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Originally Posted by MacM
Sorry. I now know hat you are referring to. Yes calculations were made but I was not party to them and they were not posted. The following is an excerpt from a public forum debate regarding the issue of superluminal distance change as a consequence of spatial length contraction:
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That looks like an interesting thread. Since it's a public forum, can you provide a reference or a link? It would be nice to know who is speaking here.
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Originally Posted by Someone
Now, while the Lorentz-Fitzgerald contraction does hold, the super-luminal velocities that bother you do not occur inside the event horizon. And after the acceleration period, the event horizon receeds at the speed of light, but when finally see the Earth again, you see it is moving away at a speed of 0.8 c. Thus you never see anything moving at superluminal speeds.
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So now we jump a bit over into philosophy. It is true that space is contracting quickly, as perceived by the accelerating electron. (Remember that in spacetime there is no problem. The proper distance (rest time times the speed of light) is the same in all reference frames.) But you don’t see the distant object. And whenever you actually can see it, you find that it is well-behaved. This is all consistent with relativity. Relativity simply tells you how different observers will perceive a situation. (And perceive in this context isn’t some wishy-washy thing. It means time and position.)
So the bottom line is the electron will never see the Earth approach at superluminal speeds.
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Note that the answer to your quandary is here as well. Although you might calculate that it would be travelling toward you at superluminal speeds, you'll never actually
see it do that.
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Originally Posted by MacM
But the results are the same once you cease acceleration and become inertial at the higher velocity you will once again see the earth and it will be closer than it was when you first began to accelerate "Away" from it, "IF" the original distance is substantial and the terminal velocity is relavistically high, this change in spatial dimension will have been at superluminal rates and the distance will have become reduced even though your vector is away from the earth.
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Nope. Read the above more closely. "And after the acceleration period, the event horizon receeds at the speed of light, but when finally see the Earth again, you see it is moving away at a speed of 0.8 c." If you work out the math, you'll note that by the time you can see the Earth again, it will be farther away than it was when it started, and there will never be a point at which it needed to have moved at superluminal velocities to reach an observed location. By the way, this is
exactly why it doesn't make sense to talk about these questions in vague generalities. There are plenty of conclusions that seem like obvious results from the basics of special relativity that do not in fact logically follow from special relativity if you work out the math. Often even setting up the problem is sufficient to see the mistake in reasoning. For example, in the classic twin paradox, you have two observers moving relative to each other, so you might naively suppose that they should see the other as younger. But even just setting up the problem without working it out, you'll quickly realize that there's an asymmetry in the problem, and that there are three reference frames involved, not two.
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Originally Posted by MacM
You are mis-stating the case and what I have said.
1 - The data we have does not violate the prediction.
2 - Some predictions have never been tested or have emperical data support.
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That is absolutely
not what you said. You said, "SR's prediction of reciprocity has been inconsistant with data, observation and logic." You did not say it hasn't been tested, you said it is
inconsistent with data and observation. That's a claim that there is data that directly contradicts those predictions. If you now acknowledge that there is no data that contradicts the predictions of special relativity, then please stop stating that there is.
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Originally Posted by MacM
If there is experimental evidence that supports special relativity reciprocity or length contraction, please provide it. Or, if you agree that there is no such evidence, please acknowledge that, and stop waffling about it.  |
I have not waffled about that. Waffling means switching one's claims, as you did above, where, in the same message, you both acknowledged that there is no data that contradicts special relativity, and then claimed that there
was data inconsistent with special relativity. My position has been clear from the beginning. I recently gave you an example of an entire class of experiments which verify length contraction and time dilation together. You said you were familiar with that type of experiment, but that you would like to look into it in more detail. Out of curtesy, I offered to wait to discuss them until you had a chance to do so. I'm perfectly willing to give you time to do that, but that does not mean that you can simply dismiss those results without examining them.
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Originally Posted by MacM
I tought it was clear that synchronization was not done and is not required as demonstrated by the resulting agreement that gamma = 2 at 0.866c because B and C accumulated 18,000 seconds in a 36,000 second test period according to the resting clock.
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I'm not certain what you mean by a lack of synchronization here. If you have a test period in frame A, and you want to know what the clock at B measured during that period, you have to have clock B start and stop at the same time as clock A, right? Isn't that synchronization? I've already pointed out that if you don't do that, and just start and stop the clocks when they reach certain values, then all you have is clocks that read values that you preset, with no way to tell whether they have any relation to each other at all.
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Originally Posted by MacM
I did. The equal test period was in the rest frame, not some undefinable universal absolute frame.
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Sure, but then you've stated that it wouldn't be valid to take B's perspective of when clock started and stopped. Why can't I do that?
By the way, you haven't responded at all to my comments about what is necessary to show an internal inconsistency or an experimental contradiction of theory, and I consider that a crucial point. Maybe it's because I didn't ask a specific question. I'll repeat that section here
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Originally Posted by MacM
Simply a false concept. One must adhere to bonafide basic physics not the formalisim and conclusion of the theory in question. To apply such a standard makes it defacto unimpeachable regardless of any actual validity or lack thereof as long as the theory has been made mathematical consistant by fiat.
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Originally Posted by Grey
No, I'm afraid you're mistaken about this. Suppose someone wants to show that theory X has a contradiction or that it is not consistent with experimental evidence. But instead of taking the postulates of theory X as the basis, he takes some other set of postulates (some of which may be similar to those of theory X, but the whole set is not the same; call this theory Y), and derives a contradiction. Does this show that theory X leads to a contradiction? Of course not. It shows that theory Y leads to a contradiction. Or, looking for contradictory experimental evidence, he makes a prediction based on theory Y, and finds that it disagrees with experiment. Does that show that theory X is inconsistent with observation? Again, of course not. That shows that theory Y is not consistent with observation.
If you want to show that theory X leads to either an internal contradiction or a disagreement with observation, you have to find out what theory X really says.
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So, I'll ask a specific question. Do you still insist that it's not necessary to work within the rules of a theory in order to show either an internal or external contradiction?