Fergus Simpson, a scientist at the Institute of Cosmic Sciences at the University of Barcelona, believes that aliens are big. As , he used a mathematical model that assumes that organisms on other planets obey the same laws of conservation of energy seen on Earth.
“Throughout the animal kingdom, species that are physically larger invariably have lower population densities, possibly due to their higher energy demands,” Simpson says.
He says that “most inhabited planets are likely to be closer in size to Mars than to Earth,” leading him to surmise that “since population density is widely observed to decrease with increasing body mass, we conclude that most intelligent species are expected to exceed 300 kg.”
So you’re speculating that most intelligent aliens weigh an impressive 650 pounds.
SETI Institute senior astronomer Seth Shostak also suggested that intelligent aliens are likely larger than humans. But he acknowledges the speculative nature of these kinds of studies. “It’s interesting, but there’s really no hard data to work with,” he says.
Duncan Forgan, an astrobiologist at the University of St Andrews’ School of Physics and Astronomy, believes that “Simpson’s estimate of average size is reasonable.” He but he criticizes the paper for not “addressing the correlation between body mass and gravity on the planet’s surface.”
Newsweek notes that “We only have our planet and its inhabitants to serve as a model for what life is like. This paper, like others, assumes that Earth is a ‘typical’ or average planet, and uses information from here to make assumptions about the unknown. But it’s impossible to know if that’s appropriate, from a scientific standpoint.”
Simpson’s article is posted on .