The question of whether to send messages to the stars is fraught with difficulty. The big fear is attracting a more advanced civilization with nefarious intent. Why take the risk?

Indeed, various commentators have pointed out that this fear might explain the famous Fermi Paradox which asks why we haven’t heard from other civilizations. The answer being that either there aren’t any others or that the best strategy for survival is to keep silent lest a more advanced civilization find and destroy you.

But an interesting question is whether the paradox can be resolved in another way. Now Eamonn Kerins at the University of Manchester, U.K., says the paradox can be avoided by using game theory to determine how best to search for and communicate with extra-terrestrial civilizations.

READ MORE FROM ASTRONOMY MAGAZINE ARTICLE

The Copernican principle is the idea that Earth does not sit at the center of universe or is otherwise special in any way. When Nicolaus Copernicus first stated it in the 16th century, it led to an entirely new way to think about our planet.

Since then, scientists have applied the principle more broadly to suggest that humans have no special privileged view of the universe. We are just ordinary observers sitting on an ordinary planet in an ordinary part of an ordinary galaxy.

This form of thinking has had profound consequences. It led Copernicus to the idea that Earth orbits the sun and Einstein to his general theory of relativity. And it regularly guides the thinking of physicists, astronomers and cosmologists about the nature of the universe.

Now, Tom Westby and Christopher Conselice at the University of Nottingham in the U.K. have used the Copernican principle to come up with a new take on the existence of extraterrestrial civilizations. They point out that the principle implies there is nothing special about the conditions on Earth that allowed intelligent life to evolve. So, wherever these conditions exist, intelligent life is likely to evolve over about the same timescale as it evolved here.

This “astrobiological Copernican principle” has important implications for the way astronomers estimate the number of extraterrestrial civilizations that might be capable of communicating with us. Indeed, Westby and Conselice have crunched the numbers and say that, given the strongest limits they can place on the numbers, there are probably about 36 civilizations in the galaxy right now with this capability. But the numbers come with a significant caveat that also throws light on the Fermi Paradox, which famously suggests that if intelligent aliens exist, surely we ought to have seen them by now.