Borderlands of Science

by Charles Sheffield

  We are no different from the groups who met Clever Hans. We all want certain answers to be true. Given a mass of evidence, we tend to notice the facts that agree with our preferences, while explaining away the inconvenient ones that would tell us otherwise. And AIDS is a disease so complex and so widespread that you can find what appear to be exceptions to any general rules about its cause, spread, or inevitable effects.

  That, however, is only half the story. The other reason there can be such intense arguments about AIDS applies equally well to half the things—or maybe today it's ninety-nine percent of the things—in our lives. We have actual experience in certain areas: boiling water hurts; you can jump off a ten-foot ladder but you can't jump back up; the moon will be full about once a month; it's colder in winter than in summer; coffee with salt instead of sugar tastes terrible.

  But there are a million other things in everyday life for which we have no direct experience and explanation. Can you tell me how a digital watch works? Why is a tetanus shot effective for ten years, while even with an annual flu shot you are still likely to get the flu? What does that computer of yours do when you switch it on? How does e-mail from your computer travel across the country to a friend on the opposite coast, or halfway around the world? Just what is plastic, and how is it made? How does your refrigerator work? When you flip a light switch, where does the electricity come from? It's not like turning on a faucet, where we know that somewhere a huge reservoir of water sits waiting to be tapped. So how come the electricity is there just when you need it?

  I can give answers to these, in a hand-waving sort of fashion, but if I want any sort of details I have to go and ask questions of specialists whom I trust. And most of the questions that I've just asked are not new, or even close to new. The refrigerator was patented in 1834. The first plastics, like our electricity supply, go back to the beginning of the twentieth century.

  Good answers are available to every one of my questions, all we have to do is seek them out. But what about the newer areas of research, for which AIDS forms a fine example? When the experts themselves are still groping their way toward understanding, and still disagreeing with each other, what chance do the rest of us have?

  Not much, provided that we insist on direct evidence. Every one of us must decide for ourselves who and what to believe. We, like the audience of Clever Hans, are going to believe what we want to believe until evidence to the contrary becomes awfully strong.

  And maybe even after that. We, as ornery humans, tend to go on believing what we prefer to believe.

  A.21. Where are they? Our "local" galaxy contains about a hundred billion stars. We see only a few thousand of the closest as actual points of light, though millions of others merge into a broad and diffuse glow that we notice on clear nights and call the Milky Way.

  A hundred billion is such a big number that it's hard to have a real feel for it, so let's put it this way: there are enough stars in our galaxy for every human on earth to own sixteen apiece. Not only that, our galaxy is just one of the hundred billion galaxies that make up the known universe. If humans owned the whole cosmos, each of us could lay claim to more than a trillion stars. That's the astronomical equivalent of everyone being owed the National Debt, with each star and its planets priced at about a dollar.

  Of course, there's a big "if" in there. We can only claim the universe if no others are out there to stake counterclaims and assert property rights. Which leads to the big question: Are there other living beings in the universe, at least as intelligent as we are; or are we the only smart, self-aware objects in creation? As the late Walt Kelly remarked, long ago, either way it's a mighty sobering thought.

  Some people insist that intelligent aliens in the universe have appeared right here on Planet Earth, occasionally taking selected individuals for a space ride but otherwise keeping a low profile. I am not in that group of believers. I can't see why anyone would bother to travel such gigantic distances and then remain in hiding. The idea that aliens have actually crash-landed in remote parts of the country, and had their presence covered up by the government, has even less appeal. If anywhere, Washington, D.C., is the place to look for aliens.

  Let's take another approach. We have a rough idea of the total number of stars in all the galaxies. How many of those stars have planets? Ten years ago we had no direct evidence of any, but today some new planet around another star is discovered at least once a month. Suppose, then, that only one star in a thousand has a planet around it—a very low estimate. That still gives us a hundred million planets as candidates right here in our own galaxy. If just one percent of those can support life, a million other worlds have living things on them.

  The next step is the hardest one. If a world has life, what are the chances that one of those living creatures will develop intelligence and technology, enough to build a starship, or at least to send out a signal to us?

  We don't know. Let me state that more strongly: we have not the slightest idea. But we can listen, and we do, for evidence of alien existence. We listen not with sound waves, but with radio waves. For the past forty years, a search for extraterrestrial intelligence (SETI) program has been carried on in this country and around the world. Using radio telescopes capable of picking up the tiniest trickle of energy, we eavesdrop on the sky and hope to discover the organized series of pulses that would announce the presence of other thinking beings.

  So far we have found nothing. This is sometimes called the Great Silence, sometimes the Fermi Paradox (Fermi asked the simple question, "Where are they?"). On the other hand, forty years of listening is no time at all in a universe at least ten billion years old, particularly since the SETI program is run on a shoestring. It has no government funding. It is paid for and operated by people who believe that a positive result to the search would change the way we think about everything.

  Speaking for myself, I would just love to change the way we think. For instance, if we were willing to spend as much money listening to the stars as we do on, say, land mines, we might detect and decipher that world-altering message from the sky.

  Are we alone in this galaxy, as an intelligent life form? It is hard to imagine a more profound question. I'd gladly give up any claim to the trillion-plus stars that represent my share of the universe, to know the answer.

  And while I'm at it, I'll gladly give up my share of land mines.

  Note: If you own a personal computer and a modem, you can become directly involved in analyzing radio data that may contain evidence of alien signals. Contact me if you would like to know how.

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