Bernoulli's principle says that in a steadily flowing fluid, where the flow speeds up, the pressure drops, and where it slows down, the pressure rises. The idea relates pressure, speed and height, and it applies to air as well as water. Daniel Bernoulli published it in 1738 in his book Hydrodynamica, while Leonhard Euler derived the equation in its familiar form in 1752. The principle follows directly from Newton's second law: fluid moving from high pressure toward low pressure gets pushed forward and speeds up. It also follows from energy conservation, since gains in kinetic energy come at the cost of pressure and potential energy.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.