By John N. Howard, OPN Contributing Editor
In physics history, we associate several events with sudden insight by the discoverer. The most famous such event was perhaps when King Hiero of Syracuse (308-215 B.C.E) received a new crown, fashioned by a goldsmith, and Hiero had asked his science adviser Archimedes how could one check that the crown was really solid gold, and not merely a thin layer of gold over some cheaper material. Archimedes was supposedly pondering this problem when he went for a soak in a public bath, filled to the brim with water. As he got into the bath, some water sloshed out, and he suddenly realized that he could determine the density of that golden crown by measuring how much water it displaced when immersed. He already knew that pure gold should be eight times as heavy as water.
According to the story—or, perhaps, the myth—Archimedes then happily ran back to his house —naked—shouting “Eureka!” (“I have found it!”).
Image from Wikimedia Commons. It shows how Archimedes may have used buoyancy to determine whether his crown was less dense than gold.