This is the second in a series of posts that will be reviewing and responding to the arguments of Dr. Feser's The Last Superstition. This was part 1. I haven't read many books of philosophy, and none aimed at popular audiences, so when I note that Dr. Feser starts out with a list of claims that he promises to demonstrate later, I have no idea if that is standard procedure or not. It does make the first chapter, Bad Religion, devoid of meaningful content with regard to establishing Dr. Feser's claims. However, one of the things I want to do is to in this post is list all these promises Dr. Feser makes in Chapter 1. After I review the last chapter, I will return to this list and we will see what has actually been proven.
Claims Dr. Feser says he will demonstrate
Secularism is inherently immoral and irrational, only a specific sort of religious view can be moral, rational, and sane
On intellectual grounds, atheism can not be true
Secularism can never spring from reason; its true grounding is from a willfulness and desire for it to be true
The basic metaphysical assumptions that make atheism possible are mistaken
Secular propaganda is the source of fideism
It is as impossible to say nature has no meaning or purpose as it is to square a circle (more on that below)
Secularism is parasitic on religion for all its important ideas, it is strictly a negation
What is characterized as a war between science and religion is really a war between competing metaphysical systems
The classical metaphysical picture is rationally unavoidable, and thus so is the traditional Western religious view derived from it
Given atheism and naturalism, there is no persuasive argument that allows you to trust in either reason or morality
Edit on 2009-NOV-17 to add: The abandonment of Aristotle's metaphysics has led to the abandonment of any rational or moral standards that can be used to justify moral positions, and is responsible for the curent civilizational crisis of the West.
Dr. Feser allows himself a full 241 pages in the next five chapters to accomplish all this. Of course, with so modest an undertaking, he leaves himself plenty of space to continue to denigrate atheism, secularism, the New Atheists (Dawkins, Dennett, Harris, and Hitchens), Hume, and many more in those chapters as well.
I do have a few other comments on some of Dr. Feser's remarks in chapter 1. While I still intend to avoid responding to the mere demagoguery that he indulges himself in, there are a few points that reveal interesting and noteworthy aspects of both him and his opinion of his audience.
There is nothing particularly noteworthy or striking about his claim that the less people know, they less they realize their ignorance. In fact, I read similar thoughts from a variety of science books and scientists growing up, typically along the lines of 'The more you know, the more you realize how little you know'.
I do not agree that attempts to account for phenomena such as the mind without referencing God is a religious discussion. You might as well say that attempts to account for lightning without referencing God is a religious discussion. Then again, perhaps Dr. Feser would say that. I would not be surprised at all to see him claim that any discussion of any natural phenomenon is inherently religious.
One of the common hallmarks of purveyors of woo is a sense of persecution that results from being treated equally. This comes out twice in Chapter 1, where first Dr. Feser complains that some philosophical positions distasteful to him are considered still worth discussion even when they can't be demonstrated, while the subject of religion is considered not to have made its case. Of course, the second standard is a far higher hurdle than the first, and certainly not to be awarded lightly. To imply that religion must be granted the second when other positions are granted the first, or else the supporters of the second are receiving unfair treatment, sounds very much like a persecution complex. Shortly after that, he complains that the distasteful propositions are referred to as making people think, whereas in this context religion is apparently not worthy of a moment's notice. He acknowledges that most people are raised religiously, but somehow misses the point that immersing people in thoughts they already find comfortable will be doing the opposite of making them think, it is much more likely to lull them to stupor. However, the concern seems to be for some sort of time equality, not purpose, because otherwise religious ideas are just not being treated fairly.
Dr. Feser pulls out the old saw about the desire to disbelieve in hellfire being a motivation for atheism. Oddly, I have met very few Christians who believed they, personally, were going to hell. I certainly never did, back in the day. He doesn't seem to understand the human tendency for exceptionalism, or to be deliberately ignoring it.
Dr. Feser declares that the notions of a selfish gene, or design via natural selection, can only be true and interesting if by these terms we attribute some superhuman, literal intelligence to the gene and the process. I'm not sure what to make of this. Obviously he knows the terms are metaphors that describe the complex interactions of various feedbacks mechanisms. He doesn't think that the study of feedback mechanisms is interesting, that the feedback mechanisms are not true, or that the use of metaphor makes the concept untrue or uninteresting?
Dr. Feser complains about 'Easter Bunny comparisons to God', which he disdains. This is all fine for him, but the authors upon whom he heaps this disdain are do not have the audience of his peers in mind; their books are for the general public, and often specifically the religious members thereof. The Easter Bunny example actually strikes right at the heart of what many of these people believe. If the religious group doesn't have their followers trained in the ideas of Aristotle, why should it be the job of Dennett, et. al., to train them? Later on, Dr. Feser says that this is an example of these authors not being willing to take on the real issues against the formidable opposition. With all the diminutions hurled against these authors, you would think he believe this is the appropriate level of opposition for them, but I suppose he thinks even more poorly of his fellow believers in this regard. At any rate, while I might not have the training of a Dennett, I am happy to accommodate Dr. Feser by engaging his ideas directly. Having read through Chapter 4 so far, I have not found any reason to see his presentation of reason, faith, and religion as having a superior metaphysical basis to your typical Sunday preacher.
Finally, Dr. Feser likes to make great use out of the metaphysical absurdity of square circles. He is unaware that all circles are indeed squares, under the taxicab metric (I'll devote a separate post to that). This is a problem with his metaphysical analysis that we’ll cover in more detail later. For now, let’s just say that like any other formal system, Aristotle’s metaphysics will turn out to be founded on arbitrarily chosen premises that are inherently improvable and not obviously better than a variety of alternatives as a description of reality.
Monday, October 19, 2009
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«Oldest ‹Older 1601 – 1677 of 1677He probably shoulda put himself in a box before he jumped because then he wouldn't be able to see the street comin at him, and, that way, he couldn't ever hit the street. He woulda just been floatin in space for decades.
Let's bet. Your position, as I understand it, is this:
Any and all objects in the entire universe which are on "a geodesic," irrespective of just what that particlar geodesic for any one object, all "age the same," i.e., have the same local time.
I want this question framed in a SR context. As you have put it, in that context (flat spacetime, etc.), all objects which are in any inertial frame, not necessary any "shared" inertial frame where they are both going the same speed, but ANY interial frame whatsoever, will have clocks that read the same.
That your position?
Within the context of our discussion, sure. If we are going to present this to an outside source, especially a physicist, we'll need to include more context to make the question intelligible.
Something like: "When you ignore the viewpoints of different observers and consider only the amount of time that passes locally for two clocks moving inertially, but which are moving at .6c relative to each other, does time move at the same rate for both clocks?" Do you think that is a fair question?
$10, payable Feb 28th at a mutally agreed-upon location?
What judging procedure do you suggest?
One Brow said: "If you had the knowledge you needed to understand the evidence, you would have figured out the examp[les I have presented by now."
I have figured out by now that the concepts you think you are relying on to prove your point are irrelevant, time delay, relativity of simultaneity, etc., are misguided, and have told you why.
I think I know exactly where you are making your mistake, and I have pointed it out to you. Let's just bet.
The only points of your argument I can glean are that you feel they mean SR makes no predictions (not true) and that since nat all types of motion can be treated relativistically, none of them can be (seems a little extreme).
Another way to put the question: "Two observers, each travelling in a straight line at a uniform speed without any external forces acting upon them in flat spacetime, are separating from each other at the rate of .5c.
Does SR predict that they will age the same, under those circumstances?"
If we ask the question that way, and don't qualify it at all that the answer needs to be viewpoint-independent, we will get the same type of answer we have gotten from colton, that it will look different in different viewpoints. We might get that answer anyhow, no matter how much we qualify it. Physicists tend to think empirically.
Another way: "Two cars are travelling down interstate 64. One is moving at a uniform speed of 40 mph and one at 80 mph. In other words, an hour from now, they will be an additional 40 miles apart. The two have NEVER met and synchronized watches.
Does SR predict that they will age the same, under those circumstances?"
Note that using "40 mph" and "80 mph" implies the rest frame is the ground. In that rest frame, the car traveling 80 mph ages less.
One Brow said: "Earlier, I gave you an example of two objects that left the same point in different directions, where the one in the geodeisic traveled further and faster to get to the same point."
This is wrong. It is the one not on the geodesic who travels "further and faster." The one on the geodesic does, however, experince "more time," even though it is taking the "shortest path," as I said. Which proves the point in question. Time slows down for the traveller "going faster."
When space curves, geodeisics are no longer always the shortest path between two points.
"In Riemannian geometry geodesics are not the same as "shortest curves" between two points, though the two concepts are closely related. The difference is that geodesics are only locally the shortest distance between points, and are parametrized with "constant velocity". Going the "long way round" on a great circle between two points on a sphere is a geodesic but not the shortest path between the points. The map t→t2 from the unit interval to itself gives the shortest path between 0 and 1, but is not a geodesic because the velocity of the corresponding motion of a point is not constant."
http://en.wikipedia.org/wiki/Geodesic
I am ignoring any gravitational time contraction, of course, which is not required. I am only speaking of the kinematic dilation effects.
When you are separating "gravitational time contraction" from "kinematic dilation effects", you uare using a field interpretation of GR, which is often the interpretation used to make calculations. However, when you discuss geodeisics, you are using a geometrical interpretation of GR (and SR). Under the geometrical interpretation, there are no separate effects.
Since you keep denying this also, here's yet another authoritative source:
"In 1918, Einstein described Mach's principle as a philosophical pillar of general relativity, along with the physical principle of equivalence and the mathematical pillar of general covariance. This characterization is now widely regarded as wishful thinking. Einstein was undoubtedly inspired by Mach's relational views, and he hoped that his new theory of gravitation would "secure the relativization of inertia"...The term "general relativity" is thus something of a misnomer, as pointed out by Hermann Minkowski and others. The theory does not make spacetime more relative than it was in special relativity. Just the opposite is true: the absolute space and time of Newton are retained."
http://einstein.stanford.edu/SPACETIME/spacetime2.html
I'm not sure what the part you think I am denying is. I find the wording odd. Spacetime either is or is not relative in varying ways, this does not change because we accept one theory or another, so relativity could not "make" spacetime anything. It can treat certain concepts as relative even when we can use tools outside the theory of relativity to say they are not, and make for a successful theory. Are you saying the paragraph refutes that position? I don't see how.
"One Brow said: "Riffing on the ontological implications is missing the point of K'. K' is not offered to explain ontological phenomena...
Einstien describes different effects emerging from the acceleration in K versus that in K'. If they were the same thing in his mind, he would have described them as having the same effects."
====
"But the distinction between “pseudo-gravity” and “true gravity” is precisely what Einstein denied.
The acceleration of U2 in K is not due to gravity nor to pseudo-gravity. Whether you consider the acceleration of U1 in K' to be by gravity or pseudo-gravity, it is still fundamentally different from the acceleration of U2 in K. For that matter, the stationariness of U1 in K is fundamentally different from the stationariness of U2 in K'. Any discussion of the realness of the gravitational forces in K' is not relevant to the distinction between the acceleration that occurs in K versus that of K'.
SR purportedly deals with uniform motion, not accelerated motion (although many seem to claim that accelerated motion is perfectly analyzable in SR terms). Everyone seems to concede that acceleration does NOT cause the kinematic time dilation caused by uniform motion at differing speeds.
I agree, for a given definition of acceleration. By the way, you still have not specified which of the two different meaning you are adopting, but I have been assuming you mean "deviation from a straight line and/or constant speed".
GR deals with a separate issue, i.e., accelerated motion, and calls it "gravity." Accelerated motion, or gravity, if you prefer, has its own effects on time, but these are separate and apart from, and in addition to, the kinematic effects produced by uniform motion.
In one type of interpretation.
SR predicts, as you have acknowledged, that as a object speeds up, time slows down for it. If it does NOT speed up, time will not slow down. It is not a matter of who knows what about *whether* it has actually slowed down, it is simply a matter of what will happen at higher rates of speed. As between two objects, the one travelling at the higher rate of speed will age less rapidly, and the one travelling at the lower rate of speed will age more rapidly.
Therefore, two objects, moving at different rates of speed in uniform (inertial) motion simply cannot age the same in SR. Taking an LR view, which merely posits an absolute frame of reference, such as the CMBR, they could be aging the same, because each could be going the exact same "absolute speed," and not necessarily a "different" speed. But for SR, any difference in speed in considered a true difference, because there is no absolute reference frame. In SR, two objects cannot be going the same speed if they are separating from each other. Therefore, they cannot age the same.
