How far can sound travel through space, since it’s so empty? Is there an echo in space? – Jasmine, age 14, Everson, Washington In space, no one can hear you scream. You may have heard this saying.

What if you could listen to music or a podcast without headphones or earbuds and without disturbing anyone around you? Or have a private conversation in public without other people hearing you? Newly ...

That now classic tagline (from Alien, one of the greatest science-fiction horror movies ever made) hinges on a big assumption that most of us broadly make: space is empty. And it is—mostly. But there ...