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.
We could guide stars into a graphstellation—a constellation that is also a form of writing.
The fleet assembles to adjust the trajectories of some of the larger Kuiper belt objects, cometlike bodies at the periphery of the solar system. (Moving those around won’t cause problems for inner planets like Earth.) Over a long period, the reconfigured Kuiper belt objects serve as a larger gravitational tractor to tilt the plane of the solar system and then to change the trajectory of the sun through the Milky Way. Meanwhile, we also will have sent clusters of spacecraft to 15 or so nearby stars. It could take many tens of thousands of years for the spacecraft to reach these stars and a much longer time to change their trajectories.
Why move stars around? Because then they could be guided into orbital formations that almost certainly would not have occurred naturally. An imaginable set-up period of tens of thousands of years could therefore be leveraged into a much longer period—billions of years, perhaps—during which aliens could observe the fruits of our efforts. A group of stars organized to present a sign in this way might be called a “graphstellation” (like a constellation, but also a form of writing).
To state the obvious, there are enormous challenges to doing this. The idea of a gravitational hedge fund is entirely speculative for now and might not be workable. Even if it can be done, our solar system is a poor candidate for manipulation. The mass of the entire Kuiper belt is perhaps one one-millionth the mass of the sun, so there isn’t much to work with. The coming decades will see a survey of the structures of nearby solar systems, however. Perhaps some nearby systems are better arranged for gravitational hedge fund action. An ideal solar system would have suitable gradations of adjacent orbital masses. Failing that, perhaps some other method of nudging a star’s path will come along.
The playfulness, open-mindedness, and intellectual generosity of the best scientists always amaze me, never more so than when I called Piet Hut at the Institute for Advanced Study to talk about the prospects for graphstellations. (He has, among many other things, been at the forefront of the study of strange but possible orbital structures.) The fact that we haven’t proved we can move asteroids, much less stars, doesn’t faze Piet at all. If the motivation for creating a graphstellation is valid and there is no proof that the idea is impossible, his view is that it is worth contemplating.
Piet immediately suggested a design for a multiply nested binary star graphstellation that would have the delightful technical designation “hyper-super-duper double-star system”: a pair of a pair of a pair of double stars, 16 total. This configuration would be stable and unlikely to interact with nearby stars. It also would do no harm to the solar system or life on Earth, should we end up as part of the formation. The set-up phase would coax pairs of stars into headings destined to bring them into mutual embrace in such a way that the pairings would eventually pair as well, and so on. Such a structure would be vanishingly unlikely to come about naturally, and it would be recognizable at a great distance. An alien observer wouldn’t have to be able to discern all the individual stars in order to notice that something funny was going on; the alien would only have to note subtle changes in the qualities of the light, wobbles in the position, and other clues.
Piet and I had an interesting exchange comparing graphstellations to the Egyptian pyramids. Is there something inherently macho about rearranging the stars, in the way the pyramids seem macho to us, or is it more like a lonely cry in the wilderness?
An interesting comparison can be made to the Dyson Sphere. In 1960 physicist Freeman Dyson suggested that an advanced civilization might want to capture all the solar energy from a star, and so might build a spherical structure all around it. He suggested looking around to see if there are any such spheres out there. None have been found thus far. A graphstellation would have far less utilitarian value to its creators, but it also would probably be far easier to build and detect than a Dyson Sphere.
The obvious next step is to look around and see if anyone out there has already created a graphstellation. This will not be a trivial exercise. There are a lot of stars, and we have to consider the potential range of graphstellation designs, not only the ones that have already occurred to us. But I am in the process of engaging my astronomer friends in the hunt. I have also been talking to people who plan space missions. Crazier things have happened.