SETI Search Methods

Traditional radio SETI listens for narrowband signals at frequencies like the hydrogen line (1420 MHz), which any technologically advanced species would know about. The Breakthrough Listen program is the most comprehensive effort, surveying a million nearby stars.

Optical SETI instead hunts for brief laser pulses aimed across interstellar distances. Other approaches look for signs of mega-engineering: Dyson spheres that dim a star's light, or industrial pollution in exoplanet atmospheres. The search has expanded far beyond simply listening.