[guard-of-terra]

It's interesting, but a bit like trying to detect a large and advanced by looking for products of horse manure decomposing in huge heaps. I think it was Mendeleev who thought that getting rid of horse shit will be the main problem of ever-growing cities in XX century.

The need for energy is definite, but the amount and character of such need is debatable. Maybe civilizations shrink and don't use so much energy? Maybe they mine million of stars at once? Maybe they get their energy out of thin vacuum?