THE RARITY OF LIFE IN THE UNIVERSE
It’s far harder for a planet to survive in the habitable zone than we think. You need a relatively peaceful galactic neighborhood. And a star that lives long enough and is stable enough for evolution to compute the possibility of complex life. You need a third or fourth-generation star so that there are metal elements available. You need a relatively rare type of star (yellow dwarf) that will provide a stable habitable zone. You need a metallic planet, which requires something like Jupiter or Jupiter AND Saturn to ‘clean the neighborhood’. You need a molten core on that metallic planet, and a large moon to keep it liquid, producing a protective magnetic field. And you need enough atmosphere, and enough water, and enough volcanic activity to start life.
I mean, you’d think that there would be lots of life out there given that under the right conditions it’s going to likely emerge over time. But the bigger problem than calculating life is the environment in which the universe can calculate life.
Tiny possibilities. Tiny. Likely a few per galaxy and they might not overlap in time.
