So I just finished watching a documentary about "alien civilizations" and something just keept bothering me......

One of the arguments against us ever making contact with intelligent alien civilizations is that they would have to exist for tens of millions of years, or else they would 'fade away' before we could find them.

But how can a scientist presume to know the longevity of a civilization? There is only one civilization that we know anything about - human civilization - and human civilization has not yet expired. Who alive today can know what will become of human beings in the far distant future? The best anyone can do is guess, and without having any knowledge of future technology or sociology, it's not even an educated guess, but rather wild speculation.

And even if you did know for sure the ultimate fate of humanity, which you do not, but if you did you still could not make any assumptions about alien civilizations based solely on what human beings have done. Who can say that aliens would think and behave the same way humans do? That's a rather arrogant way of looking at the universe. If there are aliens, I'm sure there is more about them that is different from us than the same. Just because we may someday destroy ourselves through global war (and again, we may very well not) does not mean that some other distant civilization is as self-destructive as us.

The argument that civilizations don't last has always bothered me. You just can't say that. It's bad science to make conclusions without evidence.