COSMIC TIME DILATION

The observed apparent time dilation of supernovae light curves claimed recently by Leibundgut et al. to establish directly the ''expansion o f the universe'' is, rather, a general implication of fundamental phys ics. In particular, it applies to chronometric cosmology, in which it appears explicitly as a generalized Lorentz-Fitzgerald contraction. Th e dilation effect was earlier shown in the proper motion-to-redshift r elation of superluminal sources, as analyzed in the frame of chronomet ric cosmology by Segal, providing an estimate of the cosmic distance s cale.