Any object placed in a fluid is pushed upward by a force equal to the weight of the fluid it pushes aside. This is true whether the object is fully or only partly submerged. A steel ship floats because its hull displaces a huge volume of water, and the upward push of that water equals the ship's full weight. Archimedes of Syracuse formulated the principle, and it remains a foundation of fluid mechanics. The same idea explains why a helium balloon rises and why a swimmer feels lighter in a pool.

In 1909 D. W. Griffith made a 14-minute film about a speculator who corners the wheat market and doubles the price of bread. A farmer sows his field while a 'Wheat King' gambles in the Chicago wheat pit; bakers raise the loaf from five cents to ten and the poor line up for bread. Griffith cut back and forth between the farm, the feast and the breadline, a technique called parallel editing, so audiences saw both ends of the economy at once. The film drew on Frank Norris's stories and on a real scheme: months earlier Chicago financier James Patten had cornered wheat, sent bread prices up and made about $5 million, roughly $185 million today.