Albert Einstein got it wrong. Not once, not twice, but countless times. He made subtle blunders, he made outright goofs, his oversights were glaring. Error infiltrated every aspect of his thinking. He was wrong about the universe, wrong about its contents, wrong about the workings of atoms. Yet Einstein’s mistakes could be compelling and instructive, and some were even essential to the progress of modern physics. “Most scientists would give their eyeteeth to make even one of Einstein’s mistakes,” says theoretical physicist Fred Goldhaber of the State University of New York at Stony Brook.

But they were still mistakes. In 1911 Einstein predicted how much the sun’s gravity would deflect nearby starlight and got it wrong by half. He rigged the equations of general relativity to explain why the cosmos was standing still when it wasn’t. Beginning in the mid-1920s, he churned out faulty unified field theories at a prodigious rate. American physicist Wolfgang Pauli complained that Einstein’s “tenacious energy guarantee[s] us on the average one theory per annum,” each of which “is usually considered by its author to be [the] ‘definitive solution.’ ” And, while other physicists built careers describing the random antics within atoms, Einstein never even allowed that God *might* play dice with the universe.

Einstein’s blunders reveal the unique mind behind his winning thoughts. Einstein’s mistakes get upstaged by a few of his good ideas. Still, his errors deserve scrutiny, and not just for the schadenfreude. “There is no logical path to these laws; only intuition . . . can reach them,” Einstein said. In retrospect, however, his discoveries seem eminently logical. Only his errors preserve the doubts, quirks, and prejudices that fed his intuition. If his triumphs describe how the universe works, then his mistakes describe how he worked.

In 1916 Einstein found what he considered a glitch in his new theory of general relativity. His equations showed that the contents of the universe should be moving— either expanding or contracting. But at the time, the universe seemed the very definition of stasis. All the data, facts, and phenomena known in the early 1900s said that the Milky Way was the cosmos itself and that its stars moved slowly, if at all. Einstein had presented the definitive version of the general theory of relativity to the Prussian Academy of Sciences the previous year, and he was not inclined to retract it. So he invented a fudge factor, called lambda, that could function mathematically to hold the universe at a standstill. The term implied that space itself had energy that resisted the contraction caused by gravity or the expansion from the stretching of space.

Lambda “was not justified by our actual knowledge of gravitation,” Einstein said. But he stood by the ideal of the unchanging heavens until the moment, in 1929, when American astronomer Edwin Hubble discovered that the universe is expanding.

Einstein later called lambda his greatest blunder. But a greater embarrassment—with the benefit of hindsight—was his failure to predict universal expansion. He should have questioned the plausibility of a paralyzed universe, says emeritus physicist James Peebles of Princeton University: “A static universe isn’t physically self-consistent. The sun can’t shine forever. He didn’t recognize that, and I’ve always found that startling.”

EINSTEIN’S GREATEST MISTAKE G THE COSMOLOGICAL CONSTANT: LAMBDA In 1917 Einstein published an equation that described an expanding universe. But he inserted a fudge factor called lambda (in yellow) to allow the equation to describe a static universe. In 1929 Edwin Hubble found that the universe is, in fact, expanding. |

Some of Einstein’s peers recognized it in the master’s own equations. When Dutch astronomer Willem de Sitter pointed out that one interpretation of general relativity looked awfully like an expanding universe, Einstein sought a flaw in his reasoning. Russian mathematician Alexander Friedmann showed that general relativity explicitly posits a cosmos in motion; Einstein responded by publishing a short note claiming that the analysis was downright wrong. In a second paper, he conceded that the model was mathematically correct but dismissed it as physically absurd.

Why was Einstein so set on an immobile universe? Part of his insistence may have been fatigue. He had just completed the last mile of a decadelong intellectual marathon that made his earlier breakthroughs—special relativity, say, or the discovery of light quanta—look like a sprint. General relativity was the first, and remains the only, theory capable of uniting space, time, mass, energy, motion, and light in a grand vision of the nature and the fate of the cosmos. Its formulation had cost Einstein so much effort that it quite literally made him ill—he collapsed with stomach pains and lost more than 50 pounds in the winter and spring of 1917.

“You have to remember, he started the game. He did all the heavy lifting,” says Goldhaber. “He said, ‘Let’s make a model of the universe.’ Nobody else even had the tools to begin that. He couldn’t be expected to get it all right.”

Einstein never questioned the longstanding evidence for a static universe, even when new observations gave the first hints of expansion. When de Sitter showed him data from the Lowell Observatory in Arizona that suggested distant nebulas were speeding away in all directions, Einstein balked: OK, quasi-stationary then, he said. Einstein was as much an aesthete as a scientist, and he seemed to have a fundamentally aesthetic reason for preferring a stable cosmos. Although he never fully articulated it, this instinct for beauty would surface again and again in his very particular sense of how a proper law of physics worked, what proper math looked like, and the way nature should operate. He gave primacy to “free inventions of the mind,” as he called them, which were aloof from facts and phenomena. The German mathematician Felix Klein accused Einstein of working “under the influence of obscure physical-philosophical impulses.”

Those impulses drove his imagination beyond common sense and ordinary insight to radical and fundamental truths. But he sometimes turned against the daring implications of his ideas—especially when such implications were presented by someone else. General relativity provoked a welter of secondhand analyses, and it seemed to gall Einstein to watch other theoreticians spin webs of sticky perplexities from the silk of his great achievement. He was often disapproving of the claims colleagues made based on his equations. “In my personal experiences I have rarely learned better to know the shadiness of people than in connection with this theory,” he wrote to a friend.

Einstein objected when one colleague dared use general relativity—a geometric description of pliant space-time—to predict a cosmic phenomenon in which space, time, and the laws of relativity cease to exist. The phenomenon is now known as a black hole.