On Wed, Feb 19, 2014 at 9:50 PM, Eric Walker <eric.wal...@gmail.com> wrote:
> On Wed, Feb 19, 2014 at 3:25 PM, H Veeder <hveeder...@gmail.com> wrote: > > Imagine two friends with synchronized watches. One friend boards a train >> and zips away for a time at near c and then gets off and walks back to his >> friend >> so that they can compare the time on their watches. Which watch is ahead? >> >> Using the principles of SR I can come up with contradictory answers. >> > > I'm curious what the two scenarios are. > > Eric > > Each friend should see the other's watch tick more slowly according to special relativity. Therefore when they meet up again, both watches should record the same elapsed time, but what happened to the time-dilation effect on the passage time? SR ends in contradiction when watches are compared after the travelling. Dave mentions that acceleration might play role in resolving the contradiction. I have heard that reason too, but it strikes me as hand waving. Even if acceleration has to be factored in, the ratio of time spent accelerating to the time spent travelling at uniform speed near c can be assumed to be arbrarily small so that the acceleration becomes irrelevant. Harry
