Why in the world would Einstein suggest....

@layman,

Okay. Maybe i misunderstood who was saying what. Basically it's a mistake to think that relativity means ALL frames of reference are equivalent. This is only true of inertial ones.

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@Olivier5,

Quote:

Okay. Maybe i misunderstood who was saying what. Basically it's a mistake to think that relativity means ALL frames of reference are equivalent. This is only true of inertial ones.

Once again, I agree completely.

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Yup. Specifically inertial frames.

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@layman,

Good, then. Case solved.

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@layman,

I said:

Quote:

Once again, I agree completely.

Of course that is a qualified statement, as far as "equivalence" goes. They are equivalent for adhering to the same laws of physics. That does not, of course, mean that they are equivalent in EVERY other possible sense. It does not, for example, mean that each clock is slower than the other if they are in motion relative to another and both inertial. Of course, that particular claim could never be true under any circumstances. Yet it is made routinely.

Go figure.

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@layman,

Indeed, one clock beats slower than another, if and only if the twins departs in the same place and end up in the same place. They then compare their clocks (which showed the same date and time prior to departure) and these clocks show a certain time difference delta T, and not two or three different delta T...

But if two observers wheeze past one another in space, at a relative speed of say C/2, each following an inertial trajectory in opposite directions, then their two frames of reference are equally valid. Now whose clock is ticking faster?

Not sure the question means anything...

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@Olivier5,

Quote:

Not sure the question means anything...

That's where we might "disagree," Oliver. I fail to see any reason to claim the question is "meaningless."

http://able2know.org/topic/265997-29#post-5892706

http://able2know.org/topic/265997-28#post-5892298

Certainly the theory of SR itself does not claim that its assumptions and predictions are ONLY correct (or applicable) IF you can compare two clocks, side by side. So I would also disagree with this:

Quote:

Indeed, one clock beats slower than another, if and only if the twins departs in the same place and end up in the same place.

The faster clock ALWAYS beats slower, per SR, even if you don't know which one it is in any given instance.

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@layman,

Your coin metaphor does not apply here. Relativity does. Eg simultaneity means not the same thing in a relativist universe, ie at high velocity.

Quote:

In physics, the relativity of simultaneity is the concept that distant simultaneity – whether two spatially separated events occur at the same time – is not absolute, but depends on the observer's reference frame.

According to the special theory of relativity, it is impossible to say in an absolute sense that two distinct events occur at the same time if those events are separated in space. For example, a car crash in London and another in New York, which appear to happen at the same time to an observer on the earth, will appear to have occurred at slightly different times to an observer on an airplane flying between London and New York. The question of whether the events are simultaneous is relative: in the stationary earth reference frame the two accidents may happen at the same time but in other frames (in a different state of motion relative to the events) the crash in London may occur first, and in still other frames the New York crash may occur first. However, if the two events could be causally connected (i.e. the time between event A and event B is greater than the distance between them divided by the speed of light), the order is preserved (i.e., "event A precedes event B") in all frames of reference.

http://en.m.wikipedia.org/wiki/Relativity_of_simultaneity

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@Olivier5,

Quote:

Your coin metaphor does not apply here. Relativity does. Eg instantaneity means not the same thing in a relativist universe, ie at high velocity.

A few comments/responses to this assertion, Oliver:

1. The whole concept of the relativity of simultaneity is dubious. This is the question I raised in my first post.

2. That aside, even applying relativity, the concept of "relative simultaneity" would not change anything re the twins. SR says that the travelling twin would age slower both on his way to, and on his way back from, some point away from earth. It also predicts that if he just stopped when he got there, but didn't come back, he would STILL have aged less (except it would be only half the amount than if he returned).

3. You certainly were not applying the concept of relative simultaneity when you were talking about using the solar barycenter to determine net time differences. You were using the concept of "absolute simultaneity," not "relative simultaneity."

1 Reply

@Olivier5,

Let me ask you the same question I have asked others (but have never received an answer to), Oliver.

Assume that A and B are moving relative to each other (and they both agree on this). Now then:

1. SR requires A to assert that he is motionless, and that only B is moving.

2. At the same time, SR requires B to assert that he is motionless, and that only A is moving.

These requirements are, by the way, imposed by the notion of the "relativity of simultaneity."

Now, the question is:

Is it logically possible for them BOTH to be motionless, and there still be relative motion between them?

Wouldn't at least one of them HAVE to be moving?

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@layman,

Because the twins start and end in the same place, the same frame of reference. That makes a big difference. Simultaneity applies there and allow the clocks to be compared. But if one guy starts from Vega and another from the solar system and they fly in opposite direction, when exactly can they compare their clocks?

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@Olivier5,

Quote:

when exactly can they compare their clocks?

They can't. But that's not the issue. I have already pointed out why it isn't. What have I said so far, in particular, that you think is wrong?

Let me say it again, maybe in a different way. The premises and implications of SR lead to certain predictions. The validity of those predictions, within the theory, is not, in any sense, conditioned upon two parties comparing clocks.

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@layman,

If SR predicts a certain time difference in any hypothetical situation, and the parties can thereafter compare clocks in some way, that's great. That way you can test whether the predictions are actually consistent with empirical observations.

