On Thu, Feb 6, 2014 at 6:40 PM, Edgar L. Owen <[email protected]> wrote:
> Jesse, > > OK, what I don't understand in this clearer example near the end of your > post is you say "The coordinate time of an event *is* just clock time on > the local coordinate clock that was at the same point in spacetime as the > event". > > This clock, call it C, on the grid that was at the same point in spacetime > as the meeting event (which takes place on earth) is also a clock on earth, > at earth's location on the grid. Twin B's clock also stayed at that exact > same x,y,z point on the coordinate grid during the trip, and there was no > relative motion between B and C. > > So why does B's clock read 40 years and clock C, which you claim gives the > t-value of the meeting event, read 50 years when they were both at the same > location during the trip? > My scenario never specified that we were using a coordinate system where B was at rest. But yes, if B was at rest next to clock C the whole time, clock C would measure a coordinate time interval of 40 years between A leaving Earth and A returning. That still doesn't necessarily mean that C would actually read 40 years when A returns--it could be that clock C was set to 0 10 years before A departed, for example. It is most common in twin paradox analyses to use a coordinate system where the twins depart at a coordinate time of 0, though. > > Aren't you mistaken here since clocks B and C are comoving throughout the > duration of the trip and thus must remain synchronized? > > If that is true you seem to be saying that we must preferentially take the > stay at home twin's clock time as the correct t-value of the same point in > spacetime that the meeting occurs, the clock time of the observer that > didn't move from the start to end point. Is that correct? > > If so, again it's just a definition, and a strange one at that, because no > matter if the traveling twin resets his clock to that t-value you claim is > the correct/natural? t value of the meeting event, his age still remains > just 30. > I never said the t-value was correct/natural, it is just the coordinate time in one particular coordinate system, which is no more correct/natural than any other coordinate system. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
