Exoplanets like Earth have been discovered but not all Earth-like planets are equal when it comes to alien life.

Astronomers discovered the TRAPPIST-1 system, a family of tightly packed planets swarming a red dwarf star, about eight years ago. Credit: Mark Garlick / Science Photo Library / Getty Images ...

The Search for Extraterrestrial Intelligence (SETI) focuses on finding technosignatures—potential signs of alien technology. If we look carefully, we might have a chance at detecting their ...