'One in 10 billion trillion is incredibly small,' says Frank. Using this approach, Frank and Sullivan calculate how unlikely advanced life must be if there has never been another example among the universe's ten billion trillion stars, or even among our own Milky Way galaxy's hundred billion. If the actual probability is greater than the pessimism line, then a technological species and civilization has likely happened before.' 'But using our method we can tell exactly how low that probability would have to be for us to be the only civilization the universe has produced. 'Of course, we have no idea how likely it is that an intelligent technological species will evolve on a given habitable planet,' says Frank. With that, Frank and Sullivan then calculated the line between a universe where humanity has been the sole experiment in civilization and one where others have come before us. Rather than guessing at the odds of advanced life developing, they calculate the odds against it occurring in order for humanity to be the only advanced civilization. 'The idea behind our research is that, if an entire galaxy had been colonised by an advanced spacefaring civilisation, the energy produced by that civilisation's technologies would be detectable in mid-infrared wavelengths,' said Dr Wright. The Glimpsing Heat from Alien Technologies Survey (G-Hat), published in the Astrophysical Journal, details how the team thought they might see the infrared signature of a race far more advanced than ours. The study was led by Dr Jason Wright from the Center for Exoplanets and Habitable Worlds at Penn State University in Pennsylvania. Within these galaxies, the researchers said it was possible that an alien race could be harnessing the power of the stars - emitting huge amounts of noticeable heat in the process. These galaxies were found to be emitting 'unusually high' levels of radiation - possibly indicating 'the presence of a highly advanced civilisation.' Last year, scientists said they had found 50 galaxies that may contain intelligent alien races. 'The fact that humans have had rudimentary technology for roughly ten thousand years doesn't really tell us if other societies would last that long or perhaps much longer,' he explained.
'So one of the three big uncertainties has now been constrained.'įrank said that the third big question - how long civilizations might survive - is still completely unknown.
'Thanks to Nasa's Kepler satellite and other searches, we now know that roughly one-fifth of stars have planets in 'habitable zones,' where temperatures could support life as we know it. 'We didn't know how many of those stars had planets that could potentially harbor life, how often life might evolve and lead to intelligent beings, and how long any civilizations might last before becoming extinct.' 'We've known for a long time approximately how many stars exist. 'The question of whether advanced civilizations exist elsewhere in the universe has always been vexed with three large uncertainties in the Drake equation,' said Adam Frank, professor of physics and astronomy at the University of Rochester and co-author of the paper. In fact, the odds of an advanced civilization developing need to be less than one in 10 billion trillion for humans to be the only intelligent life in the universe.īut Kepler data places those odds much higher, which means technologically advanced aliens are likely to have existed at some point. The study shows that unless the odds of advanced life evolving on a habitable planet are astonishingly low, then humankind is not the only advanced civilization to have lived.