- #1
matheinste
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This extract is from Bridgman, A Sophisticate's Primer of Relativity. 1962 Page 28. Only the last couple of sentences are relevant but the rest is included to put it in context.
He starts---
Velocity IS a relative concept, and whenever the physicist allows himself to speak of velocity with an implication of absoluteness, he is either forgetting something or is tacitly implying something he has not taken the trouble to make explicit. Sometimes, for example, the Michelson-Morley experiment is described as showing that "absolute" velocity does not "exist." Of course it does not exist, because it is not that sort of thing BY DEFINITION. What the physicist is actually saying here is that there is no evidence for the existence of the old-fashioned ether, which if it existed could be taken as a universal frame with respect to which velocities could be measured.------
So far so good. Then he continues-----
One of the most insidious, and because it is so insidious, one of the most vicious formulations of this point of view is; "Relativity theory says that if two frames of reference are moving with respect to each other, it is impossible to say which frame is 'really' moving". The usual implication here is that nature is so constructed that it is impossible to make the decision. The impossibility is entirely man-made. This point of view is behind some of the intuitive difficulties exploited in some recent discussions of the paradox of the "space traveler".-------
Does anyone know What he means by that. I can think of one or two interpretations, none of which fit in with SR.
Matheinste
He starts---
Velocity IS a relative concept, and whenever the physicist allows himself to speak of velocity with an implication of absoluteness, he is either forgetting something or is tacitly implying something he has not taken the trouble to make explicit. Sometimes, for example, the Michelson-Morley experiment is described as showing that "absolute" velocity does not "exist." Of course it does not exist, because it is not that sort of thing BY DEFINITION. What the physicist is actually saying here is that there is no evidence for the existence of the old-fashioned ether, which if it existed could be taken as a universal frame with respect to which velocities could be measured.------
So far so good. Then he continues-----
One of the most insidious, and because it is so insidious, one of the most vicious formulations of this point of view is; "Relativity theory says that if two frames of reference are moving with respect to each other, it is impossible to say which frame is 'really' moving". The usual implication here is that nature is so constructed that it is impossible to make the decision. The impossibility is entirely man-made. This point of view is behind some of the intuitive difficulties exploited in some recent discussions of the paradox of the "space traveler".-------
Does anyone know What he means by that. I can think of one or two interpretations, none of which fit in with SR.
Matheinste