Tuesday, August 26, 2008

Sci-fi innumeracy

From Death by Black Hole by Neal deGrasse Tyson

The 1997 film Contact, inspired by Carl Sagan's 1983 novel of the same name, contains an especially embarrassing astro-gaffe. (I saw the movie and never read the book. But everyone who has read the book says, of course, that it's better than the movie.) Contact explores what might happen when humans find intelligent life in the galaxy and then establish contact with it. The heroine astrophysicist and alien hunter is actress Jodie Foster, who recites a fundamental line that contains mathematically impossible information. Just as she establishes her love interest in ex-priest Mathew McConaughey, seated with the largest radio telescope in the world behind them, she says to him with passion: "If there are 400 billion stars in the galaxy, and just one in a million had planets, and just one in a million of those had life, and just one in a million of those had intelligent life, that still leaves millions of planets to explore." Wrong. According to her numbers, that leaves 0.0000004 planets with intelligent life on them, which is a figure somewhat lower than "millions." No doubt that "one in a million" sounds better on screen than "one in ten," but you can't fake math.

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