Are we alone in the universe? It’s a question with unnerving implications whatever the answer proves to be. And now scientists have put a call-out to the public to help them solve the mystery.
The task: scouring through a colossal mountain of data in search of signals from alien civilisations.
Collected over several years by two radio telescopes tuning in to the hum of the cosmos, it consists of over a million billion bytes. If downloaded in full, it would fill the hard drives of over a thousand laptops. Which is why the Breakthrough Listen Initiative, based at the University of California, Berkeley, is looking for help.
Set up by billionaire Israeli-Russian venture capitalist Yuri Milner with $100 million, the BLI project team has the public playing a key role in searching for evidence of alien intelligence.
The basic idea is simple: signals carry information, and that reveals itself in the form of non-random patterns. By dividing up the data into manageable chunks, the public can speed up the search for such patterns.
The problem is that aliens are not the only possible source of regular signals. For decades, humans have been blasting out electromagnetic emissions from everything from ground-based radar to orbiting satellite TV.
To weed out the earthbound interference, the BLI team has been training the radio telescopes on target stars, and then comparing what they receive with transmissions coming from points nearby.
The idea is that Earth-bound transmissions will remain even when the radio telescopes shift their gaze, while signals coming from aliens on planets orbiting the target stars will fade away. Looking back at the stars once more, the signal should then reappear.
While it creates even more data to wade through, this procedure cuts the risk of false alarms. And over the years, there have been several of these, most famously in 1967, when astronomers in the UK picked up regular radio signals from deep space. Initially named LGM-1 — Little Green Man 1 — the astronomers soon realised they had discovered the first-ever “pulsar”, a rapidly-rotating remnant of a star.
The BLI team wants members of the public with programming skills anywhere in the world to sift through data that will ultimately encompass over a million stars.
They have already made a start by examining signals apparently coming from 20 stars in our cosmic backyard. These were chosen by the team after asking themselves a question: if they were aliens trying to make contact with us, how would they know where to beam their signals?
Since the mid-1990s, astronomers have identified over 4,000 planets orbiting other stars. Many were revealed through the slight dip they caused in the brightness of their parent star as they passed across its face.
The BLI team flipped this argument around and found 20 stars in the right part of the galaxy to allow aliens to detect the Earth through the dimming effect it would have on our sun.
After screening out all the Earth-based interference, the team ended up with four unexplained signals. Further analysis revealed, however, that they all came from orbiting satellites.
This does not prove there are no aliens orbiting any of the 20 stars. Because the stars were all relatively nearby, it means that none of them are using a radio transmitter as powerful as those on Earth to beam signals in our direction.
And there’s plenty more data still to hunt through. The team estimates that they have so far examined the equivalent of one bath-full of data out of a total equivalent to all the water in the world’s oceans.
Their call-out to the public for assistance is part of a resurgence of interest in 'SETI' — the Search for Extraterrestrial Intelligence. For years, the field has been in the doldrums, with governments chary of spending huge sums on a quest with such a seemingly low probability of success.
But that has changed with an influx of private funding — and the discovery that around 20 per cent of stars have potentially habitable planets in orbit around them.
This month, at the prestigious annual conference of the American Association for the Advancement of Science, leading researchers described a slew of new strategies for tracking down aliens.
They include the first-ever survey of the entire sky by the Very Large Array (VLA), the vast network of radio telescopes in New Mexico made famous by their role in the 1997 movie Contact, where — fittingly — they were responsible for the discovery of the first-ever alien signals.
Work is now under way to send data collected by the VLA to a purpose-built supercomputer designed specifically to spot unusual transmissions from deep space.
Plans are also being drawn up to exploit other ways in which aliens might reveal their existence. They include Panoseti, an instrument designed at the University of California, San Diego, which will look for so-called “technosignatures” — signs of alien technology such as powerful lasers flashing across space.
Meanwhile, a giant orbiting telescope to be launched next year will examine three planets orbiting a nearby star called Trappist-1. Discovered in 2015, the planets are Earth-sized and lie in the so-called habitable zone of the star, where conditions allow liquid water to exist.
The James Webb Space Telescope will search for signs of atmospheres around the planets — which would further boost the chances of life existing on them.
But not everyone will welcome the renewed interest in making contact with aliens. The late physicist Stephen Hawking warned in 2016 that ETs may prove so intelligent and powerful they “may not see us as any more valuable than we see bacteria”.
In truth, it is too late to worry about alerting aliens to our existence. Powerful military radar systems have been blasting signals into space since the 1950s. Travelling at the speed of light, they will now have served as a calling-card to anyone — or anything — up to 60 light years away. According to current estimates, that means the signals will have passed by several thousand stars — along with several hundred planets capable of sustaining life.
Seen in that context, finding out if there are aliens out there might just be a prudent bit of defence planning.
Robert Matthews is Visiting Professor of Science at Aston University, Birmingham, UK