To get a more accurate number, the correction function F must be computed. In general this must be done numerically, and the results for a range of cosmological parameter values are shown in the figure. For the Planck values ( Ω Ω m , Ω Ω Λ Λ ) = (0.3086, 0.6914), shown by the box in the upper left corner of the figure, this correction factor is about F = 0.956 . For a flat universe without any cosmological constant, shown by the star in the lower right corner, F = 2 / 3 is much smaller and thus the universe is younger for a fixed value of the Hubble parameter. To make this figure, Ω Ω r is held constant (roughly equivalent to holding the cosmic microwave background temperature constant) and the curvature density parameter is fixed by the value of the other three.