Fleets of robotic space probes from alien civilisations could already have arrived in our solar system, a mathematical study has found.
The study quotes scientists who warn that we may not be able to detect them with our technology – the probes may also be so hi-tech they can “conceal” themselves.
Earth’s own Voyager probe has only just reached the edge or our solar system – but older alien civilisations could have launched probes long ago, using knowledge far beyond ours, “slingshotting” round stars using their gravity, according to a paper in the International Journal of Astrobiology.
Duncan Forgan and Arwen Nicholson of the University of Edinburgh analysed how a “fleet” of probes could travel through space – and says that probes which “self-replicate”, building new versions of themselves from gas and dust in space, would have had time to arrive here already.
But the fact we have not seen any may mean our galaxy is a lonely place, Dr Forgan warns, “The fact we haven’t seen probes of this type makes it difficult to believe that probe building civilisations have existed in the Milky Way in the last few million years”
The probes would only need to travel around 10% of the speed of light to explore our whole galaxy within 10 million years.
“Interstellar probes can carry out slingshot manoeuvres around the stars they visit, gaining a boost in velocity by extracting energy from the star’s motion around the Galactic Centre,” the researchers say.
Our own Voyager probes used a similar “slingshot” technique using large planets in the solar system – but using the gravity of a star would offer a far bigger boost.
The discovery – using computing power that would not be available to earlier generations of scientists, ignites once again the most famous question in the search for extraterrestrial life – the “Fermi Paradox”.
In 1952, the physicist Enrico Fermi posed the question ‘Where is everybody?’ The new paper shows that it is technically possible, at least, that alien probes could be here – once again begging the question of why they have not communicated with us.
“We can conclude that that a fleet of self-replicating probes can indeed explore the Galaxy in a sufficiently short time.. orders of magnitude less than the age of the Earth,” the researchers say.
The probes would have to be programmed so as not to arrive in large numbers – “it could be interpreted as hostile, causing panic,” say the researchers. Other scientists have warned that they may already be here.