On 12/26/2013 8:12 AM, John Clark wrote:
On Mon, Dec 23, 2013 at 2:10 PM, Edgar L. Owen <edgaro...@att.net <mailto:edgaro...@att.net>> wrote:

    > The proof is simply the fact that the time traveling twins meet up again 
    different clock times, but always in the exact same present moment. This 
    beyond any doubt there are two kinds of time, clock time which varies by
    relativistic observer, and the time of the present moment (what I call 
P-time) which
    is absolute and common to all observers across the universe.

It's all a question of simultaneity, sometimes observers can agree that 2 events were simultaneous, and sometimes they can not, it all depends on the circumstances; and the amount of disagreement can vary from zero to as large a value as you'd care to name. So I don't see why zero is more special or "absolute" than any other number.

And nothing that happens in the Andromeda Galaxy 2 million light years away can have any effect on me for 2 million years, and nothing I do can have any effect on Andromeda for 2 million years. So even asking "what are things like right now on Andromeda?" is a ambiguous question. Does it mean how things look in my telescope when light left Andromeda 2 million years ago? Or does it mean Andromeda 2 million years in the future when something I do here can make a change there? So what does "right now" even mean?

It does have a meaning in most models of cosmology. "Now" is defined by a comoving frame in the expanding FRW universe. Operationally it means anybody who sees the CMB at the same isotropic temperature is sharing the same "now". But this is selecting a preferred frame based on empirical boundary conditions. Edgar refers to his P-time as being related to curvature of spacetime, so maybe this is what he's talking about, but in spite of my asking several times he hasn't replied.


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