Aliens are often portrayed as diminutive beings , but in ‘ reality ’ they could be much larger and heavier than science fiction films suggest . Scientist Fergus Simpson has calculated the minimum size needed for intelligent life to survive , based on the laws of conservation of energy seen on Earth . And from this , he calculates that if intelligent extraterrestrials exist they will typically weigh 650lbs ( 300kg ) - the median weight of a polar bear . Aliens ( illustrated with a stock image ) are often portrayed as diminutive beings , but in ‘ reality ’ they could be much larger , one scientist claims . Fergus Simpson from University of Barcelona applied a mathematical formula to assume aliens obey the same laws of conservation of energy as animals on Earth . Mr Simpson came to this conclusion by applying a mathematical formula that assumes aliens obey the same laws of conservation of energy as animals do on Earth . This means that larger animals need more resources to survive , so are less common than plentiful ants , for example . The cosmologist ’ s calculations are also based on the idea that there ’ s a minimum size needed for intelligent life , but don ’ t factor in an alien planet ’ s gravity . ‘ Throughout the animal kingdom , species which are physically larger invariably possess a lower population density , possibly due to their enhanced energy demands , ’ he wrote in a paper , published at arXiv.org . He said there must be a minimum body size necessary for supporting intelligent life , based on the range of body sizes of intelligent animals such as apes and humans , found on Earth . ‘ As a result , we should expect humans to be physically smaller than most other advanced species. ’ ' ... we conclude that most species are expected to exceed 300kg in body mass . The median body mass is similar to that of a polar bear . ' He claims that just as it is on Earth , there are probably more small animals than larger ones in the universe , but that the larger a planet or biosphere the more likely it is to have evolved an intelligent species . Mr Simpson said there must be a minimum size necessary for supporting intelligent life , based on the range of body sizes of intelligent animals such as apes and humans , found on Earth . And , if they exist , he believes intelligent aliens typically weigh more than 650 lbs ( 300kg ) - around the size of a polar bear ( stock image ) His argument follows that if clever aliens are large , there may be fewer of them , as they will likely live in a society with low population densities to ensure they have the resources they need . Study claims aliens are larger than those portrayed in sci-fi ( stock image ) . But the calculations do n't take into account an alien planet ’ s surface gravity . Commenting on the study , Duncan Forgan , a Research Fellow at the University of St Andrews , told NewsWeek : ‘ I think the average size calculation is reasonable ’ . Seth Shostak , a researcher at the SETI Institute in Mountain View , California , added that it is not the first time scientists have suggested that aliens may be large , because big animals tend to live longer . A longer lifespan makes creatures potentially more likely to develop knowledge and invent technology needed to make contact with humans one day . Mr Simpson continued : ‘ Higher intelligence enables the development of technologies which can sustain larger population sizes. ’ While the research has been described as interesting by Dr Shostak , he said ‘ there ’ s no concrete data to work with ’ and that Earth is being used as a model to predict what life looks like elsewhere in the universe – but aliens may be completely different . He pointed out that it is humans ’ thumbs , bipedal stance and brains , rather than our bulk , that has enabled us to thrive on Earth , so body mass is only one indicator of intelligence . ‘ 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 , ’ he said . Mr Forgan also noted that the research doesn ’ t take an alien planet ’ s surface gravity into account . He explained that planets with stronger gravity might be expected to be home to smaller life forms than those with weaker gravity , which means that the calculation is incomplete .
Fergus Simpson said aliens probably weigh more than 650 lbs ( 300kg ) Calculations based on idea that there ’ s a minimum size for intelligent life . Larger aliens are more likely to live long enough to make advanced tech . Comment: