With thousands of planets outside Earth’s solar system, there’s a pretty good chance that some of them have the conditions needed for life. If alien life does exist, scientists aren’t quite sure what it would look like, but they might be able to see how much these foreign “beings” might weigh. Most of these creatures will be big — nearly 314 kilograms. One cosmologist says.

Fergus Simpson, of the University of Barcelona, outlines his statistical argument on the prepublished site arXiv. The finding is based on a model called Bayes’ theorem and a branch of mathematics called Bayesian statistics. The purpose of such techniques is to estimate the probabilities that change depending on the information available.

But although Simpson’s mathematical experiment may get scientists and others thinking about the possibilities of alien life, some researchers say some of his statistical assumptions may not hold true.