ABSTRACT
Einstein claimed that various phenomena synthesized by his Special Theory
of Relativity had the consequence that
we cannot attach any absolute signification to the concept of simulta-
neity, but that two events which, viewed from a system of coordinates,
are simultaneous, can no longer be looked upon as simultaneous events
when envisaged from a system which is in motion relatively to that
system. (Einstein 1923: 42-43)
I argue in this paper that Einstein gave good, but not compelling grounds
for supposing that the concept of absolute simultaneity would have no
application in a universe empty of matter and so governed entirely by the
laws of Special Relativity. But I claim that there is absolute simultaneity in
our homogenous and isotropic universe of galaxies receding from each
other with a metric described by the Robertson-Walker line element. ‘‘Cosmic Time’’ provides a correct standard of absolute simultaneity.