The search for extraterrestrial intelligence (SETI) relies on radio telescopes outfitted with extremely sensitive receivers. Early hunts used telescopes intended for conventional astronomical observations. The Allen Telescope Array, pictured here, is the first radio telescope designed specifically for SETI; it can probe several stellar regions and frequency bands at once. To learn about SETI’s connections to artificial intelligence and our own future, see the article by Rebecca Charbonneau on page 36 . (Image by Linus Platt via Getty Images.)