On March 17,1905: Albert Einstein finished a scientific paper that would change the world. His radical insight into the nature of light would help transform Einstein from an unknown patent clerk to the genius at the center of 20th-century physics. Scientists call 1905 Albert Einstein's annus mirabilis — his year of miracles. The first paper described his particle theory of light, which became one of the foundations of modern physics. Just as popular legend has it, Einstein really was a patent office clerk when he conceived his radical theories — but he was also a doctoral candidate who spent his free time debating cutting-edge physics with his friends.