Death of Fred Whipple

This article is an obituary of Fred Whipple, a man who deduced that comets were "dirty snowballs" -- a collection of ice and dust -- rather than flying piles of sand, as had been thought. His book The Mystery of Comets was the first astronomy book I ever read. It came out in 1985 (when I was in 6th grade) as part of the run-up to the return of Halley's Comet. Whipple was a very intelligent, very practical man, and he lived to the ripe old age of 97.