# Re: Another stab at the universal present moment - a gedanken..

Jason,

What clock measures your coordinate time? Apparently none. It's beginning
to sound just like another name for Present time.

What's the difference?

Edgar

On Monday, January 6, 2014 9:47:36 AM UTC-5, Jason wrote:
>
>
>
> On Jan 6, 2014, at 6:55 AM, "Edgar L. Owen" <edga...@att.net <javascript:>>
> 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
>>
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