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 1201 – 1400 of 1677 Newer› Newest»I generally agree with the distinction you are making between not having weight through a lack of gravity and the sensation of weightlessness in orbit (which is free-fall). However, locally, you can't detect such a difference.
You completely bypassed my explanation that your explicitly requested regarding why people don't perceive the effects of free-fall acceleration like they do other means of acceleration. Are you still considering it? Are you understanding why the floating wine glass matters in that discussion?
AintNoThang: But again, they are not truly in "free fall," they are merely being accelerated at high speeds in a direction perpendicular to the earth IN ADDITION to being subjected to gravity).
This is not correct. The only acceleration on an orbiting body is the downward acceleration of gravity. Unless the orbit needs to be corrected for some reason, there would be no acceleration perpendicular to that. There is the effect of inertia perpendicular to the acceleration of gravity, but that effect is not an acceleration.
AintNoThang: ... then you MUST say that an object is free fall is being accelerated, whether one feels a resistance to that acceleration (i.e., feels weight) or not.
We don't disagree that in K'. U1 is being accelerated. Where we disagree is whether U1 is in an inertial environment (one that behaves as if it were inertial). That is, we disagree whether U1 can detect acceleration locally.
AintNoThang: The question was simply about whether a person can detect acceleration caused by gravity alone (free fall). Sudden shifts in acceleration (as Einstein has in his example) can, and are routinely, detected by anyone with senses.
What sense will detect acceleration by free-fall within the local environment? How does that detection happen?
AintNoThang: How can a person go FROM a state free fall INTO a state of free fall?
If all you are are doing is examining the effects of adopting K and K', this is irrelevant.
AintNoThang: Now we have two opposing forces, each supposedly putting him in "free fall." Can his change of direction and speed be detected?
Locally, no, because in this example both forces are gravitaitonal, so they both operate on all objects in the local environment identically. There is no puching of any object against another because of these gravitational effects.
An outside observer would detect it.
AintNoThang: Yeah, and this was the whole point of the "Stella turn-around" where she "doesn't move" during the turn-around.
Stella, in the equivalent of K', counters the graviational force with rocket propulsion, not a second gravitational force. Even though, to an outside observer, her frame is inertial, Stella does not experience an inertial frame locally. If Stella releases the wine glass, it drops.
AintNoThang: The result is that she experiences an inertial net force. ... This is, in fact, the whole presumption underlying the contention that the experiences of the twins in the paradox are not equivalent. To recap that "resolution:"
Omit the intervening paragraph, and this is correct.
AintNoThang: Arbitrarily choosing to ignore that history when defining a "inertial" state is just that...arbitrary, for definitional purposes, without regard to objective reality.
Actually, when we use phrases like "inertial", we always mean local with regards to time and space, occasionally extendede to a lengthier scenario but at its heart still a local phenomenon. If you think that means we are arbitrarily restricting the discussion, fine, but that is what the words mean.
AintNoThang: 2. You try to equate "local" with "not arbitrarily large," but that is nothing short of sophistic word-play.
I don't know what your math background is. If you took calculus, "local" means the same thing that if means for the parabola y=x^2 to have slope 2 when x is 1. It is the standard definition of "local" used throughout physics and analytic mathematics, to my knowledge. You might not understand the terminology, but it is not sophistry nor word-play, but a well-defined, well-understood concept taught at the undergraduate levels in various disciplines.
A coordiate system, like K or K', is a mathematical construct. I have never argued for the reality of mathematical constructs. In fact, my point with Feser has always been, to the degree that mathematical constructs are real, the universe is not Euclidean.
AintNoThang: Knowledge of the recent accelerative history gives you those facts. Igorance of them does not make them non-existent.
Knowledge of that history lets you know who has changed inertial frames of reference, and who has not. This has nothing to do with who is "going faster".
AintNoThang: 1. One can easily, for mathematical purposes, treat either of two objects in relative motion as being "at rest" (but NOT simultaneously, which you deny).
You can't use two coordinate systems at the same time. This doesn't mean one of the coordinate systems has to be wrong.
AintNoThang: 3. But no true scientist (as opposed to a true mathematician) would ever claim that any two given frames are "equally valid" as an ontological matter.
You say this based on your extensive polling of scientists?
AintNoThang: 4. SR, by it's own theoretical formulas and premises, gives you an empirical basis of detecting which of two relatively-moving objects has been "really" moving (or at least moving faster): simply see which clock recorded less time during the period of relative motion.
The clock that changed inertial frames will record less time, *even if it was moving more slowly*, whatever "slowly" means here.
AintNoThang: 5. The mere philosophical assertion that "all reference frames are equally valid" does not, as Einstein hoped, make all motion (including accelerated motion) "truly relative." It is my understanding that most physicists, while they accept GR as a valid, if imperfect, theory of gravity, reject it as a valid theory of "relative motion."
Your understanding is highly inaccurate here.
colton's first answers:
1. In the twin paradox listed in and http://en.wikipedia.org/wiki/Twin_paradox, does the answer to which twin is younger depend in any way on the notion that the ship twin is moving and the earth twin is stationary, as opposed to looking at relative motion between the ships only?
Absolutely, although you should substitute the word "accelerating" or perhaps "changing reference frames" in place of "moving". The key to resolving the paradox is that one twin has been following a “geodesic” (the twin on earth), while the other one has been going out and back. Hopefully the term “geodesic” is familiar to you in this context. 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).
The Wikipedia article is correct, as far as I know, when it states things like this, “…the asymmetric aging is completely accounted by the fact that the astronaut twin travels in two separate frames, while the earth twin remains in one frame. Using Minkowski's spacetime formalism, Laue went on to demonstrate that the world lines of the inertially moving bodies maximize the proper time elapsed between two events.”
2. In Einstein's dialog http://en.wikisource.org/wiki/Dialog_ab ... relativity, in coordinate system K', does U1 experience acceleration?
First of all, I would protest against using coordinate system K’. I haven’t had a lot of General Relativity (a single class, about 15 years ago), but in Special Relativity, one is only permitted to use constant velocity reference frames as the origin of your coordinates. Thus, in that context the question is poorly framed.
However, I read Einstein’s explanation of the how things look according to K’, in the right hand column, and I accept that viewpoint as permissible within the confines of General Relativity. Therefore, the answer is yes, U1 experiences acceleration. That is produced by a gravitational field: “A homogenous gravitational field appears, that is directed towards the positive x-axis. Clock U1 is accelerated in the direction of the positive x-axis until it has reached the velocity v, then the gravitational field disappears again.” (In the context of Newtonian physics, or probably even S.R., we would call that a fictitious field, just like moving a car around a corner to the left produces a fictitious force that “pulls” objects to the right.)
3. Is there ever a case where acceleration by free fall is not an inertial environment?
This may be largely a definition issue, but by the definition I’m familiar with, “inertial” is defined as “non accelerating”. So the answer would be: yes, always. See this Wikipedia page:
http://en.wikipedia.org/wiki/Inertial_reference_frames
At the end, it points out that inertial frames do not exist extending out forever, as is assumed in S.R. “This phenomenon of geodesic deviation means that inertial frames of reference do not exist globally as they do in Newtonian mechanics and special relativity.” But as far as I know, the definition of “inertial environment” has not been changed away from “non-accelerating environment”.
paragraph’s answer.
6. Within relativity theory, can there be there such a thing as a wrong viewpoint or frame of reference to use?
In S.R., all constant velocity frames (aka inertial frames) are equally good. There is no wrong inertial frame.
I don’t have much personal experience with G.R., but judging from the Einstein dialog you steered me to above, all frames (even non inertial ones) are equally valid, as long as you account for the (fictitious?) gravitational fields that arise when you have an accelerating frame. That’s not to say all frames are equally useful, though. The simplest-behaving ones are probably the most useful.
colton's first answers, continued:
4. Pat and Chris are born on widely separated planets in approximately the same rest frame, and Pat is then accelerated to .6c in the general direction of Chris. When Pat passes Chris, both are exactly 12,000 days old. As long as neither accelerates, will you be able to say that Pat will be younger than Chris from then on?
This part of the question is incorrect, or poorly phrased: “When Pat passes Chris, both are exactly 12,000 days old.” You must specify the reference frame being used to make the time measurement. You have three choices, I guess: (1) Chris’s frame (an inertial frame). (2) Pat’s birth frame (actually, this is the same as Chris’s frame). (3) Pat’s “self-frame” (a term I may have just made up), which is a non-inertial frame.
Using frames 1 or 2, if Chris is 12,000 days old, then Pat will be less than 12,000 days old. This is just like the second half of the twin paradox. Using frame 3 (caveat: I haven’t worked it out completely) I suspect when Pat considers himself to be 12,000 days old, he will perceive Chris as being younger than 12,000 days old. (A separate problem, possibly related, but possibly unrelated, is that since there is no simultaneity in S.R., Pat’s now-moving frame would not consider Pat and Chris to have been born at exactly the same time.)
To answer the final question, “…will you be able to say that Pat will be younger than Chris from then on?” you must again specify the frame. I believe (see caveat above) that in frame 1/2, Pat will always be younger, and in frame 3 Chris will always be younger. You ask, “But which one is *really* younger?” (Sorry to put words in your mouth.) To see which is “really younger”, you would have to bring the two people into the same frame, next to each other. To do that, you would either have to accelerate Chris, in which case they would likely end up being essentially the *same* age, or you would have to decelerate Pat, in which case it’s like the twin paradox, where Pat ends up being younger.
5. Pat sees himself as at rest, Chris sees himself as at rest. Assume Pat is right. Relative to Chris, at least, he is in fact at rest. Chris is therefore wrong. Chris will be younger, even if he thinks Pat is younger, and even if they never meet again. End of story. Assume Chris is right. Relative to Pat, at least, he is in fact at rest. Pat is therefore wrong. Pat will be younger, even if he thinks Chris is younger, and even if they never meet again. End of story. In neither case are P and C "both correct" or "equally correct" in their mutually exclusive assumptions. And 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 can not be correct, one must be incorrect." Is this accurate?
I may be misunderstanding the situation. Are we still talking about Pat & Chris moving relative to each other? In that case, I would say both are correct. The duration of an event (aka the age of someone) depends on the reference frame of the person measuring the event. So Pat can measure Chris to be younger at the same time Chris measures Pat to be younger. If you want to know “who is really younger”, if that’s what you are getting at, see my note at the end of the previous paragraph’s answer.
6. Within relativity theory, can there be there such a thing as a wrong viewpoint or frame of reference to use?
In S.R., all constant velocity frames (aka inertial frames) are equally good. There is no wrong inertial frame.
I don’t have much personal experience with G.R., but judging from the Einstein dialog you steered me to above, all frames (even non inertial ones) are equally valid, as long as you account for the (fictitious?) gravitational fields that arise when you have an accelerating frame. That’s not to say all frames are equally useful, though. The simplest-behaving ones are probably the most useful.
colton's first answers, last part
7. Tom and Ron are born on widely separated planets in the same rest frame, and Tom is then accelerated to .6c in the general direction of Ron. At the time Tom accelerated, he and Ron are the same age, according to their identical respective time frames. As long as neither accelerates, will you be able to say that Tom will be younger than Ron from then on?
No, I don’t think so. See my comments about Pat and Chris, above.
8. Are there distinct things that could be thought of as unaccelerated free-fall and accelerated free-fall?
I don’t really understand this question. Free-fall is, in the S.R. context, defined as accelerated motion. In the G.R. context, it is by definition geodesic motion in the presence of a gravitational field—which I believe Einstein said was equivalent to accelerated motion, even if perhaps not quite defined as such. See here, for example: http://www.astronomynotes.com/relativity/s3.htm. “There is no experiment a person could conduct in a small volume of space that would distinguish between a gravitational field and an equivalent uniform acceleration.”
Thanks.
You’re welcome. It was an interesting hour of thinking & typing. Feel free to ask for clarification if any of my answers are unclear.
I responded with:
Looking for some clarifications on these.
1. So the key is following the geodeisic? When you are following the godeisic is your local environment always inertial?
2. What sorts of acceleration effects does U1 experience in K'? How is it different from being in an inertial environment?
3. What are some of the differences you would detect in your environment if you were accelerating by free-fall, as opposed to being in an inertial environment?
8. Is there some difference in the local environment between free-fall directly toward a planet (accelerated) and free-fall in orbit (unaccelerated)?
One more:
9. When you remove the consideration of gravity and non-inertial reference frames, does G.R. become S.R.? In other words, could you say that S.R. is really a part of G.R.?
colton's second responses:
1. So the key is following the geodeisic? When you are following the godeisic is your local environment always inertial?
Yes, the key is following the geodesic. No, your local environment is not necessarily inertial when you follow a geodesic. (Picture the earth's orbit around the sun, for example. The earth follows a geodesic, but we are well within the sun's "gravity well", so space is curved. "Inertial" = "essentially no gravitational force" = "flat space-time".)
2. What sorts of acceleration effects does U1 experience in K'? How is it different from being in an inertial environment?
G.R. view: U1 experiences a back-and-forth acceleration in K'. This is caused by a back-and-forth gravitational field. (What I would term a "fictitious field", as mentioned before.) The question of "How is it different from being in an inertial environment?" is an excellent one. The answer must be "There is no difference", because (as is clear from viewing the situation in frame K) U1 *is* in an inertial environment. But how the two statements are juxtaposed within a G.R. context is beyond my knowledge. I'm not sure if it's just a definition thing, or if it's more than that. Sorry!
S.R. view: K' is not a valid frame. U1 does not experience any acceleration in any inertial frames. It is in an inertial environment.
3. What are some of the differences you would detect in your environment if you were accelerating by free-fall, as opposed to being in an inertial environment?
The one that comes to mind is the bending of light rays. There's a picture about half-way down this page that depicts that: http://www.astronomynotes.com/relativity/s3.htm
Light rays will appear to bend in an accelerating by free-fall environment (and, equivalently, in a gravitational field). Light rays will not appear bent in an inertial environment.
But you ask: "How does one define "bent", when all of the surrounding space is also bent?" My answer: Probably has to be done via parallel rays. That is, light rays which start off parallel will never converge/diverge if the environment is inertial. Light rays which start of parallel *can* converge/diverge if space time is curved (or equivalently, if they are in an accelerated enviroment).
colton's second response, continued:
8. Is there some difference in the local environment between free-fall directly toward a planet (accelerated) and free-fall in orbit (unaccelerated)?
Free fall in orbit *is* accelerated motion, even if the object is not speeding up/slowing down. That's "centripetal acceleration", acceleration which changes the *direction* of the velocity, rather than changes the *magnitude* of the velocity. For an object going at constant speed in a circular path of radius R, the value of the centripetal acceleration (not including relativity, which likely changes this equation) is acceleration = v^2/R. That's measured in m/s^2, just like "regular acceleration".
Anyway, the answer is there is no difference in local environments between the two cases. In the G.R. context the space-time warping will be the same(*). In a non-G.R. context, the accelerations will be the same because the acceleration is given by the amount of gravitational force, which is the same for both situations. (Just depends on positions & masses, not on orientations.)
(*) If the object doing the orbiting is massive enough, I think there is a G.R. effect called "frame dragging" which may be different between the two situations. Or perhaps that's an effect which can occur if the planet/star is massive enough, and rotating. I don't remember enough about that to say for sure. But I don't think you have in mind that type of situation.
One more:
9. When you remove the consideration of gravity and non-inertial reference frames, does G.R. become S.R.? In other words, could you say that S.R. is really a part of G.R.?
Yes, S.R. is a part of G.R. You can say G.R. reduces to S.R. when you remove gravity and non-inertial reference frames (or equivalently, when space-time is flat). I think it's very similar to how S.R. reduces to Newtonian physics when you remove the possibility of relative velocities approaching the speed of light. In both situations, the more complicated case (G.R. compared to S.R., or S.R. compared to Newton) involves additional terminology/concepts which are not needed in the simpler case.
I have asked for one more clarificaiton.
One Brow wrote: what are some of the differences you would detect in your environment if you were accelerating by free-fall, as opposed to being in an inertial environment?
colton wrote: The one that comes to mind is the bending of light rays. There's a picture about half-way down this page that depicts that: http://www.astronomynotes.com/relativity/s3.htm
Light rays will appear to bend in an accelerating by free-fall environment (and, equivalently, in a gravitational field). Light rays will not appear bent in an inertial environment.
Looking at the picture, the light will bend the source of the acceleration/gravity. If you are in free-fall, you will also be accelerating toward that source (in the picture, he is accelerating from it). Would the acceleration in the direction of the light beinding not be enough to compensate (it looks less bent in that direction), exactly enough to compensate (it looks straight to you), more than enough to compensate (it acutally bends in the reverse direction from what you see), or is this indeterminate?
Are there any other effects you can think of that might distinguish acceleration by free-fall from a truly inertial environment?
My general thoughts so far:
I may have been misusing the term inertial to refer to certain situaitons, coltons usage was much closer to yours. I'll try to correct that in the future. However, given that he confirmed U1 is in an inertial environment in K' in the clarification, and says he is not sure how to resolve that in GR, I'm not sure what to make of the term right now.
Needsless to say, I was happy with the original answers on 4. thourgh 7., as they seem to comport with what I have been telling you. I'm trying to get at the difference between a truly inertial frame and one in free-fall, and will correct my opinions on that based on the dialog.
