- #1
rajeshmarndi
- 319
- 0
There is no valid reference frame where this is true.if we start to deaccelerate, will we see events in reverse order in the direction of motion
the now plane
rajeshmarndi,
[...]
from page 10
"c. Thirdly, for events in quadrant IV, as the value of t increases the associated value of (tau) would decrease, so that the normal ordering given by the progression of time is reversed. This suggests that we have already passed into an unacceptable region. Only I is correctly treated by these coordinates."
I tend to agree with this conclusion....none of them is "proper"...
what if he then immediately accelerates in the direction away from her (so as to immediately achieve his original velocity away from her)? The CMF then says that she rapidly gets younger, and after this second turnaround, she is much younger than he is ... she is again the same young age that she was before the first turnaround. This application of the CMF analysis (with his acceleration being AWAY from her) is often said to be invalid (because it produces a previous age for her).
For example, in the standard idealized twin "paradox" scenario with an instantaneous turnaround, right before the turnaround, the traveler (he) says that the home twin (she) is much younger than he is. He then accelerates toward her to reverse course, and the CMF analysis says that (from his perspective) during the turnaround she rapidly ages, and after the turnaround she is then much older than he is. This analysis is usually considered to be acceptable
I am not certain exactly what you mean by "the CMF analysis" (as Nugatory mentioned, you could mean analysis in a MCIF or you could mean a non-inertial frame constructed by using the simultaneity convention defined in each MCIF). However, the rule which is applied is perfectly consistent. The rule is:The idea that the co-moving-frames ("CMF") analysis can be allowable in some circumstances, but not allowable in other situations, seems inconsistent to me.
Does an immediate back-to-back (matched) pair of instantaneous course-reversals leave all ages the same as before?
IF he is allowed to use the co-moving-frames (CMF) analysis for the first course-reversal, then he will say that her age suddenly increases during that first reversal. But if her age is the same before and after the matched pair of reversals, it is necessary that her age must decrease during the second reversal, by the same amount that her age increased during the first reversal. And this decrease in her age during the second reversal is exactly what the CMF says will happen.
It depends on how you want to play the game. In the game I play based on the radar method the answer is yes.But the still unanswered question is this:
Does an immediate back-to-back (matched) pair of instantaneous course-reversals leave all ages the same as before?
In the game I play, all the ages stay the same even in between the two instantaneous velocity changes. You don't have to play a game that creates discontinuities of age in remote objects under any circumstances.I.e., if the traveler instantaneously changes his velocity (wrt the home twin) from +V (away from her) to -V (toward her), but then immediately instantaneously changes his velocity from -V to +V, is the net effect the same as if there had been no reversals at all?
A good reason not to play the game according to CMF rules and to switch to radar rules.If the answer to that question is "yes", then it seems to me that the following is implied:
IF he is allowed to use the co-moving-frames (CMF) analysis for the first course-reversal, then he will say that her age suddenly increases during that first reversal. But if her age is the same before and after the matched pair of reversals, it is necessary that her age must decrease during the second reversal, by the same amount that her age increased during the first reversal. And this decrease in her age during the second reversal is exactly what the CMF says will happen.
As others have mentioned, this depends entirely on your convention for non-inertial reference frames. In the radar time convention they would be left the same.Does an immediate back-to-back (matched) pair of instantaneous course-reversals leave all ages the same as before?
You have already been told that this is wrong by multiple people in multiple different ways and with multiple references to the professional literature. There is no excuse for you to continue with these disproven assertions.And this decrease in her age during the second reversal is exactly what the CMF says will happen.
the Lorentz equations, which fundamentally are about simultaneity at a distance.
I understand that coordinates are basically meaningless in general relativity, but I don't think that need be the case in special relativity, which assumes a flat universe of infinite extent, with no gravitational fields.
It isn't that they are meaningless. It is that they are conventional. You can pick meaningful conventions, but they are still conventions.I understand that coordinates are basically meaningless in general relativity, but I don't think that need be the case in special relativity
The Lorentz equations only apply to Inertial Reference Frames and they have become a standard convention.If simultaneity at a distance is as meaningless in special relativity as the prevailing opinions on this forum seem to indicate, it's odd that Einstein put so much emphasis on the Lorentz equations, which fundamentally are about simultaneity at a distance. I understand that coordinates are basically meaningless in general relativity, but I don't think that need be the case in special relativity, which assumes a flat universe of infinite extent, with no gravitational fields.