Part 1/6:

The Principle of Least Action: The Single Rule Underlying All of Physics

The Brachistochrone Problem

The story begins with a simple problem - finding the shape of a ramp that will allow a mass to slide from point A to point B in the fastest time. Common sense might suggest a straight line, but Galileo showed that a curved ramp in the shape of a circle is actually faster.

In 1696, Johann Bernoulli posed this "brachistochrone" problem as a challenge to the best mathematicians. After several months, Newton submitted a solution, though Bernoulli's own solution was ultimately more elegant.