Atmospheric Pressure

Have you ever felt a hug that you can’t see? It’s a gentle, all-over squeeze that is with you every single moment of the day. You feel me when you sip juice through a straw. I am the one pushing down on the juice, helping it climb up into your mouth. When you fly high in an airplane and your ears feel a little funny, that’s me, changing how much I am hugging you as you go way up into the sky. Most people don't even notice I'm there, but I am everywhere, all the time, wrapping the whole world in a big, invisible blanket. I am Atmospheric Pressure, but my friends just call me Air Pressure.

For a very long time, people didn't know I existed. I was a big secret. In the early 1600s, a super smart scientist named Galileo Galilei noticed something strange. He saw that miners who were trying to pump water out of deep mines could only lift the water up a certain height, and then it would stop. It was a giant puzzle, and he couldn't figure it out. But his student, a man with a big imagination named Evangelista Torricelli, had a brilliant idea. In 1643, he thought, 'What if the air has weight and is pushing down on everything?' To test this, he did a very clever experiment with a heavy, silver-colored liquid called mercury. He proved that I was pushing down on the mercury in a dish, which held up a column of it inside a glass tube. A few years later, another scientist named Blaise Pascal wanted to test the idea even more. On September 19th, 1648, he had a special instrument carried all the way up a tall mountain in France. Just as he thought, the instrument showed that my hug gets weaker the higher you go. The mystery was solved. I really do have weight.

Now that people understand me, I get to help out in so many amazing ways. I am a very important helper for people who study the weather, called meteorologists. They measure how hard I am pushing to predict if your day will be sunny and bright or cloudy and rainy. I also help airplanes know how high they are flying above the ground. The pilot can look at a special tool that measures my push, and it tells them if they are high up in the clouds or getting closer to the ground. Even though I am invisible, I am always here, working hard to help your world spin just right. The next time you drink from a straw or see a plane soaring in the sky, you can give a little wave and say hello to me, your helpful friend, Air Pressure.