Dirac Large Numbers Hypothesis
For an electron orbiting a proton, both electric and gravitational forces are inverse square laws of separation distance.
1. The ratio of elec to grav force is 10^39
2. Age of universe in atomic units is approx. 10^39
Because 1. is unitless there is prob a reason for it. Since 2 is not a constant, perhaps electric force compared with the gravitational force is not constant but increases with age of universe. In other words G decreases over time, when fixing electric force.
This requires a modification of the general theory of relativity along lines of Milne’s.
Number of elementary particles in universe is approx. the square of the age, currently 10^78.
In general Dirac suggested whenever you get large numbers of this order of magnitude, they cannot be constant and must be connected with the age of the universe.