After numerous posts, we’ve now reached an analysis of the final term in the Drake equation, L, the average lifespan of high-tech civilizations. If you thought putting a value on f_c, the likelihood of an intelligent civilization developing a high enough technology to make its existence known across interstellar distances, was a prime avenue for political and ideological axe grinding, this one is even more.
Still, we have to try. First, we’ll look at some factors supporting a large value for L, then, some factors supporting a small value. If you’re playing along at home, pick the one that most appeals to you.
Factors supporting a large value for L
Sustainability is one of those teeth-grating buzzwords of contemporary life, but it’s still the case that a civilization not much more advanced than ours could sustain contemporary US levels of per capita energy consumption for billions of years. Capturing energy from hydrogen fusion would consume just 0.1% of the oceans’ volume by the time the sun turns into a red giant and swallows our planet. Even nuclear fission, making use of relatively rare isotopes, could fuel a contemporary level of civilization for 5 billion years. Covering a tiny fraction of the Earth’s surface with solar panels would do the same.
(We don’t have the technology for hydrogen fusion or long-range transmission of solar power, you ask? True, we don’t. Yet. But today’s nuclear fission would give us more than enough time to develop those technologies, if we need to).