Main Question or Discussion Point
How does the gravitational red shift causes time dilation?
Google them both and you'll find some pretty decent explanations. If after you've done that it's still not clear, come back with a more focused question about exactly what's not clear and we'll be able to come up with a more helpful answer.Is there any relationship between the gravitational red shift and gravitational time dilation? What is it?
- http://en.wikipedia.org/wiki/Gravit...l_redshift_versus_gravitational_time_dilationWhen using special relativity's relativistic Doppler relationships to calculate the change in energy and frequency (assuming no complicating route-dependent effects such as those caused by the frame-dragging of rotating black holes), then the Gravitational redshift and blueshift frequency ratios are the inverse of each other, suggesting that the "seen" frequency-change corresponds to the actual difference in underlying clockrate. Route-dependence due to frame-dragging may come into play, which would invalidate this idea and complicate the process of determining globally agreed differences in underlying clock rate.
While gravitational redshift refers to what is seen, gravitational time dilation refers to what is deduced to be "really" happening once observational effects are taken into account.
That is a pretty reasonable statement. The only further thing to add is that the separation between gravitational redshift and ordinary Doppler is itself coordinate dependent, thus I don't view them as separate phenomena. To see this consider how SR or GR analyzes redshift between the front and back of an accelerating rocket: front sees redshift from and slower clocks on the bottom; back sees blueshift from and faster clocks on the top. Sounds like gravitational redshift. However, in an inertial frame it is absolutely nothing but ordinary Doppler (by the time light from the back has reached the front, the front is moving away faster, so it is seen redshifted; by the time light from the front reaches the back, the back is moving towards it faster, so it is blue shifted). Gravitational redshift is ultimately nothing but Doppler between non-inertial emitter and receiver that maintain a constant distance. In the case of static observers at different elevations on earth, if you analyze using normal coordinates for a free fall observer, you see pure Doppler with tiny corrections on the order of tidal forces (unmeasurable compared to the primary effect which is pure Doppler).someone at the wikipedia had this to say:
Please read my last post. All questions you ask are fully answered there. Given an emitter and receiver at the top and bottom of a tall building, analyzed from the point of view of a free falling observer you find the detectible effect is 100% due to velocity difference between the emitter at emission time and receiver at reception time. Thus, who is observing (more precisely, which coordinates you use) determines whether a given observation is explained by Doppler, gravitational red shift, or any mixture.Doesn't Doppler work on different velocities whereas Gravitational redshift works only in gravitational fields ? (or according to EEP to accelerating frames)
That is an important difference, I think.
I agree with Topicwriter that Timedilation and Gravitational Redshift seem to work opposite in stead of in similar direction.