The critical density is proportional to the square of this quantity over the universal gravitational constant.
The critical density is proportional to the square of this quantity over the universal gravitational constant. Its time evolution is described by the deceleration parameter, and it can be defined as the logarithmic time derivative of the scale factor. The first Friedmann equation relates its square to the curvature, the total density and the cosmological constant. It is approximately equal to one over the age of the Universe, and it appears in an equation relating redshift and distance. FTP name this constant of proportionality between distance and recession velocity of galaxies in a namesake law describing the expansion of the Universe.
The critical density is proportional to the square of this quantity over the universal gravitational constant.
{Hubble}’s constant or parameter