It’s There!

3 It's There! Allison is a friend of mine who loves science. She loves to prove things using simple experiments. I, on the other hand, love reading and writing, but not science. One day she said to me, “ We just learned about air pressure in our science class. I wonder how much you know about it?" “ Not too much, " I confessed. She made a funny face. " If you fill a glass with water and put a piece of paper on top, and then turn the glass over, what will happen?" “ You'll get the floor wet, " I answered. “ No. The water will stay in the glass, " she said. I told her to prove it. Allison loves a challenge. The next day, I met Allison at her house. She had a glass filled with water, and a small sheet of paper. She placed the paper on top of the glass and pressed down hard on the paper. Next, she held one hand on the paper and turned the glass over.

I stood watching with a smile on my face. Surely all the water would spill onto the floor. “ Are you afraid to move your hand?" I asked with a smug look. She didn't answer. Suddenly, she took her hand away. I quickly stepped back, thinking my feet would get wet when the water rushed out from the glass. But nothing happened! Not a drop of water spilled from the overturned glass. Allison smiled. “ See, " she said, “ this little paper holds all the water back. Do you believe me now?" I should have known she would be right. “ You can see that the paper holds the water back, but you can't see why, " Allison continued. " It's air pressure. It's all around us, but we can't see it. We can only see its effects. Air pressure on the paper holds it in place. It's stronger than the gravity that is trying to force the water out. " As the expression goes, " Seeing is believing. " Now, I had to believe in the existence of air pressure. It's some- thing we can't see, but it's there.