This was not obvious to me from the title, but what they're talking about is ways that with tomorrow's telescopes, we could infer via observation how a technolo

This was not obvious to me from the title, but what they're talking about is ways that with tomorrow's telescopes, we could infer via observation how a technological civilization had destroyed itself, and therefore that an advanced extra-terrestrial civilization had been on that planet. They seem to say that given Fermi's paradox and the possibility that most civilizations self-annihilate, this is actually a good way to do SETI. Makes sense.