[_heimdall]

I'd be curious to hear a few more details for the question.

Does it matter whether the aliens have visited earth, or only that life exists elsewhere in the universe?

Do they need to be intelligent aliens, by some definition of intelligent?

And do they have to still exist today, or is it enough to think life may gave existed elsewhere at some point?

[otherayden]

Let’s focus specifically on aliens that exist somewhere in the universe, regardless of intelligence. My one criteria is that if it was seen by an average human that they would think “yep, this is definitely life”