Scale Factor History
Scale factor history for the concordance (2005) model, shown on both linear and log scales. The time axis is in units of the Hubble time (tH,o = Ho-1) and is set to zero at the big bang. The age of the model (when a = 1) is 0.993 tH. Times of relativistic/matter equality, and matter/vacuum equality are also shown, at which points the expansion growth changes form. On the log plot, the change from t1/2 and t2/3 isn't particularly obvious, though the change to exponential certainly is. The radiation era is, of course, invisible on the linear plot. The curves were calculated from t/tH =
da / aE(a) (0 to a).
Figure made for this website.