On Jan 6, 2014, at 6:55 AM, "Edgar L. Owen" <[email protected]> wrote:
Brent,
No it's not "an observation that the two twins are together at
particular spacetime coordinates" because the spacetime t
coordinates are different.
Their proper times are different, but not their coordinate times.
A clock time is only a representation of how much speed (and
accordingly distance) had to be given up to travel through space. It
is not an actual coordinate in space time, for that you use coordinate
time. All things travel equal distances through space time in equal
coordinate times, but not all things travel equal distances through
proper time (clock time) in equal coordinate times. It is when the
coordinate times are equal that two things can interact.
Since the spacetime t coordinates are different WHEN are they
together?
Their coordinate times are equal.
Certainly not in a simultaneous clock time as proved by their
differing clocks.
Right, their proper times are different.
When are they together Brent? Obviously in a present moment which is
a kind of time that clearly is not the same as clock time.
They are together when their spatial coordinates: x,y,z and coordinate
time t are the same. You are right this t is not the same as proper
time.
Your conclusion that there must be a global present for this to work
is unneccessary.
Jason
Edgar
On Monday, January 6, 2014 12:18:16 AM UTC-5, Brent wrote:
On 1/5/2014 12:00 PM, Edgar L. Owen wrote:
> Brent,
>
> No, the present moment is NOT just a "label". It's an empirically
verifiable observation
> (measurement). And not only that both twins agree on that
measurement, namely that they
> have different clock times in the same shared present moment.
>
> There is simply no way around that....
>
> Edgar
Of course it's an observation. It's an observation that the two
twins are together at
particular spacetime coordinates. I have no problem with you
calling that a present
moment (although everyone else calls it an event). The problem is
not that you can't
define a global time at which they meet, it's that you can't define
a *unique* global
time. There are infinitely many choices of coordinate time and they
will all agree that
the twins meet at the same coordinate time - but they will not agree
as to which other
distant events in the universe are at the same time as the meeting.
Brent
--
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.
--
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.
