The origin of life on Earth might not have been in a primordial pool of organic goo, but rather, according to the panspermia hypothesis, it may have come from another planet in perhaps another solar system. Panspermia is one of the more popular alternative theories for the origins of life on Earth, but is it really testable? If panspermia isn’t falsifiable, if you can’t make predictions that allow the theory to be tested, it’s not science. (“A theory that explains everything, explains nothing.” – Karl Popper.)
This paper by Henry Lin and Abraham Loeb tackles this hypothesis’s falsifiability by simulating panspermia as life spreading throughout the galaxy like an epidemic. The galaxy is effectively simulated as a lattice of stars each with a habitable world, where, in the beginning, all planets are uninhabited. At each time step in the simulation, a certain fraction of randomly chosen uninhabited planets become inhabited. In other words, there’s a chance for life to form spontaneously on each planet at any time.
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