Research network to search for extraterrestrial intelligence launched in U.K.

more extreme than normally thought.  “If life or intelligence is rare, it must be millions or billions of times rarer; if advanced societies wipe themselves out, or decide to not go exploring, they need to converge to this outcome with extremely high probability, since it only takes one that escapes this fate to fill the universe,” said Sandberg.

The work of Dr. Austin Gerig, senior research fellow in Complex Networks at the University of Oxford, estimates the fraction of civilizations in the universe that are long-lived and analyses the human race’s prospects for survival.

Dr. Gerig said, “We know that (1) we exist and that (2) our birth number within our civilization is approximately 70 billion (i.e., approximately 70 billion people were born before us). From such little information, we can reasonably, and perhaps surprisingly, conclude that (1) many other civilizations exist and that (2) most of these civilizations are small, i.e., most will die out before producing trillions of people.”

Gerig and his colleagues have focused on a specific consequence of this reasoning, called the “universal doomsday argument”: long-lived civilizations must be rare because if they were not, we would find ourselves living in one.

“If most civilizations are small, then our own civilization is likely to be small, i.e., it is likely to die out within the next few centuries.  Our research indicates this is the case, but that our estimates of survival are greater than previously thought using a more traditional form of the doomsday argument,” said Gerig.

Duncan Forgan, from the Royal Observatory Edinburgh, is looking at the possibility of detecting large structures built by civilizations orbiting other stars.  The transit method of detecting extrasolar planets involves measuring the dip in starlight as a planet passes in front of its star.  The Kepler Space Telescope has detected a whole host of new exoplanets using the transit technique, and there are many future telescopes and missions lined up to succeed it.  Forgan has investigated whether the obstruction of the stellar disc by a large orbiting structure would make a detectable difference in the shape of the lightcurve of an exoplanet transit.

“I looked at one type of megastructure, which is essentially a very large mirror.  The mirror reflects the star’s own radiation and produces thrust, much like a sail produces thrust from wind.  This thrust could be used to move a civilization’s host star from its ‘natural’ orbit if it posed some harm to the civilization, for example a dangerous close approach to another star or dust cloud,” said Forgan.

Forgan’s study showed that a giant mirror of this type would leave a characteristic trace in exoplanet transit data, which could be detectable with the next generation of telescopes.

“While the odds of seeing megastructures are probably very low, we will soon have a huge archive of exoplanet data to search for these objects – at no extra cost to SETI scientists.  We may detect the presence, or remains, of an alien civilization that felt the need to move their star!” said Forgan.