6 WHY HAVE WE SEEN NO SIGN OF ALIENS?

In 1950, Enrico Fermi, the man who built the first nuclear reactor, was having lunch in the canteen of the Los Alamos bomb lab in New Mexico when he suddenly said: “Where is everybody?” Everyone around the table knew exactly what he meant.

Decades later, Fermi’s question was examined independently by the American physicists Michael Hart and Frank Tipler. Hart considered aliens spreading throughout our Milky Way and Tipler considered self-replicating machines that, on arrival at a planetary system, exploit the resources to build two copies of themselves that continue voyaging. Both concluded that, even at modest speeds of travel, every star in the Galaxy would be visited in a fraction of the age of the Milky Way. As Fermi realised, the aliens should be here on Earth. They do not appear to be. This became the ‘Fermi paradox’.

Hundreds of explanations have been proposed. They include the ideas that we are the first intelligence to arise in the Galaxy and so are totally alone, and that we are a nursery world, off-limits to advanced civilisations that might adversely affect our development. A more mundane possibility is that there is no paradox, because any signs of visitation in the distant past would be erased by wind, rain and geological processes. Recently, however, a team led by Dr Jonathan CarrollNellenback of the University of Rochester, New York, has proposed that our Sun may simply have been bypassed by a wave of extraterrestrial expansion.

There remains the question of why we have seen no sign of extraterrestrials in our Galaxy, despite searching with telescopes for more than half a century. However, a Pennsylvania State University team led by Dr Jason Wright says there is no mystery: we have searched a mere fraction of the Galaxy, equivalent to the water in a hot tub compared to that in Earth’s oceans. As Douglas Adams observed so perceptively in The Hitchhiker's Guide To The Galaxy: “Space is big. You just won't believe how vastly, hugely, mindbogglingly big it is.”

“We have searched a mere fraction of the Galaxy, equivalent to the water in a hot tub compared to that in Earth’s oceans”