Gamma Ray Bursts as a Reason for the Sterility of the Universe

One answer to the Fermi paradox is that we are in fact alone, because life - at least intelligent life - is vanishingly rare or completely absent. If we ever get probes to other star systems, we may well find that any water world has its local cyanobacteria, but nothing beyond that.

And what exactly is it that this star system has been so lucky to avoid by accident? Gamma ray bursts are an obvious candidate. A 2014 paper by Piran and Jimenez use the known frequency and distribution of GRBs and calculate the likelihood of an ecosystem-annihilating one. What they find is that for systems within 13,000 LY of the galactic center, there is a 95% chance of a lethal GRB in the last 500 million years, and out where we are it's about a 50% chance. They speculate that some of our past mass extinctions may well have resulted from a GRB (the Ordovician-Silurian extinction event has been speculated without much evidence to be such an an extinction.)

So, it may well be that the Great Filter, or at least a major component of it, is not something endogenous to the sequence of evolution, but rather something completely random and external. It is therefore meaningless to talk about the Great Filter being "in front of" or "behind us."

This may also mean that we really are alone in terms of intelligences which, though boring, is the options we should wish for, it were up to us.