Is there intelligent life elsewhere in the universe? It’s a question that has been debated for centuries, if not millenia. But it is only recently that we’ve had an actual chance of finding out, with initiatives such as SETI (Search for Extraterrestrial Intelligence) using radio telescopes to actively listen for radio messages from alien civilizations.
What should we expect to detect if these searches succeed? My suspicion is that it is very unlikely to be little green men – something I speculated about at a talk at a Breakthrough Listen (a SETI project) conference.
Suppose there are other planets where life began and that it followed something like a Darwinian evolution (which needn’t be the case). Even then, it’s highly unlikely that the progression of intelligence and technology would happen at exactly the same pace as on Earth. If it lagged significantly behind, then that planet would plainly reveal no evidence of extraterrestrial life to our radio telescopes. But around a star older than the Sun, life could have had a head start of a billion years or more.
Human technological civilization only dates back millennia (at most) – and it may be only one or two more centuries before humans, made up of organic materials such as carbon, are overtaken or transcended by inorganic intelligence, such as AI. Computer processing power is already increasing exponentially, meaning AI in the future may be able to use vastly more data than it does today. It seems to follow that it could then get exponentially smarter, surpassing human general intelligence.
Perhaps a starting point would be to enhance ourselves with genetic modification in combination with technology – creating cyborgs with partly organic and partly inorganic parts. This could be a transition to fully artificial intelligences.
AI may even be able to evolve, creating better and better versions of itself on a faster-than-Darwinian timescale for billions of years. Organic human-level intelligence would then be just a brief interlude in our “human history” before the machines take over. So if alien intelligence had evolved similarly, we’d be most unlikely to “catch” it in the brief sliver of time when it was still embodied in biological form. If we were to detect extraterrestrial life, it would be far more likely to be electronic than flesh and blood – and it may not even reside on planets.
We must therefore reinterpret the Drake equation, which was established in 1960 to estimate the number of civilizations in the Milky Way with which we could potentially communicate. The equation includes various assumptions, such as how many planets there are, but also how long a civilization is able to release signals into space, estimated to be between 1,000 and 100 million years.
But the lifetime of an organic civilization may be millennia at most, while its electronic diaspora could continue for billions of years. If we include this in the equation, it seems there may be more civilizations out there than we thought, but that the majority of them would be artificial.
We may even want to rethink the term “alien civilizations”. A “civilization” connotes a society of individuals. In contrast, extraterrestrials might be a single integrated intelligence.
If SETI succeeded, it would therefore be unlikely to record decodable messages. Instead, it may spot a byproduct (or even a malfunction) of some super complex machine far beyond our comprehension.
SETI focuses on the radio part of the electromagnetic spectrum. But as we have no idea of what’s out there, we should clearly explore all wavebands, including the optical and X-ray parts. Rather than just listening for radio transmission, we should also be alert to other evidence of non-natural phenomena or activity. These include artificial structures built around stars to absorb their energy (Dyson spheres) or artificially created molecules, such as chlorofluorocarbons – nontoxic, nonflammable chemicals containing carbon, chlorine, and fluorine – in planet atmospheres. These chemicals are greenhouse gasses that can’t be created by natural processes, meaning they could be a sign of “terraforming” (changing a planet to make it more habitable) or industrial pollution.