So many solar systems out there, life evolved in many planets for sure. No proof but no doubt.
replies(8):
If we become a space-faring civilization, how long will it take us to colonize the galaxy, such that there are few places you can go and not find evidence of humans around? Not more than a million years or so.
So if intelligent life -- capable of becoming a space-faring civilization -- is common, why is the galaxy not colonized already?
Kursgesagt has a good video on this: https://www.youtube.com/watch?v=UjtOGPJ0URM
The Milky Way is 100,000 light-years across. So at least that long assuming we can ever attain near-light-speed travel (unlikely). And due to cosmic inflation, many other galaxies are receeding at faster than light speed, so we could never get there.
There could be a lot of intelligent life (as intelligent as us, maybe more so) that can never realistically travel beyond their local star systems, and we'd never notice them.