|Looking for a lone signal from some far-flung alien civilization is one thing — looking for its handiwork on galactic scales is quite another. But a handful of astronomers are still hopeful that if hyper-advanced extraterrestrial civilizations can survive through cosmic time, they|
might choose to macro-engineer whole galaxies in ways that would be detectable in the electromagnetic spectrum.
“If a civilization has engineered half a galaxy, some fraction of the energy being used should glow in the infrared,” James Annis, an astrophysicist at Fermilab, told me. Annis and colleagues conducted the first such search for KIII civilizations in 1999.