So far in the series, we’ve gotten a range for N, the number of detectable civilizations in the galaxy, to [5e-7 to 8e-6] * f_c * L. Today’s post will estimate the value of f_c, the fraction of intelligent species that go on to develop a civilization detectable (through electromagnetic transmissions and/or probes travelling at a sizable fraction of lightspeed) across interstellar distances.
A common assumption in science fiction is that intelligent life forms will inevitably build high-tech civilizations. Similarly to the typical view of inevitable evolutionary progress toward intelligence which I demolished previously, this common assumption smacks of whig history. Of course progress is a law of nature. It gave rise to the pinnacle of existence: us.