I’m a supporter of SETI—the Search for Extraterrestrial Intelligence. It’s worth devoting resources to find out if we humans have company in this universe in the form of other intelligent life forms. There are lots of good reasons to want to know, especially if it doesn’t require us to do more than look and listen for signs of other civilizations. But recently some scientists have become impatient that SETI hasn’t detected anything in the past thirty years, and feel that we should be more proactive about the search. That impatience is understandable. SETI methods are painstaking. Space is vast. Even though our ability to search the skies has increased enormously over the decades, SETI astronomer Jill Tarter is quoted in an excellent Washington Post article about the subject, saying, “We’ve explored one eight-ounce glass of water out of the ocean”.

So the impatient scientists believe we’ve been going about things the wrong way. Since the Kepler Space Telescope and other projects have now identified more than a thousand likely planets circling other stars, and a fair number might be the right distance from their star to provide conditions that support life, these folks think we should start beaming strong radio signals toward those star systems, inviting any alien civilizations there to become “part of a conversation”.

Now hang on just a minute. Imagine yourself taking a walk in a strange neighbourhood at night. Would you keep your ears tuned to hear if anyone was around? Sure. Would you jump up and down and yell, “Helloooo! Anybody out there? Anybody feel like getting together for a coffee?

I don’t think so.

For one thing, who do you figure is most likely to respond to your invitation: Mr. and Mrs. Nice-to-know-you, or the neighbourhood muggers?

I’ve always wanted to believe that a species advanced enough to travel between the stars would be peaceful. But there’s no evidence to support that, and plenty of evidence from human history to suggest that I’d do as well to believe in unicorns and leprechauns. Humans advanced enough to travel between continents certainly weren’t peaceful. Ask native North Americans or the Aztecs. In fact, experience on this planet has shown that technological progress is most often for reasons of aggression. Should we compare the research and development budgets of the military around the world to private R & D spending? And of all the reasons for expending resources to get into outer space, population pressures and a desire to exploit what we find rank high. Making new friends probably isn’t even on the list.

Even if extraterrestrial travellers weren’t malevolent, they would surely be so far ahead of us that we’d be curiosities by comparison, or even lab rats worthy of further study but certainly no treatment as equals. The knowledge of their existence alone could destroy all motivation for the human race to make progress of our own.

The point is that we have absolutely no way to know if intelligent aliens would be nice, or very, very bad. But once we let them know we’re here, there’s no putting the cat back in the bag.

Some 28 (so far) notables in the scientific community, including Elon Musk and David Brin, have signed a petition condemning so-called active-SETI. Stephen Hawking thinks it’s a crazy idea. Even the originator of the SETI movement, Frank Drake, believes it’s too soon and a waste of time.

As we venture out into interstellar space on our own we may discover we’re not alone, but by then we’ll be much better equipped to deal with whatever—and whomever—we find. For now, let’s be content with paying attention and not calling for attention.