Spaceships make no sound in empty space
Q:
Why is there no sound when spaceships fly--
Jayant, las palmas de gran canaria, Spain
A:
Sound is a vibration of some medium, like air. Spaceships make no sound in the vacuum of space because space lacks
enough molecules to jiggle into a sound wave.
Right: [NASA] 1966, Astronaut Aldrin, outside Gemini 12
The sound of a plucked guitar string travels because the vibrating string compresses the air, then rarefies it, then compresses,
then rarefies... The sound travels to your ear in this fashion, but a vacuum has nothing to impose a wave pattern on. There's
nothing to compress and then rarefy, nothing to move.
"Sound is a wave of alternating density," says Sergei Smirnov physical chemist at New Mexico State University. "...you need to have a 'dense' object to have
sound: liquid, solid or gas. Vacuum or emptiness has density of zero-- thus no sound."
(Answered by April Holladay, science correspondent, August 15, 2001)
Further Surfing:
USATODAY.com, WonderQuest: How sound and light travel
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