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The Debunker: Is There A "Dark Side" Of The Moon?

by Ken Jennings

Last month, Neil Armstrong died at age 82. One of the best test pilots of his generation, Armstrong thought that his chances to be an aviation pioneer had passed him by in 1947 when his future colleague Chuck Yeager became the first human to fly faster than speed of sound. That all changed when he entered the space program, of course, and in 1969, Armstrong made history when he became the first man to walk on the moon. (If that doesn’t ring a bell to you kids, just picture the astronaut on the MTV Video Music Award.) The day of his August 31 memorial service was, appropriately enough, a “blue moon”—the second full moon in the same month, an astronomical oddity that won’t happen again until 2015. In honor of Neil Armstrong and the Apollo astronauts, we’ve asked Jeopardy! champ Ken Jennings to run down some common misconceptions that lots of people still believe about the moon. Did you know it’s not even made out of green cheese? Science ruins everything.

Moon Myth #1: I’ll See You on the Dark Side of the Moon.

It should be obvious that, indeed, one half of the Moon is always lit by the Sun, and one half is dark. But, despite the impression you may have gotten from bad science-fiction movies and prog-rock albums, it’s not always the same side...

The phrase “the dark side of the Moon” became cemented in the public mind during the years of the Apollo space program, and helped inspire Pink Floyd’s top-selling album. But it’s a little misleading. NASA used the term colloquially to refer to the far side of the Moon—that is, the side that always faces away from the Earth. (In a millennia-long process called “tidal locking,” the Earth has gradually altered the Moon’s orbit so that it rotates on its axis exactly as often as it rotates around the Earth, every 27.3 days, so we always see the exact same lunar features from Earth.) But that far side isn’t dark at all—it gets exactly as much sunlight as the hemisphere we see. It’s just “dark” in radio parlance—that is, transmitters on Earth couldn’t reach it and vice versa.

So there’s no truth to the popular idea of a mysterious, unlit half of the Moon’s surface where anything (aliens, Transformers, General Zod from Superman II) could be lurking unseen in the darkness. The far side of the Moon was a mystery until the Space Age, but Soviet probes began photographing it in 1959, and its features were pretty well mapped by 1968, when the first human beings—the crew of Apollo 8—set eyes on the surface. They later told science-fiction author Arthur C. Clarke that they’d been tempted to radio back a description of large black 2001 monolith on the back of the moon, but finally decided against it, thus ruining what would have been the best prank in American history.

Quick Quiz: The first two singles on Pink Floyd’s The Dark Side of the Moon had titles that were synonyms—according to Ben Franklin, anyway. What were the songs called?

Ken Jennings is the author of Brainiac, Ken Jennings's Trivia Almanac, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.