Sound Waves

I am the whoosh of the wind in the trees and the thump-thump of your heart when you run. I am the happy splash you make when you jump in a puddle and the soft purr of a kitten curled up on your lap. You can’t see me, but I am everywhere. I travel like a secret message through the air, wiggle through water, and can even sneak through walls to bring all sorts of news to your ears. To make me, all you have to do is make something wiggle back and forth really, really fast. That wiggle is called a vibration, and it tickles the air around it, passing the message along until it reaches you. What am I? I'm a Sound Wave.

For a very long time, people heard me but didn't quite understand how I worked. Then, long, long ago, a curious man who loved music started to figure me out. His name was Pythagoras. Around the year 530 BCE, he was playing with strings, like on a guitar. He discovered that when he plucked a short string, it made a high-pitched sound, like a little bird chirping. But when he plucked a long string, it made a low-pitched sound, like a big bear growling. He realized that the wiggles, or vibrations, were the secret. The strings were wiggling back and forth to create me. Much, much later, a scientist named Robert Boyle did a super cool experiment around the year 1660. He put a ringing bell inside a big glass jar. He could hear it perfectly. Then, he used a special pump to suck all the air out of the jar, creating an empty space called a vacuum. Guess what happened? The bell was still wiggling, but the sound was gone. It was totally silent. Robert proved that I need something to travel through. I can't just float through empty space—I need a ride on the air or water to get to your ears.

Today, you use me for almost everything, and I love being so helpful. I am the reason you can shout to a friend across the playground and hear them shout back. I carry your voice through a telephone wire so you can talk to your grandma who lives far away. I fill your house with music from a speaker, making you want to get up and dance all around the room. But I also have some amazing secret jobs you might not know about. Doctors use my super-high-pitched cousins, called ultrasound waves, to take pictures of babies while they are still growing inside a tummy. Ships in the big, wide ocean use a special version of me called sonar to find their way. They send me down to the bottom of the sea, and when I bounce back, I paint a picture of what’s down there. I carry stories, laughter, songs, and even warnings. So the next time you hear a bee buzz or a friend whisper a secret, just smile and remember me—the invisible, wiggling messenger making it all happen.