ON THE COVER: The comet Kohoutek streaks across the sky in this NASA photograph.

Immanuel Velikovsky proposes that a comet much like this was ejected from Jupiter about 3000 years ago and passed dangerously close to the earth. During its several near collisions with the earth, Velikovsky says, the comet caused the “sun to stand still,” manna to fall in the Sinai Desert, the plagues of flies and frogs in Egypt, and the parting of the Red Sea.

In “A Scientist Looks at Velikovsky’s ‘Worlds in Collision,’” Pulitzer Prize-winning author and astronomer Carl Sagan considers Velikovsky’s basic thesis.