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How to Make a Pythagorean Cup

The Pythagorean cup, also called "the greedy cup," is one of many science devices Pythagoras created. This ancient mathematician was interested in far more than numbers. With a working knowledge of siphons and some clever pottery work, he created a cup that punishes the greedy. If you fill the cup just up to the designated line inside, you'll be allowed to quench your thirst. Try to fill past the line, and the liquid will drain away.

Things You'll Need

Two sturdy plastic cups (stackable)
High-speed rotary tool
1/4-inch diameter drill bit
1/16-inch diameter drill bit
.5-inch diameter plastic test tube
.75-inch diameter plastic test tube
Rotary cutting wheel
Hot glue
Permanent marker
Water

Instructions

- 1
  Set one of your stackable plastic cups aside. Flip over the other cup and drill a hole through the center of the bottom with a high speed rotary tool and a 1/4-inch diameter drill bit. Smaller cups, from 8 ounces to 12 ounces, work best.
- 2
  Snap a cutting wheel onto your rotary tool. Cut 1 inch from the bottom of a .5-inch diameter test tube. This tube will act as the siphon that "punishes the greedy."
- 3
  Run a bead of hot glue around the (uncut) opening of the .5-inch diameter test tube. Center the tube's opening over the hole in the bottom of the cup. Push the tube down inside the cup, over the hole. Let the glue dry for 10 minutes.
- 4
  Draw a line with your marker around the inside of the cup right below the top of the cut test tube. This is the fill line.
- 5
  Snap a 1/16-inch drilling bit onto your rotary tool. Press the bit about 1/8 inch from the opening of a .75-inch diameter test tube and drill a hole there. Drill a second hole on the opposite side of the tube.
- 6
  Hot glue the .75-inch test tube upside-down over the .5-inch test tube. Let the glue dry for 10 minutes.
- 7
  Set the holed cup down inside the intact cup. Fill the cup with water to just above the fill line. When the water rises above the cut end of the .5-inch test tube, it forms a siphon that pulls the water out of the top cup and into the bottom one.

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