The idea is to put the time evolution of the entire universe into the metric, as a dimensionless function a(t) such that ds² = c²dt² − a²(t)dr². Using Einstein's field equations for gravity, you can then extract simple differential equations satisfied by a, the Friedmann equations.

Alexander Friedmann (1889 - 1925). George Gamow was one of his students.
A modern fan
The Early Universe!
Back