Stephen Hawking turns 75. Congratulations! Here�s what to celebrate.

If people know anything about physics, it�s the guy in a wheelchair who speaks with a computer. Google �most famous scientist alive� and the answer is �Stephen Hawking.� But if you ask a physicist, what exactly is he famous for?

Hawking became �officially famous� with his 1988 book �A Brief History of Time.� Among physicists, however, he�s more renowned for the singularity theorems. In his