This all follows from the most elementary of SR principles, yet you complain that no one addresses the claims of your novel position. SR addresses them, as I have been pointing out for about 1400 posts now.
The misundestanding of SR you reveal in the preceding paragraphs is profound.
For example, "as an object speed up" not only implies acceleration, but that there is a reference frame for the previous speed of the object that is can comparitively speed up. Otherwise, how can you tell the difference between speeding up and slowing down?
Let's say you're traveling in parallel with another ship at a speed we'll call .8c. You ship hits its rockets and is now going .6c. That means time will move slower for you, compared to the other ship and what your ship was expereincing.
In the wiki example, the travelling twin ages less. With this in mind, you have nonetheless been all over the board with respect to how that result could ever be an accurate prediction.
I have? No, I don't think so.
1. Most recently, you have repeatedly and emphatically (in the most cocksure manner) insisted that SR predicts they will age the same. Even Al's bogus "GR" proof does not make this claim.
No not once have I made this claim. I have said that, to the degree that such a discussion can be made at all without referencing outside viewpoints, Pat and Chris age the same. There are fundamental differences between Pat/Chris and the twins (Stella/Terrance).
a) Neither Pat nor Chris deviates from their geodeisics. Stella deviates from a geodeisic at least three times.
b) Whether you use the view that Pat is stationary or that Chris is stationary, there are no gravitational fields needs to explain the motion of Chris or Pat. When you take the position STella is stationary, you need to invoke the field (pseudo- or otherwise) to explain the motion of Terrance.
c) Stella and Terrance are reunited at the end of the scenario, so their age difference will look the same (at least, proportionately) to all observers. Chris and pat will have different age differences for different observers.
It is a mistake to take any comments I have made about Pat/Chris and apply them to the traveling twin scenario.
2. You have previously asserted that SR says that if both insist that only the other is aging less rapidly, then both "are correct."
They are both correct within the respective coordinate frames established.
Both of these statements contradict SR predictions, but you try to draw some meaningless distinction to prove the wiki result will vary from case to case. Irrelevant claims such as "In the wiki example, one twin had red hair, in this example, neither twin has red hair, therefore the two cases are obviously different." Heh.
I did not make the first claim. The second is the standard SR prediction.
Stanford.edu said: "Einstein was undoubtedly inspired by Mach's relational views, and he hoped that his new theory of gravitation would "secure the relativization of inertia."
Note that the "relativization of inertia" would also be the "relativization of acceleration," just as the relativization of "tall" would also be the relativization of "short."
Nice try, Al, but....
The great thing about being a scientist is that you are remembered chiefly for your successes, even if your failures outnumber them.
1 outta 3 aint a complete shutout.
Even if it were, he'd be remembered for 1905 in and of iteself.
For any two point, A & B, there is a third point, C, which is halfway between them. Light signals from A and B will therefore reach C at the same time.
Wow! That's absolutely amazing! So, what does that mean?
"That means that occupants of A and B will age the same, that's what!!
No, not at all. In the traveling twin scenario, if you look at a ship that stays half-way bewteen the Stella and Terrace, it will see Stella age less than Terrance on the return journey.
Since Pat/Chris has fundamental differences from Stella/Terrance, you get a different result.
One Brow said: "Nothing that colton nor I has said implies this, and I have actively argued against."
Colton was given a problem where, like the wiki problem, it was stipulated one object was moving away from another. In (partial) response, he claimed that no one could say which one was aging less rapidly unless and until the two were brought back together. You did NOT argue against his position. On the contrary, you enthusiastically endorsed it.
Yes, that is what I meant. The position I have actively argued against was yours, not colton's.
His statement implies that the clear predictions of SR are worthless
Not at all.
and tell us nothing unless and until we can confirm the facts of each particular example where predictions come into play.
Just because you CAN compare clocks IF they come back together does NOT mean that you MUST compare clocks to know what SR predicts.
However, the predictions of SR , and GR for that matter, always take into account the viewpoint used to analyze the situation.
Nor does it mean, as your "reasoning" suggests, that because you can compare clocks if they come back together, as long as you don't compare them, SR predicts they will age the same.
You have taken reasoning specific to the Pat/Chris scenario and tried to generalize it inappropriately.
Stanford.edu said: "The theory does not make spacetime more relative than it was in special relativity. Just the opposite is true: the absolute space and time of Newton are retained."
Synge said: “The Principle of Equivalence performed theessential office of midwife at the birth of general relativity . . . I suggest that the midwife be now buried with appropriate honours and the facts of absolute space-time faced”
Denialists say: "Face the "facts" of absolute space time!? Are you NUTS, Synge!? It's a straightup LIE and you have the audacity to call it a fact!? As long as I deny it, it CAN'T be true. I got my story and I'm stickin to it, see? I and all other physicists claim otherwise. Well, maybe except for that fool Bondi. Not Minkowsi, cause he aint even a physicist, he.s a mere mathematician, and probably a poor one at that. Ya can kiss my lilly white ass if you don't like it. Moron."
I feel sorry for the denialists. I also feel sorry for the poor fools who can't tell the difference between "relativity treats this things as if they are the same" and "these things are exactly the same in reality".
"[General Relativity] was the crowning achievement of Einstein's scientific career. Its name, however, is something of a misnomer. The theory does not extend the principle of relativity for uniform motion to nonuniform motion. It retains the notion of absolute acceleration—that is, acceleration with respect to space-time rather than with respect to other bodies. In this sense, general relativity is no different from Newtonian theory or special relativity....From the point of view of modern physics, the question to what extent general relativity fulfilled Einstein's original hopes of relativizing all motion is of secondary importance."
http://science.jrank.org/pages/8034/Relativity.html
Secondary importance!? Another moronic infidel, eh? Who's startin all these slanderous lies, I wonder?
Your point being?
One Brow said: "SR predicts that different observers will see different things. However, the predictions of SR are not dependent on the existence or thoughts of observers."
OK, fair enough, but in very paragraph preceding that, you claim: "If you are talking the effects of time dilation on objects that stay in a geodeisic, it is entirely about how they look to outside observers. Time dilation effects don't become objective until two objects are so close together that the differences based on the relativity of simultaneity are overshadowed by the other relativistic effects."
Heh, and you claim *I'm* confused. Besides contradicting yourself, you are simply wrong. The "gravitational" (as opposed to kinematic) time distortion is absolute in GR. It is seen the same by all observers, or so they say.
You are confused if you think those statements contradict each other. SR does not say that two different observers in the same inertial frame standing right next to each other will see different things. It says that different observers in different reference frames will see different things. Further, these differences seen are not functions of the observers themselves, but of the underlying aspects of the motions of the observers (or their proxies). Whether there is an observer or not, that observer is awake or not, etc. does not affect what relativity theory says. That an oberserver would have a viewpoint of being in motion A or motion B compared to a scenario does effect what relativity theory says about what that observer would see, if they were present.
There is no such thing as an absolute time distortion. An oberserver passing the solar system at (1 - 0.1^100)c compared to the sun would see the GPS satellite delay as being much larger, in seconds, than an observer on earth counts for the entire revolution of the satellite.
I said: "It tells you that you have just said a "meaningless" thing, that's what. ...Anyone who pretends to have reasonable grounds to prefer one view over another is simply a parochial bigot."
Your response: "Or, is using a concept external to relativity theory, such as the conservation of mass-energy."
External to relativity theory?
"If we suppose that a particular star is sufficiently distant, then the x component of its radial velocity (which is uniform and linear) will exceed the velocity of light. Such a circumstance being forbidden, we are forced to conclude that the earth is spinning, rather than the star revolving around the earth. We see that, in this sense, the limit c can be used to imply a specific frame of reference."
http://www.angelfire.com/az3/nfold/relativity.html
You said: It tells you that you have just said a "meaningless" thing, that's what. For all that can be ABSOLUTELY PROVEN, it could simply be that the car is standing still and that interstate 64, all towns, all trees, and all other things moving with the earth are simply moving west. Since it can't be ABSOLUTELY PROVEN, no one can possibly know which is which. Anyone who pretends to have reasonable grounds to prefer one view over another is simply a parochial bigot.
There is a difference between "... the earth are simply moving west" and "the earth is spinning". Pretending to refute one with the other is sophistry.
l said: "The Einstein of 1915 implies that if two objects have two different velocities, we must regard one as having an absolutely higher velocity than the other because one object has been "really" accelerated."
You want to say: "Yet one might conjecture that if two objects move with different velocities wherein neither has a prior acceleration, then the spacetime curvature would be identical for each object and the objects' clocks would not get out of step."
Problem is: "But such a conjecture would violate the limiting case of special relativity (and hence general relativity); specifically, such a conjecture would be inconsistent with the constancy of the vacuum velocity of light in any reference frame. So then, general relativity requires that velocity differences are, in a sense, absolute."
http://www.angelfire.com/az3/nfold/relativity.html
"The commentator, Paul Conant, is a science-minded journalist with no science degrees. Though he is able to follow the technicalities of special relativity, he is not conversant with differential geometry, and hence untutored in the field equations of general relativity."
Being able to follow the technicalities does not mean he understands the underlying theory.
"The paradox stems from the fact that one cannot say which velocity is higher without a "background" reference frame. In Newtonian terms, the same issue arises: if one body is accelerating away from the other, how do we know which body experiences the "real" force? No answer is possible without more information, implying a background frame....
You could say the one departing from a geodeisic experiences the real force.
So, as I said about 1400 posts ago, the paradox is "resolved" simply by retracting the erroneous claim that generated it, to wit: He had to quit "favoring the idea that only purely relative motions are meaningful" and cave in to absolute rest, absolute motion, and absolute acceleration.
Thank goodness for science-minded journalists with no science degrees. Otherwise those darn scientists might believe all sorts of crazy things.
Two populated planets, 30 light years apart. Neither is moving with respect to the other, so, in other words, they are going the same speed, whatever it is. They have the same time frame (although certainly NOT simultaneity of events, but that is totally irrelevent; it has nothing whatsover to do with clock rates).
Joe travels from planet A to planet B, never to return. What does SR predict with respect to the aging of Joe versus the inhabitants of each planet?
It predicts that during the time he travels, Joe will age less than the inhabitants of both planets. Why? Because while he is travelling, he is moving faster than all inhabitants of both planets.
Actually, the result is the same if Joe is moving slower than the in habitants of both planets. He still ages less.
In the above example, Joe is approaching planet B and distancing himself from planet A. Due to doppler effects, the clocks on planet appear to be even slower and the ones on planet B faster.
So who will age more, while Joe is travelling, A or B? Neither, they will age the same. Why? Because they are going the same speed, and the doppler effect is totally irrelevant.
What if some guy somewhere sees it differently? Don't matter, totally irrelevant and won't change nuthin.
Agreed.
But how about Joe? Will he age more than inhabitants of one planet than the other? Stupid question, how can he age more than himself?
Agreed.
9-11-01: Some guy is hangin around on the 123rd floor of one of the twin towers, and it's gittin awful damn hot, so he decides to leave the building via the window.
He thinks to himself: "Cool! This is EXACTLY the same thing as bein in an inertial state in space." He don't think that for long, though, because once he busts himself up on the street he aint think nuthin. I guess it wasn't EXACTLY the same after all, eh? Purty close though, I betcha!
He probably shoulda put himself in a box before he jumped because then he wouldn't be able to see the street comin at him, and, that way, he couldn't ever hit the street. He woulda just been floatin in space for decades.
Your parody misses the point, as usual.
One Brow said: "Something like: "When you ignore the viewpoints of different observers and consider only the amount of time that passes locally for two clocks moving inertially, but which are moving at .6c relative to each other, does time move at the same rate for both clocks?" Do you think that is a fair question?"
Yeah, just make it an SR question, to avoid confusion. It's a bet!
One Brow said: "What judging procedure do you suggest?"
Since you only seem to believe Coloton, if Colton cares to join us, that would be a fair starting point. I don't just want a yes or no answer from him, although we could start with that. If he disagrees with me, and will join us to answer questions, if any, he may persuade me that he is right. If he doesn't, then let's look to the web, there are PLENTY of places that say what SR predicts.
One Brow said: "Something like: "When you ignore the viewpoints of different observers and consider only the amount of time that passes locally for two clocks moving inertially, but which are moving at .6c relative to each other, does time move at the same rate for both clocks?" Do you think that is a fair question?"
On second thought, this question is a little ambiguous. I don't like this phrasing, because it's not clear what is being asked: "...consider only the amount of time that passes locally for two clocks..."
