In my freshman astronomy class, filled with unwilling non-science majors unhappily meeting an unappreciated general education requirement, I show the PBS video series "Stephen Hawking's Universe." The script for the series was well done, the visuals engaging and enlivened by the occasional appearance of Hawking.

The six-part series and its companion text were not actually about Hawking and were just capitalizing on the cosmologist's rock-star stature. But some of his ideas were discussed—and, wherever possible, the director would arrange a shot of Hawking in his wheelchair, going to his office or scooting across a college campus somewhere, en route to a lecture.

To keep the students awake in a darkened room with reclining seats—and salvage some of the money their parents had ponyed up for their education—I made them write reports on the videos. One student, an aspiring filmmaker, reviewed the video series from a technical point of view as well as for the content I wanted them to learn. He expressed puzzlement about why the PBS director chose to have "some guy in a wheelchair repeatedly crossing the screen for no apparent reason."

The student obviously missed the point, but his question, enlarged, is still a good one. Why has "some guy in a wheelchair"—Stephen Hawking—been repeatedly crossing in front of us, most recently floating weightlessly in space sans wheelchair, for the past quarter century?

A Brief History of A Brief History

Hawking is the best-known physicist since Albert Einstein and one of the scientific community's rare celebrities. His signature work of science popularization, A Brief History of Time, has sold one copy for every 750 people on earth—an astonishing record; it has been translated into 40 languages and has turned its author into a major public figure, capable of filling large lecture halls and even getting multiple guest spots on The Simpsons, the ultimate measure of cultural cachet.

Hawking's extraordinary scientific ...

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