There was a time when the solar system, like life itself, was simple and orderly. There were nine planets, one asteroid belt and a reasonable number of well-behaving moons. The planets orbited the sun in a predictable fashion. Everything seemed not only neat and tidy, but rather bourgeois.

That solar system has been destroyed by the latest generation of astronomers. You may have heard that there's now a 10th planet. No one needed a 10th planet, no one really wanted a 10th planet, but it's there, and now there's not a dang thing anyone can do about it.

Astronomers hellbent on disordering the solar system are now saying that neither Pluto nor this new planet, "2003UB313," are really "planets," but rather are "Kuiper Belt objects." The Kuiper Belt is a kind of tent city on the edge of town, with thousands of planetoids, planetisimals, planetudinals and assorted riffraff that would never be admitted to the better Zip codes of the solar system.

Even farther out is a relatively new subdivision called the Oort cloud, a gaggle of icy objects, arguably an unnecessary addition to the solar system, serving little purpose other than to aggrandize Dr. Oort.

A case can be made that astronomers need to stop discovering things that mess up perfectly good models of the universe. If it ain't broke, don't fix it. Unfortunately, science is kind of compulsive: It keeps going. It keeps poking, prodding, measuring, falsifying and very occasionally proving. With new instruments, we look into the guts of molecules and then out to the cosmic horizon. What we discover is that nature isn't simple and orderly. It's hideously complicated, unruly, unpredictable, radical. The dang thing refuses to behave.

At the deepest level of the physical universe, there doesn't seem to be any hard ground at all. All that quantum duality: Light doesn't have to make up its mind about whether it's a particle or a wave. (It will say to itself, "I'm feeling kind of particulate today.") The Uncertainty Principle fogs up the joint. Even the constants of nature, we now hear, aren't actually constant. The gravitational constant, for example, once a pillar of the community, may turn out to be a little bit moody. The cosmological constant, governing the expansion of the universe, appears to have hit a manic phase a few billion years back, mashing the gas pedal like a teenager on a joyride. The latest estimate is that, at the rate we're going, the whole universe will eventually dissipate into an incomprehensibly dull, vapid, poofy nothingness. (Kind of like Washington in August.) These revelations confirm a fundamental fact about science: It is always telling us things we don't really want to know. It's like an irritating houseguest who points out faults in the plumbing. Two discoveries are particularly upsetting: Human beings are related to the lowest orders of pond scum, and the Earth is a trivial little speck, a nodule on the edge of a mote of dust, in the vast cosmic sea. Scientists are pretty blunt: The universe doesn't appear to be about us.

Naturally there are various folks who would like to restore our primacy, our centrality, our self-respect. They're not eager to embrace the multiple diminutions of mankind offered by science. This battle has been going on, under one name or another, since Copernicus kicked the Earth to the curb in 1543. The central question never goes away: Are we special? Or are we just totally beside the point?

Go back to that new planetoid, out there beyond Pluto. It has almost surely never seen anything so sublime as a drop of water, much less a bacterium, or a flower. Survey all the worlds and worldlets in our solar system, and you'll see one nasty, cold, parched, bleached, hostile place after another. Clever astronomers have found more than 100 planets orbiting distant stars, but nothing yet that looks like a plausible place to grow tomatoes. Life, as we know it on Earth, is amazingly adaptive and resourceful. Because life is so ingenious and adaptive, it's probably out there, somewhere, indeed in many places, in that big cosmic sea, but what we know so far is only that there are a lot of ways for a world to be dead, to be absolutely sterile.

In the nearly 400 years since Galileo aimed his tube at the night sky, we've never seen anything that looks like Earth. So, yeah, call it special. Science will get around someday to showing otherwise. But for now, even if we're not the point, it's still good to be us.

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