einstein
einstein
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Turn of the Century<br />
CHAPTER FIVE<br />
THE MIRACLE YEAR: Quanta and Molecules, 1905<br />
At the Patent Office, 1905<br />
“There is nothing new to be discovered in physics now,” the revered Lord Kelvin reportedly told the British Association for the Advancement of<br />
Science in 1900. “All that remains is more and more precise measurement.” 1 He was wrong.<br />
The foundations of classical physics had been laid by Isaac Newton (1642–1727) in the late seventeenth century. Building on the discoveries of<br />
Galileo and others, he developed laws that described a very comprehensible mechanical universe: a falling apple and an orbiting moon were<br />
governed by the same rules of gravity, mass, force, and motion. Causes produced effects, forces acted upon objects, and in theory everything<br />
could be explained, determined, and predicted. As the mathematician and astronomer Laplace exulted about Newton’s universe, “An intelligence<br />
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<br />
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<br />
future as well as the past would be present to his eyes.” 2<br />
Einstein admired this strict causality, calling it “the profoundest characteristic of Newton’s teaching.” 3 He wryly summarized the history of physics:<br />
“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<br />
impressed Einstein were “the achievements of mechanics in areas that apparently had nothing to do with mechanics,” such as the kinetic theory he<br />
had been exploring, which explained the behavior of gases as being caused by the actions of billions of molecules bumping around. 4<br />
In the mid-1800s, Newtonian mechanics was joined by another great advance. The English experimenter Michael Faraday (1791– 1867), the<br />
self-taught son of a blacksmith, discovered the properties of electrical and magnetic fields. He showed that an electric current produced<br />
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<br />
vice versa, an electric current is produced. 5<br />
Faraday’s work on electromagnetic induction permitted inventive entrepreneurs like Einstein’s father and uncle to create new ways of combining<br />
spinning wire coils and moving magnets to build electricity generators. As a result, young Albert Einstein had a profound physical feel for Faraday’s<br />
fields and not just a theoretical understanding of them.<br />
The bushy-bearded Scottish physicist James Clerk Maxwell (1831–1879) subsequently devised wonderful equations that specified, among other<br />
things, how changing electric fields create magnetic fields and how changing magnetic fields create electrical ones. A changing electric field could,<br />
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<br />
electromagnetic wave.<br />
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<br />
extend the work of the Scotsman. Here was a theorist who had shed prevailing biases, let mathematical melodies lead him into unknown territories,<br />
and found a harmony that was based on the beauty and simplicity of a field theory.<br />
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:<br />
A new concept appeared in physics, the most important invention since Newton’s time: the field. It needed great scientific imagination to<br />
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<br />
description of physical phenomena. The field concept proved successful when it led to the formulation of Maxwell’s equations describing the<br />
structure of the electromagnetic field. 6<br />
At first, the electromagnetic field theory developed by Maxwell seemed compatible with the mechanics of Newton. For example, Maxwell<br />
believed that electromagnetic waves, which include visible light, could be explained by classical mechanics—if we assume that the universe is<br />
suffused with some unseen, gossamer “light-bearing ether” that serves as the physical substance that undulates and oscillates to propagate the<br />
electromagnetic waves, comparable to the role water plays for ocean waves and air plays for sound waves.<br />
By the end of the nineteenth century, however, fissures had begun to develop in the foundations of classical physics. One problem was that<br />
scientists, as hard as they tried, could not find any evidence of our motion through this supposed light-propagating ether. The study of radiation—<br />
how light and other electromagnetic waves emanate from physical bodies—exposed another problem: strange things were happening at the<br />
borderline where Newtonian theories, which described the mechanics of discrete particles, interacted with field theory, which described all