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The Greedy Cup

The Greedy Cup

By Umay Salma

And there are hungers that can never be satisfied, and thirsts that can never be quenched. Appetites that will stay forever, and cravings that are destined to remain unfulfilled. If I could personify what I just wrote, it would be a simple yet amazing Pythagorean cup a.k.a Greedy cup.

At first glance, it seems like an ordinary drinking cup. Although there is an odd hump in the middle, but apart from that it’s normal. As you pour water into this, initially everything goes fine. The cup fills with water. But as it reaches a critical level, suddenly the water starts to drains out. It eventually empties itself entirely.

Have a long at its see-through version:

 The Greedy Cup

The secret behind this cup is in its construction. A hollow pipe-like chamber follows an opening, starting from the bottom of the liquid-holding part of the cup, up to the top of the central column that makes up the cup’s core, and back down 180 degrees, out the bottom.

The Greedy Cup Working
If the cup is only filled till below this limit, you’ll never have a problem. It’s when you get greedy and begin pouring too generously, that you end up with a wet lap and an empty cup.

This phenomenon called the siphon is created due to a reduction in pressure at the higher end of the siphon. The gravity pulls the water column down the pipe of the Pythagorean cup.  The lower pressure thus created on the other end causes the liquid there to be overwhelmed, subsequently allowing itself to be “dragged” along, stopping only when the water level either falls below the intake, or the outlet.

This explanation has been surprisingly controversial, however, as it has been demonstrated that some siphons can work in vacuum, suggesting that intermolecular forces can play a significant role in “dragging” the liquid through the tube.
Some modern toilets operate on the same principle: when the water level in the bowl rises high enough, a siphon is created, flushing the toilet.

Like many others, Pythagoras might be known to you as the author of a2 + b2 = c2 .However, there was far more to Pythagoras’ philosophy than this: he was a deep thinker on religion, the nature of the soul, and the harmony of the cosmos. With the “Pythagorean Cup” he illustrated to his students the virtues of moderation: when filled halfway, it retains its contents, but if it’s too full, all of the liquid drains out through a hole in the bottom.

In another story, Pythagoras was supervising workers at the water supply works on Samos and invented the “fair cup” (or “greedy cup”) to moderate the workers’ wine intake.  Provided they filled their cups only to a moderate level, they could drink in peace.  The truth to both stories is, however, unknown.

The Pythagorean cup is sold in the shops of Samos as a Greek souvenir. Whether it teaches moderation or not, it does teach a simple scientific principle and, you need to have this on your shelves if you want to impart this knowledge to your kids or if you’re in a mood to play 1st April prank! And also, if you want your guests to watch how much they drink!

References:

http://en.wikipedia.org/wiki/Pythagorean_cup

http://www.epmagazine.org/storage/431.aspx

http://tribelesshispursuitofhappiness.blogspot.ro/2012/05/pythagorean-cup-and-siphons.html

http://www.thenakedscientists.com/HTML/questions/question/2612/

http://www.raafatrola.com/

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