The fruitless search for extraterrestrial intelligence
If Russian dotcom billionaire Yuri Milner had read Shakespeare, he might not have been so keen to punt $US100 million on finding other intelligent life in the universe, even with the enthusiastic urging of Stephen Hawking and other scientific luminaries.
The Bard’s advice on the subject appears in Henry IV –
Glendower: I can call spirits from the vasty deep.
Hotspur: Why, so can I, or so can any man;
But will they come when you do call for them?
Milner plainly hopes the spirits will come when he calls. Last month, Milner announced that his Breakthrough Initiatives program will use some of the world’s most powerful telescopes, one of which is in Australia, to scan the heavens for signs of extraterrestrial intelligence.
But is it worth it? There is a good argument to be made that, despite its cosmic pretensions, the latest Search for Extraterrestrial Intelligence (SETI) project is futile.
There is something about SETI that makes hardened sceptics ecstatically credulous and almost heroically persistent. Scepticism suddenly becomes as rare as voices from the cosmos.
The SETI Institute, set up in 1984, claims that nearly two million people have signed up to [email protected], an easily downloadable program that runs as a screensaver on personal computers and collectively analyses a small portion of raw data from SETI’s instruments. Proponents of SETI reason that because intelligent life on Earth has been blaring radio waves into space ever since it knew how, chances are that any aliens will be doing the same.
Space is drenched in radio waves – almost every stellar body emits them – but the natural emissions from stars and quasars are repetitive drones. So SETI looks for specifically complex signals, patterns and wavelengths that no inanimate phenomenon could produce. After years of listening, astronomers have detected nothing but cosmic white noise.
But considering the vastness of space, it seems almost selfish to assume we have it all to ourselves. In an interview with Time, Milner agreed: “If we were alone, it would be such a waste of real estate.”
Speculation on the plurality of worlds has been common since the Greeks. The atomist philosopher Epicurus reasoned that, as there was an infinite number of atoms, their endless combinations would produce “infinite worlds both like and unlike this world of ours”. By default, there would be other mortal, physical peoples.
By the 19th century, the notion of extraterrestrial life being intelligent and civilised – parallel to humanity – was part of the intellectual landscape. Kant was convinced of it, as was Darwin and the mathematician Carl Gauss, who suggested cutting down large segments of forest to form huge triangles visible from space that would show Martians earthlings had discovered plane geometry.
Given cosmic numbers, the notion of extraterrestrial intelligence seems self-evident, an intuition bordering on inevitability. The reasoning is simple: intelligent life evolved on Earth, and Earth-like planets are almost certain to be extremely common, so we can expect intelligent life to evolve elsewhere.
Except there is not a shred of evidence to indicate this has happened – and logically, if it happened, the evidence should be readily available, perhaps even unpleasantly so.
The Italian Nobel prize-winning physicist Enrico Fermi hit upon this problem in the 1950s, and it is thus named the Fermi paradox. It roughly states: “The age and size of the universe inclines us to think that advanced civilisations exist, and yet there are none of the signs we would expect if this was the case.”
Fermi’s paradox throws Milner’s Breakthrough Initiatives project – both its assumptions and methods – into serious question. Milner’s project will survey more than a million stars – a minute fraction of the 200 billion stars that make up the Milky Way. Its success – as for the SETI Institute with which it is involved – is predicated on there being a large number of intelligent life forms. If there are but a few intelligent species existing at any one time in the galaxy, then the chances of them ever detecting each other are impossibly small.
The time scales involved tax ordinary comprehension, but should there have been an occurrence of intelligent life elsewhere in the universe, it is all but certain that the time difference between us and them will be tens or hundreds of millions of years.
Hawking recently noted that a civilisation receiving our signals “could be billions of years ahead of us”. The gap could be so great as to resemble the difference between human life and pond slime and attempts to find or contact them would be as meaningless as ants swarming around an iPod.
So how would any civilisation develop, not over thousands, but millions of years? Would such an advanced intelligent species – compared with us – sit around broadcasting radio signals, but otherwise stay put? In fact, the colonisation of space, even of it occurred over immense time spans, is virtually inevitable.
The intellectual groundwork for this kind of speculation was laid more than 50 years ago by Fermi’s friend, John von Neumann, a mathematical genius who speculated in this vein when he wasn’t making fundamental contributions to almost every branch of human knowledge or agitating for a pre-emptive nuclear strike against Soviet Russia.
Von Neumann theorised that any species would first explore space via self-replicating machines, being cheaper than sending actual people. These exploratory machines would be launched at a target solar system, and when they arrived, the machine would begin to make copies of itself, which would in turn be launched at further stars, where they would repeat the process.
The number of machines grows at a runaway rate, like bacteria. Travelling between a 10th to 100th of the speed of light – a tentative, although certainly plausible speed – von Neumann machines could have reached every star in the galaxy in less than 20 million years. It would take only one exploratory species – and remember, SETI presumes that there are many species – and the galaxy would be overrun in a relatively short time.
Here von Neumann’s problem begins: if life is as common as SETI requires, the visible universe should be full of such self-replicating machinery.
In a more speculative vein, the great American physicist Freeman Dyson argued that intelligent life would not stop at simple planetary colonisation. In a famous paper published in 1960, Dyson proposed that to best conserve energy, a species would eventually enclose their entire sun in a vast sphere of solar panels. It sounds far-fetched, but technology developed over vast periods of time and driven by a Malthusian need for new resources makes it the most likely outcome. So perhaps if we want to look for aliens, Dyson suggested, we should look for their engineering, for huge, stellar building projects.
But there are none, or at least, none have been seen or heard.
And here’s the crunch: the SETI project has detected no signals in half a century of cosmic earwigging. No von Neumann machines. No Dyson spheres. Nothing that would be expected if intelligent life is anywhere near as common as SETI is betting on to be successful.
Either intelligent life is extremely rare, or intelligent life is so advanced that they don’t interfere with the universe in a recognisable way.
These are old arguments, but it’s unlikely they will deter SETI diehards. You only have to listen to their public statements to realise that the search for extraterrestrial intelligence has taken on an almost religious dimension. When asked during a radio interview whether anything is out there, a SETI spokeswoman said she didn’t know, but she was “confident that we’ll find out”. In the absence of any way to come up with a negative outcome, this has as much scientific validity as if she had said the same thing about the existence of an afterlife – I don’t know, but eventually I’ll find out.
There is something poignant about SETI, in its sunny optimism and bright manifestos and incentives, the way it tries to domesticate the inhuman reaches of space, much as our measurement terminologies – the light-year, powers of 10 – tend to euphemise the reality of stellar distance.
Still, it could be argued that Milner might have done better to spend his $US100 million helping intelligent life on Earth.
This article was first published in the print edition of The Saturday Paper on Aug 22, 2015 as "Not even close encounters". Subscribe here.