Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Old Stars



Seems like the answer is tied up in general relativity and the
geometry of the Universe. Let me pose the same question a little
differently.
If about 12 billion years ago our friend 'Q' (from STNG) turned on a
flashlight for 1 second while standing at the 'center' of the Universe
(from previous Paul Camp writings I suspect there is no such
place--but--), where are the photons from that flashlight today? In a
Euclidian geometry the photons would be 12 billion lightyears away
(provided they didn't pass too near any large massive bodies and
provided the Universe itself isn't inside a black hole). But what
does GR say about these photons? Without knowing the mass and size of
the Universe, do we really know enough about it's geometry so as to be
able to answer the question?

Rick Tarara

----------
From: James Mclean <jmclean@chem.ucsd.edu>

Consider a cosmic background photon which was originally emitted
someplace
which I'll call 'there', and is just now getting 'here'. Say this
photon
comes from an event that was 10^10 years ago. How far apart were
'here'
and 'there' when the photon was emitted? How far apart are 'here'
and
'there' now? If space has been expanding, it's not clear to me that
the
answer to either question is 10^10 lightyears.