Aliens - Are they out there? Have they visited us? And related questions

[theVOID]

Just an opinion. We don't know everything about our past nor how old this planet is. Therefore it is likely that aliens have visited us.

That's equally as unjustified as saying: "We don't know everything about our past nor how old the planet is, therefore it is likely that the atlanteans existed", you can't say anything about the likelihood of one thing being true based on our ignorance of another thing.