Tuesday, July 15, 2003

How Do Sounds Travel In Space?

Everyone loves movies, they can make us laugh or cry or jump out of our seat! But when it comes to science, movies do not always tell the whole story.

Movies set in space are a great example. Have you ever watched a movie that is set in outer space and heard an explosion? This would never happen in space. As most of us know, space is a vacuum; this means there is a whole bunch of nothing in the air. The air here is made of tiny molecules like oxygen, nitrogen and carbon dioxide. In space, these molecules are few and far between. Sound is a wave, like in the ocean and needs molecules to be carried. So just like ocean waves need molecules of water, sound waves need molecules of air to move and be heard.

We are able to see in space because light travels in a different kind of wave called an electromagnetic wave. Electromagnetic waves do not need molecules to send their wave. Another thing related to light and sound is that they do not travel at the same speed. Sound travels at 760 miles per an hour here on earth. I would like to see Jeff Gordon beat that! In space because there are so many less molecules, it would be much slower. We are not talking slow like a turtle, but slow like going only a foot or two over millions of years. Light travels at 671,080,887 miles per an hour in a vacuum like space. We would see the explosion long before we would hear it. This is the same thing that allows us to see lightning before we hear it.

And just another point about space settings is the ever-present exploding planet or spaceship. Pieces of the planet or spaceship created from exploding objects would have an extremely high initial speed, like on earth, and then continue forever in a strait path through space. Here on earth we have gravity to slow exploding objects, in space there is little or no gravity, so the debris would travel outward in straight lines ideally forever until it impacts with something. These exploding pieces would have about the same energy or force they had at the moment of explosion, so if they impacted a ship or planet, no shield would be able to protect you!

Little Lion Experiment:

Explore physics for yourself! A common physics topic is pressure. Pressure is just the amount of force distributed over the amount of area that force is given. For instance, if you took your finger and pressed it into the arm of your sibling or parent, it would hurt quite a bit. If you used the same amount of strength and pressed into their arm with your entire hand, it would not hurt much at all. Lets try the same thing a different way!


  • Paper Cups
  • Big thin book or piece of flat, thin plywood


  1. Step down on a single cup. What happens?
  2. Take the paper cups and lay them in a square a little bigger than the size of the book or plywood. Fill in the square with cups so that the cups are all right next to each other.
  3. Place the book or wood on top of the cups.
  4. Have your parents help you as you step on top of the book or wood. What happens? Do the cups break as they did when you stepped on just the one?

So what happened is the force (your weight) is distributed over all the cups instead of just one cup. So the cups are able to hold you up! This is the same way a bed of nails works. If you lay on one nail, OUCH! But because your weight is distributed over several nails, it is just a little prickly.