Siphons

gravity · physics · water

Gravity does the work. A siphon moves liquid up and over a curved tube by using gravity. Once you start the flow, gravity pulls the liquid down the other side, which creates a vacuum that sucks liquid up from the starting point. No electricity or pump needed.

U-shaped tube trick. The classic siphon is shaped like an upside-down U. Liquid flows up one side and down the other, as long as the exit point is lower than where the liquid started. It's like the tube does the lifting work while gravity does the pulling work.

Must prime first. To get a siphon started, you need to fill the tube with liquid first. This is called priming. Once the tube is full and you position it correctly, the flow keeps going on its own because of gravity pulling on the liquid.

Nature uses them too. Many creatures use siphons in their bodies. Squid and octopuses have siphons they use to move through water. Some clams use siphons to pull in water for food and oxygen.

Still used today. Modern siphons help drain pools, move gasoline, and transfer liquids in science labs and factories. They're simple, cheap, and reliable, which is why people still use them after thousands of years.