A short history of nearly everything (17 page)

Called “On the Electrodynamics of Moving Bodies,” it is one of the most extraordinary scientific papers ever published, as much for how it was presented as for what it said. It had no footnotes or citations, contained almost no mathematics, made no mention of any work that had influenced or preceded it, and acknowledged the help of just one individual, a colleague at the patent office named Michele Besso. It was, wrote C. P. Snow, as if Einstein “had reached the conclusions by pure thought, unaided, without listening to the opinions of others. To a surprisingly large extent, that is precisely what he had done.”

His famous equation,E =mc2, did not appear with the paper, but came in a brief supplement that followed a few months later. As you will recall from school days,E in the equation stands for energy,m for mass, andc2 for the speed of light squared.

In simplest terms, what the equation says is that mass and energy have an equivalence. They are two forms of the same thing: energy is liberated matter; matter is energy waiting to happen. Sincec2 (the speed of light times itself) is a truly enormous number, what the equation is saying is that there is a huge amount—a really huge amount—of energy bound up in every material thing.[18]

You may not feel outstandingly robust, but if you are an average-sized adult you will contain within your modest frame no less than 7 x 1018joules of potential energy—enough to explode with the force of thirty very large hydrogen bombs, assuming you knew how to liberate it and really wished to make a point. Everything has this kind of energy trapped within it. We’re just not very good at getting it out. Even a uranium bomb—the most energetic thing we have produced yet—releases less than 1 percent of the energy it could release if only we were more cunning.

Among much else, Einstein’s theory explained how radiation worked: how a lump of uranium could throw out constant streams of high-level energy without melting away like an ice cube. (It could do it by converting mass to energy extremely efficiently à laE=mc2.) It explained how stars could burn for billions of years without racing through their fuel. (Ditto.) At a stroke, in a simple formula, Einstein endowed geologists and astronomers with the luxury of billions of years. Above all, the special theory showed that the speed of light was constant and supreme. Nothing could overtake it. It brought light (no pun intended, exactly) to the very heart of our understanding of the nature of the universe. Not incidentally, it also solved the problem of the luminiferous ether by making it clear that it didn’t exist. Einstein gave us a universe that didn’t need it.

Physicists as a rule are not overattentive to the pronouncements of Swiss patent office clerks, and so, despite the abundance of useful tidings, Einstein’s papers attracted little notice. Having just solved several of the deepest mysteries of the universe, Einstein applied for a job as a university lecturer and was rejected, and then as a high school teacher and was rejected there as well. So he went back to his job as an examiner third class, but of course he kept thinking. He hadn’t even come close to finishing yet.

When the poet Paul Valéry once asked Einstein if he kept a notebook to record his ideas, Einstein looked at him with mild but genuine surprise. “Oh, that’s not necessary,” he replied. “It’s so seldom I have one.” I need hardly point out that when he did get one it tended to be good. Einstein’s next idea was one of the greatest that anyone has ever had—indeed, the very greatest, according to Boorse, Motz, and Weaver in their thoughtful history of atomic science.“As the creation of a single mind,” they write, “it is undoubtedly the highest intellectual achievement of humanity,” which is of course as good as a compliment can get.

In 1907, or so it has sometimes been written, Albert Einstein saw a workman fall off a roof and began to think about gravity. Alas, like many good stories this one appears to be apocryphal. According to Einstein himself, he was simply sitting in a chair when the problem of gravity occurred to him.

Actually, what occurred to Einstein was something more like the beginning of a solution to the problem of gravity, since it had been evident to him from the outset that one thing missing from the special theory was gravity. What was “special” about the special theory was that it dealt with things moving in an essentially unimpeded state. But what happened when a thing in motion—light, above all—encountered an obstacle such as gravity? It was a question that would occupy his thoughts for most of the next decade and lead to the publication in early 1917 of a paper entitled “Cosmological Considerations on the General Theory of Relativity.” The special theory of relativity of 1905 was a profound and important piece of work, of course, but as C. P. Snow once observed, if Einstein hadn’t thought of it when he did someone else would have, probably within five years; it was an idea waiting to happen. But the general theory was something else altogether. “Without it,” wrote Snow in 1979, “it is likely that we should still be waiting for the theory today.”

With his pipe, genially self-effacing manner, and electrified hair, Einstein was too splendid a figure to remain permanently obscure, and in 1919, the war over, the world suddenly discovered him. Almost at once his theories of relativity developed a reputation for being impossible for an ordinary person to grasp. Matters were not helped, as David Bodanis points out in his superb bookE=mc2 , when theNew York Times decided to do a story, and—for reasons that can never fail to excite wonder—sent the paper’s golfing correspondent, one Henry Crouch, to conduct the interview.

