Little green men coming to visit would make some people nervous, but what if aliens were the size of bears? Even without "To Serve Man," that could be quite intimidating!
Fergus Simpson, of the University of Barcelona, outlines his statistical argument on Cornell University Library's prepublished site arXiv.
Simpson started his calculations with a few assumptions. He estimated that an alien civilization would likely have about 50 million individuals. To compare, consider Earth. "If you were to pick any single person from Earth, that individual would be more likely to be from China (1-in-5 chance) than from New Zealand (about a 1-in-1,600 chance). However, there are a lot more New Zealand-size countries than China-size ones, so if you were to pick country names at random, you'd be much more likely to pick a Spain- or Mozambique-size country than a Russia-, China- or United States-size nation," explained Live Science.
"Throughout the animal kingdom, species which are physically larger invariably possess a lower population density, possibly due to their enhanced energy demands," Simpson wrote.
OK. So, we know how many aliens there would be, based on a bell-curve scale. Now, what would they look like?
Considering that the smaller an alien is, the more of them there would be, Simpson estimated the median size of an alien living on a planet slightly larger than Earth would be 692 lbs. (314 kg).
"Since population density is widely observed to decline with increasing body mass, we conclude that most intelligent species are expected to exceed 300kg," Simpson wrote. Yikes.
But as Seth Shostak, researcher at the SETI (Search For Extra-Terrestrial Intelligence) Institute told Newsweek: "Polar bears are large but do not write great literature and build radio towers and a lot of that is probably because they are walking around on all fours."
Shostak isn't ready to commit to the idea of huge aliens because of the lack of concrete data. Michael Kopp, a professor of theoretical biology and evolution at Aix-Marseille University in France, disagrees for another reason.
Kopp isn't sure the calculations are correct since we aren't sure than Earthlings are a random sample population. "The prediction that most civilizations contain less than 50 million individuals is based on the assumption that the distribution of civilization sizes corresponds to the distribution of species sizes ... but there are no particular reasons to believe this is so," Kopp told Live Science.
Despite those who aren't ready to change the Hollywood image of aliens, Shostak thinks Simpson succeeded at getting the science community thinking. "It should be applauded," Shostak said, according to Live Science.