If you would like to submit any clarifications, I will be happy to send them verbatim and provide you with a verbatim reply.
One Brow said: "I am using the same definition, and talking about the same phenomenon, as all those articles."
You may think you are, but ya aint. Suppose a rocket, sitting on the ground, is blasted straight up by a force sufficient to accelerate it to about 100 m/s. It is now in "free fall" by this definiton. The passengers are feeling 10g's of force. Well, they would be, anyway, if they hadn't all blacked out.
AintNoThang: But again, they are not truly in "free fall," they are merely being accelerated at high speeds in a direction perpendicular to the earth IN ADDITION to being subjected to gravity).
"This is not correct. The only acceleration on an orbiting body is the downward acceleration of gravity. Unless the orbit needs to be corrected for some reason, there would be no acceleration perpendicular to that. There is the effect of inertia perpendicular to the acceleration of gravity, but that effect is not an acceleration."
Well, yeah, according to whose definition of "acceleration" you use. Newton would say they are accelerated (changing direction). But I really intended to just say "moving" at high speeds, to avoid the issue.
There is a side issue here. If I greatly accelerate an object by applying external force, and it finally settles into uniform speed, is that orginally "accelerating force" now built into it as a "force of inertia?" I don't really want to get into that right now, but I think it does help highlight the problem of trying to view dynamic things from a strictly static point of view.
One Brow said: "What sense will detect acceleration by free-fall within the local environment? How does that detection happen?"
That might vary depending on the state you were in immediately prior to entering a state of free fall. Like I said, a rocket, accelerating upwards at a force of 10 g, is in "free fall."
AintNoThang: How can a person go FROM a state free fall INTO a state of free fall?
One Brow said: "If all you are are doing is examining the effects of adopting K and K', this is irrelevant."
Well, no, not really. For Einstein the two states are equivalent (inertial = free fall). But that aside, we are not just discussing the specific details of Al's example but also the implications of it.
One Brow said: "Knowledge of that history lets you know who has changed inertial frames of reference, and who has not. This has nothing to do with who is "going faster".
Whatever you think this means, take it to the math geek board. Someone says to me "I fell down." In response, I say "you changed reference frames, that has nothing to do with "falling down."
In my hood, that would git a cap busted in your ass. You think you have said something meaningful about "reality" with this kind of statement? Get real.
To anyone but a head-up-his-ass-math-geek the exact opposite would be true. Falling down, and busting your head, has NOTHING to do with "changing reference frames."
I'm sorry, but I'm serious. If the only terms you can, or care to, speak in terms of are technical mathematical definitions and concepts, we don't have much to say to each other.
You may think you are, but ya aint. Suppose a rocket, sitting on the ground, is blasted straight up by a force sufficient to accelerate it to about 100 m/s. It is now in "free fall" by this definiton.
If by "now" you mean after the rocket stops blasting, while the rockets is still going up, I absolutely agree that is free-fall.
If we do discuss what gets stored in a projectile after it is accelerated (which would be energy, not force), please do not use "force of inertia". Forces do not get conserved, they come into existence and disappear. Momentum and mass-energy are conserved.
The rocket is not in free-fall while it is accelerating upwards at 10g. Free-fall starts atfter the rocket has turned off.
The implications of going from K to K', ontologically, are nil. All that you have changed are coordinate frames. colton confirmed this for you. Did you want him to clarify that, or anything else?
One Brow said: "The clock that changed inertial frames will record less time, *even if it was moving more slowly*, whatever "slowly" means here."
Again, if you can't understand such terms as faster and slower, best keep out of any non-mathematical discussions. Not that "frame of reference" is mathematical, just ontologically meaningless, that's all.
One Brow said: "Knowledge of that history lets you know who has changed inertial frames of reference, and who has not. This has nothing to do with who is "going faster".
Whatever you think this means, take it to the math geek board. Someone says to me "I fell down." In response, I say "you changed reference frames, that has nothing to do with "falling down."
I refer you to this example:
Clocks V1 and V2 are synchronized. A satellite launches from Earth with V2, in the opposite direction from the Earth's revoluton. The satellites follows the orbital path of the earth at 1/3 the orbital speed (from the viewpoint of the earth). From the viewpoint of the earth, after nine months, the satellite adn the earth will meet again. At this time, V1 will show nine months have passed, but V2 will have shown *less than nine months* have passed, despite V2 moving slower than V1.
I understand that, without a third reference frame, there can be no true "faster" or or "slower". In the example I just provided, that tihrd frame is, by implication, the sun.
I have just (briefly) read Colton's answers without trying to digest them. I would definitely have some follow-up questions, though, I can tell that. I will try to compose some later.
One Brow said: "The rocket is not in free-fall while it is accelerating upwards at 10g. Free-fall starts atfter the rocket has turned off."
Who said anything about rockets being turned on, then off? If I throw a ball is it in "free fall" once it leaves my hand, or only once it stops accelerating and come to a stop ("accelerating" used here to include deceleration)?
I'll be glad to help out, and I'll try to avoid making the same mistakes again.
The ball is in free-fall (ignoring the friction effects of the atmosphere, of course) once it leaves your hand and until it lands (after it is on the ground, it is no longer in free-fall).
However, if the rocket is never turned off, the propulsion system on the rocket will be an additional source of acceleration, so the rocket will not be in free-fall. After the rocket (propulsion) is switched off, it is in free-fall.
One Brow said: "The implications of going from K to K', ontologically, are nil. All that you have changed are coordinate frames. colton confirmed this for you"
Colton said this, among other things: "Absolutely, although you should substitute the word "accelerating" or perhaps "changing reference frames" in place of "moving". He is basically saying that "changing reference frames" is synonomous with "motion," which he points out is accelerated motion in this case. As I understood you, you conceded this yourself a long time ago. What's to clarify?
Latest from colton:
One Brow wrote: Looking at the picture, the light will bend the source of the acceleration/gravity. If you are in free-fall, you will also be accelerating toward that source (in the picture, he is accelerating from it). Would the acceleration in the direction of the light beinding not be enough to compensate (it looks less bent in that direction), exactly enough to compensate (it looks straight to you), more than enought to compensate (it acutally bends in the reverse direction from what you see), or is this indeterminate?
I'm not exactly following the question. Compensate for what?
Maybe this will help: G.R. says that all effects that arise from being at rest in a gravitational field (i.e., not in free-fall) will be the same as the effects that one can observe in an elevator undergoing constant acceleration. So, the right-most elevator picture on that page, accelerating towards the top of the page, the light will be bent downwards (as perceived by people in the elevator). Similarly, if a large gravitational field exists (pointing downwards), light will be bent downwards (as perceived by people at rest in the field).
Ah... I think I see where you are going with this, now. You're asking: "What if you are not at rest in the field? If the elevator is accelerating downward, and the light is also bending downward, will the people in the elevator be able to tell that the light is bending?" Is that it?
I think the answer to that is: if the elevator is small enough that there is essentially no space-time curvature inside the elevator, then the people will *not* be able to perceive that the light is bending, and they will assume that they are in an inertial environment. If there is measurable curvature inside the elevator, then the people *will* be able to see the converging/diverging light rays, as mentioned in my previous PM.
Are there any other effects you can think of that might distinguish acceleration by free-fall from a truly inertial environment?
Well, it all has to do with the curvature of space. If the elevator region is small enough, then you cannot tell it's not a true inertial environment. I believe that's another statement of Einstein's equivalence principle. If the elevator region isn't quite that small, then the curvature of space will be made manifest... and the "parallel light rays converging/diverging" is probably the standard way of visualizing that curvature. But any other effects that arise from the curvature of space will also be present (tidal effects, for example, where there are unbalanced forces on the top & bottom of the elevator).
Tell you what--there are a couple of my colleagues who study G.R. I think I'll send all of your questions and my answers to them to make sure I'm not getting anything wrong.
One Brow said: "The satellites follows the orbital path of the earth at 1/3 the orbital speed (from the viewpoint of the earth)."
I really don't understand this example at all. What is the "viewpoint of the earth" in this question? Is that the same "viewpoint" you are trying to use consisently in this example, or are you using different ones at different times?
One Brow said: However, if the rocket is never turned off, the propulsion system on the rocket will be an additional source of acceleration, so the rocket will not be in free-fall. After the rocket (propulsion) is switched off, it is in free-fall.
OK, not saying it is practically feasible, but that's all I meant. You give the rocket one large impetus, at ground level, and it accelerates. Like a baseball bat hitting a ball, ya know? Point is that it can be in "free fall" with increased g's as well as reduced g's and that, if significant, each acceleration can be detected.
Look, one problem here, that I have refrained from addressing at length because there are so many other questions on the table is the equivocation about terms such as "acceleration" and "intetial" between SR and GR.
GR completely redines "inertial," and hence, by strict implication, "acceleration" also.
Einstien trys to reduce accelerated frames to SR inertial frames. He does this by saying, in effect, "we can't tell if we are accelerated, so we "could" be in a gravitational field instead," The converse, "we can't tell if we are in a gravitational field, so we could be accelerated instead" is not really consistently applied in his defintions of inertial and acceleration, that I can tell, however.
What he ends up saying, as I understand it, is that since a person orbiting the earth cannot "feel" his acceleration, we can treat him as being unaccelerated. Since he is now unaccelerated, he is inertial. That means we can treat him as though there is really no gravity acting upon him either. So we ignore the gravity, and the acceleration (because he can detect neither, at least not as being distinct from each other) and say he is in an "inertial" state. He is neither accelerating NOR in a gravitational field, because he can not detect which is which. Does this really make any sense?
What started out as being "it could be EITHER gravity or acceleration," is in effect, turned into "it can be NEITHER gravity or acceleration." This is just wrong.
Once we treat BOTH the accleration and the gravity as "non-existent" then every type of sensible explanation of "free fall" in orbit disappears. There is no gravity (or so we say) and there is no acceleration either. From a classical standpoint, this is like saying there is no earth (a mass with gravitational forces), there is no orbit, and there is no motion (around the globe).
The very thing that is "accelerated" in SR is "inertial" in GR. All of the sideways motion of the satellite "disappears" in SR, it is simply treated as non-existent. The gravity also "disappears" and "inertial" is now simply a geodesic or "geodesic devition" (whatever that is). It makes any attempt to even talk about "inertial frames of reference" almost impossible on a consistent basis if you first talk about SR, and then GR. Just another reason why that is not a technical term I can to speak in terms of.
Edit: Meant to say: "All of the sideways motion of the satellite "disappears" in GR [not "SR"], it is simply treated as non-existent."
Sorry, slight change:
I refer you to this example:
Clocks V1 and V2 are synchronized. A satellite launches from Earth with V2, in the opposite direction from the Earth's revoluton. The satellites follows the orbital path of the earth at 1/3 the orbital speed (from the viewpoint of an observer one billion miles from the sun). After nine months, the satellite and the earth will meet again. At this time, V1 will show nine months have passed, but V2 will have shown *less than nine months* have passed, despite V2 moving slower than V1 from that viewpoint.
second edit: "Just another reason why that is not a technical term I care [not "can"] to speak in terms of."
Before I answer any of that, did you mean any of this as a question for colton?
One Brow said: "The satellites follows the orbital path of the earth at 1/3 the orbital speed (from the viewpoint of an observer one billion miles from the sun)."
I still don't even understand the logic behind the example, and I haven't even tried to. I am talking about the relative velocity of two objects only. When we send a rocket in between, then from our standpoint, and that of the rocket, it is the rocket which is really moving, as between the two." How is might look to someone a billion miles away is simply irrelevant to that.
One Brow said: "Before I answer any of that, did you mean any of this as a question for colton?"
No, it was not meant for him, but I do think this type of equivocation is affecting his answers (not sure, I haven't really studied his answers, in relation to the questions asked).
edit "When we send a rocket into space [not "in between"]....
In that example, you don't think the Earth is really moving around the Sun, or that it is not moving faster than the rocket?
If you feel my way of wording things is affecting his answers, I encourage you to submit your own wording.
One Brow said: "The satellites follows the orbital path of the earth at 1/3 the orbital speed (from the viewpoint of an observer one billion miles from the sun)."
Again, the whole thing is irrelevant, as I see it, but is this hypothetical observer looking at our north pole and the satellite goes around the equator, or what? Don't bother answering, I don't care. Just another reason I can't even tell what you are trying to say, exactly.
No, the satellite goes in the opposite direction from the earth, but it follows the earth's orbit in that direction. It makes this journey in nine months, going 1/4 of an orbit, while the earth goes for those same nine months in the other 3/4 of the orbit. In nine months, the earth covers three times as much distance as the satellite.
Like I said, I don't really care about the example, so I really don't even care about the details. While you refer to "the earth," I assume you are referring to a particular point on the earth.
Who cares? Whichever clock has recorded less time is, if SR is correct, the one that has been moving faster.
The question is "what is the point?" What is the point in my example that I can position 4 people around me and they will all see different sides of the same coin, or not see the coin at all. What does that tell you? Does it tell you that the one seeing heads is *not* really seeing heads, or what?
One Brow said: "colton's first answers:"
1. In the twin paradox listed in and http://en.wikipedia.org/wiki/Twin_paradox, does the answer to which twin is younger depend in any way on the notion that the ship twin is moving and the earth twin is stationary, as opposed to looking at relative motion between the ships only?
Absolutely, although you should substitute the word "accelerating" or perhaps "changing reference frames" in place of "moving".
====
Does this response lead you to reconsider any of the claims you have made in this thread and/or any conclusions you have formed?
For Colton:
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/the_twin_paradox#ixzz0amGd0GVD
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.
====
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.
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."
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."
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.
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? 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?
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?
If your answer is "no," could you explain why? Is it because the theoretical predictions of SR are simply unreliable, or some other reason?
Eric, maybe you can clean that last question up for me before submitting it to Colton. Delete this:
"If your answer is "no," could you explain why? Is it because the theoretical predictions of SR are simply unreliable, or some other reason?"
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?
One Brow said: "I don't know what your math background is. If you took calculus, "local" means the same thing that if means for the parabola y=x^2 to have slope 2 when x is 1. It is the standard definition of "local" used throughout physics and analytic mathematics, to my knowledge. You might not understand the terminology..."
What "local" means in calculus is all very interesting, no doubt, but what does that have to do with Einstein's EP? Is that the meaning of "local" that you have been using in all your posts on this topic?
"The Einstein equivalence principle states that the weak equivalence principle holds, and that:
The outcome of any local non-gravitational experiment in a freely falling laboratory is independent of the velocity of the laboratory and its location in spacetime.
Here "local" has a very special meaning: not only must the experiment not look outside the laboratory, but it must also be small compared to variations in the gravitational field, tidal forces, so that the entire laboratory is freely falling. It also implies the absence of interactions with "external" fields other than the gravitational field."
http://en.wikipedia.org/wiki/Equivalence_principle
"Very special meaning," eh? Limitations and restrictions worth noting:
1. "non-gravitational experiment"
2. "the experiment [must] not look outside the laboratory"
3. "implies the absence of interactions with "external" fields other than the gravitational field."
"Local" seems to boil down to this:
"Please note that this holds for pointlike testparticles only, it is no longer true for extended or spinning objects, or for objects that significantly disturb the background."
http://www.yearofscience2009.org/themes_physics_technology/2009/03/the-equivalence-principle-by-sabine-hossenfelder.html
wiki says this: "The principle does not apply to physical bodies"
http://en.wikipedia.org/wiki/Equivalence_principle
Doesn't apply to "extended objects" or "phyical bodies," eh? Now that's what I call local, sho nuff.
Who cares? Whichever clock has recorded less time is, if SR is correct, the one that has been moving faster.
So, the notion of "moving faster" means "recorded less time"? It has no independent meaning besides that? I don't think you would agree to that.
The earth, and more specifically the clock on the earth, travels three times the distance that the clock on the satellite does before they meet up again, yet experiences more time, not less. This result does not break SR, rather it is predicted by relativity theory. I'm not surprised you don't care for the example, because it really turns your notions of it on their head. The faster-moving earth still experiences more time passage.
The question is "what is the point?" What is the point in my example that I can position 4 people around me and they will all see different sides of the same coin, or not see the coin at all. What does that tell you? Does it tell you that the one seeing heads is *not* really seeing heads, or what?
I have been presuming the point of your coiin analogy, and the others like it, is that there is supposedly some underlying truth beneath all the relative observations that can be had without first specifying an absolute rest frame. It seems to vex you on some level that such a truth does not exist in any meaningful way until you spcify that absolute rest frame.
colton: Absolutely, although you should substitute the word "accelerating" or perhaps "changing reference frames" in place of "moving".
====
Does this response lead you to reconsider any of the claims you have made in this thread and/or any conclusions you have formed?
I have been insisting all along that the key notions were the relative movement. Acceleratinig and chaninging reference frames are descriptions of relative movement. If the only thing you mean by "really moving" is this relative movement, then we were both right. I don't see how what he said disagrees with what I said, thought. Perhaps you could expand on what you see as the difference.
What "local" means in calculus is all very interesting, no doubt, but what does that have to do with Einstein's EP? Is that the meaning of "local" that you have been using in all your posts on this topic?
It the standard meaning of "local" in physics, as well.
