Other scientists are less cynical. Jill Tarter, the former director of the SETI Institute, has said any civilization that lasts long enough to figure out interstellar travel would have had to work out its internal problems first. “If aliens were able to visit Earth, that would mean they would have technological capabilities sophisticated enough not to need slaves, food, or other planets,” she said in response. “If aliens were to come here, it would be simply to explore.”
As Lubin points out, it doesn’t really matter whether we want to beckon E.T., because Earth is loud, electromagnetically speaking. There is nothing anyone can do to stop the noise from Game of Thrones and cell phone conversations and Donald Trump on CNN. “Every time you send out an email that says we should not broadcast, you are broadcasting,” Lubin says. “Every time you turn on your cell phone and order a pizza, you are ordering an interstellar pizza.”
The Milky Way alone has countless other planets, many of which are rocky and may be nestled in the “Goldilocks zone” of their stars, where conditions are just right for water to exist in liquid form (and maybe life). Many of these planets are much older than Earth, allowing plenty of time for another civilization to mature enough to build a lighthouse like the one Lubin envisions. “Hopefully they are vegetarians and have gotten beyond the point of eating each other," he says. Maybe their beacon is already sweeping the galaxy.
Lubin suggests a targeted search of planets in the putative habitable zones of Sun-like stars. He outlines how this would work in a new paper accepted in the aptly named journal REACH, Reviews in Human Space Exploration. The upshot is that it would actually be very easy. Thanks to rapid advances in optics and computers, that includes most people with a good digital camera. Ultimately, finding extraterrestrial life might be as simple as seeing a light in the dark.
How would we know—and how would aliens know—that a newly bright spot was a signal, not just a supernova? Lubin says it would not be hard to produce a signal with obvious unnatural forms, like radio modulation or a non-random structure — think Morse code, or a message along similar lines. The structure of such signals is an active area of debate in the SETI community.
“We might think, look at that bright thing, in a very narrow band in the optical or infrared. We’ve never seen anything like that. Is that thing made by nature, or made by nurture?” he says. “Is it an unusual kind of light? Are they pointing at me? Do they flash on and off? Then you start looking for patterns. You look for signatures of things that are not natural.”
None of this answers the really big question, of course. That is, if we located someone else’s beacon, what would we expect to find? And for that matter, what would we say in return?
Lubin thinks it might be very simple.
“We are here,” he says. “Or, ‘we were once here.’ That’s my hope, that there is some sort of intelligent civilization that has adopted that philosophy. SETI is based on things being not like us. They want people to find them; they want things to find them. They are not skittish like we are.”