## Einstein

### Best course on relativity

This superb biography of Einstein is really a biography of his ideas. It mines the newly opened archive of Einstein’s prolific correspondence for clues into his theories. We watch his ideas stir in embryonic form out of witty exchanges with his family and other scientists. We hear the evolving defense of his unorthodox approaches, and his lovely explanations to those who don’t understand. Einstein turns out to be a wonderful writer — as is Walter Isaacson, his biographer — and someone who thought and spoke in pictures. Although I’ve read explanations of special relativity and unified field theory many times, reading this biography was the first time I really came close to fully understanding them. A scrutiny of an idea’s origins is perhaps the best path to its understanding. One thing this vivid biography of concepts makes clear is that Einstein’s chief talent was not his genius, but his imagination. “Imagination,” Einstein wrote, “is more powerful than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand.”

— KK

Einstein: His Life and Universe

Walter Isaacson

2007, 704 pages

$20

Available from Amazon

Sample excerpts:

The group would usually make their way to the Congress hall together, working on ways to refute Einstein’s problem. “By dinner-time we could usually prove that his thought experiments did not contradict uncertainty relations,” Heisenberg recalled, and Einstein would concede defeat. “But next morning he would bring along to breakfast a new thought experiment, generally more complicated than the previous one.” By dinnertime that would be disproved as well. Back and forth they went, each lob from Einstein volleyed back by Bohr, who was able to show how the uncertainty principle, in each instance, did indeed limit the amount of knowable information about a moving electron. “And so it went for several days,” said Heisenberg. “In the end, we — that is, Bohr, Pauli, and I — knew that we could now be sure of our ground.” “Einstein, I’m ashamed of you,” Ehrenfest scolded. He was upset that Einstein was displaying the same stubbornness toward quantum mechanics that conservative physicists had once shown toward relativity. “He now behaves toward Bohr exactly as the champions of absolute simultaneity had behaved toward him.”

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In Santa Barbara, 1933. “Life is like riding a bicycle. To keep your balance you must keep moving.” — Albert Einstein, in a letter to his son Eduard, February 5, 1930.

*

As with his letter six months earlier, Einstein went on to reveal quite casually a momentous scientific breakthrough, one that would be expressed by the most famous equation in all of science: “One more consequence of the electrodynamics paper has also crossed my mind. Namely, the relativity principle, together with Maxwell’s equations, requires that mass be a direct measure of the energy contained in a body. Light carries mass with it. With the case of radium there should be a noticeable reduction of mass. The thought is amusing and seductive; but for all I know, the good Lord might be laughing at the whole matter and might have been leading me up the garden path.”

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