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.<p>They seem to say that given Fermi's paradox and the possibility that <i>most</i> civilizations self-annihilate, this is actually a good way to do SETI. Makes sense.
>> As a star’s gravitational well will likely be the
deepest in the system, it is also energetically efficient to launch material on a stellar intercept
trajectory.<p>Quite the opposite, that's one of the most delta-v expensive trajectories to embark upon. In fact from earth it's about twice as expensive as leaving the solar system.
I believe it was Vernor Vinge who made the comment that perhaps unexplained gamma ray burst were the last gasp of a planet or star that had been obliterated in anger by an adversary.<p>That said, if, for example, humans kill themselves off with a climate change it would have very little external signature.