"Local" seems to boil down to this:
"Please note that this holds for pointlike testparticles only, it is no longer true for extended or spinning objects, or for objects that significantly disturb the background."
http://www.yearofscience2009.org/themes_physics_technology/2009/03/the-equivalence-principle-by-sabine-hossenfelder.html
wiki says this: "The principle does not apply to physical bodies"
http://en.wikipedia.org/wiki/Equivalence_principle
Doesn't apply to "extended objects" or "phyical bodies," eh? Now that's what I call local, sho nuff.
It's very closely tied into the notion of continuity:
http://en.wikipedia.org/wiki/Continuity_(mathematics)
Basically, given an error range of E any non-zero size, you can find at any location P a radius D so that, within a distance D of P, the equivalance principle describes the surroundings accurately to within E. Generally, E is determined by your measurement error size.
So, saying it holds only for point masses, etc. is not quite right.
"The earth, and more specifically the clock on the earth, travels three times the distance that the clock on the satellite does before they meet up again, yet experiences more time, not less. This result does not break SR, rather it is predicted by relativity theory. I'm not surprised you don't care for the example, because it really turns your notions of it on their head. The faster-moving earth still experiences more time passage."
Can you show me how and where this is "predicted by SR." Are you getting this from some prepared explanation on the web? Your example, as presented by you, is very vague and ambiguous. To begin with, no satellite could possibly take 9 months to travel 1/4 revolution...at that speed it would hit the ground in a few minutes, if not seconds, I would expect. How is "time" being measured? In calendar months, atomic clocks, or what? SR takes into account the fact that clocks at, say, the equator are also in motion.
Your example simply makes no sense as it stands. To say it turns my notions on their head is to say, as usual, nothing concrete.
One Brow said: "I have been insisting all along that the key notions were the relative movement."
Placing (misguided)reliance on Einstein's bogus "resolution," you have been insisting that the twin in the ship would be younger even if the earth was the one moving.
You asked Colton if consideration of "only the relative motion," (presumably meaning as opposed to answering the question of which one had been moving/accelerated) was sufficient. He said no. And now you reiterate that relative motions are the "key," while asking why Colton's response should make you reconsider? Heh.
One Brow said: "I have been presuming the point of your coiin analogy, and the others like it, is that there is supposedly some underlying truth beneath all the relative observations that can be had without first specifying an absolute rest frame."
No, that's not the point. The point is that ANY observation, made ANYWHERE, by ANYONE, can always be seen differently from an entirely different perspective. So what? Does this invalidate every scientific observation ever made, because a guy not there wouldn't have seen it, or because a guy looking through the microscope upside down would have seen "something different?" This has nothing to do with relativity theory, per se.
Again: A guy a billion miles from us would perceive it from a different perspective, and therefore perhaps differently. So what???
I said: Who cares? Whichever clock has recorded less time is, if SR is correct, the one that has been moving faster.
One Brow said: So, the notion of "moving faster" means "recorded less time"? It has no independent meaning besides that? I don't think you would agree to that.
How in the hell does your "so..." follow from my statement?
For Colton:
In his "dialogue," where Einstein claims "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" that if you imagine magically-appearing and disappearing pseudo-gravitational fields, during which clock U1 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 U2). 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 amount the greater/lesser degree of time passage.
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.
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?
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.
Have I asked this in a way that you understand the question, and the point?
Edit: Meant to say "Bottom line seems to be: GR will agree with SR predictions about [not "amount"] the greater/lesser degree of time passage.
Edit question for Colton: I said:
"This is because the gravitational field would have ADDED a substantial amount of time to the now travelling clock (clock U2)."
Wrong, I meant:
"This is because the gravitational field would have ADDED a substantial amount of time to the now stationary [not "travelling"] clock (clock U2)."
I see another correction, so let me just re-do the whole question, which should read:
For Colton:
In his "dialogue," where Einstein claims "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 U1 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 stationary clock (clock U2). 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.
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.
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?
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.
Have I asked this in a way that you understand the question, and the point?
Damn! I keep getting my clocks mixed up. Final form (I hope) of question to Colton:
For Colton:
In his "dialogue," where Einstein claims "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, while U2 is moving, and hence, given SR predictions, clock U1 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 stationary clock (clock U2). 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.
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.
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?
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.
Have I asked this in a way that you understand the question, and the point?
No, still not right, missed an intended correction:
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.
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.
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?
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.
Have I asked this in a way that you understand the question, and the point?
One Brow: "The faster-moving earth still experiences more time passage."
Can you show me how and where this is "predicted by SR."
It's predicted by relativity theory because the earth remains in a timelike geodeisic, the satellite does not.
Are you getting this from some prepared explanation on the web? Your example, as presented by you, is very vague and ambiguous. To begin with, no satellite could possibly take 9 months to travel 1/4 revolution...at that speed it would hit the ground in a few minutes, if not seconds, I would expect.
The sun does not have a "ground" to hit. Did you mean the sun's corona? Did you miss the part about the satellite going in the opposite direction from the earth? Let's just say a rocket keeps in the earth's orbital path at a speed slower than the earth.
How is "time" being measured? In calendar months, atomic clocks, or what? SR takes into account the fact that clocks at, say, the equator are also in motion.
Nine months passes according to a clock on the earth. Do you have a preferred clock?
Your example simply makes no sense as it stands. To say it turns my notions on their head is to say, as usual, nothing concrete.
I really don't see what is so hard to understand, unless you are having real trouble with the fact the satellite is going in the opposite direction of the earth.
One Brow said: "I have been insisting all along that the key notions were the relative movement."
Placing (misguided)reliance on Einstein's bogus "resolution," you have been insisting that the twin in the ship would be younger even if the earth was the one moving.
Even in K', the normal physical interpretation would normally be that the ship is really moving.
However, if the earth were moving according to the dictates of K' (in free-fall only), then the earth would be following the geodeisic, the ship would not, and the earth would still experience more time.
You asked Colton if consideration of "only the relative motion," (presumably meaning as opposed to answering the question of which one had been moving/accelerated) was sufficient. He said no. And now you reiterate that relative motions are the "key," while asking why Colton's response should make you reconsider? Heh.
I asked if the notion depended on who was really moving, and he said "absolutely", and then provided qualificaitons. My vocabulary was inferior, and I will try to correct it. However, the idea of following a geodeisic versus accelerated motion is what I have been trying to tell you.
No, that's not the point. The point is that ANY observation, made ANYWHERE, by ANYONE, can always be seen differently from an entirely different perspective. So what? Does this invalidate every scientific observation ever made, because a guy not there wouldn't have seen it, or because a guy looking through the microscope upside down would have seen "something different?" This has nothing to do with relativity theory, per se.
Again: A guy a billion miles from us would perceive it from a different perspective, and therefore perhaps differently. So what???
If that is all you are trying to say, I agree. I had thought this was supposed to support your notion that, for example, either Pat was really wrong or Chris was really wrong (or both). If instead, you are only claiming that people seeing different things doesn't mean different things exist, sure. However, that statement alone doesn't get you to saying Pat or Chris must be wrong.
How in the hell does your "so..." follow from my statement?
Because I can't see any other reason you would interpret a satellite that has gone 1/4 of an orbit as being faster than a planet covering the other 3/4 in the same amount of time.
I have sent all your clarifications to colton.
colton:
I'd like to wait for my colleague's reply on my first three PMs before taking the time to answer this PM and the previous PM. Hopefully that'll be in the next day or two.
One Brow said: "The sun does not have a "ground" to hit. Did you mean the sun's corona? Did you miss the part about the satellite going in the opposite direction from the earth? Let's just say a rocket keeps in the earth's orbital path at a speed slower than the earth."
I dom't think it could do that. At a different speed it would have to be in a different orbit (altitude from the sun). I never did look at the thing that closely to begin with, so I now see what you were trying to say. Your point is what? I'm concerned with 2 objects here. A ship that blasted off from the earth, and the earth. If your only point is that different perspectives could see it differently, I get that. So what?
Either way, until you can show me how the question is even relevant, I don't care.
One Brow said: "I asked if the notion depended on who was really moving, and he said "absolutely", and then provided qualificaitons. My vocabulary was inferior, and I will try to correct it. However, the idea of following a geodeisic versus accelerated motion is what I have been trying to tell you."
Colton himself said the K vs K' prime "comparison" was dubious. Geodesics have nothing to do with SR, and he wasn't answering the twin paradox question in terms of geodesics, so I really don't even know what you are talking about anymore (I'm not convinced that you do, either, by the way).
One Brow said: "I have sent all your clarifications to colton."
Thanks.
A satellite with a rocket can follow pretty much any path, why not the earth's orbit?
Let's be clear:
Do you agree that in the example I offered, the earth is moving faster than the satellite?
Do you agree that the earth clock will show more time has passed?
If you agree with both of these, do you feel this has any effect on your claim that "faster = slower"?
I haven't really thought about it much, but if you launched a satellite it would simply stay moving with the earth (around the sun) within earth's gravitational field, unless it had escape velocity. After that, thing might depend on which way it was pointed. I aint no rocket scientist, so I'm not sure what would happen, depending. In any case it could not stay in the earth's orbit without maintaining the same speed as earth. Mercury travels much faster in it's orbit than earth, and mars travels slower. You hypothetical is impossible and therefore proves nothing about relative speeds.
Even if it did, I'm taking you to be talking about apparent speed from some other perspective--who cares?
One Brow said: "A satellite with a rocket can follow pretty much any path, why not the earth's orbit?"
"A satellite in orbit moves faster when it is close to the planet or other body that it orbits, and slower when it is farther away. When a satellite falls from high altitude to lower altitude, it gains speed, and when it rises from low altitude to higher altitude, it loses speed."
http://www.freemars.org/jeff/speed/index.htm
One Brow said: "Do you agree that in the example I offered, the earth is moving faster than the satellite?"
Only by definition, which you say is 1/3 of the earth's orbital speed. After that, no. I'm guessing, but the thing would probably start falling toward the Sun, at least until it picked up enough speed to maintain a stable orbit.
The "stable orbit" would probably be highly eccentric, rather than nearly circular, like the earth. On the other hand, without looking it up, I'm not convinced that 1/3 of the earth's speed of revolution would even exceed escape velocity.
Just curious, did you even read my question to Colton about Einstein's dialogue? If so, did you understand the question? Have any of your own thoughts about it? I've already mentioned this to you, but you completely ignored it, as I recall.
One Brow said: "However, that statement alone doesn't get you to saying Pat or Chris must be wrong."
I didn't claim that it would. As I recall, I didn't make any particular claim, I just asked you what you thought the philosophical significance was.
It does take at one small step towards the point that just because two (or more) people can see the "same thing" differently, does not mean that the "thing" in question is exactly what, and only what, one person perceives it to be.
A second point to be made is that this "profound" idea that you need to specificy your "frame of reference" to adequately convey your thoughts and observations is by no means exclusive to Einstien's relativity theory, and it never has been. It is neither unique nor original, and could be asked a thousand times in everyday conversation if you thought that was the only question ever worth asking.
You never commented on this, so, in light of your "geodesic" talk, especially, I'm going to repeat it.
Al reasoning appeared to be this:
1. An orbiting astronaut can't feel his acceleration, therefore we will say he is NOT accelerating (sure, his perceptions are the product of illusions, and we refuse to let him look out the window or perform gravitational experiments, but so what, let's call his misperceptions "reality).
2. If he is not accelerating, as we have just stipulated, then he is in an inertial state.
3. His speed is uniform, and his state is inertial, so therefore his "direction" cannot be changing. That means he is moving in a "straight line."
4. We will call this (circular) straight line a "geodesic" and, as stipulated call a geodesic path an "intertial state."
End result seems to be that in GR all accelerated states are inertial and, conversely, all inertial states are accelerated, just depending on your whim at the time. Nice way to have your cake, and eat it, too, eh?
Like I said before, don't even talk to me about "inertial frames" if this is also your definition. It is senseless and meaningless.
That aint even the end of it, though. Since he can't feel gravity, we also say there is no gravity. This too, is required, because an object in "inertial" motion is not being acted upon by any external forces. No gravity, no acceleration = uniform motion in a straight line. Geodesic, I tellya! Inertial state, ya know?
Decartes, expressing systematic doubt, reasoned that he had, at time while dreaming, thought he was awake, and concluded that he could not therefore know if he was even awake. He didn't seem to ask himself if he had ever been "really" awake and somehow thought he was dreaming. The two states (sleeping and awake) were simply indistinguishable.
But he finally hit on it!: Cogito, ergo sum...I think, therefore I am. Once he knew THAT, he could suddenly deduce EVERYTHING he could ever want to know. The existence of God, and on down the line.
Renny Descartes was out drinkin with his homeboys one night. He was pretty drunk, and about to puke, when they asked him: Hey, Renny, want another one? He said: "I think not."
Then, alla sudden, he just up and disappeared, ya know?
One Brow said: "However, that statement alone doesn't get you to saying Pat or Chris must be wrong."
You don't need much to get to that, at any rate. There are moving at a high speed relative to each other. Pat says: I'm at rest. Chris says: I'm at rest.
Looks like ya aint got but two choices:
1. They aint movin, or
2. One of them is wrong.
Uhhh, I think Imma say number 2, there, eh?
Pat and Chris are looking at two different sides of a normal coin.
Pat says: I see heads.
Chris says: I see tails.
OK, I'll buy that, but if
Pat says: I see heads
Chris says: "I see heads," then I aint got much choice except to say....
One of them is wrong.
Let's start over with my example. I want to clear some of the detrius and misconceptions, so I will rework it.
Two rockets are docked while in nine-month orbit around the sun in a direction we will call clockwise (there is no major planetary body near their orbit). They synchronize a pair of clocks. They separate, and one rocket (R1), having clock C1, continues in the orbit for six months, covering 2/3 of the orbit. The other rocket (R2), with clock C2, uses its engine to go counter-clockwise, firing the engine as needed so that the path of the rocket follows the orbital path, covering the other 1/3 of the orbit. They meet and compare their clocks. C1 will show more time has passed than C2.
Is what I am describing unclear in some fashion?
Do you agree R1 covered twice the distance as R2?
Would you say R1 went faster than R2?
Do you agree/accept that C1 will show more time has passed than C2?
If all of those answers are yes, do you understand why you can't say that "faster objects have time move slower" is true in relativity theory?
Only by definition, which you say is 1/3 of the earth's orbital speed. After that, no. I'm guessing, but the thing would probably start falling toward the Sun, at least until it picked up enough speed to maintain a stable orbit.
If it fired the engine directly toward the Sun, it can maintain the orbital path at a slower speed.
Just curious, did you even read my question to Colton about Einstein's dialogue? If so, did you understand the question? Have any of your own thoughts about it? I've already mentioned this to you, but you completely ignored it, as I recall.
I think your question still reflects an artificial distinction between SR and GR. GR is an expansion of SR, not a different thing. For example, SR considers only stright-line geodeisics, GR considers a wider variety of geodeisics.
You asked, '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).' U2 was always the one that changed reference frames, if by that you mean inertial frames. This is true in K' as well as in K.
You asked: '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.' U2 was the moving clock in K. K doesn't have any pseudo-gravitational fields needed to accout for the relative motion, so no calculations are required based upon these fields. Does that address what you are asking?
You asked: '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. Regardless of whether you uce coordinate system K or K', GR agrees that U2 will experience less time, because U1 follows the geodeisic.
It does take at one small step towards the point that just because two (or more) people can see the "same thing" differently, does not mean that the "thing" in question is exactly what, and only what, one person perceives it to be.
Agreed.
A second point to be made is that this "profound" idea that you need to specificy your "frame of reference" to adequately convey your thoughts and observations is by no means exclusive to Einstien's relativity theory, and it never has been. It is neither unique nor original, and could be asked a thousand times in everyday conversation if you thought that was the only question ever worth asking.
Agreed.
You never commented on this, so, in light of your "geodesic" talk, especially, I'm going to repeat it.
Al reasoning appeared to be this:
1. An orbiting astronaut can't feel his acceleration, therefore we will say he is NOT accelerating (sure, his perceptions are the product of illusions, and we refuse to let him look out the window or perform gravitational experiments, but so what, let's call his misperceptions "reality).
2. If he is not accelerating, as we have just stipulated, then he is in an inertial state.
3. His speed is uniform, and his state is inertial, so therefore his "direction" cannot be changing. That means he is moving in a "straight line."
4. We will call this (circular) straight line a "geodesic" and, as stipulated call a geodesic path an "intertial state."
End result seems to be that in GR all accelerated states are inertial and, conversely, all inertial states are accelerated, just depending on your whim at the time. Nice way to have your cake, and eat it, too, eh?
Like I said before, don't even talk to me about "inertial frames" if this is also your definition. It is senseless and meaningless.
Let's distinguish between 'truly' inertial as colton used it (motion in a straight line with no acceleration, outside forces, etc.) and empirically inertial (behaves as if it is moving in a staight line with no acceleration, outside forces, etc.). The environment of the astronaut would then be empirically inertial, and following the timelike geodesic in a GR environment will always be empirically inertial. So, does 'this particular state is empirically inertial' become 'all states are empircally inertial'? No, not at all. For example, if the rocket is sitting on a sizable planetoid, even if the planetoid itself, and therefore the rocket, is in an truly inertial state, the state of the rocket is not empircally inertial, because of the effects of gravity from the planetoid acting on the rocket. So you can be truly inertial but not empircally inertial, and you can be empirically inertial byut not truly inertial. Of course, you can also be both or neither.
I have been using inertail to mean empircally inertial, and I think this has been a problem. I will be more careful.
