einstein

Turn of the Century
CHAPTER FIVE
THE MIRACLE YEAR: Quanta and Molecules, 1905
At the Patent Office, 1905
“There is nothing new to be discovered in physics now,” the revered Lord Kelvin reportedly told the British Association for the Advancement of
Science in 1900. “All that remains is more and more precise measurement.” 1 He was wrong.
The foundations of classical physics had been laid by Isaac Newton (1642–1727) in the late seventeenth century. Building on the discoveries of
Galileo and others, he developed laws that described a very comprehensible mechanical universe: a falling apple and an orbiting moon were
governed by the same rules of gravity, mass, force, and motion. Causes produced effects, forces acted upon objects, and in theory everything
could be explained, determined, and predicted. As the mathematician and astronomer Laplace exulted about Newton’s universe, “An intelligence
knowing all the forces acting in nature at a given instant, as well as the momentary positions of all things in the universe, would be able to
comprehend in one single formula the motions of the largest bodies as well as the lightest atoms in the world; to him nothing would be uncertain, the
future as well as the past would be present to his eyes.” 2
Einstein admired this strict causality, calling it “the profoundest characteristic of Newton’s teaching.” 3 He wryly summarized the history of physics:
“In the beginning (if there was such a thing) God created Newton’s laws of motion together with the necessary masses and forces.” What especially
impressed Einstein were “the achievements of mechanics in areas that apparently had nothing to do with mechanics,” such as the kinetic theory he
had been exploring, which explained the behavior of gases as being caused by the actions of billions of molecules bumping around. 4
In the mid-1800s, Newtonian mechanics was joined by another great advance. The English experimenter Michael Faraday (1791– 1867), the
self-taught son of a blacksmith, discovered the properties of electrical and magnetic fields. He showed that an electric current produced
magnetism, and then he showed that a changing magnetic field could produce an electric current. When a magnet is moved near a wire loop, or
vice versa, an electric current is produced. 5
Faraday’s work on electromagnetic induction permitted inventive entrepreneurs like Einstein’s father and uncle to create new ways of combining
spinning wire coils and moving magnets to build electricity generators. As a result, young Albert Einstein had a profound physical feel for Faraday’s
fields and not just a theoretical understanding of them.
The bushy-bearded Scottish physicist James Clerk Maxwell (1831–1879) subsequently devised wonderful equations that specified, among other
things, how changing electric fields create magnetic fields and how changing magnetic fields create electrical ones. A changing electric field could,
in fact, produce a changing magnetic field that could, in turn, produce a changing electric field, and so on. The result of this coupling was an
electromagnetic wave.
Just as Newton had been born the year that Galileo died, so Einstein was born the year that Maxwell died, and he saw it as part of his mission to
extend the work of the Scotsman. Here was a theorist who had shed prevailing biases, let mathematical melodies lead him into unknown territories,
and found a harmony that was based on the beauty and simplicity of a field theory.
All of his life, Einstein was fascinated by field theories, and he described the development of the concept in a textbook he wrote with a colleague:
A new concept appeared in physics, the most important invention since Newton’s time: the field. It needed great scientific imagination to
realize that it is not the charges nor the particles but the field in the space between the charges and the particles that is essential for the
description of physical phenomena. The field concept proved successful when it led to the formulation of Maxwell’s equations describing the
structure of the electromagnetic field. 6
At first, the electromagnetic field theory developed by Maxwell seemed compatible with the mechanics of Newton. For example, Maxwell
believed that electromagnetic waves, which include visible light, could be explained by classical mechanics—if we assume that the universe is
suffused with some unseen, gossamer “light-bearing ether” that serves as the physical substance that undulates and oscillates to propagate the
electromagnetic waves, comparable to the role water plays for ocean waves and air plays for sound waves.
By the end of the nineteenth century, however, fissures had begun to develop in the foundations of classical physics. One problem was that
scientists, as hard as they tried, could not find any evidence of our motion through this supposed light-propagating ether. The study of radiation—
how light and other electromagnetic waves emanate from physical bodies—exposed another problem: strange things were happening at the
borderline where Newtonian theories, which described the mechanics of discrete particles, interacted with field theory, which described all