Aliens visited Earth, took one look and left, hurriedly ...

[dogtag]

yep,
we will have discovered their past, no idea what the present will be for them

That's a funny idea - we could see each others past.

[Vern Humphrey]

So, if we suddenly discover an Alien civilization 100 light years away,
how do we get to meet or maybe trade with them ?
Assuming they're stuck with the same problem we have in that
nothing with mass can approach light speed, it makes the idea moot.

Make a list of all the burning scientific questions of two hundred years ago -- then cross off all those we have found answers to. If we could communicate with another civilization a hundred light years away, by the time we got their reply, it would all be old stuff.

[lyman]

That's a funny idea - we could see each others past.

at that distance, when did the signal originate? and how long did it take to get here?

[dogtag]

If we discovered a civilization just a handful of light years away,
we could send a multi generational ship. But who'd volunteer to
live on, breed on, and die on a spaceship ?

[lyman]

If we discovered a civilization just a handful of light years away,
we could send a multi generational ship. But who'd volunteer to
live on, breed on, and die on a spaceship ?

didja ever watch Wall-E?

[dogtag]

No, but there's several excellent science fiction stories on the subject

[JB White]

Aliens aren't so smart. Covert observation under cover of darkness, yet they turn on all their lights?

[lyman]

https://www.youtube.com/watch?v=slSb72vwaBc