulational system (a set of premises) from which empirical laws are deducible as theorems. Thus, it can have an abstract logical form, with axioms, formation rules, and rules for drawing deductions from the axioms, as well as definitions for empirically interpreting its symbols. In practice, however, theories are seldom structured so carefully."
http://www.britannica.com/EBchecked/topic/528971/scientific-theory
Do you understand what they're getting at? Noting regularities in nature (empirical laws) is a completely different thing than framing a theoretical explanation of those observations. The "laws" are indeed emprical, but the theory is not.
Eric, I quoted from an article in the Encyclopedia Brittanica and would like to get your response/analysis of it, but I don't even see the post anywhere, so I don't know if I'm also unable to see your response. This comment will presumably be invisible also, but I thought I'd try.
I am showing 402 comments. When I go to "401-402 of 402, I see nothing. Am I doin sumthin wrong? If you see this, and I don't maybe you can explain it to me in another thread, like ths Sloan thread, eh?
YOU'RE speaking for 95% of the scientific community? Did you even read the article? It was a peer-reviewed review of the existing literature with about 80 footnotes and a ton of math.
Peer-review isn't perfect, and I'm not sure reviews of existing literature even require peer review in many publications. Still, the article might be worth reading. Which one are you referring to here, and why do you think it's relevant?
No, he won't measure an earth mile, he will measure his distorted 1/2 mile.
How do you know which of the miles is the distorted one?
That's what SR is about. It tells you who is WRONG in their measurments, and tells you how they should be corrected.
SR tells you how the measurements are different, and how to convert one system into another. To determine which one is right or wrong, you need to use something outside SR.
Back to the subjective "everyone is right, and all frames of reference are equally valid positon," eh?
I'm not sure what you mean by "right" and "equally valid", and you have not offered a direct defintion of what you mean. The EEP says you can't distinguish between different frames under certain conditions. Under other definitions of "valid", the two frames could certinaly not be equally valid.
Who cares what it "looks like?" Why do you keep bringing this up? One is deluded. SR says one of the two is REALLY shortened, and one isn't. Don't you get that?
Well, that depends on the "valid" reference frame. For example, both could be shortened by the exact same amount.
His yardstick is not "ordinary." It is shortened and therefore defective.
Unless yours is the one that is shortened.
I suspect we read entirely different things into this. You probably think this distinguishes physics from mathmatics. I don't. I see the "life of it's own" in string theory and all kinds of theories of different dimensions and universerves, space "expanding" to avoid a speed faster than light, and all sorts of fanciful metaphysics brought on by an undisciplined interpretation of the math upon which GR (just for example) is based.
The difference is that, if we can ever find experiments that would prove or disprove string theory, and it was disproved beyond reasonable salvation, physicists would drop it. By contrast, there is no empirical standard by which a field of mathematics can be judged, so there would be no reason to drop it. When the Banach-Tarsky paradox was discovered, people did not stop using the Axiom of Choice.
Let me get this straight, OK? Space has no mass, but "behaves" as though it has mass, that right?
I'm not sure why you are saying the curvature of space is the same as space is behaving as though it has mass.
Why can space do this, but not light?
I am guessing you mean, "Why do we interpret spacetime to do this, but not light"? Light does give off a granitational field of its own, but it is not strong enough to explain the curvature of light using Newtonian equations and E=mc^2 alone.
Your argument was that space MUST be bent,
No, my argument has been and continues to be that any new theory replacing GR needs to explain why space behaves as if it is curved.
because (you claimed) light has no mass--and, hence, presumably cannot be affected by gravity. But "space" can? How does that work, exactly?
I probably overstated things if I gave you the impression light was immune to gravity.
How do they operate differently? I already asked to if you could point out an important difference between the way GR and Euclidean geometry operate. What's the difference?
Mathematical theories get abandoned when they get boring or stale. Scientific theories get altered when then stop agreeing with experiemental results, no matter how interesting or boring they may be.
I believe Al was addressing phenomena such as the Shapiro delay. We know the exact distance that a planet like Mars is from us, but when we bounce light off of it when we have to pass close to the sun to do it, there is a "delay" in the expected return time. Just another way of saying it slowed down.
Of course the "modern" interpretation is probably mostly along the line that "time slowed down," not the light. As if that makes any sense. Why would our time, on earth, slow down, just because we are observing an object with the sun between us?
Actually, it would be that gravitational time dilation. that time speeds up as gravity increases. It's not that our time slowed, but that time sped up for the radar beam, causing the delay (as near as I can determine).
Nice little trick, even if it is completely non-sensical, eh?
Since when does reality, much less desciptions thereof, need to make sense?
Eric, you seem to have a unique ability to conflate and congomerate many disparate things so as to make them all "the same" (to you, that is).
I am someone who sees the whole over empahsis on the parts. That doesn't makes the parts "the same" thing, but it clarifies what their limitations are withing the whole.
From the Encyclopedia Britannica:
I didn't see anything in the article that would dispute the notion of science being a unified process that combines empirical and theoretic methods.
Do you understand what they're getting at? Noting regularities in nature (empirical laws) is a completely different thing than framing a theoretical explanation of those observations. The "laws" are indeed emprical, but the theory is not.
I don't see "cannot ordinarily be tested and accepted on the same grounds as laws" as being equivalent to "can not be tested empirically". Im not sure why you would see it that way. Numerous theories have been discarded/replaced/heavily revised over the centuries because they failed to match empircal testing (humour theory of disease, spontaneous generation of life in dead matter, Newton's mechanics).
Eric, I quoted from an article in the Encyclopedia Brittanica and would like to get your response/analysis of it, but I don't even see the post anywhere, so I don't know if I'm also unable to see your response. This comment will presumably be invisible also, but I thought I'd try.
It was in the spam filter.
I am showing 402 comments. When I go to "401-402 of 402, I see nothing. Am I doin sumthin wrong? If you see this, and I don't maybe you can explain it to me in another thread, like ths Sloan thread, eh?
When I took your comment out of the spam filter, the comment count jumped from 403 to 405. So, it's obviously malfunctioning.
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