#48: Dyson Spheres | The Extraterrestrial Megastructure

The concept of a Dyson Sphere was first proposed in a scientific way by late physicist Freeman Dyson. It consists of an idea where an advanced extraterrestrial civilization would have reached the technological level to build a structure (called a Dyson Sphere) that could extract the energy from a star or group of stars. Such activity might be readily detectable by Earth's instruments. What is the history of the concept of the Dyson Sphere, and how close are we to actually detecting one at this time?