Our difference was about what SR predicts, so let's just phrase it that way, e.g.:
"When you ignore the viewpoints of different observers and consider only the amount of time that passes for two clocks moving inertially, but which are moving at .6c relative to each other, does SR predict that will time move at the same rate for both clocks?"
How's that?
The only points of your argument I can glean are that you feel they mean SR makes no predictions (not true) and that since nat all types of motion can be treated relativistically, none of them can be (seems a little extreme).
That is satire, but it seems to be the implication of most of your claims. You can, of course, "treat" anything relativistically, but the mere claim that "it's all relative" says nothing, and is bascially self-contradictory.
Actually, I want to refine the question. Our discussion wasn't even about just two objects, it was about ALL objects moving inertially aging the same, and I don't want to lose the flavor of that extreme and ridiculous claim.
One Brow said: "Note that using "40 mph" and "80 mph" implies the rest frame is the ground. In that rest frame, the car traveling 80 mph ages less."
Of course, there is always an implied rest frame, in every SR and GR problem, what else is new?
One Brow said: "Going the "long way round" on a great circle between two points on a sphere is a geodesic but not the shortest path between the points. The map t→t2 from the unit interval to itself gives the shortest path between 0 and 1, but is not a geodesic because the velocity of the corresponding motion of a point is not constant."
I simply meant shortest "possible" path. I don't take this to be saying anything more than that the "shortest" path between LA and NY is a euclidean straight line which would tunnel through the earth for the most part. Do you read something more into it?
If the definition is simply the shortest possible path IF you maintain a constant speed, then that would be consistent with my elementary understanding of the geodesic concept, since it is basically designed to serve as a concept of "inertia," however bastardized.
I note that wiki also says: "In the presence of a metric, geodesics are defined to be (locally) the shortest path between points on the space."
SR and GR have "metrics" present, don't they?
"In general relativity, a geodesic generalizes the notion of a "straight line" to curved spacetime. Importantly, the world line of a particle free from all external force is a particular type of geodesic. In other words, a freely moving particle always moves along a geodesic...In theories such as special and general relativity, spacetime is treated as a Lorentzian manifold. Geodesics on a Lorentzian manifold fall into three classes according to the sign of the norm of their tangent vector. With a metric signature of (-+++) being used..."
http://en.wikipedia.org/wiki/Geodesic_(general_relativity)
Metric signature? What's that?
Anyway, that wasn't even the question. One Brow said: "Earlier, I gave you an example of two objects that left the same point in different directions, where the one in the geodeisic traveled further and faster to get to the same point."
You implied that anything on a geodesic travels "farther and faster" than any other object it eventually re-unites with. That is wrong. Are you claiming otherwise?
One Brow said: "However, when you discuss geodeisics, you are using a geometrical interpretation of GR (and SR). Under the geometrical interpretation, there are no separate effects."
I don't buy this, certainly not with SR. As far as I know there is no "geometrical" interpretation of SR. There is no graviation in SR, so why should there be?
Let's just go with Al's interpretation in his attempt to resolve the paradox, eh? He clearly used separate SR formulas for calculating the aging difference due to uniform (as opposed to accelerating) motion.
One Brow said: "The acceleration of U2 in K is not due to gravity nor to pseudo-gravity. Whether you consider the acceleration of U1 in K' to be by gravity or pseudo-gravity, it is still fundamentally different from the acceleration of U2 in K. For that matter, the stationariness of U1 in K is fundamentally different from the stationariness of U2 in K'. Any discussion of the realness of the gravitational forces in K' is not relevant to the distinction between the acceleration that occurs in K versus that of K'."
I agree with all this, which is just another reason why the so-called "identity" of the two cases is BS. But you are just giving your opinion, I thought the question was about Al's view, and you simplle denied his view, it seems.
"But the distinction between “pseudo-gravity” and “true gravity” is precisely what Einstein denied."
No problem there, most physicists do reject his view. But you can't have your cake and eat it too. You can't insist that the two can't be distinguished, and are identical cases, and deny it at the same time.
One Brow said: For example, "as an object speed up" not only implies acceleration, but that there is a reference frame for the previous speed of the object that is can comparitively speed up. Otherwise, how can you tell the difference between speeding up and slowing down?"
I don't even understand this: "Let's say you're traveling in parallel with another ship at a speed we'll call .8c. You ship hits its rockets and is now going .6c. That means time will move slower for you, compared to the other ship and what your ship was expereincing."
You're going .8c, hit your rockets and "slow down" to .6c? Who is going .8c here?
All problems and solutions of SR and GR have a reference frame. Are you claiming that a reference frame is impossible? Al freely admitted that acceleraton was "absolute" under SR, ya know?
This was NEVER any part of the bet, I hope your not claiming that it is:
One Brow said: "They are both correct within the respective coordinate frames established."
One Brow said: "No not once have I made this claim. I have said that, to the degree that such a discussion can be made at all without referencing outside viewpoints, Pat and Chris age the same."
Do I have to go back and cut and paste the 6-8 times that you emphatically said what SR predicts? Nothing can be said about anything (for example, how old you are) without some context, some "outside viewpoint." We were talking about what SR predicts, which always requires some context. The context was given in the Pat and Chris problem, as re-formulated. One has been accelerated to .6c, the other has not. The only dispute there was about whether SR/GR could would make any "predictions" if they never met again.
But our bet was not even about that problem. It was about your claim that all objects "on a geodesic" age the same.
I said: "Nor does it mean, as your "reasoning" suggests, that because you can compare clocks if they come back together, as long as you don't compare them, SR predicts they will age the same."
You have taken reasoning specific to the Pat/Chris scenario and tried to generalize it inappropriately.
Heh, it seems to me that YOU are the one making wild extrapolations. All objects on a geodesic age the same, eh?
Are you now conceding that SR makes predictions, so long as the assumptions are specified, even if the two moving objects do not re-unite?
With respect to our bet, I now see equivocation. It was about "all geodesics," including, but not limited to, straight line "geodesics" in SR (or, what amount to the same thing, flat spacetime as dealt with by GR).
I asked you about your position, and you said it was correct as it related to our discussion. However, the way you framed the question was with respect to only one problem (which should be sufficient to prove the point, but still not the bet).
One Brow said: "Being able to follow the technicalities does not mean he understands the underlying theory."
Are you DENYING that what he says is correct, or just making your obligatory ad hominem attack?
One Brow said: "Thank goodness for science-minded journalists with no science degrees. Otherwise those darn scientists might believe all sorts of crazy things."
Yeah, I bet he gave Bondi, Synge, Minkowski, and virtually every other professional philosopher/historian of physics, mathematician, astronomer, and physicist this crazy idea, eh? Or maybe he just read and understands them....naw, that would be impossible.
One Brow said: "Actually, the result is the same if Joe is moving slower than the in habitants of both planets. He still ages less."
Got an authority for that? Are you bringing in pseudo gravitation again, that it? Are you assuming that each planet moves toward him, but stay the same distance from each other, or what? This statement is simply incomprehensible. Who told you this?
Question: How could he ever travel the 30 light years between them if he was moving slower?
Are you claiming that the twins age differently in the wiki example ONLY BECAUSE they came back together? That re-uniting was the "cause" of the age difference?
Are you claiming that the acceleration in the wiki problem is the sole cause of the age difference?
If so, you should read what Al had to say about those things...he denied those were the causes.
What causes this age difference?
Or are you simply saying there is no age difference, and that wiki is simply mistaken?
January 19, 2010 1:32 PM
I said: "As I have already pointed out: SR predicts asymmetry with differing relative speeds it does NOT predict that "Pat and Chris are always the same age, as long as both stay in an inertial environment."
You said: "Since both Pat and Chris follow the geodeisic, this is exactly what it predicts.
====
January 19, 2010 6:42 PM
One Brow said: "Since both Pat and Chris follow the geodeisic, this is exactly what it predicts."
Isaid: Cite me one authority saying this is so.
colton said: It can be proven (I think I did in a class, once) that when two objects start and end at the same point in space-time (same position at the same time), if one object follows a geodesic, it will always have the greater “proper time” (time elapsed for the object).
===
January 20, 2010 10:58 AM
I said: And from that statement of Colton's, you get this!?: "[SR predicts that] Pat and Chris are always the same age, as long as both stay in an inertial environment."
You said: "In the flat space of Pat and Chris, geodeisics are inertial paths. Any object following a geodeisic will experience the maximal proper time. Therefore, Pat and Chris experience the same amount of time passing."
====
January 20, 2010 11:13 AM
I said: "Nor does it predict that they will always be running the same."
You said: "If both observers are following geodeisics, that is exactly what it predicts."
====
January 20, 2010 2:14 PM
One Brow said: "If both observers are following geodeisics, that is exactly what it predicts."
I said: "Say it a million more times. Then find an authoritative source to support your whimsical asssertions."
You said: "colton already did. It's your turn. Find an actual physicist that disagrees, and we can play dueling experts."
====
January 20, 2010 6:22 PM
I said: "...Take objects D, E, F, G, etc., ad infinitum. Progressively add 1 mph, or any fraction thereof, to the rate of its separation from A.
You can end up with an infinite number of objects all moving at different rates of speed, all uniform, all in straight lines, etc., all of which have a different local time. In every case, the faster it moves (with respect to object A, let's say), the MORE time dilation it experiences."
January 21, 2010 2:12 PM
One Brow said: "Of course, my answer is that time flows at the same rate for H as it does for A, J and all the other letters.... Of course, my answer is that time flows at the same rate for H as it does for A, J and all the other letters."
January 15, 2010 10:15 AM
You said: "...the correct answer is that, as long as Pat and Chris both stay in the geodeisic (assuming they don't approach too near a gravitational body, this will form a straight line), they age at the same rate ontologically. Neither will age faster than the other. Geodeisic travel always experiences maximal time passage."
====
January 21, 2010 10:00 AM
You said: "One way to see that Pat and Chris experience the same local time passage is to find a reference frame that at all times has the same delay in the travel of light between this third frame and Pat as between this third frame and Chris....The only observer that always sees Pat and Chris simultaneously (in this sense) sees them age at the same rate."
====
Some, but not all, of the flat assertions you have made about inertial states all having the same time, regardless of speed.
This, ultimately, is what the bet is about.
Do you NOW deny any of those positions? I am basing the bet on what you said, not what you now say you said.
The way Planck put it, if two objects are moving with respect to each other, they are equally entitled to claim that they are "at rest" with respect to empty space.
Does this mean they are NOT moving with respect to each other (forget about empty space)?
In the wiki problem, was the travelling twin moving with respect to empty space, or merely with respect to the earth?
Is there some "implied frame of reference" here, ya figure?
If someone tells me that A is taller than B and that B is taller than C, then, assuming those statements are correct, I can confidently say that A is taller than C.
Your objections would be along the following lines:
1. NO, you can't say A is taller than C. There is no absolute tall. What is tall? 5 feet? 6 feet? 1000 feet? The whole concept of tall is meaningless, and you can conclude nothing about what is tall.
2. NO, you can't say A is taller than C. You don't even know how tall A is. Is he 5 feet tall? 6 feet tall? 1000 feet tall? Since you don't KNOW that, NOTHING can be said about who is taller.
I asked: "In the wiki problem, was the travelling twin moving with respect to empty space, or merely with respect to the earth?"
If he was moving with respect to the earth, would he not also be moving with respect to "empty space?"
Remember, Al ended up saying the ether was real (although not in a strict lorentzian sense). Al also admitted that SR relied absolute acceleration and the newtonian concept of "inertia" (non acceleration). If acceleration is absolute, the inertia must be also. Physicists and philosophers of science will tell you, and you have apparetly agreed to this, that:
"the theory does not make spacetime more relative than it was in special relativity. Just the opposite is true: the absolute space and time of Newton are retained."
Your comment: "I'm not sure what the part you think I am denying is."
GR ends up using "spacetime" as the absolute reference frame that Newton called absolute space. You consistentlyl deny this in your claims, even if you admit it when it comes to lip service.
The "motion" in GR is motion with respect to spacetime, not other objects, get it?
Four people, all different heights, ranging from 5' 11" to six feet tall, walking down the street. Two are walking next to each other, and are approaching the other two who are 1/2 mile away. For all concerned, the guy next to them looks taller than the two in the distance.
Since they have not met yet does that mean none can be either "really" taller or "really shorter" than the ones they are approaching? In other words, what the hell does the fact that they are not standing side-by-side have to do with their height?
A square table top may look "unsquare" from different distances and angles. Does that mean that it's corners do not "really" form right angles and that all it's sides are not "really" the same length? It may "look" square from only a limited number of perspectives, but does that change it's angles and dimensions?
I don't think so! Homey don't play dat.
