1. Sep 14, 2012

consider a following situation,where a person A is on earth and another one B far from earth where his proper time is not influenced by earth's gravity field.now whats time flow felt by A wrt A and wrt to B.?
I get the answer for it but i need a explicit explaination..Is there any link where I can get formulae for this using GR.??thanks in advance

2. Sep 14, 2012

### harrylin

http://en.wikipedia.org/wiki/Gravitational_time_dilation

3. Sep 15, 2012

what does this mean----
"If a distant observer is able to track the light in
a remote, distant locale which intercepts a time
dilated observer nearer to a more massive
body, he sees that both the distant light and
that distant time dilated observer have a
slower proper time clock than other light which is coming nearby him, which intercepts
him, at c, like all other light he really can
observe. When the other, distant light
intercepts the distant observer, it will come at c
from the distant observer's perspective."

4. Sep 15, 2012

### harrylin

That's very messy formulation. Gravitational time dilation and length contraction imply that in GR the speed of light is only a local constant.

-> that is also mentioned in par.5 of chapter 22 here:
http://www.bartleby.com/173/22.html

For example, take the measurement of the speed of light of a horizontally propagating light ray at great height, using a standard ruler, a clock and a mirror. For simplicity assume this is done in vacuum and ignore the rotation of the Earth (or have it measured in an airplane that flies against the rotation of the Earth, thus cancelling it).
Then the speed as measured with those local instruments will be c. However, according to a reference system with otherwise identical instruments at sea level, the ruler in the airplane has the same length but the airplane clock is running fast.

BTW, do you understand the equations given in the wiki?

Last edited: Sep 15, 2012