Let me start out by linking the article that inspired this post (my first one on medium) — http://praxtime.com/2013/11/25/sagan-syndrome-pay-heed-to-biologists-about-et/

The piece is entitled “Avoiding Sagan syndrome” — the author defines the Sagan syndrom as the inclination to automatically assume that there must be extra-terrestrial being (ETBs) out there in our galaxy. Its a great article that (in time-honored Scientific Philosophy tradition) tries to zoom out and observe “the scientists at work in their natural habitats” to compare Biologists’ and astronomers’ answers to the Fermi paradox. And he finds the differences to be night and day in terms what each profession has to say about the existence of ETBs.

Biologists tend to look at life through the lens of Darwinian evolution — luck driven accumulation of changes over millions of years. The astronomers, on the other hand, mostly play a statistical game considering the number of stars, number of planets and so on, and concluding that the earth is no special place by any account, but one of billions of worlds where similar physical conditions exist. Judging by the title of his article, you can guess where Taylor falls on this spectrum. I personally tend to take the Sagan position, however I do like the following point from Taylor’s article:

The first perspective shift is to step back in time, and realize the universe is very young. With 20 trillion years of star generation ahead, the universe has only covered 13.7 billion years or roughly .07% of its life span. Compare this to a person who expects to live 70 years, and you’d get .07% * 70 years = roughly 18 days. So in human terms the universe is a three week old baby. No wonder there’s not too much life out there yet.

This is a very valid point. We might well be the very first (or at least one of the very first) intelligent beings to evolve in the Milkyway. However, Taylor then urges another shift in perpective regarding the amount of space to consider when dealing with Fermi’s paradox. Instead of just looking at the Milkyway, we should look at the entire Virgo super cluster, in order to make the paradox go away, since it could take billions of years for ETBs or indeed even information to travel between galaxies. The Virgo supercluster is a group of galaxy clusters, one of which is the Local group, which contains the Milkyway, Andromeda, and about 54 other galaxies. The Virgo supercluster is comprised of a 100 such clusters. Then the wider field in Taylor’s view contains about 5000 or so galaxies. The prosposal being that life is so rare that there may be one or two cililizations in this entire zone containing the 5000 galaxies. (For what its worth — while the inclusion of the entire super cluster does increase the involved distances greatly to about 110 million light years, thus solving Fermi’s paradox, it does not do much for the statistics involved in calcuating the chances of other planets harboring life as expressed by Drake’s equation. When discussing the number of planets in any given region, 3 extra zeros next to 14 zeros makes little difference).

My main problem with Taylor’s article is this — he uses time scales for the evolution of life and intelligent life based on Earth’s history. This is fair as the Earth is the only example one can use. But this implicitly assumes that earth must be a typical planet, and that all other planets must follow similar time scales. But this is the very thing he argues against — the notion that Earth is infact typical in its ability to harbor life. If one wishes to establish these time scales from a biological standpoint, then one must use biological or even chemical processes as the basis for such proclamations (from “first principles”). Taylor submits no such evidence. One must either assert that earth is typical, or be forbidden from holding it up as an example of how other planets must behave. Aside from this little slight of hand, i thought it was an excellent article and definitely worth a read.

• Mikiyas