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Aliens Apart

For years scientists have wrestled with a puzzling fact: The universe appears to be remarkably suited for life. Its physical properties are finely tuned to permit our existence. Stars, planets and the kind of sticky chemistry that produces fish, ferns and folks wouldn't be possible if some of the cosmic constants were only slightly different.

Well, there's another property of the universe that's equally noteworthy: It's set up in a way that keeps everyone isolated.

We learned this relatively recently. The big discovery took place in 1838, when Friedrich Bessel beat out his telescope-wielding buddies to first measure the distance to a star other than the sun. 61 Cygni, a binary star in our own back yard, turned out to be about 11 light-years away. For those who, like Billy Joel, are fond of models, think of it this way: If you shrank the sun to a ping-pong ball and set it down in New York's Central Park, 61 Cygni would be a slightly smaller ball near Denver.

From Space.com