Einstein's Unfinished Symphony
Main Takeaways, Questions, Moments of Genius
In ancient Greece philosophers developed the concept of the Pneuma aperion- a vacancy that allowed for a separation of things. Democritus, father of atomic theory, required this void- a nothingness bereft of matter. In order for his atomic theory to work, space had to be an empty extension, which allowed his bits of matter- his atoms- to move about.
A Greek philosopher named Archytas asked what would happen if you journeyed to the end of the world and stretch out your hand. Would your hand be stopped by the boundaries of space? Lucretius, Democritus’s pupil answered no; he asked: Suppose a man runs forward on the very edge of the world’s borders and throws a winged javelin. Unable to conceive that anything could get in the Javelin’s way, Lucretius concluded that the universe must stretch on and on without end. Aristotle on the other hand, took the opposite stand. He stated that it was “clear that there is neither place nor void nor time beyond heaven.” For him, the universe has finite. If a stone falls to the Earth to find its natural place at the center of the universe, he argued, then fire moving upward in the opposite direction must also face a limit. In Aristotle’s physics, upward and downward motions had to be balanced. These fierce intellectual debates concerning space continued for centuries, and by medieval times, theological concerns often prejudiced the arguments. To think of an immovable void, as outlined by the Greek atomists, was to imagine that God created something he could not bugde, which challenged his omnipotence.
Newton’s conception of an absolute time and space influenced the course of physics for some two hundred years, but it was not universally accepted. There were critics who raised their voices loudly. The most notable were the British philosopher George Berkely and the German diplomat and mathematician Leibniz, who was Newton's archrival for his claim to have invented the calculus first. To these two men, space and time were not fixed entities at all. Leibniz declared that “space and time are orders of things, and not things.” space and time could only be defined with their relation with objects of matter.
Maxwell’s equations revealed that an oscillating electric current- charges moving rapidly back and forth- would generate waves of electromagnetic energy coursing through space- he even worked out the speed these waves would travel. The results turned out to be exactly equal to the speed of light. Maxwell argued against those who said initially this was just a coincidence. He concluded that light itself was a propagating wave of electric and magnetic energy, an undulation that moved outward in all directions from its source.