Yet, again, lip service to the contrary notwithistanding, you think you can refute every assertion by claiming that some other guy can see it differently, with the implication that therefore there is no "fact of the matter," no objective reality, and that any claim to the contrary is meaningless. Well, unless the statement in question happens to be made by wiki, maybe.
1. Meaningless question: A guy is floating, all alone in space. Who is he moving faster than?
2. NOT a meaningless question, even if you don't know the answer. Two guys, in space, are moving apart from each other. Who is "really" moving? At least one of them has to be. Who is moving faster? With respect to what? I don't care, pick something useful: The CMBR, the "absolute" speed of light, spacetime, a distant galaxy, whatever. But remember, the question will not then become "how does it look from a distant galaxy." If the two objects are the earth and the sun, then the question is as between those two objects. The question is whether the the sun is "really" moving across the sky, or just "appears" to do so because of the earth's rotation.
Again, Planck's statement that each is entitled to say he is "at rest" with respect to empty space does not, and cannot, mean that each IS, ontologically, at rest with respect to empty space, whether each, or either, knows it, or not.
Obiously, SR does NOT purport to answer the question of which one is "really" moving. No one ever claimed that it did. But once it is posited that one is moving SR makes predictions based on that. Without some informational input, SR predicts NOTHING. It does not NEED to know which one is "really" moving to make predictions (although it needs other specific information in every case), but if "it" does know, then it can give specific answers.
The only reason two observers can both see the other's clock as moving more slowly than theirs it precisely, and ONLY, because they are not moving at the same rate of speed. If they were, then no time difference would appear. There would be no "slower" or "faster" clock. Because they each see the other's clock as running at a different rate, you know that they are moving with respect to each other, whether either or both is moving with respect to the sun, or Cairo, Egypt, or not.
But we know you deny all this. As long as they are inertial, they will see no time difference between themselves, whatever the relative speed between them. That's what our bet is about.
I said: "The only reason two observers can both see the other's clock as moving more slowly than theirs it precisely, and ONLY, because they are not moving at the same rate of speed."
I don't want to say it every time I address the same issue we have been addressing for about 1400 posts now. When I say "only" I am of course talking about kinematic time dilation only. Just assume that's the context, unless I say otherwise.
You talk about a "geometric" interpretation which says time distortion due to speed and gravitation are "the same." Any support for, or particular article addressing, this supposed difference? I have never seen any mainstream physicist claim they are caused by the "same thing" (although some alternate theories may suggest this).
Whatever their particular "interpretation," they all say the two effects have different causes and physical explanations. By "geometrical interpretation" are you simply saying that, when doin math problems, there is no need to treat them differently, or what? A sample from wiki:
"According to the theory of relativity, due to their constant movement and height relative to the Earth-centered, non-rotating approximately inertial reference frame, the clocks on the satellites are affected by their speed... For example, the relativistic time slowing due to the speed of the satellite of about 1 part in 1010... <--- speed dilation
"The effect of gravitational frequency shift on the GPS system due to general relativity is that a clock closer to a massive object will be slower than a clock farther away." <--- gravitational frequency shift, an entirely different phenomenon.
http://en.wikipedia.org/wiki/Global_Positioning_System#Relativity
I have read a little more about geodesics (more than I ever cared to read) and now see how formal, abstract, definitional, and non-physical these notions are. I also see that one who thinks only in these terms can lose all touch with the relevant physics (as opposed to the math) and easily confuse himself.
You have apparently been talking at times about ways to arrive at "proper time" and/or "proper length." These concepts are simply SR's way of "absolutizing" time and distance, but have nothing to do with relative motion per se.
Of the many possible spacetime paths between two "events" (and this is the only comparison being made, i.e., between "events," and NOT between moving observers) the one which records the "maximum proper time" (for a "timelike," and opposed to a "spacelike" geodesic) is the one which has maintained a constant velocity, and is hence "inertial."
In the context of the wiki twin paradox problem, let's say the "two events" are (1) the event of the traveller blasting off, and (2) the event of the traveller returning to earth. The question is now who "really" accelerated, the earth, or the traveller, because that will tell us who aged less. In this case, the earth twin experienced "more time" and is therefore "on," or at least closer to, a geodesic spacetime path, than the traveller, according to the definition of geodesic. So the earth maintained "constant velocity" while the traveller accelerated, using the definition of a (timelike) geodesic.
Of course, this is a completely backwards way of looking at it. The traveller is known to have been accelerated because they loaded up his ship with rocker fuel and blasted his ass off into space, NOT because, on return, he experienced less time.
Any claim that you can only know who has been accelerated is by bringing the two together and then seeing who has expericed less time is pure bullshhit. In SR, the reason we know that he has experienced "less time" is precisely because SR says that the faster an object moves, the more time slows down for that object. Without that premise (which is necessary for the speed of light to be constant as measured from all frames moving inertially, even when travelling at different relative speeds) is the ONLY reason it is speculated that there is any "age difference" to begin with.
One thing that a geodesic is NOT, is what you have been claiming that it is, i.e., representive of the same time frame for all inertial observers, irrespective of the relative motion between them. Only objects with NO relative motion between them age the same. Of course, as I said at the beginning of this particular discussion, that is immediately obvious to anyone who understands and applies the most elementary principles of SR to the question.
Simply put, SR predicts that:
1. Observers who are not moving with respect to each other (regardless of distance between them) will age at the same rate.
2. Observers who ARE moving with respect to each other (regardless of distance between them) will NOT age at the same rate.
These predictions hold whether or not any two such observers ever have, or ever will, be at the same place at the same time.
The question of whether two objects will age at the same RATE is entirely different than the question of who is ABSOLUTELY older. Just like the question of which of two people is "taller" is entirely different than the question of who is ABSOLUTELY tall.
With respect to the concept of a "geodesic" path indicating who has maintained "constant velocity," that is a merely a question of "proper time," as specially defined by relativity. Whether a object departing from the geodesic speeds up or slows down, it will experience less "proper time," which merely tells you that it has been "accelerated" (including the notion of "decleration"). So, ultimately, the concept of geodesic merely defines "inertia" and has nothing to do with either a higher or lower relative speed, per se. It merely tells you which one has moved at a non-constant velocity. It does not really tell you who has "aged more rapidly," it just tells you who has changed speeds. It is the one who travels at a relatively higher speed that ages less rapidly, and that could be the one "on the geodesic" when the nongeodesic object has slowed down rather than speeded up.
As with any other concept, the use of the same term ("geodesic" in this case) does not mean that the reference is necessarily to the same thing. With respect to the center of gravity between the earth and the sun, the earth is "on a geodesic." With respect to the center of gravity between a "free falling" earth satellite and the earth itself, the satellite is "on a geodesic." They are not one and the same "geodesic," and, needless to say, they are not moving uniformly with respect to each other. They therefore do not share the same time local time frame and do not age the same.
I said: "It is the one who travels at a relatively higher speed that ages less rapidly, and that could be the one "on the geodesic" when the nongeodesic object has slowed down rather than speeded up."
An example: Two objects (1) the earth and (2) a spaceship loaded with fuel are on the same (earth/sun) geodesic. The ship blasts off (leaves that particular geodesic). Right after blastoff it collides with a meteor and loses all acceleration. If it could magically then just hold it's place (it couldn't, but just if) a year later the earth would pass by it. Under those circumstance, the earth would have "aged less" (experienced less time) than the ship, because, relative to the satellite, the earth has been moving (at a "constant velocity" according to GR) while the satellite has been "at rest." The earth has obviously been "moving faster" because it has been moving (that it has been moving at a "constant velocity" is irrelevant), while the satellite has been at rest.
I have no doubt that you will disagree with this, of course, because you have, among other things, confused "maximum proper time on a timelike geodesic" with the relative speed between two objects.
Getting back to "proper length" and "proper time" as I understand them now:
If I want to measure a foot, then I can put a ruler down on a piece of paper and make a pencil mark at each end of it. This will give me two marks, one foot apart, on the piece of paper.
But his will not work if the ruler is moving while I make my marks. Between the time I make the first and second marks it will have moved, and my marks will therefore be more or less than one foot apart.
So what is a "proper foot" when dealing with two frames which are NOT motionless with respect to each other? Well, you can always find some accelerated object from whose perspective it will "appear" that I have made my marks at the same time, even if I haven't from my perspective. However a foot is measured in that particular accelerated (with respect to me) is now a "proper foot."
But one can't always find an accelerated viewpoint from which two event appear to be simultaneous if the two events are widely separted in time, if not in space. For example, take event 1 to be Jack the Ripper cuttin some ho in London 150 years ago, and event 2 to be a guy smokin a joint on a street corner right now 1 mile away from from where Jack smoked the ho 150 years ago. There is an accelerated perspective from which the two locations can appear to be the "same place," i.e., not spatially separated. (I didn't take the time to understand how this could be the case, but I read that it is, and I'm just reciting what I thought I read like a monkey). So, now, from the perspective of one who see the two locations as the "same place," his measurement of the time passed between the two events is called the "proper time" (this is apparently called a "spacelike" interval between the two events).
But the point is this: The calculation of "proper time" and "proper length" does not relate to the relativistic different between two frames with different times (for example (1) me, "at rest" with pencil in hand, and (2) a moving ruler). Therefore defining a "geodesic," using "proper time" or "least distance" for purposes of designating which of two objects is moving with constant velocity (inertially) really has no direct relationship to the relative motion of the two objects in originally in question (me and the ruler).
That said, I trust that, with respect to me, standing next to the highway, and a guy in a car going 100 mph down the highway, SR would say that it is me, not the car driver, who is "on a geodesic" (unaccelerated).
Again, the point to note here are:
1. If you tell me two people are "not the same height" I know that one is taller than the other, even if I have no clue which one is taller.
2. You don't need any of the mathematical/tautological/semanitcal gobbledygook to understand, conceptually, that the faster an object moves, the more time will slow down. That follows conceptually, with no math whatsoever, from the fundamental postulate in both SR and GR that the speed of light appears the same to all observers irrespective of their relative motion.
What also follows is even though two observers are both maintaining a "constant velocity" (are on a geodesic path) they will NOT age the same, unless it so happens that the speed they are maintaining is itself equal.
The fact that the choice of words or definitions does not change physical facts is made all the more apparent when you consider that in both SR and classical mechanics the path of the earth around the sun is NOT a geodesic. It is "accelerated" because, although it's speed is constant, it's velocity is not because it is constantly changing direction, Whether you call the earth's orbit a "geodesic" or not does not, and cannot, change the course or nature of it's motion through space.
I have already pointed all of this out, but it might be worth doing again. Both Newton and SR say that a "particle" is "inertial" if:
1. It is "free" (i.e., not being acted upon by an external force) and
2. Unaccelerated, which means it is moving at a constant velocity, which means that:
(a) it is not changing direction (i.e., it is moving in a straight line) AND
(b) it is not changing its speed, but rather maintaining a uniform speed.
With GR, Al wanted to maintain the essence of this notion, but, because of his equivalency principle, he also wanted the concept of "inertia" to describe a "free falling" body in a gravitational field. So, now what?
Well, he's gotta change SR and Newton in at least two ways, because, under them, a particle in orbit is not "free" (it is influenced by the force of gravity) and it is not moving in a straight line.
Well, OK, then, let's do this: We will say that (a) gravity is not a force, and (b) that a curved path is basically a "straight line" (we'll call a curved straight line a "geodisic," and say it is the shortest "possible" path through spacetime. That should cover it.
An equivocator's DREAM! If he wants to dispute any claim about inertia, acceleration, and/or force made in the context of SR/Newton, he uses the GR defintion of such terms. Conversely, if he wants to dispute any claim with respect to those same terms made in a GR context, he uses an SR defintion of them.
SWEET! Let the equivocation and quibbling begin!
I said: "An equivocator's DREAM!"
Notice that Al himself was not above using equivocation in an attempt to make two distinct situations somehow seem "identical."
Remember, the whole discussion is in terms of SR. The critic sets up frames K and K' prime in the context of SR, and Al then admits, that in the context of SR, the asymmetrical time result is a problem (or at least would be, if SR dealt with it, which Al says it doesn't):
===
Critic: Surely even the most devoted followers of the theory will not assert that in the case of two clocks that have been positioned side by side, each one is running behind the other.
Al: Your last assertion is of course undisputable. However, the reason that that line of argument as a whole is untenable is that according to the special theory of relativity the coordinate systems K and K' are by no means equivalent systems. Indeed this theory asserts only the equivalence of all Galilean (unaccelerated) coordinate systems, that is, coordinate systems relative to which sufficiently isolated, material points move in straight lines and uniformly. K is such a coordinate system, but not the system K', that is accelerated from time to time. Therefore, from the result that after the motion to and fro the clock U2 is running behind U1, no contradiction can be constructed against the principles of the theory.
