- #1
- 2,257
- 7
general relativity says that gravity and acceleration produce the same effects but when an object accelerates its possible for distant clocks to appear to move backwards. gravitational time dilation doesnt do that.
general relativity says that gravity and acceleration produce the same effects but when an object accelerates its possible for distant clocks to appear to move backwards. gravitational time dilation doesnt do that.
Well the equivalent situation would be a stationary observer in a gravitational field on the top of a tall tower that drops a long rod with clocks attached to it so that the rod is free falling. That is what you would have to analyse.if you have a long line of synchronized clocks and a stationary observer that begins to accelerate at a constant rate then the clocks will become more and more out of synch. those on one side will move forward while those on the other side will move backward (at the same time all clocks are moving forward at some rate).
That's news to me. Where did you get this idea from? I never heard of it before myself. Thanks.general relativity says that gravity and acceleration produce the same effects but when an object accelerates its possible for distant clocks to appear to move backwards.
You are not describing a physical effect; you are describing a coordinate effect. (The fact that you're using the word 'synchronized' should be a big clue)just wondering what sort of gravity field would produce that effect.
Earth is a good example, if you are stationary above the Earth then anything above you will appear to run faster and anything below you will appear to run slower.you have a stationary observer and a long line of stationary clocks that are all synchronized. as the observer begins to accelerate at a constant rate the clocks which remain stationary will begin to get more and more out of synch from the observers point of view. the clocks in front of the observer will seem to him to tick faster but the clocks behind him will tick slower. clocks that are very far behind him will even seem to him to move backwards even after he corrects for time of flight of the light from the clock.
just wondering what sort of gravity field would produce that effect.
yes. but nothing runs backward. at least not from the point of view of anyone that is moving at a constant velocity.Earth is a good example, if you are stationary above the Earth then anything above you will appear to run faster and anything below you will appear to run slower.
what are you saying? that the clocks dont really run backward in time? well duh!You are not describing a physical effect; you are describing a coordinate effect. (The fact that you're using the word 'synchronized' should be a big clue)
I think he is simply mistaken, time does obviously not run backward in acceleration scenarios.That's news to me. Where did you get this idea from? I never heard of it before myself. Thanks.
Pete
I'm saying phrases like:what are you saying? that the clocks dont really run backward in time? well duh!
That means if your observer uses the same method to 'correct for time of flight of the light from the clock', he will get the same result in either circumstance.the effect of gravity is supposed to be indistiguishable from the effect of acceleration. i am just wanting to know how that is.
Clocks behind him will not run backwards. They will simply run slower, which is quite different.let me rephrase.
you have a stationary observer and a long line of stationary clocks that are all synchronized. as the observer begins to accelerate at a constant rate the clocks which remain stationary will begin to get more and more out of synch from the observers point of view. the clocks in front of the observer will seem to him to tick faster but the clocks behind him will tick slower. clocks that are very far behind him will even seem to him to move backwards even after he corrects for time of flight of the light from the clock.
Any gravitational field for which the time-time component of the metric tensor has different values at the different locations.just wondering what sort of gravity field would produce that effect.
the effect of gravity is supposed to be indistiguishable from the effect of acceleration. i am just wanting to know how that is.
Nobody knows how that is. The equivalence principle is something that is postulated to be true and as such it cannot be derived from other postulates.
In this case a coordinate effect is a physical effect. I.e. using a coordinate system which corresponds to a non-inertial frame of reference will produce measurements of physical quantities which are frame dependant.Hurkyl said:You are not describing a physical effect; you are describing a coordinate effect.
Pete
"Time running backwards" refers to the situation when, in a coordinate chart, the reading on a clock runs in the opposite direction than its time coordinate.I think he is simply mistaken, time does obviously not run backward in acceleration scenarios.
I'm confused; physical quantities are, by definition, frame independent. Time dilation, for example, is not a physical quantity. (Of course, the proper time experienced by an observer between two specified events in space-time is a physical quantity)I.e. using a coordinate system which corresponds to a non-inertial frame of reference will produce measurements of physical quantities which are frame dependant.
What does "stationary" mean? What does "synchronized" mean?well lets see if i am mistaken. you start with a long line of stationary synchronized clocks and a stationary observer.
What does "appear out of sync" mean?the clocks will appear to him to be severely out of synch