This month I seriously propose that we begin the process of repositioning the sun and other nearby stars in order to send signals to aliens, and that we begin the search for signs that aliens might have done the same for our benefit.
Perhaps I should preface this crazy-sounding idea with an explanation. Science is an emotional experience for me, sometimes even more emotional than art. The reason, I think, reflects both our current understanding of humanity’s place in the universe and the events of my childhood. Astronomy has taught us that Earth is a mere dot in an inaccessible vastness. Almost everything in the night sky is so far away that there’s little hope of our having contact with other life out there—if such life even exists. Worse than the possibility that we are alone is the feeling that it doesn’t matter even if we aren’t. My early life amplified this feeling of solitude: My mom died when I was a kid, and for a time the rest of the human species felt as distant from me as the deep universe does now.
I suspect a similar emotion is hidden in the pasts of many people who become interested in science, especially physics and astronomy. It’s the secret engine inside the archetype of the nerd, the kid who is disengaged from social games but is mesmerized by the bigger game of trying to engage reality in a fundamental way.
There is probably no more concrete, no greater contact-seeking attempt at engaging the universe than the search for alien life. The most prominent efforts, called SETI (Search for Extraterrestrial Intelligence), do that by listening for signals: We might get lucky and catch an alien radio transmission, for instance.
Luck is important to these efforts because we are confined to investigating such a tiny sector of space and time within an enormous universe. Suppose we set up a radio broadcast for aliens to hear, and suppose we could keep the transmitter going for 100,000 years—far longer than civilizations have existed, nearly as long as modern humans have. Even that duration would probably be too brief for the broadcast to be heard.
The reason is that the advent of humans easily could have been accelerated or delayed hundreds of millions of years by something as banal as an asteroid hit. If the asteroid that apparently led to the demise of the dinosaurs had missed Earth, maybe an intelligent dinosaur would have appeared 50 million years sooner than people did. Or maybe an intelligent mammal still would have appeared, but 200 million years later than we did. Since evolution on other worlds would presumably be just as sensitive to random events, it is incredibly unlikely that intelligent aliens would happen to be listening during a particular 100,000-year window when our radio broadcasts happened to be washing over their location.
So we search for better ways to make contact, some means by which to get around the tiny-time-aperture problem. One approach is to send out the equivalent of a message in a bottle, and indeed the two Voyager spacecraft are headed out to the stars carrying golden disks engraved with rudimentary information about humans and Earth. The spacecraft might last a very long time, but they have a handicap: They are physically small, so they’d probably have to pass quite close to an alien civilization to be detected.
Is there any method of reaching out to the rest of the universe that will cover a lot of time and space? The hint of a solution arises from current thinking about how to make sure we don’t go the way of the dinosaurs. If an asteroid were headed our way, we’d prefer to prevent it from hitting us. One promising way to do that is with a gravitational tractor, a spacecraft sent to fly alongside a dangerous asteroid. Over a sufficient period of time—several years, perhaps—the slight gravitational pull of the craft would divert the asteroid onto a new, safe course.
Suppose this principle of the gravitational tractor could be scaled up using what I’ll call a “gravitational hedge fund.” We send up a significant number of tractor spacecraft over many years. Eventually a fleet assembles in the outer solar system. The spacecraft are autonomous, able to operate even if the civilization that constructed them expires. They are programmed to operate for hundreds of thousands of years, like the outlandish radio transmitter I considered earlier, but they will generate a far more profound legacy than a radio signal.