Answer to problem 5.4.5
Return to Chapter 5, General Relativity Physics Dynamic Implications
The refer to the simplified answer for the transformation between the inertial frame unprimed and the accelerated primed frame:
t = gt' + g(v/c2)[x'cos(wgt') + y'sin(wgt')]
x = x'[gcos2(wgt') + sin2(wgt')] + r0sin(wgt') + (g - 1)y'sin(wgt')cos(wgt')
y = y'[cos2(wgt') + gsin2(wgt')] - r0cos(wgt') + (g - 1)x'sin(wgt')cos(wgt')
The counter rotating frame transformation to the inertial frame will also be
t = gt" - g(v/c2)[x"cos(wgt") - y"sin(wgt")]
x = x"[gcos2(wgt") + sin2(wgt")] - r0sin(wgt") - (g - 1)y"sin(wgt")cos(wgt")
y = y"[cos2(wgt") + gsin2(wgt")] - r0cos(wgt") - (g - 1)x"sin(wgt")cos(wgt")
From these relate the two accelerated frame coordinates
g
t' + g(v/c2)[x'cos(wgt') + y'sin(wgt')] = gt" - g(v/c2)[x"cos(wgt") - y"sin(wgt")]x'[gcos2(wgt') + sin2(wgt')] + r0sin(wgt') + (g - 1)y'sin(wgt')cos(wgt') = x"[gcos2(wgt") + sin2(wgt")] - r0sin(wgt") - (g - 1)y"sin(wgt")cos(wgt")
y'[cos2(wgt') + gsin2(wgt')] - r0cos(wgt') + (g - 1)x'sin(wgt')cos(wgt') = y"[cos2(wgt") + gsin2(wgt")] - r0cos(wgt") - (g - 1)x"sin(wgt")cos(wgt")
Consider what the double primed frame observer's watch reads according to the single primed frame. It is at the origin of the double primed frame, so:
g
t' + g(v/c2)[x'cos(wgt') + y'sin(wgt')] = gt"x'[gcos2(wgt') + sin2(wgt')] + (g - 1)y'sin(wgt')cos(wgt') = - r0[sin(wgt") + sin(wgt')]
y'[cos2(wgt') + gsin2(wgt')] + (g - 1)x'sin(wgt')cos(wgt') = r0[cos(wgt') - cos(wgt")]
Solve the last equation for y' and insert into the other two and simplify.
y'= {r0[cos(wgt') - cos(wgt")] - (g - 1)x'sin(wgt')cos(wgt')}/ [cos2(wgt') + gsin2(wgt')]
g
t'[1 +(g - 1)sin2(wgt')] + g(v/c2)x'cos(wgt') + g(v/c2)sin(wgt')r0[cos(wgt') - cos(wgt")] = gt"[1 +(g - 1)sin2(wgt')]x'g = - r0sin(wgt")[1 + (g - 1)sin2(wgt')] - gsin(wgt')r0 + (g - 1)sin(wgt')cos(wgt')r0cos(wgt")
Substitute the last into the previous equation and simplify
g
t' - r0(v/c2)sin[wg(t" + t')] - gt" = 0This says that the watch re-synchs with the single primed frame observer's watch at
wg
t' = wgt" = np/2These include the locations where the rockets meet.
Differentiate
dt' - w(dt" + dt')r0(v/c2)cos[wg(t" + t')] - dt" = 0
Consider those re-synch points where they meet at wgt' = wgt" = mp
dt' - w(dt" + dt')r0(v/c2)cos(2mp) - dt" = 0
dt' - w(dt" + dt')r0(v/c2)cos(2mp) - dt" = 0
Simplify to
dt' = (1 + v2/c2)dt"/(1 - v2/c2)
Let u = 2v/(1 + v2/c2)
Inserting this and simplification results in
dt' = dt'/(1 - u2/c2)1/2
This demonstrates that one rocket frame observer will observe the other as time dilated by special relativistic time dilation as they pass each other.
Return to Chapter 5, General Relativity Physics Dynamic Implications