===
So where is Al now in his dialogue with his critics? He is going to treat half of his critic's hypothetical, i.e., frame K, as an SR situation, and the other half, frame K', as a GR problem: "While the proceedings as seen from system K can be regarded as above [as regarded in SR], a totally different picture [when using GR] presents itself as seen from K', as can be seen from the following comparison:"
Comparison? Hmmm. SR has no gravity. Why not treat BOTH frame K and K' in a GR context, if that's what you want to switch to? This creates a number of false appearances, which Al doesn't seem to mind at all. As just one example, consider this:
In frame K' he has clock U1 in a gravitational "free fall." By GR definitions, this would seemingly be an inertial (unaccelerated) state because it is on a "geodesic" path. And, yet, to maintain the appearance of identity between the invalid "comparison" he says the clock U1 in frame K' prime is "accelerated" (which it is, in SR terms). He says: "Clock U1 is accelerated in free fall...."
contintued in next post...
He says: "Clock U1 is accelerated in free fall...."
Such a statement appears oxymoronic in GR, which he is supposedly using here. And, of course, in Newtonian terms it would not be in "free fall" either, not in the sense that it would be "free" from external forces, because gravity is a force in that context.
But is the phrase "accelerated in free fall" really oxymoronic? Hard to say, for sure, because the whole concept is equivocal. The very nature of gravity, in Newtonian terms, is to constantly accelerate objects it acts upon. It does NOT keep them in a state of uniform velocity, it accelerates them. Al wants to say that an object in orbit is in "free fall" is unaccelerated, and to also say that such a situation is "identical to" the situation of an object free from all gravitation in outer space. But the latter is NOT being affected by gravity. He is in flat spacetime, moving in a straight line at a constant speed, with no external forces acting upon him. A guy falling off a building IS accelerated, i.e., he is NOT maintaining a uniform speed like an orbiting satellite might be; his speed in increasing with every passing second. Al wants to say that an object in orbit maintains "constant velocity" (a change in neither speed nor direction--just like a free particle in space), but he can do so only by denying the "force" of gravity. The guy in orbit is affected by gravity, however you want to characterize it, but the "free particle" in outer space is not. How can the two states be "identical?"
So ultimately, even within GR, there is the equivocation between SR (in situations where flat spacetime occurs) and the *special* definition of acceleration used in GR (i.e., in situations where "curved space" appears). Totally different defintions apply in the two situations, yet Al treats it as though it is all the same.
I said: "Notice that Al himself was not above using equivocation in an attempt to make two distinct situations somehow seem "identical."
Al's own words on the topic: "It should be kept in mind that in the left and in the right section exactly the same proceedings are described, it is just that the description on the left relates to the coordinate system K, the description on the right relates to the coordinate system K'."
I also said: "Remember, the whole discussion is in terms of SR. The critic sets up frames K and K' prime in the context of SR..."
With this last statement of Al's, he again acts as though the K and K' frames, which were established by the critic in terms of an SR question, are the same K and K' prime frames the critic established, but they aint.
As I also said before, what Al tries (unsuccessfully, according to his critics) to do with the EP in connection with his attempt to make GR a "theory of relative motion," as well as a theory of gravity is to claim, in effect, that all accelerated states are inertial and that all inertial frames are accelerated, i.e., that there is no real distinction between the two.
Nice try, Al.
For those who want to defend the Einstien version of the EP, drastic changes from Al's conception of it must be made.
Al started by talking about about guys in a small, enclosed, lab in orbiting (or not orbiting, either way) in space doing non-gravitational experiments.
These days, the "lab" is now space so infintesimal that no matter (only point particles) can fit into it. But it don't stop there, the time must also be so limited that no experiments of meaning can possibly be done. According to the math guy, even the 10 seconds it takes to use modern detectors of acceleration is WAY too long. Not only must the space be infintesimal, but also the time.
It's kinda like sayin that if I take a picture of a hot Babe and put it in a frame on my desk, the Babe in the picture don't move. Well, Duh...
What kinda spacetime has no time and no space? Well, I guess it's the Parmenidean kind, eh?
Every accelerated frame can be reduced to an SR frame if you take a picture of it. Well, now, aint that special?
So, then, Eric, is we is or is we aint gunna bet?
Let's bet!
I think so. However, there is something I want to clear up first, specifically that I have consistently maintained the time passage is the same when you completely disregard viewpoints entirely, and you have now made a statement that viewpoints are built-in in some fashion, or something like that. I would mention it briefly, but I know how much you hate it when I only look at part of your responses, and I don't have three hours right now to devote to responding to everything.
Menwhile, I do want the bet judged by a person who can respond to questions. How about you select any physicist who is a member of scienceblogs? They should be sufficiently knowledgeable and neutral for both our tastes. I also know there are one or two over at SABDB, but you might think they were biased.
One Brow said: "However, there is something I want to clear up first, specifically that I have consistently maintained the time passage is the same when you completely disregard viewpoints entirely, and you have now made a statement that viewpoints are built-in in some fashion, or something like that."
Well, I simply don't know what you mean by "completely disregard viewpoints." To say an object is "on a geodesic," for example, requires a "viewpoint." No statement at all about anything at all can be made without a "viewpoint."
My way of putting the question might be something like this:
Assume the following:
1. Flat spacetime where SR is sufficient to provide an answer;
2. Two separate objects, each on a geodesic (i.e., an inertial state):
3. The two objects are in motion with respect to each other.
Assuming the above, will time pass at the same rate for both objects?
Note: The question is NOT asking how an observer on object a, object b, or some other object c will perceive it. It is simply asking whether time passage will be the same for all objects in inertial motion, irrespective of any relative speed difference between them.
One Brow said: "I also know there are one or two over at SABDB, but you might think they were biased."
I can get authoritative sources from all over the web, but I think you would probably just misinterpret them to support your viewpoint, no matter what they said. Pick a guy of your choosing, so long as he appears qualified, from SABDB (whatever that is) and let's start there. If one of us not satisfied with the answers and explanations he gives, then the burden will be on them to come up with support for the contrary view. Is the question, as posed above, sufficiently free from "viewpoints" to suit you?
Back to Al for a second:
Critic: "...would anyone get it in his head to actually use the possibility offered by the theory of relativity to relate the motions of the celestial bodies of the solar system to a geocentric coordinate system that on top of that is participating in the rotation of the Earth? Would anyone really be allowed to see this coordinate system as "at rest" and as equally valid, relative to which the fixed stars are tearing around with tremendous speed? Doesn't such an approach collide head on with common sense, and with the demand of economy of thought?"
In response, Al says: "Nobody will use a coordinate system that is at rest relative to the planet Earth, because that would be impractical. However as a matter of principle such a theory of relativity is equally valid as any other. The situation, that the fixed stars are circling with tremendous velocities, when one bases an examination on such a coordinate system, does not constitute an argument against the admissibility, but merely against the efficiency of this choice of coordinates..."
Don't zakly sound right, does it? There IS a good argument against ADMISSIBILITY (not merely against the "efficiency") of a geocentric universe. Well, inadmissible in the context of SR/GR, anyway, because the distant stars would have to far exceed the speed of light to rotate around the earth every 24 hours, know what I'm sayin?
That Al, he's sucha card, eh!?
That phrase, "equally valid" has such an appealing, egalitarian ring to it, ya know? Could maybe be the basis of a whole school of philosophy, called "relativism," or sumthin like that. When it comes to philosophy, who cares about common sense or facts, know what I mean? That aint even the point:
Critic: "I really don't see why for the sake of some conceptual preference - namely for the concept of relativity - one ought to accept the burden of such gruesome complications and calculational difficulties."
Al: "There are several reasons that compel us to willingly accept the complications that the theory leads us to. In the first place, it means for a man who maintains consistency of thought a great satisfaction to see that the concept of absolute motion, to which kinematically no meaning can be attributed, does not have to enter physics."
The goal of philosophy is simply to attain "great satisfaction," I figure. Who needs stupid-ass facts, I ax ya?
I said: "An equivocator's DREAM! If he wants to dispute any claim about inertia, acceleration, and/or force made in the context of SR/Newton, he uses the GR defintion of such terms. Conversely, if he wants to dispute any claim with respect to those same terms made in a GR context, he uses an SR defintion of them."
Of course he will deny that there is any difference between the two (flat and curved spacetime) and insist that it is all one "theory of relativity." When you refuse to acknowledge valid and meaningful distinctions between phrases and ideas, just about any ole claim is possible!
I betcha Al done studied up good on that old-ass Greek sophist, Protagoras, ya know?
He said: "Man is the measure of all things; of them that is, that they is; of them that aint, that they aint."
And, of course: "The same wind that feels warm to one guy feels cool to another."
Critic: "But isn't this gravitational field merely fictitious? Its existence is conjured up by a mere choice of coordinate system. Surely, real gravitational fields are brought forth by mass, and cannot be made to disappear by a suitable choice of coordinate system. How are we supposed to believe that a merely fictitious field could have such an influence on the pace of a clock?"
Al slaughters this jerk with this here comeback, eh?: "In the first place I must point out that the distinction real - unreal is hardly helpful."
Reality, it kinda bites, sho nuff.
I expect to be putting together a response Sunday morning.
Our difference was about what SR predicts, so let's just phrase it that way, e.g.:
"When you ignore the viewpoints of different observers and consider only the amount of time that passes for two clocks moving inertially, but which are moving at .6c relative to each other, does SR predict that will time move at the same rate for both clocks?"
How's that?
Good for me.
One Brow: The only points of your argument I can glean are that you feel they mean SR makes no predictions (not true) and that since nat all types of motion can be treated relativistically, none of them can be (seems a little extreme).
That is satire, but it seems to be the implication of most of your claims.
However, I have not been saying anything of the sort.
Actually, I want to refine the question. Our discussion wasn't even about just two objects, it was about ALL objects moving inertially aging the same, and I don't want to lose the flavor of that extreme and ridiculous claim.
"When you ignore the viewpoints of different observers and consider only the amount of time that passes for any number of clocks, each of which is moving inertially, but which are at rest relative to any other clock, does SR predict that will time move at the same rate for all clocks?"
That about it?
Of course, there is always an implied rest frame, in every SR and GR problem, what else is new?
Rest frames need to be specified for answers to be meaningful. It would be like giving coordiantes for a ball on a lot with noting the coordinate axes and unit length. They are not implied.
I simply meant shortest "possible" path. I don't take this to be saying anything more than that the "shortest" path between LA and NY is a euclidean straight line which would tunnel through the earth for the most part. Do you read something more into it?
If the definition is simply the shortest possible path IF you maintain a constant speed, then that would be consistent with my elementary understanding of the geodesic concept, since it is basically designed to serve as a concept of "inertia," however bastardized.
A geodesic is the shortest local path in the metric of spacetime (which uses both length and duration to calculate distance).
I note that wiki also says: "In the presence of a metric, geodesics are defined to be (locally) the shortest path between points on the space."
SR and GR have "metrics" present, don't they?
Yes, they are four-dimensional metrics.
Metric signature? What's that?
It refers to the way duration is calculated into distance in relativity theory, which is different from how lengths are calculated into distance.
Anyway, that wasn't even the question. One Brow said: "Earlier, I gave you an example of two objects that left the same point in different directions, where the one in the geodeisic traveled further and faster to get to the same point."
You implied that anything on a geodesic travels "farther and faster" than any other object it eventually re-unites with.
I was referring to one particular object in one particular example, not "anything on a geodeisic".
One Brow said: "However, when you discuss geodeisics, you are using a geometrical interpretation of GR (and SR). Under the geometrical interpretation, there are no separate effects."
I don't buy this, certainly not with SR. As far as I know there is no "geometrical" interpretation of SR. There is no graviation in SR, so why should there be?
Minkowski space is a geometric interpretation of SR.
http://en.wikipedia.org/wiki/Minkowski_space
Let's just go with Al's interpretation in his attempt to resolve the paradox, eh? He clearly used separate SR formulas for calculating the aging difference due to uniform (as opposed to accelerating) motion.
If you find it too confusing too look at geometrical interpretations, OK. However, the geometric inerpretations can help provide a commonality and clarity to what might seem arbitrary in field interpretations.
