Free Astronomy Magazine July-August 2020

40 ASTROBIOLOGY Since the time of Copernicus, astronomers have adopted a statistical con- cept called the “principle of mediocrity” to help us understand the cos- mos that surrounds us. This principle extends, to all members of a cate- gory of appropriately selected objects, the attributes of only one of them that we consider to be a typical member of that category. It seems en- tirely legitimate today to extend the principle of mediocrity to the search for extraterrestrial life, but how far can we go? The principle of mediocrity and the habitability of galaxies by Michele Ferrara revised by Damian G. Allis NASA Solar System Ambassador JULY-AUGUST 2020