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.