Who is Albert Einstein from A Brief History of Time and what is their importance?

The author refers to Einstein often and his famous equation, energy equals mass times the speed of light squared. Einstein contributes much to physics, but his general theory of relativity carries the most importance for the author. This theory leads to the idea of black holes developing from stars that have consumed all their nuclear fuel (hydrogen). If a star has a mass one and one half times that of the sun, the gravity of the star overcomes all other forces and it shrinks down to a singularity, a black hole.