A horizontal platform has radius and is spinning with angular velocity in relation to an inertial frame. Suppose . According to general relativity, any accelerated frame of reference may be compared to a frame of reference that is subjected to a gravitational field. Then, if is the centripetal force an object feels while on the platform, it may be associated with a potential field . So
where is the time that passes for an observer at a distance from the center of the platform.
What is ?
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According to Einstein
Δ t 0 Δ t ′ = 1 − c 2 v 2 1 ≈ 1 + 2 c 2 v 2
if v < < c . As v = ω r < < c , we'll be able to use this approximation. Now, of course Δ t ′ = Δ t ( r ) must be a function of r , and Δ t 0 = Δ t ( 0 ) . Then the above equation becomes
Δ t 0 Δ t ′ ≈ 1 + 2 c 2 ( ω r ) 2
Now
∣ ∣ ∣ F ∣ ∣ ∣ = r m v 2 = m ω 2 r = ∂ r ∂ V ( r ) = m ∂ r ∂ φ ( r )
where V ( r ) is the potential energy associated with the force (and all forces have a "gravitational potential field" associated with it, according to Einstein). Solving for φ ( r ) will give us
φ ( r ) = 2 ( ω r ) 2
And, of course,
Δ t 0 Δ t ′ ≈ 1 + c 2 φ ( r )
Therefore A + B = 2 .