How do you know we haven't been visited? How do you know they're not here
now?


Obviously, if they were here, they'd be SOME evidence of this. There isn't, so they're not.

And of course, there is absolutely no way either aliens or man could ever traverse the vast mind bogling distances. Even at near light speed, which will practically never happen in any case, travel times would still be excessive.

What part of Distance = Speed x Time don't you understand ? !