implied the clocks were still synched after they were separated and that an arbitrary horizon could be established between Elle and Fred based on a time limit for signals to travel. Approximate synchronization and the arbitrary horizon is fine with me. What isn't is the assumption [A] that on either side of the horizon an inertial frame exists where we can conclude that either Elle or Fred made the measurement first. Relativity can only speculate about unobservable events [such as what happens to observers falling into a black hole, etc.]. For this thought experiment it is easy to show that [A] isn't correct just by allowing more time for information to arrive describing Fred's actions. How about having Fred fall into a black hole [where a natural horizon exists] and then having Elle and Fred make their measurements. It would be easy to speculate what relativity would conclude using a proper frame metric.

• Keep in mind.. - bruce - October 3, 2003 - 20:57 UTC
• Isn't SR agnostic about these things? - harvey1 - October 3, 2003 - 22:11 UTC
  • I have to leave... - bruce - October 4, 2003 - 00:33 UTC