That aint even the end of it, though. Since he can't feel gravity, we also say there is no gravity.
What? You caqn say that any effects of gravity can also be interpreted as effects of acceleration. It that what you mean?
You don't need much to get to that, at any rate. There are moving at a high speed relative to each other. Pat says: I'm at rest. Chris says: I'm at rest.
Technically, both say, 'I can analyze the effects of our relative motion as it I am at rest'. Choosing one to be at rest is choosing a cordinate system.
Looks like ya aint got but two choices:
1. They aint movin, or
2. One of them is wrong.
Uhhh, I think Imma say number 2, there, eh?
What does it mean to have a "wrong" coordinate system?
I said: "I'm guessing, but the thing would probably start falling toward the Sun, at least until it picked up enough speed to maintain a stable orbit."
But, as I said, I suspect this would depend on which direction it was pointed and the direction of it's angular momentum with respect to the sun. Under the right circumstances, I figure it would just fall straight into the sun and burn up. By the time it got there it would be going a hell of a lot faster than 1/3 of the earth's speed of revolution about the sun.
One Brow said: "Is what I am describing unclear in some fashion?"
I'm not sure. Let me make a few comments.
1. The rocket in space could not maintain the same orbit as earth unless it maintained the same speed (relative to the sun) as the earth.
2. It seems to me that, in order to do that, it would have be moving "away from" the earth at an even greater speed.
3. If this whole example is supposed to revolve around the fact that the earth is already moving in one direction (clockwise) around the sun and the rocket will be moving the other (counter-clockwise), then SR would take all those things into account.
4. Here we are trying to consider compound motion (not just the simple at-rest/moving example as in the twin paradox). This changes things, of course.
5. Given all the variables, I don't know which one is moving faster, but I will simply say that, if SR is right, the one who has moved faster will be younger.
The hafele-keating experiment flew planes in both directions, and made the corresponding adjustments necessitated by the difference in direction. Read all about it here, if you're interested:
http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment
I said: "...but I will simply say that, if SR is right, the one who has moved faster will be younger." I mean considering the speed dilation effects alone, of course. Any gravitional effects could offset these, but my statement ignores them.
One Brow asked: "U2 was the moving clock in K. K doesn't have any pseudo-gravitational fields needed to accout for the relative motion, so no calculations are required based upon these fields. Does that address what you are asking?"
No, it doesn't, it's just another case of clock number confusion on my part. I meant to say clock U1, not U2. The idea is to choose a different clock to designate as moving in K.
In light of my last post, would this response change? "No. Regardless of whether you uce coordinate system K or K', GR agrees that U2 will experience less time, because U1 follows the geodeisic."
1. The rocket in space could not maintain the same orbit as earth unless it maintained the same speed (relative to the sun) as the earth.
I'd rather stick with R1 and R2, if you don't mind. R2 can can stay in the orbital path at a slower speed, simply by pointing it's rocket directly toward to the sun and firing it just enough to counter the effects of gravity partially. I would agree that because the rocket is constantly (or at least contunioually) firing, is is not "in orbit" in that path.
... then SR would take all those things into account.
I have consistently referred to "relativity theory", not just a small part of it, in this example.
Do you agree R1 covers twice the distance of R2?
Thanks for the article. My example is probably a variation on this.
I mean considering the speed dilation effects alone, of course. Any gravitional effects could offset these, but my statement ignores them.
You seem to think these are fundamentally different things. It is always possible to choose a coordinate system where all the time effects are "speed effects", or one where all the effects are "graviational effects". That is the difference between K and K'.
I said: "That aint even the end of it, though. Since he can't feel gravity, we also say there is no gravity.
What? You caqn say that any effects of gravity can also be interpreted as effects of acceleration. It that what you mean?
No, that aint what I mean, and that's the point I made before, although there is more than one point to be made about all these shenanigans.
Al says the guy "is" inertial, or could at least be looked at that way (which puts him in an SR frame, according to Al). But here there is NO acceleration and there is NO gravity. That's the only way your circle can become a "straight line" and be interial--if there is acceleration, the state is not inertial. Likewise, if there is gravity, then the "inertial" state would not be inertial (the object would be moving under the influence of an external force, i. e., gravity)>
So, like I said before, Al turns the claim that it could be "either" acceleration or gravity into "it can be "neither" acceleration or gravity." Purty slick, eh?
If you say that, in K, U1 is moving due to some system of propulsion, that will cause U1 to leave the geodeisic, and experience time dilation.
In fact, for either clock, movement by gravitation alone means that clock remains in a geodeisic, and so has the maximal amount of time passage compared to any other reference frame. Movement/resistance to movement by propulsion/brick wall/etc. means leaving the geodeisic and experincing time dilation.
One Brow asked: "What does it mean to have a "wrong" coordinate system?"
Well, you tell me, eh?
suppose I can pick two doors. One has a car behind it, the other a jackass. Whichever one I pick I get sumthin free. I can't possibly go wrong, ya might say.
So, like I said before, Al turns the claim that it could be "either" acceleration or gravity into "it can be "neither" acceleration or gravity." Purty slick, eh?
I see it as a change of effect. When you are following the geodesic, you don't detect gravity empirically, but gravity still has an effect: it created the geodeisic you are following.
To answer that more seriously, you can't pick a "wrong" one for mathematical purposes. But, as a matter of actual reality, involving motion, one set of assumptions must be wrong. So is your question "wrong" for what purposes, math or reality?
One Brow said: "I see it as a change of effect. When you are following the geodesic, you don't detect gravity empirically, but gravity still has an effect: it created the geodeisic you are following."
Well, I don't think Al sees it that way in GR. There is no "force" of gravity for him. It's simply a matter or curves spacetime, and all, ya know?
One Brow asked: "What does it mean to have a "wrong" coordinate system?"
Well, you tell me, eh?
I don't think there is such a thing, as long as your coordinates are sufficient to cover all of space and don't assign two different numbers to the same points. Some are easier to use or more intuitively appealing, but that doesn't make them less "wrong".
suppose I can pick two doors. One has a car behind it, the other a jackass. Whichever one I pick I get sumthin free. I can't possibly go wrong, ya might say.
How can one coordinate system be the metaphorical jackass (other than being harder to use)?
Edit: Meant to say: "It's simply a matter of curved [not "or curves"] spacetime, and all, ya know?
To answer that more seriously, you can't pick a "wrong" one for mathematical purposes. But, as a matter of actual reality, involving motion, one set of assumptions must be wrong. So is your question "wrong" for what purposes, math or reality?
When it comes to a choice between K and K', you can certainly prefer K for reasons of conservation of mass-energy. I have no issue with that. Inertial reference frame respect the conservatino of mass-energy.
With Pat/Chris, both of the frames respect mass-energy. They are equally good. If neither breaks their inertial behavior, there will never be a reason to prefer either one. They will be equally correct in any meaningful, non-arbitrary way. It's only after one or both environments becmoe non-inertial that you could prefer one frame over the other.
I'm repeating this simply because, when we are both posting at or about the same time, I often miss intervening posts until much later. You may do the same, I dunno:
To answer that more seriously, you can't pick a "wrong" one for mathematical purposes. But, as a matter of actual reality, involving motion, one set of assumptions must be wrong. So is your question "wrong" for what purposes, math or reality?
Well, I don't think Al sees it that way in GR. There is no "force" of gravity for him. It's simply a matter of curved spacetime, and all, ya know?
Yes, that's what I said the effect of gravity was. It has an effect, to curve spacetime and set the geodeisic.
Perhaps you could come up with a Pat/Chris scenario, and then describe how, in reality, one is right and the other is wrong?
You did not do this when you talked about Pat acceleration X months ago. What Pat did X months ago does not affect how their clocks will compare in the future.
One Brow said: "With Pat/Chris, both of the frames respect mass-energy. They are equally good. If neither breaks their inertial behavior, there will never be a reason to prefer either one. They will be equally correct in any meaningful, non-arbitrary way. It's only after one or both environments becmoe non-inertial that you could prefer one frame over the other."
I agree with what you are saying here, with one exception (distinction). I agree that we have no way to "decide" or "know" who is right. However, it is wrong to say that they are "equally correct" in their assumptions (I thought you explicitly acknowledged this, at one point, after 100's of posts denying it). They cannot be "equally correct." Even if we don't (and can't) know "who" is incorrect, one MUST nonetheless be incorrect. They cannot BOTH be correct in their mutually exclusive assumptions that they (individually) are at rest.
See the distinction?
One Brow said: "What Pat did X months ago does not affect how their clocks will compare in the future."
Why not?
What the travelling twin did (blast off and turn around) did affect how their clocks compared "in the future," didn't it? It this case "the future" means 10.28 earth years.
10.28 earth years later, that is.
I said: "Even if we don't (and can't) know "who" is incorrect, one MUST nonetheless be incorrect."
In terms of my other analogy, I don't (and can't) know which door the car is behind, but it's still the "correct" door for me to pick. My ignorance does not change that.
I said: 1. The rocket in space could not maintain the same orbit as earth unless it maintained the same speed (relative to the sun) as the earth.
I'd rather stick with R1 and R2, if you don't mind. R2 can can stay in the orbital path at a slower speed, simply by pointing it's rocket directly toward to the sun and firing it just enough to counter the effects of gravity partially. I would agree that because the rocket is constantly (or at least contunioually) firing, is is not "in orbit" in that path.
I disagree with this, or else misunderstand the question. A satellite (of the sun, not the earth) cannot stay in the exact same orbit (same altitude, same plane) as another satellite of the sun UNLESS it is going at the same speed relative to the sun.
Like I said, if they are both going the same speed, relative to the sun, then they presumably be separating from each other at TWICE that speed, if they are going in opposite directions.
We've been through all this before, Eric, in a probability context. Some crucial distinctions must be made. Take this example.
Game show: Car behind door 1, jackass behind door 2. You know it, because you are the host. It's staying there (no one is constantly driving it back and forth between 1 & 2).
We have two contestants, each allowed to pick 1 door. Neither of them have any reason to pick 1 over 2. A picks 1, B picks 2. No one can say that either of them made a "wrong" choice from their perspective. No one "knew" it was behind 1, but picked 2 anyway. Fair enough.
That said, they are not BOTH going to get the car. A will, B won't. A was right, B was wrong.
The chances of either of them "guessing" right when picking door number 2 was 0%, given the facts, but 50%, given their limited state of knowledge. Problem is, their state of knowledge is NOT what dictates which door the car is behind. It is in fact totally irrelevant.
The "odds" of the car being behind 1 are 100%, while of being behind 2 are 0%, whether they can "tell" you that, or not.
The distinction to be made is this:
The fact that it is "impossible" for me to know for sure does NOT mean that it is impossible for X to be.
An epistemological deficiency is NOT equivalent to ontological impossibility. On the contrary, something can be ontologically certain, yet epistemologically unknown, and perhaps even unknowable, given our current circumstances.
Secondary point: Even if you are not the game show host, just a member of the audience, let's say, and even if you don't yourself know which door the car is behind, you still know that they are not BOTH going to get a car. You know that they are not "equally right." You don't even need to know where the car is to know that much.
When we send a satellite into orbit, we generally blast it off perpendicular to the earth's surface. This reduces the amount of power it takes to get it out of the earth's atmosphere. Once it clears the major part of the "drag" caused by the atmosphere, we use an IGS (inertial guidance system) and thrusters to "turn" it so is has the necessary "sideways" motion (and inertia, once the thrusters are off again) to maintain a stable orbit.
Question: If space is simply, and naturally, curved, why would we need to use power to "turn" the satellite?
As I said before, it is my understanding that, if we did not turn the satellite, it would simply fall "straight" back to earth (unless it was exceeding escape velocity). Again, if space is curved, why doesn't it just naturally "settle into" a circular orbit, instead of falling back to earth.
I said: "The "odds" of the car being behind 1 are 100%, while of being behind 2 are 0%, whether they can "tell" you that, or not."
Implied here, but left unstated, is this: Despite what they may think, or may know, the odds of them being correct are NOT 50% when they pick door #2 (they are 0%). They are NOT 50% when they pick door #1 (they are 100%). The odds simply are NOT 50/50. The 50/50 view simply comes from the standpoint of one with insufficient facts, not the actual facts.
In the context of moving bodies the same point is made as follows:
1. If 2 objects are not going at the same speed, then they are going at different speeds.
2. If they are going at different speeds, then one is going faster than the other, whether you know which one it is, or not.
Assuming that the material they are composed of started out at the same speed (say, at rest in the "cosmic egg" before the big bang), then over the course of their entire history of existence (the details of which are not known to us) one of the two objects has been, on a net basis, accelerated more/decelerated less than the other.
But forget the big bang. Compared to the CMBR (cosmic microwave background radiation) there is, logically speaking, at least one object that is moving more slowly than all others in the universe, whether we know where it is, or not. Let's call that object "slowest." Everything else is moving "faster" in relation to that.
"In cosmology, cosmic microwave background (CMB) radiation (also CMBR, CBR, MBR, and relic radiation) is a form of electromagnetic radiation filling the universe...Precise measurements of cosmic background radiation are critical to cosmology, since any proposed model of the universe must explain this radiation...The cosmic microwave background is isotropic to roughly one part in 100,000"
http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation
According to Berkeley physicist Richard Muller and his collegues, the CMBR can be used to detect the absolute motion of the earth in space:
"The new aether-drift experiment shows that the earth's net motion in space is about 400 kilometers per second."
http://muller.lbl.gov/COBE-early_history/Aether-Drift-Scienti%231E3402.pdf
My point is not to argue the technical physics invovled, I'm not qualified to do that. My main point is merely a logical one. You don't even need to know an object's "absolute" motion to know that if two are moving, relative to each other, then they are either moving at the same speed or else one is moving faster than the other, whether you can say which particular is going faster, or not.
More from Muller's experiments:
"Although it is not motion with respect to some frame of reference fixed in space, it is motion with respect to the most natural frame of reference in cosmology: the expanding coordinate system in which the galaxies are nearly at rest."
The problem I see with relativists is the prevalent thought pattern that seems to go like this:
1. If I can't determine the actual situation, then I don't know it.
2. If I don't know it, then it is impossible for me to give you an answer.
[OK, so far, so good, I have no problem with that, but then...]
3. If *I* can't possibly give you an answer, then there can be no possible answer. The facts, and all possible facts, begin and end with what *I* know.
This goes a little too far, if you catch my drift. The attitude is then reflected in an onslaught of raw, unsupported assertions that "all motion is relative, there is no abolute motion, therefore there can be no answer," all of which basically says nothing of substance; it just makes vague assertions.
If that is your position, that it is "impossible" for one thing to be moving faster than another, then demonstrate why that must be true. What leads you to that conclusion? What are your assumptions, and what is the exact reasoning upon which you base this conclusion. And please, don't use arguments which simply assume the conclusion.
One example of this would be resorting to the assertion that "relativity theory says...."
In effect that line of argument merely assumes the conclusion you are supposedly "arguing" for. Relativity theory presupposes that absolute motion can't be detected (it does NOT prove that it does not exist or that it cannot be detected in principle). The assertion that "all reference frames are equally valid," when divorced from it's strictly mathematical implications, is, as an ontological position, strictly a metaphysical, philosophical one, not a "scientific" one.
In my vocabulary, the statement that "there is motion," is basically tantamount to "there is absolute motion," and/or "there absolutely is motion."
If there is motion, then *something* is moving. As soon as that is conceded, it's only natural to ask what it is that's moving. If I take a big-ass swig from my 40, I say the bottle is moving when I lift it, etc.
Some wise-guy comes along and tells me that it's possible to view the 40 as remaining "at rest," and so it is therefore "possible" that it never moved at all. My chair, the floor, the wall, the ceiling, etc. all moved so that I came to it.
I say: What!? Is that supposed to prove something?
Since when does a "possible view" become the standard for what is reasonably possible?
I agree with what you are saying here, with one exception (distinction). I agree that we have no way to "decide" or "know" who is right. However, it is wrong to say that they are "equally correct" in their assumptions (I thought you explicitly acknowledged this, at one point, after 100's of posts denying it). They cannot be "equally correct." Even if we don't (and can't) know "who" is incorrect, one MUST nonetheless be incorrect. They cannot BOTH be correct in their mutually exclusive assumptions that they (individually) are at rest.
See the distinction?
Saying "X is at rest" is not an assumpiton, it is the selection of a coordinate system. Again, this is like saying either the polar coordinates or the Cartesian coordinates for a point must be wrong.
One Brow said: "What Pat did X months ago does not affect how their clocks will compare in the future."
Why not?
Because the clocks are synchronized as they pass each other. Clocks that are light-years apart cannot be meaningfully synchronized.
What the travelling twin did (blast off and turn around) did affect how their clocks compared "in the future," didn't it? It this case "the future" means 10.28 earth years.
The clocks were synchronized before take-off, and you can measure the difference that occur to them after synchronization.
I said: "Even if we don't (and can't) know "who" is incorrect, one MUST nonetheless be incorrect."
In terms of my other analogy, I don't (and can't) know which door the car is behind, but it's still the "correct" door for me to pick. My ignorance does not change that.
In the Pat/Chris scenario, there is only one door, that you are describing from two different angles. "Pat is at rest" and "Chris is at rest" is the same metaphorical door.
I disagree with this, or else misunderstand the question. A satellite (of the sun, not the earth) cannot stay in the exact same orbit (same altitude, same plane) as another satellite of the sun UNLESS it is going at the same speed relative to the sun.
