Newton’s gravitational constant G and Universe age.
The gravitational constant is a physical constant that is difficult to measure with high accuracy.
George T. Gillies (1997), ”The Newtonian gravitational constant: recent measurements and related studies”, Reports on Progress in Physics 60 (2): 151–225
The 2014 CODATA-recommended value of the gravitational constant is:
G = 6,67408 * 10 -11 m3 / (sec2 * Kg )