Look at a picture of the Earth at night, and the world appears to be, quite literally, glowing. Now, scientists are starting to look for signs of advanced alien civilizations by the glow given off by technology used to harvest the energy from a star or even an entire galaxy.
Theoretical physicist and mathematician Freeman Dyson first proposed the idea that advanced alien civilizations might develop technology to encircle a star and harvest most of its power, a structure now known as a Dyson sphere.