What Is Relativity in Physics?

[dcarmichael]

Homework Statement

The Principle of the astronomical measurements which indicate that the velocity of light is NOT constant relative to its source can be demonstrated by the following problem. Consider a pair of stars A,B of equal mass in circular orbit about their center of mass, C which is a distance d from earth. Assume that the orbit radius is r , the orbital velocity u and that the line of sight to earth is in the plane of orbit.
I understand where the 2nd term in part II comes from but where does πr/u come from ?

Relevant Equations

n/a

 

[TSny]

Welcome to PF.

It takes some time for star $A$ to get from position $A_1$ to position $A_2$.

 

[dcarmichael]

Thank you