The focus of Seti has been on the radio part of the spectrum. But of course, in our state of ignorance about what might be out there, we should explore all wavebands: the optical and X-ray band. Even if messages were being transmitted, we may not recognise them as artificial because we may not know how to decode them. Consider the difficulty a veteran radio engineer familiar only with the amplitude-modulation of the 20th Century might have decoding modern wireless communication.
Finding non-organic intelligence also means being alert to evidence of non-natural phenomena or activity – even within our own Solar System. It was right that the Green Bank telescope stayed pointed at Oumuamua, the anomalous object that passed through our neighbourhood recently and is believed to have originated from outside our Solar System. It’s also worth keeping an eye open for especially shiny or oddly-shaped objects lurking among the asteroids. We may also need to seek evidence for non-natural construction projects, such as a “Dyson Sphere”, a giant, hypothetical energy-harvesting structure built around a star.
In sum, astronomers like me should expect surprises. We ought to be open-minded and make sure that we wouldn’t miss anything odd.
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Scientists still don’t know whether the origin of life is rare, and only happened here on Earth. But if that’s not the case, and if life gets started elsewhere, then intelligence could evolve in all sorts of ways. There are planetary systems out there that are at least a billion years older than our own, so it’s possible that intelligence has already developed into something nonorganic.
Perhaps whatever is out there doesn’t evolve by Darwinian selection: it would be what I call “secular intelligent design” that’s a bit like machines designing better machines. And while it may not be broadcasting its existence to us, it could be found throughout the Universe.
*This article is as told to Richard Fisher. Lord Martin Rees is the UK’s Astronomer Royal, and is based at the University of Cambridge. His most recent books are If Science is to Save Us, and The End of Astronauts, co-authored with Donald Goldsmith.
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