Jesse, OK, so we agree here. Your coordinate time just references the well known fact that one can use more or less any arbitrary coordinate system in relativity, and that none is intrinsically any 'better' than any other, though some may be more useful than others. I have no problem with that at all, it's always been my understanding.
So again I find this whole digression into coordinate time irrelevant to the fundamental issue of the fact that the twins have different clock times in a single present moment. Coordinate time just says, well we could have a coordinate system that would independently label that present moment as having any clock time we want. But that does not alter the fact that the twins have real actual AGES that are different. Again I will post shortly a longer and more complete analysis of where I think the discussion stands... Best, Edgar On Thursday, February 6, 2014 7:37:21 PM UTC-5, jessem wrote: > > > > On Thu, Feb 6, 2014 at 6:40 PM, Edgar L. Owen <edga...@att.net<javascript:> > > 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