If they are consistent, fine.

If they are NOT consistent, that doesn't change the prediction. The prediction has merely been falsified.

If they are NOT compared, that doesn't change the prediction either.

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@Olivier5,

One more comment on this assertion of yours, Oliver:

Quote:

Your coin metaphor does not apply here. Relativity does. Eg simultaneity means not the same thing in a relativist universe, ie at high velocity.

I see no reason whatsoever to say it doesn't apply. Certainly nothing implied by the concept of "relative simultaneity" would make it inapplicable, at least not that I can see.

I mean no disrespect here, Oliver, but merely using the word "simultaneity" while waving your hands and posting an excerpt from an article isn't really too meaningful. In my experience, many who throw out the phrase "relative simultaneity" as an "explanation" for something haven't really analyzed it on a conceptual level.

Often they can't even tell you what it means (in comprehensible terms), let alone what it implies (how it affects other parts of the theory). Not saying you're one of those, but you have yet to demonstrate that you aren't. In fact, your claims about what using a solar barycenter as a reference frame would do appears to indicate that you are not, so far, being consistent in your claims.

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@Olivier5,

Quote:

But if two observers wheeze past one another in space, at a relative speed of say C/2, each following an inertial trajectory in opposite directions, then their two frames of reference are equally valid.

But what is "equally valid" even supposed to mean? Even Ernst Mach, the quintessential positivist, had to admit that logic limited what could be considered actually (as opposed to merely theoretically) "valid." Simply stated, while either one of two alternative might be called "equally valid" when considered alone, one could still not logically claim that BOTH were true if they were inconsistent propositions.

http://able2know.org/topic/265997-3#post-5875199

Generally speaking "valid" does not necessarily mean "true." In logic, for example, the form of an argument can be completely "valid," but the argument itself can still be utterly false from an external point of view (i.e. "unsound").

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@Olivier5,

Oliver, I have made several responses, including asking some questions of you, to your posts. I don't know if you care to discuss the topic any further. But, if you do, I would ask that you give your response to the post linked below first. I think that would be most helpful in identifying and focusing on where our differences may lie.

http://able2know.org/topic/265997-30#post-5893113

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@Olivier5,

Quote:

Not sure the question means anything...

Well said! For once I completely agree with you. What layman (worthy of his name) fails to understand and appreciate (due to his bee in the bonnet) is that all communication and observation between different frames is subject to Einstein's "speed of light" postulate. That is why the twin paradox only makes sense if they ultimately share a common reference frame. It is scientifically meaningless to talk about the reality or actuality of"faster/slower" from a God's eye view outside all reference frames. The irony is that this came from Einstein, himself a scientific realist !

Those who reject the elegance of the Einstein's postulate are just reactionaries. They owe their modus vivendi to Einstein. This does not mean that the Einstein postulate is set in stone or that less elegant (aether saving) convolutions can be offered. All paradigms are subject to limits of applicability and tend to be delimited by succeeding paradigms (as layman's reference Morin points out) . But what is missing in this lengthy diatribe is an informed appreciation of the ontological, epistemological, and social nuances involved in the status of scientific models. Such an appreciation would involve acknowledgment of the limits of traditional logic and language in accounting for physical phenomena outside of "normal" experience. Since "speed of light" issues are NOT part of such experience, it is futile to expect criteria of "meaningfulness" to be accounted for by "common sense".

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@fresco,

Quote:

...all communication and observation between different frames is subject to Einstein's "speed of light" postulate....It is scientifically meaningless to talk about the reality or actuality of"faster/slower" from a God's eye view outside all reference frames

Heh, Fresco. All of your cheer-leading for what you suppose to be some sort of post-modern, non-dualistic, subjectivist break-though would be more appropriate if the relativists would just be consistent and say that when the twin came back each would be younger than the other.

They don't. The math won't let them. Nor will the subject matter. Nor will any reasonable facsimile of logic. The part of their assertions which contradict the math is metaphysical ideology. It can't be sustained on a consistent basis in a subject like physics, which deals with "matter in motion," rather than the nebulous "concepts" of phenomenological philosophy or gestalt psychology.

People who are inclined toward mysticism love the metaphysical imposition upon the theory, no doubt. But, in the end, the relativists are forced to posit a preferred frame, all while trying to deny they did it. Again, perfect for the mystic, but...

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@layman,

Most of us can see through that strawman invention of yours of "relativists who can't account for...". That's absolute drivel as anybody doing a google search will know. And perhaps I should point out that I myself am no great "Einstein Fan" with respect to his leaning towards "realism", and have even lectured on that matter.

Your real problem as regards to your forum status here is that you actually appear to have nothing to say outside your little pot-boiling cocoon, and you are petulant and resentful to those like me that might. Your contributions to other threads (random quotations, etc) are at best mediocre and usually vacuous. Your selective "reading" suggests passing acquaintance rather than considered thinking. You are ostensibly parasitic on the comments of others. It is that which earns the title "troll".

BTW, if you want to have a go at that other strawman of "people inclined towards mysticism", don't forget to include Niels Bohr and David Bohm in that category.

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@fresco,

What are you sying here? I know the whole of relativity theories stinks!
It really are all lies.

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Why in the world would Einstein suggest....

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