Free Astronomy Magazine July-August 2020

49 JULY-AUGUST 2020 ASTROBIOLOGY period of time than that during which the Sun will allow for the habitability of the emerged lands (1-2 billion years), it is possi- ble that dozens of species might evolve up to a technological phase and then also quickly be extinguished. Taking this into consideration, the striking contrast between the number of potentially habitable planets that likely exist in the Milky Way and the total absence of commu- nications from alien civilizations could sug- gest that the extinction of a technological species coincides with the extinction of its entire biosphere, or at least of the animal species that populate the emerged lands. In this case, it is understandable that a few mil- lion or tens of millions of years would no longer be enough to go from a wild being to a technological being. However questionable the principle of medi- ocrity is, especially if applied to a single da- tum, the fact is that we exist, that other evolved species like ours do not seem to exist, and that we are doing everything to destroy the biosphere that hosts us. In this sense, the principle of mediocrity would seem to have a predictive capacity which is perhaps the case to interpret to our advantage. ! T he spiral galaxy NGC 6946, located along the Cygnus- Cepheus border, is also known as the Fireworks Galaxy for the numerous star- forming regions. This is the main feature that dis- tinguishes spirals from ellipticals (in addition to their shape). The ellip- tical galaxies are, in fact, consid- ered dead from the point of view of the formation of new stars and new planets. What type of gal- axy will be most suitable for host- ing evolved life forms? [Cima Rest Astronomical Ob- servatory, Maga- sa, Valvestino, Italy]