One Brow said: "The acceleration of U2 in K is not due to gravity nor to pseudo-gravity. Whether you consider the acceleration of U1 in K' to be by gravity or pseudo-gravity, it is still fundamentally different from the acceleration of U2 in K. For that matter, the stationariness of U1 in K is fundamentally different from the stationariness of U2 in K'. Any discussion of the realness of the gravitational forces in K' is not relevant to the distinction between the acceleration that occurs in K versus that of K'."
I agree with all this, which is just another reason why the so-called "identity" of the two cases is BS. But you are just giving your opinion, I thought the question was about Al's view, and you simplle denied his view, it seems.
"But the distinction between “pseudo-gravity” and “true gravity” is precisely what Einstein denied."
No problem there, most physicists do reject his view. But you can't have your cake and eat it too. You can't insist that the two can't be distinguished, and are identical cases, and deny it at the same time.
However, I can say that, while when looking at aspects of the physics of the situation outside relativity you can find significant differences between saying the effect is from gravity or pseudo-gravity, nonetheless when you look ar the aspects of the physics to which relativity theory addresses itself, there is no difference. I have been saying that for many pages now. If I have a steel plate that is 2.5000003 cm wide, and another pipe that is 2.5000002 cm wide, and all I am using to compare them is a ruler marked to the nearest cm, I can say that I can't tell the difference between the pipes, or which is wider. This doesn't mean the pipes are the same size, it just means I need a defferent measuring tool. Similarly, just because relatitivity theory does not see a difference does not mean the difference is invisible to all aspects of physics.
One Brow said: For example, "as an object speed up" not only implies acceleration, but that there is a reference frame for the previous speed of the object that is can comparitively speed up. Otherwise, how can you tell the difference between speeding up and slowing down?"
I don't even understand this: "Let's say you're traveling in parallel with another ship at a speed we'll call .8c. You ship hits its rockets and is now going .6c. That means time will move slower for you, compared to the other ship and what your ship was expereincing."
You're going .8c, hit your rockets and "slow down" to .6c? Who is going .8c here?
You rocket is going .8c, and hits "retro-rockets", if you like, to slow down to .6c.
All problems and solutions of SR and GR have a reference frame. Are you claiming that a reference frame is impossible? Al freely admitted that acceleraton was "absolute" under SR, ya know?
Acceleration is the change in velocity. If you label one point on a number line 5, and the other point 3, the distance between them is 2. If instead you call the first point 11, and the second 9, the distance is still 2. The distance can be absolute even if the position is not. Similarly, acceleration can be absolute even if speed is not.
This was NEVER any part of the bet, I hope your not claiming that it is:
One Brow said: "They are both correct within the respective coordinate frames established."
One Brow said: "No not once have I made this claim. I have said that, to the degree that such a discussion can be made at all without referencing outside viewpoints, Pat and Chris age the same."
Do I have to go back and cut and paste the 6-8 times that you emphatically said what SR predicts?
Feel free. I will be happy to reply by posting 10-12 times, with timestamps, where I specifically made the qualification that this statement is qualified and made without referencing outside viewpoints, going back to the point where I said it could be done at all.
Nothing can be said about anything (for example, how old you are) without some context, some "outside viewpoint." We were talking about what SR predicts, which always requires some context. The context was given in the Pat and Chris problem, as re-formulated. One has been accelerated to .6c, the other has not.
No. In basic Pat/Chris, neither has been accelerated.
The only dispute there was about whether SR/GR could would make any "predictions" if they never met again.
But our bet was not even about that problem. It was about your claim that all objects "on a geodesic" age the same.
To the degree that this can be said without adopting the viewpoint of a specific observer, yes.
I said: "Nor does it mean, as your "reasoning" suggests, that because you can compare clocks if they come back together, as long as you don't compare them, SR predicts they will age the same."
You have taken reasoning specific to the Pat/Chris scenario and tried to generalize it inappropriately.
Heh, it seems to me that YOU are the one making wild extrapolations. All objects on a geodesic age the same, eh?
Are you now conceding that SR makes predictions, so long as the assumptions are specified, even if the two moving objects do not re-unite?
SR does make predictions, but due to the relativity of simultaneity, they are not the sort of predictions that allow you to say "Pat is older" or "Chris is older" without first specifying a viewpoint. When I say that objects on a geodeisic all age at the same rate in some viewpoint-independent sense, this actually makes no predictions. YOu need a viewpoint to make predictions.
With respect to our bet, I now see equivocation. It was about "all geodesics," including, but not limited to, straight line "geodesics" in SR (or, what amount to the same thing, flat spacetime as dealt with by GR).
I asked you about your position, and you said it was correct as it related to our discussion. However, the way you framed the question was with respect to only one problem (which should be sufficient to prove the point, but still not the bet).
I have re-phrased it above.
One Brow said: "Being able to follow the technicalities does not mean he understands the underlying theory."
Are you DENYING that what he says is correct, or just making your obligatory ad hominem attack?
I think he is mis-interpreting the meaning of the claims of the 1915 Einstein. For example, "That principle (actually, introduced prior to 1915) said that there was no real difference between kinematic acceleration and gravitational acceleration. Scientifically, they should be treated as if they are the same." Is not correct. Acceleration due to gravity is very different from kinematic acceleration. It is non-acceleration within a gravitational field that is the same as kinematic acceleration.
Yeah, I bet he gave Bondi, Synge, Minkowski, and virtually every other professional philosopher/historian of physics, mathematician, astronomer, and physicist this crazy idea, eh? Or maybe he just read and understands them....naw, that would be impossible.
It's possible, but it's not true. Conant does not describe the views of Bondi, Synge, Minkowski, etc.
One Brow said: "Actually, the result is the same if Joe is moving slower than the in habitants of both planets. He still ages less."
Got an authority for that?
It's basic to the problem. Joe leaves the geodeisic, Joe will experience less time.
Are you bringing in pseudo gravitation again, that it?
no.
Are you assuming that each planet moves toward him, but stay the same distance from each other, or what?
No.
This statement is simply incomprehensible. Who told you this?
It's an elementary result of the SR equations.
Question: How could he ever travel the 30 light years between them if he was moving slower?
By going from the one in front to the one in back. He would have to move slower to do that.
Are you claiming that the twins age differently in the wiki example ONLY BECAUSE they came back together? That re-uniting was the "cause" of the age difference?
This is the only time you can meaningfully compare their age differences.
Are you claiming that the acceleration in the wiki problem is the sole cause of the age difference?
I'm not sure what "sole cause" means. The acceleration of Stella causes her to leave the geodeisic, and leaving the geodeisic means she ages less when when they are reunited.
If so, you should read what Al had to say about those things...he denied those were the causes.
What causes this age difference?
Taking differing paths in spacetime.
Or are you simply saying there is no age difference, and that wiki is simply mistaken?
No.
...
Some, but not all, of the flat assertions you have made about inertial states all having the same time, regardless of speed.
This, ultimately, is what the bet is about.
If you insist on their being a single ontological answer, the correct answer is that, as long as Pat and Chris both stay in the geodeisic (assuming they don't approach too near a gravitational body, this will form a straight line), they age at the same rate ontologically.
January 15, 2010 10:15 AM
Yes, this is what the bet is about. The the result that comes from insisting their be a single ontological answer, which must therefore be viewpoint-free. Trying to bring in implied viewpoints now is sophistry. Do you accept the revised statement, or not?
Do you NOW deny any of those positions?
No.
I am basing the bet on what you said, not what you now say you said.
So am I. I have been clear and consistent throughout that the statements were viewpoint-independent. I did not mention it every single time, but did bring it up regularly. If you misunderstood, you did.
If you want to return viewpoints back into the questions, then the answer becomes that Pat and Chris will age at different rates for different viewpoints, and no one viewpoint will be more correct.
The way Planck put it, if two objects are moving with respect to each other, they are equally entitled to claim that they are "at rest" with respect to empty space.
Does this mean they are NOT moving with respect to each other (forget about empty space)?
No.
In the wiki problem, was the travelling twin moving with respect to empty space, or merely with respect to the earth?
Both, assuming conservation of mass-energy.
Is there some "implied frame of reference" here, ya figure?
No. Any frame that preserves mass-energy will be an equally valid way to analyze the twin scenario.
If someone tells me that A is taller than B and that B is taller than C, then, assuming those statements are correct, I can confidently say that A is taller than C.
Agreed.
Your objections would be along the following lines:
1. NO, you can't say A is taller than C. There is no absolute tall. What is tall? 5 feet? 6 feet? 1000 feet? The whole concept of tall is meaningless, and you can conclude nothing about what is tall.
2. NO, you can't say A is taller than C. You don't even know how tall A is. Is he 5 feet tall? 6 feet tall? 1000 feet tall? Since you don't KNOW that, NOTHING can be said about who is taller.
Incorrect.
I asked: "In the wiki problem, was the travelling twin moving with respect to empty space, or merely with respect to the earth?"
If he was moving with respect to the earth, would he not also be moving with respect to "empty space?"
If you assume earth is at rest compared to empty space.
Remember, Al ended up saying the ether was real (although not in a strict lorentzian sense).
Evidence, please, where Einstein says ether is real in a not-strict-Lorentzian sense.
Al also admitted that SR relied absolute acceleration and the newtonian concept of "inertia" (non acceleration).
SR has no mechanism to relativize acceleration.
If acceleration is absolute, the inertia must be also. Physicists and philosophers of science will tell you, and you have apparetly agreed to this, that:
"the theory does not make spacetime more relative than it was in special relativity. Just the opposite is true: the absolute space and time of Newton are retained."
I don't recall agreeing to that.
Your comment: "I'm not sure what the part you think I am denying is."
GR ends up using "spacetime" as the absolute reference frame that Newton called absolute space. You consistentlyl deny this in your claims, even if you admit it when it comes to lip service.
Spacetime is an object, not a reference frame. Your sentence has no meaning.
The "motion" in GR is motion with respect to spacetime, not other objects, get it?
How can you tell if you are moving with respect to spacetime? What does that mean?
Four people, all different heights, ranging from 5' 11" to six feet tall, walking down the street. Two are walking next to each other, and are approaching the other two who are 1/2 mile away. For all concerned, the guy next to them looks taller than the two in the distance.
Since they have not met yet does that mean none can be either "really" taller or "really shorter" than the ones they are approaching? In other words, what the hell does the fact that they are not standing side-by-side have to do with their height?
Nothing.
A square table top may look "unsquare" from different distances and angles. Does that mean that it's corners do not "really" form right angles and that all it's sides are not "really" the same length? It may "look" square from only a limited number of perspectives, but does that change it's angles and dimensions?
OK. Can you come up wtih something relevant now?
Yet, again, lip service to the contrary notwithistanding, you think you can refute every assertion by claiming that some other guy can see it differently, with the implication that therefore there is no "fact of the matter," no objective reality, and that any claim to the contrary is meaningless. Well, unless the statement in question happens to be made by wiki, maybe.
Noting that some quantities are relative by their nature is not the same as refuting "every assertion by claiming that some other guy can see it differently".
1. Meaningless question: A guy is floating, all alone in space. Who is he moving faster than?
2. NOT a meaningless question, even if you don't know the answer. Two guys, in space, are moving apart from each other. Who is "really" moving? At least one of them has to be.
For that questions to be meaningful, you have to define what it is to be '"really" moving'. I am still waiting on your definition.
Who is moving faster? With respect to what? I don't care, pick something useful: The CMBR,
Is moving in all directions at the same time.
the "absolute" speed of light,
Looks the same to both guys.
spacetime,
how can you determine the motion of spacetime?
a distant galaxy,
Which one? One guy might be a rest compared to galaxy A, the other at rest compared to galaxy B, and both in motion compared to galaxy C. How does that determine who is '"really" moving'?
whatever. But remember, the question will not then become "how does it look from a distant galaxy." If the two objects are the earth and the sun, then the question is as between those two objects. The question is whether the the sun is "really" moving across the sky, or just "appears" to do so because of the earth's rotation.
Conservation of mass-energy allows us to say that the earth is rotating. How does conservation of mass-energy apply to the two guys moving in space?
Again, Planck's statement that each is entitled to say he is "at rest" with respect to empty space does not, and cannot, mean that each IS, ontologically, at rest with respect to empty space, whether each, or either, knows it, or not.
Correct. Planck's statement refers to the ability to select coordinate systems, aka frames of reference; it does not refer to some viewpoint-independent ontology.
Obiously, SR does NOT purport to answer the question of which one is "really" moving. No one ever claimed that it did. But once it is posited that one is moving SR makes predictions based on that.
Agreed. Once you select the viewpoint, you get an answer based on that viewpoint.
