A quick science-y (though probablly more science-fictiony) thought:

Icon illustrations for this post, 'cause one is not enough:


One of the arguments I've seen against the existence of advanced technological species beyond Earth is:

No use of energy is ever 100% efficient, thanks to this thing called "Entropy." So if there were advanced alien species on other planets, we'd expect to see extra infrared radiation coming from those planets (and if aliens pointed their detectors toward Earth, that's what they'd see). But we haven't found any, so, therefore, there must not be any advanced civilizations out there...

BUT:

What if an alien civilization figured out how to use dark energy to fuel their work? There does appear to be an excess of that...

Just a thought...