Let's say the force of gravity on R1 is 100 newtons to keep it in a circular orbit. If you point the rocket on R2 and fire it directly at the sun with a force of 75 newtons, so the net force pulling toward teh sun is only 25 newtons, it will in fact stay in the exact same orbital path as R1 if is moves at half the speed of R1. The orbital speed varies dierctly as the square root of the net force pulling R2 in.
An epistemological deficiency is NOT equivalent to ontological impossibility. On the contrary, something can be ontologically certain, yet epistemologically unknown, and perhaps even unknowable, given our current circumstances.
That this is possible generally (as I have acknowledged) does not mean it applies specifcally to the Pat/Chris scenario.
Question: If space is simply, and naturally, curved, why would we need to use power to "turn" the satellite?
Because many geodeisics would result in the satellite striking the earth or at least the atmosphere, so it needs to be guided to a geodeisic that provides for a stable orbit. Curved doesn't mean every geodeisic is an orbit.
In the context of moving bodies the same point is made as follows:
1. If 2 objects are not going at the same speed, then they are going at different speeds.
2. If they are going at different speeds, then one is going faster than the other, whether you know which one it is, or not.
Assuming that the material they are composed of started out at the same speed (say, at rest in the "cosmic egg" before the big bang), then over the course of their entire history of existence (the details of which are not known to us) one of the two objects has been, on a net basis, accelerated more/decelerated less than the other.
But forget the big bang.
You can't just choose a reference frame to say everything is moving against is, and then discard that reference frame.
Compared to the CMBR (cosmic microwave background radiation) there is, logically speaking, at least one object that is moving more slowly than all others in the universe, whether we know where it is, or not. Let's call that object "slowest." Everything else is moving "faster" in relation to that.
Microwaves are light waves, and the CMBR moves in various directions. It's not a reference frame at all.
According to Berkeley physicist Richard Muller and his collegues, the CMBR can be used to detect the absolute motion of the earth in space:
"The new aether-drift experiment shows that the earth's net motion in space is about 400 kilometers per second."
This assumes the rest frame of the location of the big bang you reference earlier.
My point is not to argue the technical physics invovled, I'm not qualified to do that. My main point is merely a logical one. You don't even need to know an object's "absolute" motion to know that if two are moving, relative to each other, then they are either moving at the same speed or else one is moving faster than the other, whether you can say which particular is going faster, or not.
Yes, the example you provided computes an absolute speed *based upon a presumed rest frame*. Nothing has a speed without a rest frame to compare it to. How can you be faster if you can't even define a speed?
"Although it is not motion with respect to some frame of reference fixed in space, it is motion with respect to the most natural frame of reference in cosmology: the expanding coordinate system in which the galaxies are nearly at rest."
The origin of which is the presumed location of the big bang, AFAICT.
The problem I see with relativists is the prevalent thought pattern
is nothing like what you presented.
If that is your position, that it is "impossible" for one thing to be moving faster than another, then demonstrate why that must be true. What leads you to that conclusion? What are your assumptions, and what is the exact reasoning upon which you base this conclusion. And please, don't use arguments which simply assume the conclusion.
Not impossible, meaningless. There is a difference. What is impossible can still be meaningful. At my wieght and physical condition, it is impossible for me to jump 7 feet off the ground. Jumping 7 feet off the ground is still a meaningful act. However, until you provide a frame of reference, it is meaningless to say one object is faster than the other. The very notion of speed requires a rest frame to compare the speed to. How can it be meaningful to discuss "faster" without a rest frame if you can't even discuss speed without a rest frame?
Relativity theory presupposes that absolute motion can't be detected
Wrong. Relativity theory gives you the same answers regardless of which description of motion is considered absolute. It doesn't say absolute motion doesn't exist, it says it doesn't care which descripiton is considered absolute.
The assertion that "all reference frames are equally valid," when divorced from it's strictly mathematical implications, is, as an ontological position, strictly a metaphysical, philosophical one, not a "scientific" one.
The assertion that all reference frames are equally valid is, ontologically, the assertion that the universe is consistent, and that what you see reflects what really happened. No more, no less.
In my vocabulary, the statement that "there is motion," is basically tantamount to "there is absolute motion," and/or "there absolutely is motion."
In practice, you do this by assuming a rest frame without mentioning what it is. Physicist try not to be that carefree, when doing science.
I say: What!? Is that supposed to prove something?
What are that guy looking to prove?
One Brow said: "Saying "X is at rest" is not an assumpiton, it is the selection of a coordinate system. Again, this is like saying either the polar coordinates or the Cartesian coordinates for a point must be wrong."
Eric, have you been talking ALL math, and nothing but math, all this time? I have repeatedly told you that I'm not approaching this topic to discuss math. Is that ALL you are capable of talking about, and the only terms you are capable of thinking in?
I don't give a rat's ass about math, I thought I made that clear, and I thought I have said repeatedly, that I have not been talking in math terms all this time.
Do you even know what the topic is? Did I ever suggest that it would wrong, as a mathematical matter, to choose it as a coordinate system? Jeez.....
One Brow said: "What Pat did X months ago does not affect how their clocks will compare in the future."
Why not?
One Brow said: "Because the clocks are synchronized as they pass each other. Clocks that are light-years apart cannot be meaningfully synchronized."
Why is there any need to "synchronize" the clocks a second time?
What the travelling twin did (blast off and turn around) did affect how their clocks compared "in the future," didn't it? It this case "the future" means 10.28 earth years.
One Brow said: "The clocks were synchronized before take-off, and you can measure the difference that occur to them after synchronization."
What does "measurment" have to do with theoretical problems and solutions? Did you, or anyone, go and measure the light years, the times, the distances, etc., involved in the wiki problem, which you said had correct answers?
Obviously not, since the trip never even occurred. How can the answers there be "correct" if you didn't go measure them. Do you even see how lame this is?
One Brow said: "it will in fact stay in the exact same orbital path as R1 if is moves at half the speed of R1."
I don't see how this would be possible. You are not going to accelerate something with great force toward the sun, then have it just "stop" in it's tracks, let alone then starting moving sideways at the speed you have said it would. I don't see how it would change anything about what SR predicts, either way. SR says faster motion results in time dilation. Are you trying to prove that SR is wrong?
Let's just drop this rediculous example, unless you have some point. Are you saying SR is wrong?
One Brow said: "In the Pat/Chris scenario, there is only one door, that you are describing from two different angles. "Pat is at rest" and "Chris is at rest" is the same metaphorical door."
What is this supposed to mean?
One Brow said: "Because many geodeisics would result in the satellite striking the earth or at least the atmosphere, so it needs to be guided to a geodeisic that provides for a stable orbit. Curved doesn't mean every geodeisic is an orbit."
I think you misunderstand the nature of the question, but never mind. Colton doesn't even act like he has a good handle on geodesics and how they work. I'm certainly not going to argue with you about the technical details of GR.
I said: "An epistemological deficiency is NOT equivalent to ontological impossibility. On the contrary, something can be ontologically certain, yet epistemologically unknown, and perhaps even unknowable, given our current circumstances."
That this is possible generally (as I have acknowledged) does not mean it applies specifcally to the Pat/Chris scenario.
And it doesn't mean it doesn't apply. Can you give me a reason (I mean a reason, not another of 1000 raw assertions) why it doesn't apply?
One Brow asked: "Yes, the example you provided computes an absolute speed *based upon a presumed rest frame*. Nothing has a speed without a rest frame to compare it to. How can you be faster if you can't even define a speed?"
I can tell you which guy wins a 100 yard dash, even if I have no clue as to what speed any of the runners were going.
Do you see this point? Do you see that you can have motion without being able to specify ABSOLUTE motion? I don't think you do. I think you confuse youreself to the point where you are, in effect, denying that any motion is ever possible.
One Brow said: "Microwaves are light waves, and the CMBR moves in various directions. It's not a reference frame at all."
You should go educate all those physicists at Berkeley, and other universities all over the world, who seem to think CMBR can be used to create a virturally motionless reference frame, eh?
One Brow said: "Not impossible, meaningless. There is a difference. What is impossible can still be meaningful. At my wieght and physical condition, it is impossible for me to jump 7 feet off the ground. Jumping 7 feet off the ground is still a meaningful act. However, until you provide a frame of reference, it is meaningless to say one object is faster than the other. The very notion of speed requires a rest frame to compare the speed to. How can it be meaningful to discuss "faster" without a rest frame if you can't even discuss speed without a rest frame?"
And all of this is saying what? Two guys racing. One wins. What is missing, and why is it not implied?
I said: "The assertion that "all reference frames are equally valid," when divorced from it's strictly mathematical implications, is, as an ontological position, strictly a metaphysical, philosophical one, not a "scientific" one."
Your reply: "The assertion that all reference frames are equally valid is, ontologically, the assertion that the universe is consistent, and that what you see reflects what really happened. No more, no less."
Does it mean that when I walk to the store, I am the one moving, and the store, and everything else in the universe is not moving toward me?
I say: What!? Is that supposed to prove something?
Your response: "What are that guy looking to prove?"
Great question! Why is this consistently brought up. What is it supposed to prove?
One Brow said: "However, until you provide a frame of reference, it is meaningless to say one object is faster than the other."
Two objects: Which is moving faster with respect to the other? Impossible to say? Wiki seems to do it OK. The spaceship is moving faster than the earth, they say. They don't have to bring in the sun, or some other object to reach that conclusion. They don't seem to need the aether to conclude that. What's the problem?
Each object simply refers to the other. One is moving faster.
In the wiki example, take the perspective of the earth. From that perspective the spaceship is moving faster.
Take the perspective of the spaceship. From that perspective, the spaceship is moving faster too.
Take your perspective, if you just see a spacehip in the sky and don't know how it got there. YOU don't know which is moving faster.
So what? Does that mean all the other people on the earth and in the spaceship are wrong? Does that mean the spaceship is no longer "really" moving faster? What does your state of ignorance have to say about the facts?
Eric, have you been talking ALL math, and nothing but math, all this time? I have repeatedly told you that I'm not approaching this topic to discuss math. Is that ALL you are capable of talking about, and the only terms you are capable of thinking in?
Discussing physics without mathematics is like discussing grammar without mentioning nouns.
I don't give a rat's ass about math, I thought I made that clear, and I thought I have said repeatedly, that I have not been talking in math terms all this time.
Is the notion of whether Pat or Chris will be younger, whether clock U1 or U2 goes through less time, a mathematical question? The questions don't seem to make sense without numbers.
Do you even know what the topic is? Did I ever suggest that it would wrong, as a mathematical matter, to choose it as a coordinate system? Jeez.....
Whether you realize it or not, by saying wither Pat or Chris must be wrong, this is exactly what you are doing.
One Brow said: "Because the clocks are synchronized as they pass each other. Clocks that are light-years apart cannot be meaningfully synchronized."
Why is there any need to "synchronize" the clocks a second time?
When do you think is the first time they were synchronized?
What does "measurment" have to do with theoretical problems and solutions? Did you, or anyone, go and measure the light years, the times, the distances, etc., involved in the wiki problem, which you said had correct answers?
Obviously not, since the trip never even occurred. How can the answers there be "correct" if you didn't go measure them. Do you even see how lame this is?
It's a thought experiement, so naturally the measurements occur as a part of the thoughts. Your claim that they are not real seems bizarre.
One Brow said: "it will in fact stay in the exact same orbital path as R1 if is moves at half the speed of R1."
I don't see how this would be possible.
Then do some research.
You are not going to accelerate something with great force toward the sun, then have it just "stop" in it's tracks,
Never claimed I would, nor is that a part of the R1/R2 scenario.
SR says faster motion results in time dilation. Are you trying to prove that SR is wrong?
Let's just drop this rediculous example, unless you have some point. Are you saying SR is wrong?
I am saying that your interpretations are naive. I am saying that something can go faster and still experience more time, in a variety of ways, of which this is one. I am trying to get you to see the bigger picture.
One Brow said: "In the Pat/Chris scenario, there is only one door, that you are describing from two different angles. "Pat is at rest" and "Chris is at rest" is the same metaphorical door."
What is this supposed to mean?
That your "car behind door 1, goat behand door two" analogy is off-base. That Pat and Chris are describing the same events with complete accuracy, and the difference between their descriptions is the difference between selecting one coordinate system over the other.
I think you misunderstand the nature of the question, but never mind. Colton doesn't even act like he has a good handle on geodesics and how they work. I'm certainly not going to argue with you about the technical details of GR.
I also don't want to talk the technical nature of GR, but if I misunderstood the question, perhaps you could re-phrase it?
And it doesn't mean it doesn't apply. Can you give me a reason (I mean a reason, not another of 1000 raw assertions) why it doesn't apply?
In order for something to be an ontological certainy, it has to have a meaningful ontological interpretation. There is no meaningful ontological interpretation to saying "Pat is wrong" or "Chris is wrong". If you say "Pat is right and Chris is wrong", this does not alter the situation in any way from saying "Chris is right and Pat is wrong". Under any scenario where you could bring compare Pat and Chris meaningfully in the future, by bringing them into the same place at the same time, the answers about the amount of time passed for Pat vs. the amount passed for Chris will be identical between assuming Pat was right and assuming Chris was right.
No, if you can supply one meaningful result of saying "Pat is right", i. e., one that changes a future calculation of their relationship after they are reunited at the same in the same place, I'll change my opinion.
You can arbitrarily pick any reference frame, and in one of those frames Pat will be right, in another Chris will be right. But you don't have a way to make the reference frame selection non-arbitrary.
I can tell you which guy wins a 100 yard dash, even if I have no clue as to what speed any of the runners were going.
The one that went faster in the reference frame where the gound was at rest, of course.
Do you see this point? Do you see that you can have motion without being able to specify ABSOLUTE motion?
There was no absolute motion, just the assumption of the ground as a reference frame.
I don't think you do. I think you confuse youreself to the point where you are, in effect, denying that any motion is ever possible.
I'm not saying anything remotely like that.
You should go educate all those physicists at Berkeley, and other universities all over the world, who seem to think CMBR can be used to create a virturally motionless reference frame, eh?
The way I read the article, teh CMBR revealed the reference frame, but was not the reference frame itself.
And all of this is saying what? Two guys racing. One wins. What is missing, and why is it not implied?
Nothing is missing. The ground being at rest is implied by the notion of "race". Any race is a contest between two points, at least one of which will be at rest or at least treated that way.
Your reply: "The assertion that all reference frames are equally valid is, ontologically, the assertion that the universe is consistent, and that what you see reflects what really happened. No more, no less."
Does it mean that when I walk to the store, I am the one moving, and the store, and everything else in the universe is not moving toward me?
A valid reference frame is not a complete interpretation of the physics of an event.
Great question! Why is this consistently brought up. What is it supposed to prove?
That you can get absolute results from strictly relative observatons.
Two objects: Which is moving faster with respect to the other? Impossible to say? Wiki seems to do it OK. The spaceship is moving faster than the earth, they say. They don't have to bring in the sun, or some other object to reach that conclusion. They don't seem to need the aether to conclude that. What's the problem?
The wiki article says the spaceship is moving because it is changing inertial frames, leaving the geodeisic. It never says it is moving "faster" than the earth.
Each object simply refers to the other. One is moving faster.
The earth is moving slower relative to the ship than the ship is realtive to the earth?
In the wiki example, take the perspective of the earth. From that perspective the spaceship is moving faster.
Take the perspective of the spaceship. From that perspective, the spaceship is moving faster too.
In both perspectives, the spaceship moves because it leaves the geodeisic.
What is the ontological interpretation, to you, of moving faster? What does it mean?
Do you even know what the topic is? Did I ever suggest that it would wrong, as a mathematical matter, to choose it as a coordinate system? Jeez.....
Whether you realize it or not, by saying wither Pat or Chris must be wrong, this is exactly what you are doing.
Whether you know it or not EVERYTHING is not math question. Do you know ANYTHING other than math? ANYTHING?
One Brow said: When do you think is the first time they were synchronized?
Let me rephrase the question. Why do their clocks EVER need to be synchronized? I don't recall the wiki problem making that a necessary condition.
One Brow said: "It's a thought experiement, so naturally the measurements occur as a part of the thoughts. Your claim that they are not real seems bizarre."
So you and I are doing a "real" experiment, not a thought experiment, that the idea?
One Brow said: "I am saying that your interpretations are naive. I am saying that something can go faster and still experience more time, in a variety of ways, of which this is one. I am trying to get you to see the bigger picture. "
Are you trying to claim that SR is incorrect, insofar as it says faster speed will result in time dilation, or not? If not, then I don't care about your unfathomable hypothetical examples.
Whether you know it or not EVERYTHING is not math question. Do you know ANYTHING other than math? ANYTHING?
I agree not everything is a math question. Specifically, the difference between regarding Pat to be at rest and Chris to be at rest is a math question. Ontologically, there is no difference between those positions.
Let me rephrase the question. Why do their clocks EVER need to be synchronized? I don't recall the wiki problem making that a necessary condition.
You can't compare how much time has passed on two clocks unless you have a point where you know what they each read at the same time.
So you and I are doing a "real" experiment, not a thought experiment, that the idea?
NO, the opposite. To object to a part of a process as being unreal, when the process as a whole is unreal, is bizarre.
Are you trying to claim that SR is incorrect, insofar as it says faster speed will result in time dilation, or not?
