Consider the possibility that a sentient species on a
planet in another star system acquires advanced fusion technology. That is,
they can not only fuse hydrogen atoms together to make helium and useable
energy, but also gold for self-enrichment or rare and heavy metals for machines
like cars, planes, and space ships. After some period of time, their fusion
industries might overweight their atmosphere in these heavier metals relative
to pre-industrial background levels. If we construct sensors that can measure
elements in distant planetary atmospheres, then would this be a way to detect
advanced alien civilizations?
