G7 – Speaking to the Man on the Moon Approaching – 03

But suddenly, something occurs to you. You remember that in that same science class you learned about how sound is transmitted. You learned that sound can only travel through a solid, liquid, or a gas. Your teacher called them a medium. So, if sound must travel through some type of medium, how could the sound have been heard in space? Space, of course, has no air.

“Grandpa,” you say, “how come everyone could hear him talking from space. Doesn’t sound only travel through matter?”

He looked at you, surprised. “That’s actually a great question. Where did you learn about something like that?”

I explained to him what I had learned in science class. “All sound begins when matter vibrates. When a tree falls and hits the ground, it causes the tree as well as the ground to vibrate. Then, sound energy is transferred from the vibrating objects through other types of matter. Sound is really just an energy transfer. Typically, we think of sound energy travelling through air and into our ears. For us, the matter that sound travels through most often is air.

If we lived like a whale or dolphin underwater, the sound would need to travel through water to our ears. Either way, sound has travelled through some type of matter, or medium.”

Your grandfather is clearly impressed. “So, you’re wondering how the sound of Neil Armstrong’s voice could have travelled through space, to the microphones, to be transferred back to Earth?”

You nod. He understood your question. You add, “My teacher did this experiment in class to help us understand how this process works. She took a bell and suspended it under a glass dome. Then, she hooked up a special tool to an opening in the glass dome that would create a vacuum by pulling out all of the air from inside. The bell continued to swing back and forth, but the sound from the ringing bell eventually disappeared. This was because there was no air under the dome anymore for the sound waves to travel through. So, if there is no air, how could there be sound?”