On 1/4/2019 6:25 PM, [email protected] wrote:
On Friday, January 4, 2019 at 2:08:39 AM UTC, Bruce wrote:
On Fri, Jan 4, 2019 at 1:03 PM <[email protected] <javascript:>>
wrote:
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]> wrote:
On Wed, Jan 2, 2019 at 5:50 PM Brent Meeker
<[email protected]> 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)^2is 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 disgracein 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 *
For the observer sitting at rest in the one location, his clock
reads both coordinate time and proper time. For an observer in
motion, his clock reads only proper time, not coordinate time.
*Still a little murky. Does coordinate time ever differ from proper
time? TIA, AG *
Of course. That's like asking does change in longitude ever differ from
distance sailed.
Brent
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