On Thursday, January 3, 2019 at 8:58:14 AM UTC, Bruce wrote: > > On Thu, Jan 3, 2019 at 12:00 PM John Clark <[email protected] > <javascript:>> wrote: > >> On Wed, Jan 2, 2019 at 5:50 PM Brent Meeker <[email protected] >> <javascript:>> wrote: >> >> *> That's like saying if two people drove different cars from L.A. to New >>> York and their odometers registered different distances then one of the >>> odometers must have measured miles differently than the other...ignoring >>> the fact that they took different routes.* >>> >> >> No it's more like you claiming the odometer which measures miles is >> telling you the time which is measures in seconds. Or it's like saying the >> readings on any odometer that went from L.A. to New York is a invariant and >> so will always give the same reading regardless of the path took, even >> though they *don't have the same reading*. In other words its nonsense >> >> >> >> The spacetime distance d is *not* the proper time, the >>>> spacetime distance is an invariant, it's the same for all observers, but >>>> proper time is *not* invariant; >>> >>> >>> * > Sure it is. It's path dependent, but it's an invariant of a given >>> path. * >>> >> >> Obviously!! If you take the same path through spacetime then you've not >> only traveled the exact same distance through time but moved the exact same >> distance through space too, otherwise it wouldn't be the same path through >> spacetime. But Einstein told us something much more interesting than X=X, >> If we travel between event A and event B by different paths we'll disagree >> on the distance through space that was required and disagree on the >> distance through time that was required but we'll both agree on the >> distance through spacetime we traversed; that's why it's a invariant and >> that's why it's useful. >> >> >>> *> The "spacetime distance" between two timelike events is the length of >>> the longest proper time path between them.* >>> >> >> Brent, this is getting silly. If d^2 = r^2 - (ct)^2 is the formula >> for spacetime distance (*AND IT IS!*) then there is no way on god's >> green earth the proper time can be the spacetime distance, one is a >> invariant and the other isn't and the two things don't even have the same >> units. I really don't know what else I can tell you except that there is no >> disgrace in being wrong but there is disgrace in refusing to admit error >> or learn from it. >> > > So learn from this! > The 't' in your formula above is the coordinate time, not the proper time. > Learn the difference! The proper time is defined as the time kept by a > perfect clock travelling on a geodesic. And a geodesic is the path along > which the rate of time is constant. >
*If time is what is read on a clock, who, what, where, is the observer who reads coordinate time, or the clock recording coordinate time? TIA, AG * > > Bruce > -- 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 https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
