A technologically advanced extraterrestrial alien race capable of traveling the galaxies will likely be creatures with huge bodies and won't be the scrawny, five foot-tall bug-eyed beings often seen in Hollywood movies.
This race will physically resemble the seven foot-tall the killer Predator in the 1987 Arnold Schwarzenegger movie rather than the midget ET in the 1982 movie of the same name. And with massive weight comes huge height.
British cosmologist Fergus Simpson came to this conclusion after calculating the minimum size needed for intelligent life to survive based on Earth's laws of conservation of energy.
Simpson's calculations are astonishing. He believes individuals in an intelligent alien race might weigh some 650 pounds or 300 kilograms. One of the few bipedal animals on Earth with that weight is an adult male polar bear, which can reach a height of three meters.
Simpson came to this assumption by using a mathematical formula that presumes extraterrestrials obey the same laws of conservation of energy as animals do on Earth. This means larger animals need more resources to survive so will be large bodied creatures.
Simpson's calculations are also based on the knowledge there's a minimum size needed for intelligent life. 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 humans and apes.
"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, an online repository of electronic preprints, or as e-prints, of scientific papers in mathematics, physics, astronomy, computer science, quantitative biology, statistics, and quantitative finance.
"As a result, we should expect humans to be physically smaller than most other advanced species".
He said the larger a planet, the more likely it is to have evolved an intelligent species. He also said that if intelligent aliens are big, there might be fewer of them since they'll likely live in a society with low population densities to conserve the resources they need to survive.
"Higher intelligence enables the development of technologies which can sustain larger population sizes," said Simpson.
Dr. Seth Shostak, a researcher at the SETI Institute in Mountain View, California, said it's not the first time scientists have believed aliens may be large because big animals tend to live longer.
A longer lifespan also makes aliens more likely to develop knowledge and invent technology needed to make contact with humans.
In his sci-fi novel, Battlefield Earth: A Saga of the Year 3000, author L. Ron Hubbard wrote about an alien race called the Psychlos that were hairy, nine foot (2.7 meters) tall, 1,000 pound killers that conquered the Earth.