Without some informational input, SR predicts NOTHING. It does not NEED to know which one is "really" moving to make predictions (although it needs other specific information in every case), but if "it" does know, then it can give specific answers.
Agreed.
The only reason two observers can both see the other's clock as moving more slowly than theirs it precisely, and ONLY, because they are not moving at the same rate of speed. If they were, then no time difference would appear. There would be no "slower" or "faster" clock.
Same rate of speed compared to what? In any case, this is not correct. As long as they are moving relative to each other, each will see the other's clock as slower even if their speed is the same.
Because they each see the other's clock as running at a different rate, you know that they are moving with respect to each other, whether either or both is moving with respect to the sun, or Cairo, Egypt, or not.
Of course.
But we know you deny all this. As long as they are inertial, they will see no time difference between themselves, whatever the relative speed between them. That's what our bet is about.
No, I never said anything of the kind. In fact, you were insistent that I not talk about what they see.
I said: "The only reason two observers can both see the other's clock as moving more slowly than theirs it precisely, and ONLY, because they are not moving at the same rate of speed."
I don't want to say it every time I address the same issue we have been addressing for about 1400 posts now. When I say "only" I am of course talking about kinematic time dilation only. Just assume that's the context, unless I say otherwise.
You mean, the way you will assume a statement that refers only to ontology, and not to what is observed, will only apply to ontology, and not to observations?
You talk about a "geometric" interpretation which says time distortion due to speed and gravitation are "the same." Any support for, or particular article addressing, this supposed difference? I have never seen any mainstream physicist claim they are caused by the "same thing" (although some alternate theories may suggest this).
I don't recall saying they were "caused by the same thing", that implies a field interpretation for starters. I said under the geometric interpretation they were the same effect.
Though Ray clearly attempts to account wholly for the dilation and asymmetry by appeal to SR, what is unclear is how this reliance on the triplets’ differences in direction establishes an asymmetrical relationship among them. If we recall that SR (and GR as well) holds that the longest proper time interval between timelike events is a geodesic, and that SR spacetime is flat, then these facts of the case, in combination with a postulate that time is unidirectional for all inertial frames, do suffice to distinguish one triplet from the others in the required manner, which presumably is what Ray alludes to in his remark about the significantly distinct directions of the triplets’ spacetime travels. This is because only one triplet can occupy the unique geodesic connecting the earliest event of encounter (by all three inertial frames) with the latest; the worldlines of the other two siblings are, in combination, necessarily longer in connecting these events ([6], p. 46). Therefore, the corresponding combined proper time interval of these latter two triplets is necessarily shorter than that of the other sibling occupying the requisite geodesic ([4], pp. 156-158 nicely develops this path-integral inequality).
http://www.manitowoc.uwc.edu/staff/awhite/ray.htm
Also, look at this:
http://www.physicspost.com/articles.php?articleId=101&page=17
Whatever their particular "interpretation," they all say the two effects have different causes and physical explanations. By "geometrical interpretation" are you simply saying that, when doin math problems, there is no need to treat them differently, or what? A sample from wiki:
"According to the theory of relativity, due to their constant movement and height relative to the Earth-centered, non-rotating approximately inertial reference frame, the clocks on the satellites are affected by their speed... For example, the relativistic time slowing due to the speed of the satellite of about 1 part in 1010... <--- speed dilation
"The effect of gravitational frequency shift on the GPS system due to general relativity is that a clock closer to a massive object will be slower than a clock farther away." <--- gravitational frequency shift, an entirely different phenomenon.
http://en.wikipedia.org/wiki/Global_Positioning_System#Relativity
Different in one interpretation, the same in another.
I have read a little more about geodesics (more than I ever cared to read) and now see how formal, abstract, definitional, and non-physical these notions are. I also see that one who thinks only in these terms can lose all touch with the relevant physics (as opposed to the math) and easily confuse himself.
Geodesics do require quite a bit of formal and abstractional ability to be understood properly, but so does Euclidean geometry. They do not cause one ot lose touch with the relevant physics, they are carefully honed descriptions of that physics.
You have apparently been talking at times about ways to arrive at "proper time" and/or "proper length." These concepts are simply SR's way of "absolutizing" time and distance, but have nothing to do with relative motion per se.
Actually, they are waysi of *localizing* time and and distance.
Of the many possible spacetime paths between two "events" (and this is the only comparison being made, i.e., between "events," and NOT between moving observers)
What does the existence of actual observers have to do with this?
the one which records the "maximum proper time" (for a "timelike," and opposed to a "spacelike" geodesic) is the one which has maintained a constant velocity, and is hence "inertial."
The velocity does not need to be constant.
Of course, this is a completely backwards way of looking at it. The traveller is known to have been accelerated because they loaded up his ship with rocker fuel and blasted his ass off into space, NOT because, on return, he experienced less time.
You are confusing one way of determining a geodesic (maximal time passage) with the effects of staying on a geodesic. The maximal time passage does not define the geodesic, it is a consequence of it.
Any claim that you can only know who has been accelerated is by bringing the two together and then seeing who has expericed less time is pure bullshhit. In SR, the reason we know that he has experienced "less time" is precisely because SR says that the faster an object moves, the more time slows down for that object. Without that premise (which is necessary for the speed of light to be constant as measured from all frames moving inertially, even when travelling at different relative speeds) is the ONLY reason it is speculated that there is any "age difference" to begin with.
Relativity theory also says that objects which change their inertia to move slower will experience less time than those that do not.
One thing that a geodesic is NOT, is what you have been claiming that it is, i.e., representive of the same time frame for all inertial observers, irrespective of the relative motion between them.
I have made no such claim. Any comments about equal time passage along geodesics were ontological, not observer-oriented.
Only objects with NO relative motion between them age the same.
Untrue. Would you like an example?
Of course, as I said at the beginning of this particular discussion, that is immediately obvious to anyone who understands and applies the most elementary principles of SR to the question.
You seem to think the most elementary principles are the most fundamental principles, and perhaps the only ones.
Simply put, SR predicts that:
1. Observers who are not moving with respect to each other (regardless of distance between them) will age at the same rate.
Agreed.
2. Observers who ARE moving with respect to each other (regardless of distance between them) will NOT age at the same rate.
Incorrect.
These predictions hold whether or not any two such observers ever have, or ever will, be at the same place at the same time.
Ofteimes this will preclude any observation at all of your points.
The question of whether two objects will age at the same RATE is entirely different than the question of who is ABSOLUTELY older. Just like the question of which of two people is "taller" is entirely different than the question of who is ABSOLUTELY tall.
OK.
With respect to the concept of a "geodesic" path indicating who has maintained "constant velocity," that is a merely a question of "proper time," as specially defined by relativity. Whether a object departing from the geodesic speeds up or slows down, it will experience less "proper time," which merely tells you that it has been "accelerated" (including the notion of "decleration"). So, ultimately, the concept of geodesic merely defines "inertia" and has nothing to do with either a higher or lower relative speed, per se. It merely tells you which one has moved at a non-constant velocity. It does not really tell you who has "aged more rapidly," it just tells you who has changed speeds. It is the one who travels at a relatively higher speed that ages less rapidly, and that could be the one "on the geodesic" when the nongeodesic object has slowed down rather than speeded up.
Whether they move faster or slower, the object that leaves the geodesic will age less.
As with any other concept, the use of the same term ("geodesic" in this case) does not mean that the reference is necessarily to the same thing. With respect to the center of gravity between the earth and the sun, the earth is "on a geodesic." With respect to the center of gravity between a "free falling" earth satellite and the earth itself, the satellite is "on a geodesic." They are not one and the same "geodesic," and, needless to say, they are not moving uniformly with respect to each other. They therefore do not share the same time local time frame and do not age the same.
What does it mean to discuss the "local time frame" of the earth? Do you realize, in your example, this is not the same thing as the time frame of a person on the surface of the earth? That you are comparing numbers sing different coordinate systems? This whole paragraph is highly confused.
An example: Two objects (1) the earth and (2) a spaceship loaded with fuel are on the same (earth/sun) geodesic. The ship blasts off (leaves that particular geodesic). Right after blastoff it collides with a meteor and loses all acceleration. If it could magically then just hold it's place (it couldn't, but just if) a year later the earth would pass by it. Under those circumstance, the earth would have "aged less" (experienced less time) than the ship, because, relative to the satellite, the earth has been moving (at a "constant velocity" according to GR) while the satellite has been "at rest." The earth has obviously been "moving faster" because it has been moving (that it has been moving at a "constant velocity" is irrelevant), while the satellite has been at rest.
You are incorrect. The ship would be following the path of higher energy, and experience less time.
I have no doubt that you will disagree with this, of course, because you have, among other things, confused "maximum proper time on a timelike geodesic" with the relative speed between two objects.
The confusion is not mine.
Getting back to "proper length" and "proper time" as I understand them now:
If I want to measure a foot, then I can put a ruler down on a piece of paper and make a pencil mark at each end of it. This will give me two marks, one foot apart, on the piece of paper.
But his will not work if the ruler is moving while I make my marks. Between the time I make the first and second marks it will have moved, and my marks will therefore be more or less than one foot apart.
So what is a "proper foot" when dealing with two frames which are NOT motionless with respect to each other? Well, you can always find some accelerated object from whose perspective it will "appear" that I have made my marks at the same time, even if I haven't from my perspective.
Incorrect. Some intervals are timelike.
However a foot is measured in that particular accelerated (with respect to me) is now a "proper foot."
But one can't always find an accelerated viewpoint from which two event appear to be simultaneous if the two events are widely separted in time, if not in space. For example, take event 1 to be Jack the Ripper cuttin some ho in London 150 years ago, and event 2 to be a guy smokin a joint on a street corner right now 1 mile away from from where Jack smoked the ho 150 years ago. There is an accelerated perspective from which the two locations can appear to be the "same place," i.e., not spatially separated. (I didn't take the time to understand how this could be the case, but I read that it is, and I'm just reciting what I thought I read like a monkey). So, now, from the perspective of one who see the two locations as the "same place," his measurement of the time passed between the two events is called the "proper time" (this is apparently called a "spacelike" interval between the two events).
But the point is this: The calculation of "proper time" and "proper length" does not relate to the relativistic different between two frames with different times (for example (1) me, "at rest" with pencil in hand, and (2) a moving ruler). Therefore defining a "geodesic," using "proper time" or "least distance" for purposes of designating which of two objects is moving with constant velocity (inertially) really has no direct relationship to the relative motion of the two objects in originally in question (me and the ruler).
That said, I trust that, with respect to me, standing next to the highway, and a guy in a car going 100 mph down the highway, SR would say that it is me, not the car driver, who is "on a geodesic" (unaccelerated).
Actually, you are both unaccelerated.
Again, the point to note here are:
1. If you tell me two people are "not the same height" I know that one is taller than the other, even if I have no clue which one is taller.
2. You don't need any of the mathematical/tautological/semanitcal gobbledygook to understand, conceptually, that the faster an object moves, the more time will slow down. That follows conceptually, with no math whatsoever, from the fundamental postulate in both SR and GR that the speed of light appears the same to all observers irrespective of their relative motion.
Except the reality is more complicated. Even looking strctly at SR, you can slow down and still experience less time.
What also follows is even though two observers are both maintaining a "constant velocity" (are on a geodesic path) they will NOT age the same, unless it so happens that the speed they are maintaining is itself equal.
The fact that the choice of words or definitions does not change physical facts is made all the more apparent when you consider that in both SR and classical mechanics the path of the earth around the sun is NOT a geodesic. It is "accelerated" because, although it's speed is constant, it's velocity is not because it is constantly changing direction, Whether you call the earth's orbit a "geodesic" or not does not, and cannot, change the course or nature of it's motion through space.
In classical mechanics, the earth's orbit is indeed a geodesic. It is not a geodesic in SR-only because SR does not account for curved space. The term "geodesic" change the course of the earth, but it does describe it.
SWEET! Let the equivocation and quibbling begin!
Why do think I have hounding you to stick to specific defintions? One the defnitions are claified, the seeming equivocations cease and real discussion can begin.
Comparison? Hmmm. SR has no gravity. Why not treat BOTH frame K and K' in a GR context, if that's what you want to switch to?
SR is GR. When you use SR, you are using GR.
He says: "Clock U1 is accelerated in free fall...."
Such a statement appears oxymoronic in GR, which he is supposedly using here. And, of course, in Newtonian terms it would not be in "free fall" either, not in the sense that it would be "free" from external forces, because gravity is a force in that context.
This dialogue does have some confusing terminology. It should not be a surprise, considering this is very early in the development of relativity theory.
