There are at least 100B stars in our galaxy. Over the last 20+ years we've gained a lot data on exoplanets. Exoplanetary systems seem to be really common. So stability, the right elements, etc no doubt all play a role but we may be talking over WWhata trillion planetary bodies (including large moons).
What's more, our understanding of where live can evolve, survive and thrive has greatly expanded in recent decades and now includes volcanic vents on the ocean floor, for example.
So yes a lot of things have to go right but we're rolling an awful lot of dice.
Yes, but the fermi paradox focuses on intelligent life. Even if there are ~10 trillion of possible planets in the galaxy for intelligent life to evolve on, that is only 10^14th power. If each of the circumstances described above is a 1 in 100 event, then that leaves only 10^5 habitable planets for intelligent life to evolve across the entire galaxy. If you then consider that there is a 5 in 4.5 billion chance that such a planet currently has an intelligent life form on it, then it's quite possible that there are no other intelligent life forms in the galaxy. However there may be millions or billions of planets with evolved forms of algae.
Now, I do not believe that these are uncorrelated probabilities - and as such I'd place the odds quite a bit higher. But the more we learn about planetary physics, the more unique earth appears to be. Meanwhile, it appears that the biochemistry of life is incredibly common.
There are at least 100B stars in our galaxy. Over the last 20+ years we've gained a lot data on exoplanets. Exoplanetary systems seem to be really common. So stability, the right elements, etc no doubt all play a role but we may be talking over WWhata trillion planetary bodies (including large moons).
What's more, our understanding of where live can evolve, survive and thrive has greatly expanded in recent decades and now includes volcanic vents on the ocean floor, for example.
So yes a lot of things have to go right but we're rolling an awful lot of dice.