There is no getting around the fact that a lot of people would be very excited if extraterrestrial life existed. But while plenty of scientists are working hard to find it, others aren't as convinced—and a team of Princeton physicists has gone as far as publishing an academic article explaining exactly why they think we're all living in a fantasy land.
In the Proceedings of the National Academy of Sciences Edwin Turner and David Spiegel, two astrophysicists from Princeton, analyze what is known about the likelihood of life on other planets using Bayesian analysis. They weigh up how many of our existing scientific conclusions about life on other planets stem from actual, real data, and how many come from the prior assumptions of scientists.
Their analysis points out that our expectations of life cropping up on other planets tend to rest on the assumption that it is only possible on other planets under the same conditions that allowed life to flourish on Earth. Sadly, our current knowledge of other planets in the universe tends to suggest Earth is a "cosmic aberration where life took shape unusually fast".
That suggests that we're all being hopelessly fantastical in assuming that other life must exist. In Turner's words, speaking to R&D Magazine:
"Fossil evidence suggests that life began very early in Earth's history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn't reveal much about the actual probability of life on other planets...
"Information about that probability comes largely from the assumptions scientists have going in, and some of the most optimistic conclusions have been based almost entirely on those assumptions..
"If scientists start out assuming that the chances of life existing on another planet as it does on Earth are large, then their results will be presented in a way that supports that likelihood. Our work is not a judgment, but an analysis of existing data that suggests the debate about the existence of life on other planets is framed largely by the prior assumptions of the participants."
Image by NASA