So ultimately, even within GR, there is the equivocation between SR (in situations where flat spacetime occurs) and the *special* definition of acceleration used in GR (i.e., in situations where "curved space" appears). Totally different defintions apply in the two situations, yet Al treats it as though it is all the same.
They are the same in very specific ways, and different in other ways.
I said: "Notice that Al himself was not above using equivocation in an attempt to make two distinct situations somehow seem "identical."
Al's own words on the topic: "It should be kept in mind that in the left and in the right section exactly the same proceedings are described, it is just that the description on the left relates to the coordinate system K, the description on the right relates to the coordinate system K'."
I also said: "Remember, the whole discussion is in terms of SR. The critic sets up frames K and K' prime in the context of SR..."
With this last statement of Al's, he again acts as though the K and K' frames, which were established by the critic in terms of an SR question, are the same K and K' prime frames the critic established, but they aint.
Because the K' of the critic is not an accurate description of the system. Einstien corrects the K' of the critic.
These days, the "lab" is now space so infintesimal that no matter (only point particles) can fit into it. But it don't stop there, the time must also be so limited that no experiments of meaning can possibly be done. According to the math guy, even the 10 seconds it takes to use modern detectors of acceleration is WAY too long. Not only must the space be infintesimal, but also the time.
You are confused on what "local" means.
Let's bet!
OK. I'm wiling to bet on the statement above.
One Brow said: "However, there is something I want to clear up first, specifically that I have consistently maintained the time passage is the same when you completely disregard viewpoints entirely, and you have now made a statement that viewpoints are built-in in some fashion, or something like that."
Well, I simply don't know what you mean by "completely disregard viewpoints." To say an object is "on a geodesic," for example, requires a "viewpoint."
No. An object on a geodesic would be on a geodesic regardless of viewpoint. It is viewpoint-independent.
No statement at all about anything at all can be made without a "viewpoint."
????
My way of putting the question might be something like this:
Assume the following:
1. Flat spacetime where SR is sufficient to provide an answer;
2. Two separate objects, each on a geodesic (i.e., an inertial state):
3. The two objects are in motion with respect to each other.
Assuming the above, will time pass at the same rate for both objects?
Note: The question is NOT asking how an observer on object a, object b, or some other object c will perceive it. It is simply asking whether time passage will be the same for all objects in inertial motion, irrespective of any relative speed difference between them.
I'm fine with that, as well. $10?
One Brow said: "I also know there are one or two over at SABDB, but you might think they were biased."
I can get authoritative sources from all over the web, but I think you would probably just misinterpret them to support your viewpoint, no matter what they said.
Funny, I was thinking the same thing about you.
Pick a guy of your choosing, so long as he appears qualified, from SABDB (whatever that is) and let's start there. If one of us not satisfied with the answers and explanations he gives, then the burden will be on them to come up with support for the contrary view. Is the question, as posed above, sufficiently free from "viewpoints" to suit you?
I opened a thread, we'll see if any volunteers show up. "Support for the contrary view" must be from a physicist who reads the question and answers it. Agreed?
Don't zakly sound right, does it? There IS a good argument against ADMISSIBILITY (not merely against the "efficiency") of a geocentric universe. Well, inadmissible in the context of SR/GR, anyway, because the distant stars would have to far exceed the speed of light to rotate around the earth every 24 hours, know what I'm sayin?
That Al, he's sucha card, eh!?
That is why he changed his view.
The goal of philosophy is simply to attain "great satisfaction," I figure. Who needs stupid-ass facts, I ax ya?
If you can come to the same description with A as without A, most scientists choose to go without A.
Of course he will deny that there is any difference between the two (flat and curved spacetime) and insist that it is all one "theory of relativity."
More correctly, "flat" is a special case of "cuirved".
Critic: "But isn't this gravitational field merely fictitious? Its existence is conjured up by a mere choice of coordinate system. Surely, real gravitational fields are brought forth by mass, and cannot be made to disappear by a suitable choice of coordinate system. How are we supposed to believe that a merely fictitious field could have such an influence on the pace of a clock?"
Al slaughters this jerk with this here comeback, eh?: "In the first place I must point out that the distinction real - unreal is hardly helpful."
Reality, it kinda bites, sho nuff.
Indeed.
colton finally got tired of waiting for his colleague. His reponses are bolded.
From: colton
To: One Brow
(I have to same, one funny thing about this is that I don't know which side of the argument is yours, and which side is aints.)
For Colton:
1. As one website put it: "One of the fundamental results of Albert Einstein's special theory of relativity is a phenomenon known as time dilation. Simply put, this result states that time moves more slowly for a moving object than it does for an object at rest."
http://physics.suite101.com/article.cfm ... z0amGd0GVD
First, that "Simply put" statement is way too much of a simplification. A much more accurate statement would be "Simply put, this result states that a stationary object will observe time moving more slowly for a moving object than for its own stationary reference frame."
One Brow wrote:
The wiki article quotes Einstein himself making the same point where he talks about a living organism making a long journey at near the speed of light.
In light of those summaries, is it fair, in your opinion, to say:
1. P & C pass each other at the relative speed of .6c and neither accelerates or decelerates for the next 20 years.
2. P sees himself as at rest,
3. C sees himself as at rest.
Assume P is right. Relative to C, at least, he is in fact at rest. C is therefore WRONG.
C WILL BE younger, even if he thinks P is younger, and even if they never meet again.
This seems very similar to something you wrote before, which I already responded to. What do you mean by, "C will be younger"? Younger as measured by whom? Answer: C will be younger, as measured by himself.
One Brow wrote:
====
Assume C is right. Relative to P, at least, he is in fact at rest. P is therefore WRONG.
P WILL BE younger, even if he thinks C is younger, and even if they never meet again.
Again what do you mean by "P will be younger"? Younger as measured by whom? Answer: P will be younger, as measured by himself.
One Brow wrote:
4. In neither case are P and C "both correct" or "equally correct" in their mutually exclusive assumptions.
5. All that is a simple matter of SR/GR theory. Those theories do NOT say "both are correct." On the contrary, both theories say "both CANNOT be correct, one MUST be incorrect."
What you seem to be missing, is that when you ask the question "Who is younger," you must specify "younger as measured by whom?" C will measure himself as being younger. On the other hand, P will measure himself as being younger. And, on the gripping hand (nod to Larry Niven), someone in-between the two, let’s say on a "stationary" position watching them both move past, one from left to right and the other from right to left, will measure P and C as both being the same age.
Therefore it is indeed fine to say that "both are equally correct".
One Brow wrote:
Clarification for Colton.
a. The questions are with respect to the statements made in 4. and 5.
b. In this context, "younger" simply means "will have aged less in the intervening 20 years."
20 years as measured by whom? When C thinks 20 years has passed for himself, he will think much less time than that has passed for P. When P thinks 20 years has passed for himself, he will think much less time than that has passed for C.
That’s at the heart of relativity: time is relative! There is no absolute clock that can determine when 20 years has passed for the universe. You seem to be assuming that there is such an absolute clock, but that’s a bad assumption.
colton, part 2
One Brow wrote:
c. In 5, "both" means both simultaneously, not both in alternative scenarios. In other words, in any one particular case at least one must be wrong (probably both) when they "assume" they are "at rest." Put another way, neither SR nor GR allows for the proposition that (1) both are at rest in a given case and (2) they nonetheless "see" themselves as separating at the speed of .6c.
They are each at rest relative to themselves. They are each moving relative to the other. They each measure the other one as aging less than themselves. Each one is correct in his own frame.
One Brow wrote:
Another question for Colton:
Colton, you say: "To see which is "really younger", you would have to bring the two people into the same frame, next to each other."
Why would you "have to" bring the two together?
I know you clarify below, but to answer that quickly, it’s because of what I said above: there is no universal clock that tells you what the time is everywhere in the universe. You can’t say, "OK, right now it’s 20 years later!" So, if you want to see how old the two are, you have to specify how old are the two *as measured by what frame of reference*. In one frame of reference, the observer will measure C to be older. In another frame of reference, a different observer might measure P to be older, So, if you want to say which one is "really" older, in some absolute sort of way, then you’ll have to make both of them agree on the measuring frame of reference. The only way to do that, that I can think of, is to have them both in the same frame of reference. I.e., you’ll have to bring them together.
One Brow wrote:
Let me ask a similar question, phrased in a slightly different way.
Assume that Earthlings send travellers into space at a speed that eventually reaches (and then maintains) .5c. Assume that, at blast-off, all parties (earthlings and travellers) agree that, relative to the earth, the spaceship has been accelerated. The spaceship continues to travel for 20 years, by which time it has left the solar system.
No party has any reason to believe that the spaceship has slowed down or speeded up or has reversed course and started to return to earth.
If, after 20 years, all parties calculate their own age, relative to the other, using SR precepts and formulas, and all parties still (rightfully) assume that the spaceship is moving away from the earth (and NOT that earth and the solar system are moving away from the ship), will they all agree that the travelling twins have aged less than their earth counterparts in the intervening time?
Why are you suddenly talking about *calculating* an age? (Maybe that was a slip on your part.) We’ve been talking about *measuring* an age. That is, the earthlings use a telescope to look at the travelers, and observe how old the travelers have become. They use that to know how old the travelers are (they would probably need to compensate for the time it took light to travel, but that’s a different effect). They would say that the travelers are younger than themselves.
Meanwhile, the travelers do the same exact thing: they use a telescope to look back at the earth, and observe how old the earthlings have become. They would say that the earthlings are younger than themselves.
If you’re asking, could the travelers calculate how old the people on earth think the travelers have become? Sure, but that’s not the same as saying "Would the travelers think that they have aged less than the earth counterparts?" The answer to that question is no, the travelers would *measure* the earthlings to be younger than themselves, so they would think that their earth counterparts had aged less than themselves.
colton, part 3
One Brow wrote:
If your answer is "yes," then would the travellers "have to" return to earth before you could say they are "really" younger than their counterparts on earth?
Replace it with: If your answer is "yes, they would still have to return to earth before you could say they are really younger," could you explain why? Is it because the theoretical predictions of SR are simply unreliable, or some other reason?
I think you meant to replace the second-to-last paragraph with the last paragraph. Regardless, the answer was "No", not "Yes". Hopefully I’ve made the point about needing to specify which frame of reference the measurement will be made in.
One Brow wrote:
For Colton:
In his "dialogue," where Einstein claims he "completely clears up the paradox that you brought up," doesn't his analysis stop short?
Here's what I mean: In the SR frame (K) clock U1 remains "at rest" from an SR standpoint, and hence, given SR predictions, records more passage of time. He then goes on to "demonstrate" (using frame K') that if you imagine magically-appearing and disappearing pseudo-gravitational fields, during which clock U2 was "not moving" (yet accelerated) clock U1 would STILL record more passage of time. This is because the gravitational field would have ADDED a substantial amount of time to the now-travelling clock (clock U1). This does not change the strictly SR calculations for each clock, however; it just more than offsets them.
Bottom line seems to be: GR will agree with SR predictions about the greater/lesser degree of time passage.
Yes, I agree so far, if I'm understanding you correctly. U1 records more passage of time, so it is "older" and U2 is "younger". Both reference frames agree on that. (And note, relative to the comments I made in my last PM, that we can talk absolutely about which is younger because the two end up in the same references frame at the end of the events.)
One Brow wrote:
But the "bottom line" would go both ways, wouldn't it? SR would also predict that clock U2 would record less time if IT had been the one accelerated (changed reference frames).
If, in frame K, clock U2 had been chosen as the moving clock, then U2 (not U1) would have been "younger." Using Einstein's analysis (in reverse) GR would also agree with THIS conclusion.
Sorry, I didn't follow that. In frame K, clock U2 *is* the moving clock, and is therefore "younger".
One Brow wrote:
GR would therefore agree with the conclusion that clock U1 is "younger" whether "moving" or not AND the conclusion that clock U2 would be younger, whether "moving" or not. See what I'm getting at?
No, I missed something. Why are you saying that GR agrees that U1 is younger?
One Brow wrote:
Put another way, SR says that whichever clock is the one "moving" (as can be detected by, and hence confirmed by, the inertial forces felt at turn-around) will be "younger." GR agrees with that, if you take Einstein at his word.
GR doesn't agree with that, the way you said it there. In the GR frame, U1 is moving and U2 is stationary. But U2 ends up younger, because of the effect of the gravitational field. Specifically, during stage three of the process, U2 is at a lower gravitational potential energy, and therefore ages substantially less. That more than makes up for the other periods of time, where U1 is moving (and aging less).
One Brow wrote:
Have I asked this in a way that you understand the question, and the point?
I'm afraid probably not.
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