What equation is this?

Question

A friend bought me a mouse pad that is simply labeled "Einstein's Theory" on the back. On the front it has an image, which I was able to find online through some searching. As this one:

Note the URL also attributes it to Einstein. However, I cannot figure out what this equation represent. Nor can I actually find any Einstein theories that include any of this. Also, due to the handwriting, I'm not sure what symbols some of those are and can't find TEX representations (for instance of that last symbol that kind of looks like a 't').

Any help would be greatly appreciated!

Answer 1

Nice find @A---B! Just to pull in the details from that wiki article:

...the equation displayed are taken from a model of the universe proposed by Einstein in May 1931 known as The Friedmann-Einstein universe. The last three lines on the blackboard are estimates of the density of matter in the universe ρ, the radius of the universe P and the timespan t of the expansion of the universe respectively ("L.J." on the blackboard indicates "light years" in German). It has recently been shown that these estimates contain a systematic numerical error.