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Seth Shostak

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Humble Pie

Posted: 01/ 5/2012 12:06 am

There's a well-known historical event that astronomers routinely cite whenever they wish to prove their modesty: it's called the Copernican Revolution. It taught us to always assume that our circumstances are typical, rather than special -- that we're just another kid on the block, another bird in the flock. But today, this comfortable modesty may be headed to a very uncomfortable extreme.

Unlike other revolutions, the one begun by Copernicus didn't feature peasants with pitchforks. Instead of taking on the aristocracy, it took on Aristotle -- who had flogged the appealing idea that all of creation pivoted around the Earth, a view that Copernicus challenged. Because Aristotle had been dead for two thousand years, he didn't fight back.

The new paradigm was that the planets orbited the Sun, rather than the Earth -- a seismic shift in cosmological thought that removed us from the center of the cosmos forever. Hubris was out, although not very far out. Copernicus shifted the nexus of the universe to the Sun which, as every school kid knows, is merely 93 million miles from the location favored by Aristotle.

By the middle of the nineteenth century, the cosmos' ground zero was moved again, to the realm of the stars. Then came the biggest step of all: astronomers Vesto Slipher, Milton Humason, and Edwin Hubble discovered that our galaxy - long regarded as the be-all and end-all of existence -- was just one of many.

How many? Well, there are at least 100 billion galaxies within the reach of our best telescopes. Our solar system -- once thought to loom so large -- is just a small bit of amusing clockwork in a stunningly vast panoply of stars, gas, and dark matter. We're not special.

Somewhat ironically, this cosmic ordinariness motivates a lot of interesting research. Two decades ago, you could argue with your roommates whether planets were commonplace or rare. But the Copernican Revolution whispered they must be commonplace, so astronomers hunted them down. The same rationale -- that we're typical -- gives impetus to the searches for habitable planets, alien biology, and intelligent extraterrestrials. They all appeal to the lesson learned nearly five hundred years ago: We're not special.

Of course, you might find being ordinary less than inspirational. People that do often take refuge in culture. After all, that's surely something we have over the Klingons, the Na'vi, or whoever you think is out there: our art, history, literature, and everything else taught by the local humanities department. I don't think any aliens would come to Earth to take our water -- they've got that in abundance wherever they are. But they don't have our rap music.

Except now there's reason to think they might. And the reason lies in the grand structure of the cosmos. In particular, its volume.

Astronomers still can't decide what the shape of our universe is. Is it closed and finite, which is to say, is there a countable tally of all the galaxies that exist, even beyond the ones we can see? Or is it infinite?

The latter possibility is still on the table. And if it's true -- if the content of our cosmos is actually uncountable -- then anything that can happen since the Big Bang has not only happened, it's happened an infinite number of times.

That's a much stronger statement than merely arguing that, because intelligent life evolved here on Earth, there's a good chance it also evolved elsewhere. In an infinite cosmos, intelligent life is guaranteed. More than that, duplicates of humans are guaranteed too, as is every variant of our culture. Someone not only has a precise copy of our rap, but every possible variation of every rap song is out there too --- somewhere. Yes, it's incredibly distant, and forever beyond our reach. But it's as real as we are.

Indeed, if the cosmos isn't finite, then far, far away floating duplicates of your brain -- with all its experiences, thoughts, and emotions -- are occasionally (and temporarily) thrown together by the random combining of atoms. Such "Boltzmann brains", as they're called, are a disturbing consequence of an unlimited universe.

If these notions aren't enough to take the starch out of your day, consider this: the mechanism of the Big Bang seems to imply that "bangs" occur all the time. The limitless content of our universe might be only one instance of a large (and possibly infinite) number of other universes.

So the next time you check your moves in the mirror and reflect on how special you are, consider that somewhere in this universe or in another parallel universe, your double might be doing the same. This would be the ultimate Copernican Revolution. Not only are we not special, we could be infinitely ordinary.