Posts Tagged ‘‘Absolution Gap’’

Radio 4 Next Monday on Possible Extraterrestrial Life

March 11, 2020

Next Monday, 16th March 2020, at 11.00 AM, Radio 4’s Out of the Ordinary is covering the subject of what aliens are probably like. The programme, ‘Aliens Are the Size of Polar Bears (Probably), has this brief description in the Radio Times:

Jolyon Jenkins concludes his series by hearing from astronomer Fergus Simpson, who predicts that if aliens exist they will be living on small, dim planets in small populations, have big bodies and be technologically backward.

This looks like a different take on the question of intelligent extraterrestrial life. Way back in the 1990s some of the astronomers involved in the hunt for it, such as SETI’s Seth Shostak, considered that aliens, if they exist, would probably be small, the size of Labradors. It’s also been an assumption of the search for intelligent aliens that the universe is old enough for alien civilisations to have arisen many times over, colonising space. Simpson’s suggestion that the aliens, if they’re out there, are probably technologically backwards, sounds like a solution to the Fermi Paradox. This was first proposed by the Italian-American physicist, Enrico Fermi, and runs: if the universe is old enough to have produced intelligent aliens, then why haven’t we found any? There are several solutions to the problem. One is that they don’t actually exist. Others are that space travel may be difficult, or that aliens don’t feel any need to expand into space. Or that advanced, technological civilisations destroy themselves in catastrophes like nuclear wars before they move outward across the Galaxy. Another solution is that they’re there, but keeping very quiet in case there are other, malign intelligences out there intent on their extermination.

This last solution is explored by the SF writer Alistair Reynolds in his novels Revelation Space, Redemption Ark and Absolution Gap. In this trilogy, humanity has expanded into space, only to be threatened by an ancient extraterrestrial menace – the Inhibitors. This is a machine culture that exists solely to destroy spacetravelling civilisations. Their reason is that millions of years ago, the Galaxy suffered a prolonged series of devastating wars as different species moved out into the Galaxy to claim territory from their rivals. In order to prevent further such wars occurring, the Inhibitors embarked on a long-term campaign of eradicating such civilisations. They aren’t enemies of intelligent life per se. Indeed, the whole policy is in order to protect such life, provided it remains confined to its home planet or solar system. But once it moves out into interstellar space, it becomes a target for eradication. And the Inhibitors themselves are quiet, dormant and so undetectable, until they discover their next prey, and wake up.

If aliens do live on small, dim planets, then they’d be difficult to discover with present astronomical techniques. Planets are too small for telescopes to detect normally, as they’re lost in the glare of their star, although some may later be seen through extremely high-power telescopes using very advanced optical techniques. And the planets that have been the easiest to discover are large worlds orbiting close to their suns. They’ve been detected because their gravitational pull has caused their stars to wobble as they orbit around them. Small planets further out would exert less force, and so caused smaller wobbles that may be difficult to detect. And if they’re technologically backwards, we would not be able to detect signs of their industrial and other activities, like radio or television transmissions, for example. If spacefaring civilisations do exist, at least close to us, then we should have detected signs of them by now. There was a paper in the Journal of the British Interplanetary Society suggesting that a light sail used within 30 light years of Earth would produce so much gamma radiation that we would be able to detect it. The fact that we haven’t may mean that such civilisations don’t exist. Simpson’s suggestion for the possible nature of extraterrestrial life is therefore one solution to the problem of the Fermi Paradox.