Why We Probably Won’t Find Aliens Anytime Soon

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Are we alone in the universe? The answer is almost certainly no . Given the vastness of the cosmos and the fact that its physical laws allowed life to emerge at least one place—on Earth—the existence of life elsewhere is effectively guaranteed. But so far, despite generations of looking, we haven’t found it. In that time, however, we’ve arguably learned enough to declare that, while we may not be alone, the interstellar gulf between us and our nearest neighbors effectively puts us in an isolation ward. This doesn’t mean we should stop looking—only that we should manage our expectations and prepare for a long and lonely voyage through space and time before meeting them, either virtually or physically.

The possibility of alien life has been discussed since antiquity. But rigorous searches for it have only been within reach for less than a century, following an approach first proposed in 1959 by physicists Giuseppe Cocconi and Philip Morrison, who showed the feasibility of interstellar communications using radio telescopes. A year later astronomer Frank Drake led the first Search for Extraterrestrial Intelligence (SETI) effort, called Project Ozma, which used facilities at the National Radio Astronomy Observatory in Green Bank, W. Va., to look for such signals from putative cosmic civilizations. As part of the preparation for a follow-up meeting on the project, he developed his now famous “Drake equation,” a probabilistic mathematical expression for estimating the number of communicable civilizations, NC, that may exist in the Milky Way.

We are the products of progressive stages of evolution. With this in mind, the Drake equation can be cast as:

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NC = astrophysical evolution × biological evolution × cultural evolution × technological evolution × lifetime of a technological civilization

In that equation, each successive evolutionary phase arises from its predecessor. For us, this progression has taken nearly the entire lifetime of the Earth, some 4.5 billion years.

Attempts to “solve” the Drake equation have been hampered by insufficient knowledge of the likelihood of each evolutionary phase’s completion. Modern observational advances, however, now allow us to make … Read More