I am saying that this is not a valid interpretation of SR, but a naive and inaccurate interpretation of it. I am sure you can appreciate there is a difference between saying SR is incorrect and saying that yoru understanding of it is inferior to what it could be.
One Brow said: "I am sure you can appreciate there is a difference between saying SR is incorrect and saying that yoru understanding of it is inferior to what it could be."
And I am sure that you can understand that I have had my fill out your fucking horseshit. For the 11,241st time you re-assert your conclusion without logic or support. In fact your claims are counter to all reason and logic, including your own. If you wish to post Colton's responses I will look at them. Even attempting to discuss this with you is one of the biggest wastes of time I've ever experienced. It's not you fault, it's mine. I should have stopped with this stupidity 1,000 posts ago.
Theories make predictions. Those predictions may be right or wrong, but if a theory doesn't make predictions, it is not a theory.
2. What does SR predict?
a. Basically that for observers on a given object, as that object's speed increases, the observers' perception of time will slow down and distances will contract.
b. If that object maintains the same speed, there will be no change in these perceptions.
c. If that one object slows down, the observers' perception of time will speed up and distances will lengthen.
That's the prediction, right or wrong.
In order to explicate how this works, SR theorists may talk about how observer A will see observer B's clock, and vice versa, but that is NOT the theory, and it is not the prediction.
SR does NOT say, because observer A sees one thing and observer B sees another, SR makes no predictions whatsover. SR does NOT say it is ONLY a theory about how observers perceive things. It does NOT say that it makes no objective predictions, and that conflicting observations render objective predicitions impossible.
That's NOT what the theory says. Anyone who thinks it is what the theory says looks pretty ridiculous telling everyone else that THEY don't understand the theory.
In an effort to be neutral I said:
"What does SR predict?
a. Basically that for observers on a given object, as that object's speed increases, the observers' perception of time will slow down and distances will contract.
b. If that object maintains the same speed, there will be no change in these perceptions.
c. If that one object slows down, the observers' perception of time will speed up and distances will lengthen."
I really should not have made any reference to "perceptions" in any of these. SR says time WILL slown down with increased speed, and that lengths WILL contract. It's not a mere matter of "perception," it is what WILL happen, or at least SR so predicts.
"What does SR predict?
a. Basically that for observers on a given object, as that object's speed increases, the observers' perception of time will slow down and distances will contract."
Assertion by misinformed know-it-all: This statement is FALSE!! Whether or not time dilates and lengths contract is 100% OBSERVER DEPENDENT! If a guy sped up, but didn't think he did, then time would NOT dilate for him! It would be IMPOSSIBLE!
SR theorist: You should leave your social/political/philosophical agenda at home when you come to study scientific theory, pal.
The year, 1916:
Interviewer: Al, I understand that your new GR theory predicts that starlight will be bent by the sun's gravity by a greater degree than Newton's theory.
Al: Wrong. My theory predicts nothing about that.
I: Why not?
Al: Because no experiment has been done yet. We will know what my theory predicts only AFTER an experiment is done to tell us what really happens.
I: Well, what will it predict then?
Al: It will predict whatever the result of the experment tells us happens. It's all observer dependent, ya see?
And I am sure that you can understand that I have had my fill out your fucking horseshit.
All I can do is lead you to water.
Theories make predictions. Those predictions may be right or wrong, but if a theory doesn't make predictions, it is not a theory.
I agree.
SR does NOT say, because observer A sees one thing and observer B sees another, SR makes no predictions whatsover.
I agree.
SR does NOT say it is ONLY a theory about how observers perceive things.
I agree.
It does NOT say that it makes no objective predictions, and that conflicting observations render objective predicitions impossible.
I agree.
That's NOT what the theory says. Anyone who thinks it is what the theory says looks pretty ridiculous telling everyone else that THEY don't understand the theory.
I agree. In fact, you look pretty ridiculous trying to say that I have said any of that.
SR says time WILL slown down with increased speed, and that lengths WILL contract. It's not a mere matter of "perception," it is what WILL happen, or at least SR so predicts.
In order for SR to say that, speed would have to be a property that an object has without reference to any other object. Relativity theory, including SR, does make actual predicitons and is not just about what observers see. However, you can only make actual predicitons about things that actually exist. Speed, as the property of a object without reference to anything else, does not exist.
Whether or not time dilates and lengths contract is 100% OBSERVER DEPENDENT!
Only true to the degree that time is dilated/contracted compared to some other reference frame, so it is dependent on there being some observer reference frame to be compared to.
I said: "Whether or not time dilates and lengths contract is 100% OBSERVER DEPENDENT!
You say: "Only true to the degree that time is dilated/contracted compared to some other reference frame, so it is dependent on there being some observer reference frame to be compared to."
Only true 100% of the time, eh? Read your post, and try to figure out what you are saying. Maybe you will see that you contradict yourself 4-5 within a single post. I'm out.
OK, see you arond later.
"To the degree" doesn't necessarily imply a percentage. It refers to a lack of quality.
One example of a case where the obligatory claim that "both are correct because ______ is not absolute but relative" claim is actually correctly advanced:
"It turns out that as an object moves with relativistic speeds a "strange" thing seems to happen to its time as observed by "us" the stationary observer (observer in an inertial reference frame). What we see happen is that the "clock" in motion slows down according to our clock, therefore we read two different times. Which time is correct??? well they both are because time is not absolute but is relative, it depends on the reference frame. Let's look at the following classic example. There is a set of twins, one an astronaut, the other works for mission control of NASA. The astronaut leaves on a deep space trip traveling at 95% the speed of light. Upon returning the astronauts clock has measured ten years, so yhe astronaut has aged 10 years. However, when the astronaut reunites with his earth bound twin, the astronauthe sees that the twin has aged 32 years! This is explained due to the fact that the astronaut's twin is traveling at relativistic speeds and therefore his "clock" is slowed down."
http://www.phy.olemiss.edu/HEP/QuarkNet/time.html
In SR, time is relative. In this example, "we are correct in "bpth" things, but it's important to see what those two things are, and what they are not. Both are correct in very precise and limited circumstances.
1. The way "we" see our clock is indeed correct for us.
2. The way we see his clock is indeed correct for him.
What is NOT correct is the claim that he would correct if he sees our clock as being "correct (for either him or us) if he assumes that he is at rest and that therefore our clock is running slower.
Why would he not be correct? Because HE is the one moving (relative to us) at a rate of 95% the speed of light. It is the one moving whose clock slows down, and if he manages to convince himself that he is at rest he is simply WRONG (according to the theory of SR, at least). "This is explained due to the fact that the astronaut's twin is traveling at relativistic speeds and therefore his "clock" is slowed down." It is the one moving faster whose clock slows down, not "both."
I no longer have any hope that you will ever see the difference or ever realize how you have been contradicting yourself for about 1200 posts now, but, who knows? Think about it, eh?
I quoted this: "This is explained due to the fact that the astronaut's twin is traveling at relativistic speeds and therefore his "clock" is slowed down."
Upon looking at this closer, it is obvious that he made typo when he said the "astronaut's twin." As the the example makes clear, it is the astronaut doing the travelling, not his twin.
Confused know-it-all: "But, but, both SEE the other's clock as moving more slowly!"
No, they don't. If they both agree on who is moving they will both calculate the same ages for both themselves and their twins and all parties will agree the travelling twins are indeed younger.
If the traveller erroneously assumes he as at rest, then of course he will simply be WRONG, and any calculations he makes based on that erroneous assumption will also be WRONG. If that's the way he "sees" thing, then he simply "sees" things wrong. He is NOT "equally entitled" to view himself as stationary, simply because he is NOT stationary.
How would you "know" who is really moving?That's a separate question, easilly answerable in many circumstances, but the theory does NOT depend on who knows what. It IS and always WILL BE the one travelling faster whose clock slows down, according to the theory. Who knows what when in NO WAY alters the theory. The theory simply predicts what it predicts, without any regard whatsover for who knows what, and when they know it. If you're not sure which one has been travelling, then just see whose clock recorded less time and that will definitively settle the question once and for all. Yes, Virginia, motion is real.
The theory does NOT say, and it never will say, that if both think they are stationary then they are both correct, not when they are separating from themselves in space, at least. Anyone who would argue this simply does not understand the theory, even if they routinely proclaim that THEY know the theory and that anyone who disagrees with them doesn't understand it.
But what if they proclaim it 11,241 times? Well, good point, then it might start to become true...it's all relative...no one can really say...there is no right or wrong answer...SR does not really predict anything, because it says EVERYTHING is true... Still, for me it might take 15,000 assertions to be convinced, not just 11,241. But that's just me, I guess.
You missed the point again, of course. It's not really a surprise.
You have again brought up the twin scenario, and attributed the notion of somedone moving as being the reason they are moving slower. However, the reason is that they left the geodeisic, and people/clocks who stay one the geodeisic always experience maximal time passage.
Whether the traveler takes the point of view that he is at rest or that the earther is at rest, the traveler's leaving of the geodeisic, and the earther's remaining in the geodeisic, is a common feature to both points of view, and in fact any other point of view.
In the basic Pat/Chris scenario, both travelers are in the geodeisic for the entire time you compare their clocks. Both experience a maxiaml passage of time, compared to anu other reference frame. It's really that simple.
I am still waiting for you to provide a meaningful ontological difference between saying Pat is traveling .4c and Chris is traveling at .1c, versus saying both are traveling .25c. Under what circumstances does that change something?
That's a separate question, easilly answerable in many circumstances, but the theory does NOT depend on who knows what.
Of course that's true. I have confirmed as much on multiple occasions. No one has claimed otherwise. Stop being a moron, start reading rather than responding.
It IS and always WILL BE the one travelling faster whose clock slows down, according to the theory.
There is no such thing as "moving faster" when comparing two bodies. Not in SR, relativity theory generally, or physics at all.
YOu're just generally ignorant, and apparently too prideful to understand why and about what. colton told you the exact same thing about Pat/Chris that I did, and it didn't faze you at all. Since you act as if know more the agreed-upon expert, apparently, I see little chance you'll be humble enough to acknowledge you don't understand this. Nevertheless, I will persevere.
One Brow said: "You have again brought up the twin scenario, and attributed the notion of somedone moving as being the reason they are moving slower."
Oh, I did that, eh? Of course YOU know more than Einstien and every other physicist, don't you?
"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/the_twin_paradox#ixzz0amGd0GVD
"If we placed a living organism in a box ... one could arrange that the organism, after any arbitrary lengthy flight, could be returned to its original spot in a scarcely altered condition, while corresponding organisms which had remained in their original positions had already long since given way to new generations. For the moving organism the lengthy time of the journey was a mere instant, provided the motion took place with approximately the speed of light." (Einstein)
http://en.wikipedia.org/wiki/Twin_paradox
That's only about the 20th time I've posted those same quotes, about the 20th you ignored/denied them, and probably the 1000th that you have suggested that ONLY YOU, and not Einstein or anybody else understands SR.
One Brow said: the reason is that they left the geodeisic, and people/clocks who stay one the geodeisic always experience maximal time passage.
That's not a reason, it's a mathematical tautology (figures that you would think it's a "reason," though).
This is nothing but a SR problem and you act like you have answered it with GR. You obviously have not understood a word about time dilation due to speed, from the moment we started discussing it in connection with GPS, about 1200 posts ago.
"The usual version of the twin paradox qualifies as a pure SR problem by modern standards. Spacetime is ordinary flat Minkowski spacetime...it needs to be emphasised that we are not using any actual General Relativity here, and no one ever needs to, to analyse the paradox."
http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_gr.html
One Brow said: "There is no such thing as "moving faster" when comparing two bodies. Not in SR, relativity theory generally, or physics at all."
Maybe you can assert that for the 1000th time, you fucking idiot. Then maybe you can scroll up and see what Einstein said about one "living organism."
If anybody ever actually paid you to teach logic, you owe it to them to take every dollar of salary you got and pay for some logic lessons.
Idiocy is annoying. ARROGANT IDIOCY is intolerable.
One Brow said: the reason is that they left the geodeisic, and people/clocks who stay one the geodeisic always experience maximal time passage.
Quite humorous, actually, especially coming from someone who claimed that even if the earth moved in the twin paradox ("left the geodesic") the clock on the ship would STILL be younger. Hahahahahahah.
Two objects, one is at rest, one is moving. Which one is moving faster?
THAT CAN'T BE ANSWERED!
Hahahahahah
One Brow said: "YOu're just generally ignorant, and apparently too prideful to understand why and about what. colton told you the exact same thing about Pat/Chris that I did, and it didn't faze you at all."
Speaking of Colton....
1. Did he ever respond to my questions?
2. Why is it that, just as soon as he says "absolutely" to the question where you said the answer is "no," you immediately deny what he said about motion being crucial?
Oh, I did that, eh? Of course YOU know more than Einstien and every other physicist, don't you?
You are responding rather than reading, again.
Einstien and every other physicist would more likely say: The ship twin is really traveling and the ship twin is leaving the geodeisic. The first does not imply the second clause. The second clause is the reason the ship twin experiences time dilation. You seem to think I disagree with the first clause, but I don't. I disagree with the implication that the first clause is the source of time dilation, when in fact it is the second clause, and so does every other physicist. Quoting passages at me that you barely understand, and that confirm what I am saying, is hardly likely to change my mind.
Maybe you can assert that for the 1000th time, you fucking idiot. Then maybe you can scroll up and see what Einstein said about one "living organism."
Maybe on that 1000th time you can point out where Einstein uses "faster" or any synonym of it. No, not yet? Maybe you can't find it because it's not there. Maybe you can't find it because you still don't get it, but you have too much hubris to realize how badly you have interpreted things.
Idiocy is annoying. ARROGANT IDIOCY is intolerable.
I feel I tolerate you well enough. In some ways, you are more amusing that annoying.
Quite humorous, actually, especially coming from someone who claimed that even if the earth moved in the twin paradox ("left the geodesic") the clock on the ship would STILL be younger. Hahahahahahah.
If the earth moved due the influence of gravitaitonal fields alone (such as in coordinate system K'), it would remain on the geodeisic. Hopefully, you'll learn this while you are laughing.
Two objects, one is at rest, one is moving. Which one is moving faster?
THAT CAN'T BE ANSWERED!
By saying "one is at rest", you have arbitrarily established a rest frame. I have always acknowledged you can do that and then say somethign is moving faster *compared to that rest frame*.
Speaking of Colton....
1. Did he ever respond to my questions?
Last I heard, he wanted to confer with a colleague who specialized more in relativity theory before continuing to answer.
2. Why is it that, just as soon as he says "absolutely" to the question where you said the answer is "no," you immediately deny what he said about motion being crucial?
colton's answer to #1:
Absolutely, although you should substitute the word "accelerating" or perhaps "changing reference frames" in place of "moving". The key to resolving the paradox is that one twin has been following a “geodesic” (the twin on earth), while the other one has been going out and back.
I have changed my vocabulary to better reflect what his response said. In particular, it is the change in reference frames of the ship twin, and the following of the geodeisic for the earth twin, that is relevant. Do you interpret his answer to say otherwise?
One Brow said: "I have changed my vocabulary to better reflect what his response said."
As always, you think hollow words give "explanations" to substantive concepts. "Geodesic" is now your magical incantation, eh? Funny, Einstien never used that term to explain the twin paradox. He used the word "journey." Calling accelerated motion a "change of reference frames" does NOT change what it is and does not change what phenomenon is being referred to, sorry. Your word-games do a good job of fooling yourself, I guess, but don't expect others to be that stupid.
"Geodesic" is just GR's way of saying "inertial frame." "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." http://en.wikipedia.org/wiki/Geodesic_(general_relativity)
As many physicists I have quoted, and as even Colton acknowledged, this is not even a GR problem. Now you want to claim that the inertial frame of participant A CAUSES participant B to age less, eh? Heh. I read Colton's answer, did you? The better question is did you even begin to understand the real world implications of his answer?
He finished by saying: "one twin has been following a “geodesic” [my insertion: maintaining an inertial frame] (the twin on earth), WHILE THE OTHER ONE has been GOING OUT AND BACK." (emphasis mine)
One twin's inertial does not CAUSE the other to age less; it is his own, independent travel OUT AND BACK which does that. He would age less than he would have on earth even if the earth blew up seconds after his launch. The earth's being "at rest" does NOT cause the traveller's clock to slow down, his own motion does that--a point which you just agreed to a post or two back. That's what makes this all so stupid. I can spend 1000 posts getting you to acknowledge the simplest of SR precepts (which you deny the whole time) and then the very next post you are back to denying it. You bring no consistency or thought to this discussion, just a woefully confused agenda which you shout over and over, and over, and over, and over, and over, and...
One Brow said: "I disagree with the implication that the first clause is the source of time dilation, when in fact it is the second clause, and so does every other physicist." After I have had to repeatedly correct your misuderstandings of both SR and GR throughout the course of this thread, you have the gall to act like you know what "every other physicist" (as if you yourself were one, of course) would say? And you want to talk about "hubris."
