Posted by: movieotaku | April 2, 2007

Explosions in Space: Follow-up

Peter Løkke from Denmark has this to say about the Explosions in Space entry:

I just passed by your site on Sci-Fi Blunders – great reading, and great entertainment!!

As an engineer however, I felt compelled to add a little something.. Being a Sci-Fi fan myself, I of course read about explosions in space and all the other stuff, and I fell across a little something about sound in space: The second problem is even more exasperating. You can’t hear sound in space. Space is a relative vacuum so there’s no matter for the sound to travel through (Remember that sound is a mechanical wave passing through stuff like air or water). To make things even worse, the ship is a dozen or more kilometers away. Even if there were sound, there is no way it’s going to reach your ship or rock at the speed of light. Sound travels much, much slower than light—roughly 331 meters per second. You would see the ship explode than a few seconds or hours later you would hear it explode, assuming you could hear anything in a vacuum.

I’m probably not the first to notice this, but the speed of soundwaves that you mention is only relevant in atmospheric air (at a certain temperature and humidity – details got a little vague over time) ;o) In solids, it is much higher! In less dense gasses than air, it is lower.. So if an exploding spacecraft for instance were to release an enormous amount of atmospheric air (or other gasses), the sound could probably travel in this medium, creating an “explosion sound” – you would however be required to be in the explosion itself to hear it ;o)

Excellent points, Peter! The distances between things tend to get completely ignored in movies and TV shows. Things take time to get from point A to point B, even light. The light from the Sun takes about 8 minutes to reach Earth.

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Responses

  1. I once read a stupid comic called Captain Victory or something where they had to blow up a planet. So they dropped a bomb, jumped through hyperspace to the safe distance of one light year, and sat down to watch the light show.
    Nobody mentioned anything about waiting a year for the light to reach them.


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