Michael A. Garrett

Traditionally, SETI has searched for narrow radio signals. But Earth's technosphere is humming ever louder, creating a broad radio background. Astronomers have developed a method to detect such a planetary hum around other stars using modern telescopes. This will allow us to find civilizations up to

A model based on exponential technological growth shows: the faster a civilization develops, the shorter the period during which it emits technosignatures we can detect. At rates comparable to Earth's after the emergence of AI, this window could be less than twenty years. Traditional narrowband sear