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granpa
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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 doesn't do that.
granpa said: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 doesn't do that.
granpa said: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.granpa said: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)granpa said: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.granpa said: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.
MeJennifer said: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.
Hurkyl said: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.pmb_phy said: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:granpa said:what are you saying? that the clocks don't 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.granpa said: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.MeJennifer said: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)pmb_phy said: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?granpa said:well let's 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
The concept of time running backwards for objects larger than the Schwarzschild radius is a topic of debate in the scientific community. According to the laws of physics, time should always move forward. However, some theories, such as the theory of relativity, suggest that time can be affected by extreme gravitational forces, such as those found near a black hole.
The Schwarzschild radius is the distance from the center of a black hole at which the escape velocity is equal to the speed of light. At this point, gravity is so strong that not even light can escape. This intense gravitational pull can warp the fabric of space-time and affect the flow of time near the black hole.
While some theories suggest that it may be possible for an object to travel back in time near the Schwarzschild radius, this is still a highly debated topic and has not been proven. The laws of physics as we currently understand them do not allow for time travel.
There are no known real-life examples of time running backwards for objects larger than the Schwarzschild radius. The intense gravitational forces near a black hole can significantly affect the flow of time, but it does not reverse it. This phenomenon is purely theoretical and has not been observed in nature.
The concept of time near a black hole is still not fully understood, and it is a topic of ongoing research. While we have made significant advancements in our understanding of black holes and their effects on space-time, there is still much we do not know. It is possible that we may never fully understand the concept of time near a black hole.