Sound in a Vacuum
I've always been fascinated by the realism of movies like
Star Wars. For a start, it just recently annoyed me in the sci-fi movie
"Wing Commander" that when an enemy spaceship passed over theirs, they
told someone to be quiet or else they'd be heard. I thought sound doesn't
travel in vacuums. Is that true?
It is true. Sound needs a medium through which to travel. It will not travel
in a vacuum. It is OK to be annoyed. Though perhaps they were speaking of
radio silence - radio waves do travel in a vacuum.
That is correct, sound needs a media to propagate.
Sound can not propagate in a vacuum.
Sound waves, unlike light, are essentially compression waves and the
sound in order to move from one place to other needs molecules to
compress and decompress against, hence the wave is transmitted. In a
vacuum, there are no molecules. Hence no sound.
Star wars the movie is still fun.
Movies are made to be entertaining, not realistic. In Star Wars Episode 1,
I noticed among other things that the battle droids' command ship broke
apart and fell downward when it was destroyed by the heroes. There would
have been no reason for it to fall down; it was already in orbit, and
noting was holding it up that was removed when it was hit. But, it looked
cool, and it was a nice special effect.
You are quite correct, there is no sound in a vacuum. So "Wing Commander"
has some careless writing. I think I'll have a heart attack and die from
Richard Barrans Jr., Ph.D.
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Update: June 2012