# I What is the velocity of light in uniformly rotating frame?

1. Apr 10, 2017

### pallab

S'-frame of reference has uniform angular velocity with respect to the frame S. what is the velocity of light in S frame w.r.t S' ?

2. Apr 10, 2017

### Staff: Mentor

What are your thoughts? What are the Relevant Equations? Is this for schoolwork?

3. Apr 12, 2017

### pallab

NO.
My friend asked me this question.but I don't know about GTR.I studied STR .According to postulate speed of light in vacuum is same in all inertial frames.But a frame with uniform angular velocity is not inertial frame and the speed of light which has same value not the velocity.

4. Apr 12, 2017

### jbriggs444

Start with something easy. What is the speed of Proxima Centauri (4.2 light years from earth) in a frame of reference anchored to the rotating earth?

5. Apr 12, 2017

### pallab

when the earth approaches toward the Proxima Centauri its speed is more than the speed ,when earth moves away from it,like the earth's movement around the sun.

6. Apr 12, 2017

### jbriggs444

The earth's velocity around the Sun is trivial. Ignore it. Forget about the Sun entirely.

The earth is rotating once every 24 hours [approximately]. You anchor a frame of reference to it at this rotation rate. How does Proxima Centauri move from the point of view of this reference frame?

7. Apr 12, 2017

### pixel

8. Apr 12, 2017

### Staff: Mentor

This is the key point. The speed of light is not limited in a non-inertial frame. It can be arbitrarily large or small.

9. Apr 12, 2017

### pervect

Staff Emeritus
The shortest totally correct answer is it depends on how you set up your rotating frame. Of specific interest is how you synchronize clocks in your "frame".

10. Apr 18, 2017

### pallab

v=2πR/T
now for earth T=86400 sec.
and R=4.2 light years i.e. (9.46*1015)*4.2
so,v=2.8*1012 m/s , >c