Stephen Hawking turned 70 on Jan. 8.

Cosmologists – scientists like Hawking who study the origins of the universe – gathered in Cambridge, UK, to pay tribute to him.

Hawking was a mathematics professor at the University of Cambridge for 30 years. He retired from that job in 2009. He still works for Cambridge, in cosmology research.

Hawking is a mathematical genius, who changed the way scientists think about the universe.