What happens when you use a straw

You've probably used a straw to drink up a glass of your favourite drink. Have you ever wondered what happens when you use a straw? You probably think that you're sucking up the drink with the straw. But that is absolutely NOT right.

Outside the straw, all the air is trying to get inside the straw. When you suck into a straw, you're sucking up all the air that is inside the straw. All the air that is outside the straw then has room to get inside it, and when it fills up the straw, it pushes the drink up with it.

Try this experiment. Get two glasses. Fill one glass halfway with water. Leave the other glass empty and a couple inches away from the other glass. Suck up some water into the straw, and then very quickly, remove your mouth from the straw and close up the opening completely with your finger. Very carefully, without taking you finger off the straw, move the straw into the empty glass. As long as your finger is on top of the straw, the water won't spill out! Take your finger off the straw, and all the water will come gushing out.