Our universe is filled with floating nebulae, spinning planets and black holes. But if we closed our eyes and listened, what would these celestial objects sound like? Would we hear a faint whoosh? Or ...

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.

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 ...