But when Hieron was presented with the crown, it didn't feel quite right.

The King suspected that the smith had put some of the gold in his pocket, and instead fashioned most of the crown out of lesser metals. But this was just a suspicion. He needed proof.

So he approached the smartest scientist in his kingdom– Archimedes– and asked him to figure out whether or not the crown was actually made of pure gold.

Archimedes pondered the problem for weeks, frustrated that he couldn't figure out a way to determine the crown's purity.

And then one day, as the legend goes, Archimedes stepped into a public bath and noticed that the water level rose based on how much of his body was submerged in the tub.

He experimented over and over with this observation, plunging different substances and metals into the water to see how much the water level rose.