Deflecting the Terrible Sword

Almost 50 years ago, the famous astronomer Bart Bok revealed that the Milky Way was filled with dense concentrations of gas that could be the birthplaces of new stars. Although these Bok globules, as they are now known, are faint and esoteric objects, they captured the public imagination, thanks to a 1957 science fiction story by astronomer Fred Hoyle, called The Black Cloud. As the story opens, astronomers using Palomar’s 18-inch Schmidt telescope (the same one used in real life to discover all the Shoemaker comets) spot a big black cloud approaching the Earth. “Such globules are not uncommon in the Milky Way,” the astronomer says, “but usually they’re tiny things. My God, look at this! It’s huge, it must be the best part of two and a half degrees across!”1 As the drama unfolds, the globule appears to get bigger as it closes in on the Earth. Finally one morning the assistant appears in a great panic: “It’s not there, sir, it’s not there!” “What isn’t there?” “The day, sir! There’s no Sun!”