As I've said many times, Sn Ia's appear to be our most
reliable "standard candles".
Recently, one was found by reviewing the Hubble N Deep Field image
(a 2 wk long,
ultra-deep exposure of a small patch of sky taken w/ the Hubble Space
Telescope). The
point is shown below at redshift z = 1.7 Note how the older points
were too recent to
distinguish between different cosmological models. Clearly one would
like more points
at high z, but the new result does suggest that we are finally looking
back to a time
when different changes in expansion rate can be distinguished.
What does the future ot the U look like?