Hahahahahahah
"In his appraisals of the theory of relativity Einstein often claimed that the general theory remedied an inherent defect in both Newtonian mechanics and special relativity, namely, the reliance on the principle of inertia, and the corresponding “inertial coordinate systems” for rendering intelligible the laws of physics...However, general relativity actually relies on more than just the topology of inertia, it relies on the metrical attributes of inertia just as much as do Newtonian mechanics and special relativity, the only difference being that in general relativity the inertial geodesics imply a curved manifold, whereas the inertial geodesics in the earlier theories were consistent with a globally flat manifold...Similarly we can express the laws of Newtonian mechanics in a way that applies to general coordinate systems if we simply define symbols to represent not only the “actual” accelerations but also whatever additional terms (e.g., Coriolis) may arise due to the use of non-geodesic (i.e., non-inertial) coordinates...This shows that the principle of inertia continues to play a crucial role...So, despite Einstein’s hopes, general relativity does not in any way explain or obviate the principle of inertia."
http://www.mathpages.com/HOME/kmath588/kmath588.htm
Since you love math so much, you should appreciate a "mathpages" website, eh? Your continuous denials notwithstanding, Einstien was clearly disturbed by the fact that neither SR or GR could really satisfy the (true, not the alleged) paradox of the twins:
"The question of whether general relativity is required to resolve the twins paradox has long been a subject of spirited debate. Einstein wrote a paper in 1918 to explain how the general theory accounts for the asymmetric aging of the twins by means of the “gravitational fields” that appear with respect to accelerated coordinates attached to the traveling twin...Many people object vigorously to any suggestion that special relativity is inadequate to satisfactorily resolve the twins paradox....Furthermore, once we recognize that the inertial and gravitational field are one and the same, the twins paradox becomes even more acute, because we must then acknowledge that within the theory of relativity it's possible to contrive a situation in which two identical clocks in identical local circumstances (i.e., without comparing their positions to any external reference) can nevertheless exhibit different lapses in proper time between two given events... It is pointed out that we can, without logical contradiction, posit the existence of a unique, absolute, and true metaphysical time at every location, and we can account for the differences between the elapsed times on clocks that have followed different paths simply by stipulating that the rate of a clock depends on its absolute state of motion (defined relative to, for instance, the local frame in which the presumably global cosmic background radiation is maximally isotropic).
The puzzling asymmetry of the spinning globes is essentially just another form of the twins paradox, where the twins separate and re-converge (one accelerates away and back while the other remains stationary), and they end up with asymmetric lapses of proper time. How can the asymmetry be explained?...this quotation serves to demonstrate how seriously Einstein took the question, which, of course, is as applicable to the twins paradox as it is to the two-globe paradox.
http://www.mathpages.com/rr/s4-07/4-07.htm
Even in the general theory of relativity, when viewed from a specific cosmological perspective, there is always a preferred frame of reference, owing to the global boundary conditions that must be imposed in order to single out a solution. This came as a shock to Einstein himself at first...Early in his career, Einstein was sympathetic to the idea of relationism, and entertained hopes of banishing absolute space from physics but, like Newton before him, he was forced to abandon this hope in order to produce a theory that satisfactorily represents our observations...The distinction between the twins cannot be expressed in terms of their mutual relations to each other, but only in terms of how each of their individual worldlines are embedded in the absolute metrical manifold of spacetime....Hopes of accounting for this asymmetry by reference to the distant stars, ala Mach, were certainly not fulfilled by general relativity...and we have no choice but to simply assume a plausible absolute inertial background field, just as in Newtonian physics, in order to actually make predictions and solve problems.
http://www.mathpages.com/rr/s4-01/4-01.htm
So much for what "all other physicists" agree with, eh?:
"There is one key element left out of this success story, however, and it is crucial to understanding why most physicists reject Einstein's claim to have eliminated absolute states of motion in GTR...Einstein thought, in 1916 at least, that the field equations of GTR are precisely this mathematical replacement for Newton's law of gravity, and that they fully satisfied the desiderata of Mach-heavy relationism. But it was not so."
http://plato.stanford.edu/entries/spacetime-theories/
"...by 1921 Einstein had already conceded, however grudgingly, that his general theory
of relativity, worked out between 1907 and 1918, does NOT make all motion relative....the prominent relativist Sir Hermann Bondi (1979) wrote: "It is rather late to change the name of Einstein's theory of gravitation, but general
relativity is a physically meaningless phrase that can only be viewed as a historical
memento of a curious philosophical observation" (181) http://philsci-archive.pitt.edu/archive/00004377/01/LoveMinusZero.pdf
"In 1907, Einstein set out to fully relativize all motion, no matter whether uniform or accelerated. After five failed attempts between 1907 and 1918, he finally threw in the towel around 1920, setting himself a new goal. For the rest of his life he searched for a classical field theory unifying gravity and electromagnetism. As he struggled to relativize motion, Einstein had to readjust both his approach and his objectives at almost every step along the way;he got himself hopelessly confused at times; he fooled himself with fallacious arguments and sloppy calculations;and he committed what he later allegedly called the biggest blunder of his career: he introduced the cosmological constant."
http://www.tc.umn.edu/~janss011/pdf%20files/generalrelativity.pdf
"The key observation on the basis of which Einstein nonetheless sought to extend the relativity principle to non-uniform motion is that, at least locally, the e ects of acceleration are indistinguishable from the e ects of gravity. Invoking this general observation, our passenger can maintain that her train is at rest, even if her coffee spills. She can, if she is so inclined, blame the spill on a gravitational field that suddenly came into being to produce a gravitational acceleration equal and opposite to what she would otherwise have to accept is the acceleration of her own train."
"Gravitational field suddenly came into being," eh? Heh.
"General relativity retains vestiges of absolute motion through the boundary
conditions at innity needed to determine the metric field for a given matter distribution.
During a visit to Leyden in the fall of 1916, Einstein was confronted with this problem by De Sitter. The solution he initially proposed was so farfetched that he never put it in print... Einstein came to accept these criticisms. As he told De Sitter in February 1917: "I have completely abandoned my views, rightfully contested by you, on the degeneration of the g...."
Even Al didn't claim this equivalency principle manipulation had any relationship to reality....
"Einstein revealed in a letter to De Sitter about a month after its publication: "From the standpoint of astronomy, I have, of course, built nothing but a spacious castle in the sky. It was a burning question for me, however, whether the relativity thought can be carried all the way through or whether it leads to contradictions. I am satified now that I can pursue the thought to its conclusion, without running into contradictions. Now the problem does not bother me anymore, whereas before it did so incessantly. Whether the model I worked
out corresponds to reality is a di erent question."
Different question, eh?
In response to the letter from which I quoted above, [De Sitter] wrote:
"As long as you do not want to force your conception on reality, we are in agreement. As a consistent train of thought, I have nothing
against it and I admire it. I cannot give you my final approval before I have had a chance to calculate with it."
http://philsci-archive.pitt.edu/archive/00004377/01/LoveMinusZero.pdf
"Absolute acceleration in special relativity thus does not violate the Principle of Sufficient Reason. Einstein failed to appreciate that special relativity had already solved what he himself identified as the problem of absolute motion....Free fall in a gravitational field (1a) and hovering in outer space (2a) are both represented as motion along the straightest possible lines in what in general will be a curved space-time. Such lines are called geodesics. Resisting the pull of gravity (1b) and accelerating in outer space (2b) are both represented as motion along crooked lines, or nongeodesics. Since no change of perspective will transform a geodesic into a nongeodesic or vice versa, there is an absolute difference between (1a) and (1b) as well as between (2a) and (2b). Absolute acceleration survives in general relativity, as in special relativity, in the guise of an absolute distinction between geodesic and nongeodesic motion.
This extended relativity postulate, it turns out, is highly problematic. What it boils down to is that two observers accelerating with respect to one another can both claim to be at rest if they agree to disagree about whether a gravitational field is present or not."
http://science.jrank.org/pages/11027/Relativity-General-Relativity.html
If they agree to disagree, eh? Like when they agree to disagree about who is "at rest," no doubt. But wait...acceleration aint absolute....I have given acceleration a NEW NAME (nongeodesic) and I have given inertial frame a NEW NAME (geodesic)! Sure, these new names are based on bogus distinctions, totally arbitrary considerations, and a general raping of all common sense, but so what? New names change absolute motion into relative motion, I tellya! Nongeodesics, NOT acceleration, is the CAUSE of time dilation, because I refuse to call it acceleration, caincha see?
Save it for the chumps who can't see past words, eh?
The math guy said: "...and we have no choice but to simply assume a plausible absolute inertial background field, just as in Newtonian physics, in order to actually make predictions and solve problems."
It's just a cryin shame that science wants to make predictions and solve problems, ya know!?
It puts some checks on your ability to go plumb hogwild with your speculative philosophical preferences. Ruins everything, I tellya.
"The prominent relativist Sir Hermann Bondi (1979) wrote: "It is rather late to change the name of Einstein's theory of gravitation, but general relativity is a physically meaningless phrase that can only be viewed as a historical
memento of a curious philosophical observation."
So GR is a "meaningless phrase" and a mere memento of "a curious philosophical observation," eh? Maybe this chump aint heard: Philosophy, it RULES! Math too, of course!
"In the preface of his textbook on general relativity, J. L. Synge admitted that he had never been able to define the equivalence principle in a way that would not make it either trivial or false, but he still recognized its heuristic value:
“The Principle of Equivalence performed the
essential 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” (Synge 1960, ix–x).
He spoke for many when he observed that “the word ‘relativity’ now means primarily Einstein’s [gravitational] theory and only secondarily the obscure philosophy which may have suggested it originally."
I guess Synge is just another of many who cannot be included amongst the group of "all physicists" whose thoughts you are intimately acquainted with, eh? And apparently he aint heard: When it comes to philosophy, the more obscure, the more better!
But philosophy don't care about no damn facts, and scientists do and, ultimately Al was a scientist. "I briefly discuss how Einstein
came to abandon his original idea of reducing all non-uniform motion to gravity...Einstein faced a choice between the philosophical promise of the equivalence principle to make all motion relative and the physical requirement of energy conservation. He opted for the latter: physics trumped philosophy."
http://www.tc.umn.edu/~janss011/pdf%20files/QuestforGR.pdf
"GTR does not uphold Machian relationalist theories of space-time, for the following two reasons: ...(2) GTR also allows one to talk meaningfully about the state of motion (i.e., acceleration) of a single object in a universe that contains only that single object. That is, a situation where the object rotates, or does not rotate, can be determined and measured by the equations/structure of GTR. This violates relationalism since, as so often discussed, since there are no other objects, or reference frames, to determine/measure its motion."
http://course1.winona.edu/eslowik/notes.htm
"Meaningful talk about the state of motion of a single object in the universe," results from GR? You really should school Einstein and these other physicists fools about what the TRUTH is, eh, Eric?
update
Sent: Wed Jan 13, 2010 12:45 pm
From: colton
To: One Brow
Sorry, I didn't mean to leave you hanging about the relativity stuff. It turns out that the guy (relativity specialist, at least much more so than I am) who said he would look over my answers to you, has a deadline of this Friday. He's been too swamped to look things over. I think he still plans to, hopefully next week. I'll let you know when I hear from him. And after that, I still plan to read through & answer the last two PMs you sent me.
With respect to my questions to Colton, these two statements, quoted above, summarize the gist of the points I am driving at:
Question 1: "...Early in his career, Einstein was sympathetic to the idea of relationism, and entertained hopes of banishing absolute space from physics but, like Newton before him, he was forced to abandon this hope in order to produce a theory that satisfactorily represents our observations."
Question 2: "...and we have no choice but to simply assume a plausible absolute inertial background field, just as in Newtonian physics, in order to actually make predictions and solve problems."
Question 3: "Furthermore, once we recognize that the inertial and gravitational field are one and the same, the twins paradox becomes even more acute, because we must then acknowledge that within the theory of relativity it's possible to contrive a situation in which two identical clocks in identical local circumstances (i.e., without comparing their positions to any external reference) can nevertheless exhibit different lapses in proper time between two given events."
"Furthermore, once we recognize that the inertial and gravitational field are one and the same, the twins paradox becomes even more acute, because we must then acknowledge that within the theory of relativity it's possible to contrive a situation in which two identical clocks in identical local circumstances (i.e., without comparing their positions to any external reference) can nevertheless exhibit different lapses in proper time between two given events."
This is the irony of it. With only SR, the question could just be side-stepped (in a completely unconvincing way, but, still...) by claiming SR does not purport to address accelerated frames. But Einstein's attempt to "completely resolve the paradox" actually exacerabates it, because he only shows that "acceleration" cannot account for the asymmetry, as many physicists had hoped. The "GR" solution simply says that depending on which clock you want to start with, clock a will "always" record less time than clock b, whether it "moves" or not AND clock b will "always" record less time than clock a, whether it "moves" or not. Al shoulda just left good enuff be, and admitted the inexplicable asymmetry (which he ended up doing anyway) rather than claiming to dispense with the paradoox.
Once again, there IS no paradox UNLESS one tries to claim that all motion is relative and that absolute motion does not exist. The "paradox" arises from the now-largely-abandoned philosophical agenda, not the physical theory itself.
Commentators have blamed the widespread reading of, and perpetuation of, Einsteins book(s) and papers between 1916 and 1920 for the lingering belief, held by some, that GR "relativized" all motion.
I am sending colton the following PM
http://www.mathpages.com/rr/s4-07/4-07.htm
This link said:
"The simplest example is to place the twins in intersecting orbits, one circular and the other highly elliptical. Each twin is in freefall continuously between their periodic meetings, and yet they experience different lapses of proper time. Thus the difference between the twins is not a consequence of local effects; it is a global effect."
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)."
Do these statements disagree?
The statements disagree to the best of my understanding, and mathpages seems to disagree with everything else I've learned about GR. Until I hear otherwise, I'm going to say that the mathpages site is likely wrong in this statement, but I will reserve judgement.
One Brow said: "I have changed my vocabulary to better reflect what his response said."
As always, you think hollow words give "explanations" to substantive concepts.
No, not at all. Hiowever, I do think that technical terminology arises by necessity, not choice. Physicists use terms/phrases like "geodeisic" because more everyday terms don't convey the same meaning or can mean different things in different context. Saying "geodeisic" doesn't make the answer substantive, but understanding what a geodeisic is, and how it differs from a path that is inertial or accelerated is substantive to understanding why the predictions of K and K' are identical.
Funny, Einstien never used that term to explain the twin paradox.
Never? Or, just not in a particular paper, written before the concept had really been applied to relativity theory? More importantly, does Einsteins description of the events in the frame K' match the understanding of what the geodeisic would be?
Calling accelerated motion a "change of reference frames" does NOT change what it is and does not change what phenomenon is being referred to, sorry.
There is a difference between "accelerated motion" and "a change in reference frames" to begin with. I agree the name change does not change the phenomenon. In fact, i have insisted on that, over and over, when saying the predictions of K' must match those of K, because they are two ways of describing the same events.
Your word-games do a good job of fooling yourself, I guess, but don't expect others to be that stupid.
Using precise terminology is not a word game. Pretending that you can use plain words to mean the same things as the precise terms invented to get around the troubles involved in using plain words is fooling yourself.
"Geodesic" is just GR's way of saying "inertial frame."
Since we have agreed that inertial frames muct be straight lines, and geodeisic are typically not straight lines, this is best read as "extending the notion of inertial frames within GR".
Now you want to claim that the inertial frame of participant A CAUSES participant B to age less, eh?
No, I never claimed such a thing. What are you talking about? Whether in K or K', clock U1 (the earth clock) stays in the geodeisic, U2 (the ship clock) does not. U1 experiences maximal time passage, U2 does not. The environment of U1 does not change that of U2, nor does the environment of U2 change that of U1.
Heh. I read Colton's answer, did you? The better question is did you even begin to understand the real world implications of his answer?
Yes, I read and understood them.
That's what makes this all so stupid. I can spend 1000 posts getting you to acknowledge the simplest of SR precepts (which you deny the whole time) and then the very next post you are back to denying it.
I am at a loss to explain the bizarre interpretations you keep trying to foist on me, except that your understanding is so poor, and your certainty so great, that you can't see what I am really saying, and instead interpret the same thing into different comparments of your world-view.
After I have had to repeatedly correct your misuderstandings of both SR and GR throughout the course of this thread,
You don't understand this well enough to correct anyone.
you have the gall to act like you know what "every other physicist" (as if you yourself were one, of course) would say?
I know what we have read of all the physicists so far.
And you want to talk about "hubris."
Relying on expert opinion is not hubris.
So much for what "all other physicists" agree with, eh?:
Is the author of "mathpages" a physicist? His topic list:
Number Theory
Combinatorics
Geometry
Algebra
Calculus & Diff Eqs
Probability & Statistics
Set Theory & Foundations
Reflections on Relativity
History
Physics
Music
Of those, only one topic is about physics.
"There is one key element left out of this success story, however, and it is crucial to understanding why most physicists reject Einstein's claim to have eliminated absolute states of motion in GTR...Einstein thought, in 1916 at least, that the field equations of GTR are precisely this mathematical replacement for Newton's law of gravity, and that they fully satisfied the desiderata of Mach-heavy relationism. But it was not so."
This (and the general invocation of Mach in this particular discussion) refers to whether or not rotation was relativistic. It turns out rotation can not be described relativistically, that rotation is an absolute concept. This has nothing to do with the concepts we have disagreed on so far.
Even Al didn't claim this equivalency principle manipulation had any relationship to reality....
The pargraph you quoted did not discuss an EP manipulation, but Mach-heavy relativity, which was where DeSitter corrected Einstein.
However, I would agree that Einstein does not consider K' reality from the standpoint of the conservation of energy.
