In order to understand how it works, you need to look at a cross-section of the Pythagoras Cup. When viewed in this manner, the hidden channel that snakes through the central column is clearly visible. As liquid is poured into the cup, it begins to make its way up the channel. Those who stop their pour just at the top of the central column will be none the wiser and can drink without issue. But, should someone get a bit greedy, the pressure becomes too much and the liquid continues to build up in the channel. From there, gravity does its work. The siphoning effect causes the liquid to spill out through the bottom of the cup until you find yourself without anything in your glass. These cups are still sold throughout Greece, where they are called o kounenos tis dikaiosynis (the Cup of Justice). If you want to give the prank a try and aren’t going to Greece anytime soon, they’re also available on Amazon. This diagram demonstrates the siphoning effect of the Cup of Justice, an ancient practical joke. Ingenious Math Trick Allows You to Easily Calculate Percentages in Your Head Ex-NASA Engineer Uses Science to Transform Hot Tub Full of Sand into “Liquid Soup” Want to advertise with us? Visit My Modern Met Media. Celebrating creativity and promoting a positive culture by spotlighting the best sides of humanity—from the lighthearted and fun to the thought-provoking and enlightening.