Legend has it that, many centuries ago,Archimedes jumped out of his bathtub and ran across town nakedscreaming "Eureka!" after he solved an especially difficultproblem. Though you may not have thought of things this way before,when you drink a glass of water, the water that you are drinkingcontains some water molecules that were in Archimedes' bathwaterthat day, because water doesn't get created or destroyed on a largescale. It follows the water cycle, which includes rain,evaporation, flowing of rivers into the ocean, and so on. In themore than two thousand years since his discovery, the watermolecules from Archimedes' bathwater have been through this cycleenough times that they are probably about evenly distributedthroughout all the water on the earth. When you buy a can of soda,about how many molecules from that famous bathtub of Archimedes arethere in that can?