If they agree to disagree, eh? Like when they agree to disagree about who is "at rest," no doubt. But wait...acceleration aint absolute....I have given acceleration a NEW NAME (nongeodesic) and I have given inertial frame a NEW NAME (geodesic)! Sure, these new names are based on bogus distinctions, totally arbitrary considerations, and a general raping of all common sense, but so what?
Can you describe what the difference is? Since when is your thoughts on common sense a limitation on reality?
New names change absolute motion into relative motion, I tellya! Nongeodesics, NOT acceleration, is the CAUSE of time dilation, because I refuse to call it acceleration, caincha see?
Save it for the chumps who can't see past words, eh?
When you can describe the difference between accelerating and not being on a geodeisic, or between being in an inertial frame and being on a geodeisic, then call it mere words. Untill then, your bluster is merely laughable. Your like a man with partial hearing saying there is no difference between the playing of a violin by a 3-year-old and a concert musician.
The math guy said: "...and we have no choice but to simply assume a plausible absolute inertial background field, just as in Newtonian physics, in order to actually make predictions and solve problems."
Yes, you have to set the coordinate system first to take measurements within it. Duh. It would be pretty stupid to have answers if you haven't set your measurement standards yet.
"The prominent relativist Sir Hermann Bondi (1979) wrote: "It is rather late to change the name of Einstein's theory of gravitation, but general relativity is a physically meaningless phrase that can only be viewed as a historical
memento of a curious philosophical observation."
So GR is a "meaningless phrase" and a mere memento of "a curious philosophical observation," eh? Maybe this chump aint heard: Philosophy, it RULES! Math too, of course!
This refers to the fact that rotational motion is not relative. It doesn't change much in our discussion.
"In the preface of his textbook on general relativity, J. L. Synge admitted that he had never been able to define the equivalence principle in a way that would not make it either trivial or false, but he still recognized its heuristic value:
You can say the same for the principle all inertial reference frames are indistinguishable, to this problem goes back to SR.
He spoke for many when he observed that “the word ‘relativity’ now means primarily Einstein’s [gravitational] theory and only secondarily the obscure philosophy which may have suggested it originally."
That's how I have been using it.
I guess Synge is just another of many who cannot be included amongst the group of "all physicists" whose thoughts you are intimately acquainted with, eh?
Because we use the words the same way?
Einstein faced a choice between the philosophical promise of the equivalence principle to make all motion relative and the physical requirement of energy conservation. He opted for the latter: physics trumped philosophy."
I have been talking about energy conservation since page 2 of these comments, at least. Did you miss that?
"GTR does not uphold Machian relationalist theories of space-time, for the following two reasons: ...(2) GTR also allows one to talk meaningfully about the state of motion (i.e., acceleration) of a single object in a universe that contains only that single object. That is, a situation where the object rotates, or does not rotate, can be determined and measured by the equations/structure of GTR. This violates relationalism since, as so often discussed, since there are no other objects, or reference frames, to determine/measure its motion."
http://course1.winona.edu/eslowik/notes.htm
"Meaningful talk about the state of motion of a single object in the universe," results from GR?
In "a situation where the object rotates".
You really should school Einstein and these other physicists fools about what the TRUTH is, eh, Eric?
School them that I agree with them?
I said: I guess Synge is just another of many who cannot be included amongst the group of "all physicists" whose thoughts you are intimately acquainted with, eh?
You responded: Because we use the words the same way?
Yeah, right, eh? A few posts back:
I said: It is my understanding that most physicists, while they accept GR as a valid, if imperfect, theory of gravity, reject it as a valid theory of "relative motion."
You responded: Your understanding is highly inaccurate here.
I quoted: Einstein faced a choice between the philosophical promise of the equivalence principle to make all motion relative and the physical requirement of energy conservation. He opted for the latter: physics trumped philosophy."
Your response: I have been talking about energy conservation since page 2 of these comments, at least. Did you miss that?
Talking about? Heh. I have seen you touting the equivalence principle as completely valid and I have seen your repeated insistence that all motion is relative.
Is the author of "mathpages" a physicist?
Do you have any idea what the use of a colon implies? Hint, it is not used to setoff something previously said.
One Brow said: "This refers to the fact that rotational motion is not relative."
Have you read this article by Bondi? Tell me, Eric, is there anything, ANYTHING at all, that you will not declare without having any knowledge whatsoever of whether it's even close to being true, so long as you think your declaration makes you look knowledgeable and/or appears to support a point you want to prove? ANYTHING?
One Brow said: "In "a situation where the object rotates".
Exactly! One object. In the whole universe. No others. Rotating. Do you have a point, or are you just stressing your admission that you have completely misstated what type of "motion" GR allows to be meaningfully considered and determined?
One Brow said: "When you can describe the difference between accelerating and not being on a geodeisic, or between being in an inertial frame and being on a geodeisic, then call it mere words."
If and when you can ever actually read and understand the statements of the experts I quote, get back to me, eh?
On second thought, don't get back to me. Once again I am simply wasting my time presenting you with reference material that you will ignore or misunderstand.
Case in point: One Brow said: "When you can describe the difference between accelerating and not being on a geodeisic, or between being in an inertial frame and being on a geodeisic, then call it mere words."
In GR there is no difference, that's the whole point. I would be the last one to claim that there is a significant difference, and you thinking that I would or should want to "describe a difference" merely demonstrates your inability to comprehend. Like the guy said: "general relativity actually relies on more than just the topology of inertia, it relies on the metrical attributes of inertia just as much as do Newtonian mechanics and special relativity, the only difference being that in general relativity the inertial geodesics imply a curved manifold, whereas the inertial geodesics in the earlier theories were consistent with a globally flat manifold."
One Brow said: "School them that I agree with them?"
Just to get the record straight, do you now agree that GR is NOT a viable theory of relative motion?
One Brow said: " Since when is your thoughts on common sense a limitation on reality?"
Since when have your comments on, and/or questions about, common sense displayed any common sense or any understanding of common sense?
Here's my idea of common sense. Say I'm sitting on my crusty couch at home and drop my 40. It hits the floor. Someone might be stupid enough to say that's normal, because both me and my 40 are in the earth's gravitational field. They might even say "common sense" tells you that, when that's the stupidest thing I ever heard. Here's what my common sense tells me:
I am NOT in earth's gravitational field because exactly 30 minutes and 7 seconds ago, all the gravitational force of the earth ceased to exist. However, at that very same second a powerful alien spacecraft started accelerating the earth with just the right amount of pseudo-force to accelerate me, the earth and my 40 towards a distant star with a force of 1 g. That's only the first part of what my common sense tells me, but my common sense doesn't tell me that's why my 40 hit the floor.
My common sense tells me that my 40 hit the floor, because, at the very second I dropped it the alien spaceship doubled the accelerating the force it was exerting on everything in the room except for my 40, which the aliens singled out for special treatment, just as you would expect them to do. Furthermore at that very same instant a pseudo-gravitational field magically arose which pulled me in the opposite with a force of 1 g, so I don't notice any change. But my 40 does, because it now has no net forces acting upon it and therefore is, in effect, in "free-fall." While it is in free fall, the floor came up and busted it.
Simple common sense, I tellya.
Well, at least Al, unlike some, knew the difference between math and reality, eh?
“As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.” (Einstein)
Yeah, right, eh? A few posts back:
I said: It is my understanding that most physicists, while they accept GR as a valid, if imperfect, theory of gravity, reject it as a valid theory of "relative motion."
You responded: Your understanding is highly inaccurate here.
I have seen nothing from you to change this opinion.
Your response: I have been talking about energy conservation since page 2 of these comments, at least. Did you miss that?
Talking about? Heh. I have seen you touting the equivalence principle as completely valid and I have seen your repeated insistence that all motion is relative.
I don't recall addressing rotational motion, but that is an example of non-relative motion. Outside of that, all of those statements a true. All non-rotational motion is relative, the EP (which does not address rotational motion) is valid locally, and the using the conservation od mass-energy to choose one reference frame over another that violates strikes me as valid reasoning. That you think these ideas are in opposition somehow is your ignorance.
Is the author of "mathpages" a physicist?
Do you have any idea what the use of a colon implies?
So, no.
One Brow said: "This refers to the fact that rotational motion is not relative."
Have you read this article by Bondi?
Rotational motion is the type of motion that Einstien acknowledged he could not describe relativistically. I suppose Bondi could be talking about other types of motion, but I assumed he was speaking competently.
One Brow said: "In "a situation where the object rotates".
Exactly! One object. In the whole universe. No others. Rotating. Do you have a point, or are you just stressing your admission that you have completely misstated what type of "motion" GR allows to be meaningfully considered and determined?
Before your comments on January 12 and following, we were not discussing rotational motion. I have no idea why you have connected this to motion along geodeisics, freefall, acceleration, or what is means to be moving "faster", or any of the the other topics we have been discussing. I don't know why you think the non-relative nature of rotations means I have a different opinion on the geodeisic moitons described in GR. rankly, it all smacks o a desparate attempt to prove me wrong somehow about something. Have you really sunk so low?
If and when you can ever actually read and understand the statements of the experts I quote, get back to me, eh?
Done and done.
On second thought, don't get back to me. Once again I am simply wasting my time presenting you with reference material that you will ignore or misunderstand.
Nothing annoys you more than my reading the reference material and noting that it conirms what I have been telling you, it seems. Meanhile, even when colton confirms my interpretations, you just disregard them. You can keep pretending I don't understand. I know better.
Case in point: One Brow said: "When you can describe the difference between accelerating and not being on a geodeisic, or between being in an inertial frame and being on a geodeisic, then call it mere words."
In GR there is no difference, that's the whole point.
Previously you claimed an inertial frame was motion in a striaght line at a constant speed. That is not what a geodeisic is. If you want to keep playing with the definition of an inertial frame, it justs makes you look more desparate.
Still, I'll play along for now: is an inertial frame motion in a straight line at a constant velocity, or is it following a geodeisic, in your definition?
Just to get the record straight, do you now agree that GR is NOT a viable theory of relative motion?
Do you have a reference that the EP is not a viable concept? Hint: trivial concepts are viable.
Since when have your comments on, and/or questions about, common sense displayed any common sense or any understanding of common sense?
I know enough about common sense to know it is short-hand for "because I say so" 90% of the time.
I quoted: "In the preface of his textbook on general relativity, J. L. Synge admitted that he had never been able to define the equivalence principle in a way that would not make it either trivial or false, but he still recognized its heuristic value"
You responded: "You can say the same for the principle all inertial reference frames are indistinguishable, to this problem goes back to SR."
You can say the same, but it wouldn't be the same. Al made a fair case for the indistinguishability of inertial frames, but SR regards acceleration as absolute. The attempt to "make" accelerated motion strictly "relative" seems to have failed miserably. Of course indistinguishability as a matter of fact in a particular, abstract case is NOT the same indistinguishability in theory or in principle. Something you don't seem to understand.
First you say this: "I have seen nothing from you to change this opinion." Then you say this: "Nothing annoys you more than my reading the reference material and noting that it conirms what I have been telling you, it seems."
Are you SERIOUS!? I have given you references which flatly contradicts not only what you have been saying, but further contradicts what you claim all physicists say? Can you really not even read?
One Brow said: "Rotational motion is the type of motion that Einstien acknowledged he could not describe relativistically. I suppose Bondi could be talking about other types of motion, but I assumed he was speaking competently."
Are you suggesting that if Bondi was not talking only about rotational motion, then he is incompetent?
Yes, you are, but I want you to repeat it. I want to you make it clear just how deep your wildly exagerated, but unwarranted, esteem for your own seriously misguided opinions runs, and just how quick you are to call a giant in the field of relativity incompetent if he does not agree with your crap. Your hyperolic ARROGANCE truly amazes me.
I asked: Do you have any idea what the use of a colon implies?
You replied: "So, no."
I didn't think you did. Thanks for playing.
One Brow said: "All non-rotational motion is relative, the EP (which does not address rotational motion) is valid locally, and the using the conservation od mass-energy to choose one reference frame over another that violates strikes me as valid reasoning. That you think these ideas are in opposition somehow is your ignorance."
Yeah, right. My ignorance and all of those experts and researchers I just cited.
Once again you merely demonstrate your inability to read and comprhend. The author quoted said NOTHING about using the conservation of energy to "choose one reference frame over another. He said, that Einstien (try very hard to read this carefully):
"...came to abandon his original idea of reducing all non-uniform motion to gravity...
One Brow said: "Before your comments on January 12 and following, we were not discussing rotational motion. I have no idea why you have connected this to motion along geodeisics, freefall, acceleration, or what is means to be moving "faster", or any of the the other topics we have been discussing. I don't know why you think the non-relative nature of rotations means I have a different opinion on the geodeisic moitons described in GR. rankly, it all smacks o a desparate attempt to prove me wrong somehow about something. Have you really sunk so low?"
Are you that blind? You have been telling me that with only two objects (let alone just one) it would be impossible to tell which one was moving and, heh, therefore IMPOSSIBLE for one to actually be moving faster than another. And all this, according to you was "dictated" by relativity theory.
And if you think all these physicists expressing their rejection of GR as a theory of relative motion are talking ONLY about rotation, then, again, you simply demonstrate that you understand nothing I provide you with to read.
One Brow said: "Meanhile, even when colton confirms my interpretations, you just disregard them. You can keep pretending I don't understand. I know better."
I didn't see where Colton supported your interpretation of the twins in any way, shape, or fashion. He said accelerated motion was critical to the solution and denied that the "relative motion alone" could account for it. He certainly did NOT say, as you claimed, that even if the ship twin stayed stationary while the earth moved the ship twin would STILL be younger. That is just prima facie absurd, yet you appear to cling to it, ignoring what Colton said.
Your way of conceding that you were wrong is always the same (in the unlikely event that you ever do concede it): You simply deny that you ever said what you said.
One Brow said: "Previously you claimed an inertial frame was motion in a striaght line at a constant speed. That is not what a geodeisic is. If you want to keep playing with the definition of an inertial frame, it justs makes you look more desparate."
I said in SR, but that's what it is, but, in essence, it is the same in GR too (in a real non-sensical way). I went to some length to explain how Al tried to conflate acceleration and inertia. But in his theory a geodesic "is" a "straght" line. A planet in orbit in moving at a uniform speed in a "straight" line, and is hence unacceleratd (contrary to what Newton and SR say). His definition of inertia in GR is basically the same--a "free" (not acted upon by external forces) particle moving at a uniform speed. The problem was he also tried, without success, to claim that he had "abolished" the whole notion of "inertia," so his statements on it are not really reliable. Again, see the critique quoted above from the math guy.
The problem is, as these phsyicists I cited have pointed out, his attempt to say accelerated motion is relative failed. His idea was that if you could substitute an imaginary psuedo-gravitational field for acceleration, that made acceleration relative. Fraid not. Insofar as it attempts to "relativize" accelerated motion GR is a failure, they say.
I know that your unshakable faith in the indisputable truth of any and all prior opinions you have already formed will make it impossible for you to even CONCEIVE of any other possibility, so I won't expect it. You could have a thousand experts and 1,000,000 facts disproving your opinion and you would simply not comprehend a word they were saying, or make any otherwise inescapable inference.
One Brow said: "Still, I'll play along for now: is an inertial frame motion in a straight line at a constant velocity, or is it following a geodeisic, in your definition."
It's not *my* definition which matters. See if you can understand this sentence from the math guy:
"the only difference being that in general relativity the inertial geodesics imply a curved manifold, whereas the inertial geodesics in the earlier theories were consistent with a globally flat manifold."
There are, according to him, "inertial geodeics in BOTH SR and GR, but they are differnt things. In SR, Al's definition of "inertia" in simply Newton's. He basically reverses his defintion in GR, as I have repeatedly pointed out. Standing alone "geodesic" means nothing in particular. You must first specify the type of spacetime you are assuming (flat or curved)>
According to Euclid, a line (straight line) is the "shortest distance between two points." This does not change in GR. Nongeodesics in GR are "crooked lines" (accelerated). Geodesics (inertial) in GR are "straight" (with the qualification being that "straight" means "straighest possible" in a curved medium). Do you get this? Do you get that there is no ONE definition of geodesic?
Newton himself made the point that what might appear to be a "straight" line from one perspective could appear curved from another. But for him (and not for Al either) "straight" was NOT defined solely in terms of how "someone" might see it. It had an objective meaning and "true" straight lines must be distinguished from merely "apparent" straight lines.
From what I read, astronomers repeatedly conclude that the vast majority of space is "flat." Even with GR, Al also thought space was "flat" in places. Depending on what type of space a body is in, it's "geodesic" might be "straight" according to euclidean geometry or "straight" according to reimannian geometry.
What Al originally tried to do, with his EP, was "reduce" all accelerated frames to an SR frame, on a (VERY STRICTLY, that is to say "infintesimal) "local" basis. From that standpoint, accelerated particles were moving at a uniform speed in a (euclidean) straight line, with no external forces acting upon them. Nice try, Al.
Even a sharply curved line will be straight if you only look at an "infintesimal" segment of it, ya know?
One variation of the EP, one which still accepted, is the equvalence (proportionately, at least) of inertial and gravitational mass. The EP is still considered "valid" in this sense. Most physicists reject the idea (as Al himself eventually did) that gravity is equivalent to acceleration for the purpose of claiming that all accelerated motion is "relative."
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