4. Gathering momentum as a fellow at Cambridge, Hawking calculated that the Big Bang, which gave birth to the universe, must have created tiny black holes, each about the size of a proton but with the mass of a mountain. Then, upsetting the universal belief that nothing, not even light, can escape from a black hole, he used the quantum theory to demonstrate that these miniholes (and larger ones too) emit radiation. Other scientists eventually conceded that he was correct, and the black-hole emissions are now known as Hawking radiation.

5. Engrossed as Hawking is with his work, the authors say, "ALS is simply not that important to him." He certainly does not dwell on his handicap. His succinct, synthesized voice comments are often laced with humor, he enjoys socializing with his students and colleagues, attends rock concerts and sometimes takes to the dance floor at discos, wheeling his chair in circles. But he can be stubborn, abrasive and quick to anger, terminating a conversation by spinning around and rolling off, sometimes running one of his wheels over the toes of an offender.

6. Hawking can also be wrong. In 1985, for example, he brashly proclaimed that when and if the universe stopped expanding and began to contract, time would reverse and everything that had ever happened would be rerun in reverse. Eighteen months later, he sheepishly admitted his mistake. Earlier, after trashing another scientist's notion that the 19th century theory of thermodynamics could be applied to black-hole theory, he recanted and began applying it himself.

7. Without his wife Jane, Hawking has always emphasized, his career might never have soared. She married him shortly after he was diagnosed with ALS, fully aware of the dreadful, progressive nature of the disease, giving him hope and the will to carry on with his studies. They had three children in the early stages of their marriage, and later, as he became increasingly incapacitated, she devoted herself to catering to his every need.