Proper time Definition and 155 Threads

Working on pervect's "messy unsolved" problem has led me to an interesting result. Let \left( x , t \right) be a global inertial coordinate system for Minkowski spacetime. Consider the worldline given by t \left( \tau \right) = \frac{\tau^3}{3} - \frac{1}{4 \tau} x \left( \tau \right) =...

Finding the "proper time" I'm currently working through the book "A first course in general relativity" by Bernard F. Schutz, and I am kind of stuck on one of the problem on page 56 question 19. Problem A body is said to be uniformly accelerated if its acceleration four vector \vec{a} has...

An interesting time dilation experiment I thought of was to send a radio signal with two pulses a certain time apart to a receiver moving toward the emitter. I believe that the effect is that the accelerated reciever undergoes time dilation and would time the two pulses of light as closer...

If a passing spaceship sends a beam from the back to the front in their time of L/c andthen immediately the beam is reflected from front to back, can an stationary observer using proper time determine the length contraction formula? I don't see how to set this up. Thanks for any help.

A commonly accepted modern SR/Gr statement is "timelike geodesics are maxima of the proper time". I really shall not dispute with these experts, who are all professors. But this statement is clearly questionable. It bothered me for a long time. The H & T experiment and GPS all show the...