How Recent is Cosmic Acceleration?

Abstract

Possibly the most peculiar expectation of the standard fine-tuned cosmological paradigm is that cosmic acceleration is to only be a very recent (z<1) phenomenon, with the universe being required to be decelerating at all higher redshifts. Detailed exploration of the Hubble plot out to z=2 or so will not only provide an absolute test of this expectation but will also allow for testing of conformal gravity, a non fine-tuned alternate cosmological theory which provides equally good fitting to the current z<1 Hubble plot data while requiring the universe to be accelerating at higher z instead. With both standard and conformal gravity being found to be compatible with a very recently reported z=1.7 data point, additional data points will thus be needed to determine whether the universe is accelerating or decelerating above z=1.