Crouch was hopelessly out of his depth, and got nearly everything wrong. Among the more lasting errors in his report was the assertion that Einstein had found a publisher daring enough to publish a book that only twelve men “in all the world could comprehend.” There was no such book, no such publisher, no such circle of learned men, but the notion stuck anyway. Soon the number of people who could grasp relativity had been reduced even further in the popular imagination—and the scientific establishment, it must be said, did little to disturb the myth.

When a journalist asked the British astronomer Sir Arthur Eddington if it was true that he was one of only three people in the world who could understand Einstein’s relativity theories, Eddington considered deeply for a moment and replied: “I am trying to think who the third person is.” In fact, the problem with relativity wasn’t that it involved a lot of differential equations, Lorentz transformations, and other complicated mathematics (though it did—even Einstein needed help with some of it), but that it was just so thoroughly nonintuitive.

In essence what relativity says is that space and time are not absolute, but relative to both the observer and to the thing being observed, and the faster one moves the more pronounced these effects become. We can never accelerate ourselves to the speed of light, and the harder we try (and faster we go) the more distorted we will become, relative to an outside observer.

Almost at once popularizers of science tried to come up with ways to make these concepts accessible to a general audience. One of the more successful attempts—commercially at least—wasThe ABC of Relativity by the mathematician and philosopher Bertrand Russell. In it, Russell employed an image that has been used many times since. He asked the reader to envision a train one hundred yards long moving at 60 percent of the speed of light. To someone standing on a platform watching it pass, the train would appear to be only eighty yards long and everything on it would be similarly compressed. If we could hear the passengers on the train speak, their voices would sound slurred and sluggish, like a record played at too slow a speed, and their movements would appear similarly ponderous. Even the clocks on the train would seem to be running at only four-fifths of their normal speed.

However—and here’s the thing—people on the train would have no sense of these distortions. To them, everything on the train would seem quite normal. It would be we on the platform who looked weirdly compressed and slowed down. It is all to do, you see, with your position relative to the moving object.

This effect actually happens every time you move. Fly across the United States, and you will step from the plane a quinzillionth of a second, or something, younger than those you left behind. Even in walking across the room you will very slightly alter your own experience of time and space. It has been calculated that a baseball thrown at a hundred miles an hour will pick up 0.000000000002 grams of mass on its way to home plate. So the effects of relativity are real and have been measured. The problem is that such changes are much too small to make the tiniest detectable difference to us. But for other things in the universe—light, gravity, the universe itself—these are matters of consequence.

So if the ideas of relativity seem weird, it is only because we don’t experience these sorts of interactions in normal life. However, to turn to Bodanis again, we all commonly encounter other kinds of relativity—for instance with regard to sound. If you are in a park and someone is playing annoying music, you know that if you move to a more distant spot the music will seem quieter. That’s not because the musicisquieter, of course, but simply that your position relative to it has changed. To something too small or sluggish to duplicate this experience—a snail, say—the idea that a boom box could seem to two observers to produce two different volumes of music simultaneously might seem incredible.

The most challenging and nonintuitive of all the concepts in the general theory of relativity is the idea that time is part of space. Our instinct is to regard time as eternal, absolute, immutable—nothing can disturb its steady tick. In fact, according to Einstein, time is variable and ever changing. It even has shape. It is bound up—“inextricably interconnected,” in Stephen Hawking’s expression—with the three dimensions of space in a curious dimension known as spacetime.

Spacetime is usually explained by asking you to imagine something flat but pliant—a mattress, say, or a sheet of stretched rubber—on which is resting a heavy round object, such as an iron ball. The weight of the iron ball causes the material on which it is sitting to stretch and sag slightly. This is roughly analogous to the effect that a massive object such as the Sun (the iron ball) has on spacetime (the material): it stretches and curves and warps it. Now if you roll a smaller ball across the sheet, it tries to go in a straight line as required by Newton’s laws of motion, but as it nears the massive object and the slope of the sagging fabric, it rolls downward, ineluctably drawn to the more massive object. This is gravity—a product of the bending of spacetime.

Every object that has mass creates a little depression in the fabric of the cosmos. Thus the universe, as Dennis Overbye has put it, is “the ultimate sagging mattress.” Gravity on this view is no longer so much a thing as an outcome—“not a ‘force’ but a byproduct of the warping of spacetime,” in the words of the physicist Michio Kaku, who goes on: “In some sense, gravity does not exist; what moves the planets and stars is the distortion of space and time.”

Of course the sagging mattress analogy can take us only so far because it doesn’t incorporate the effect of time. But then our brains can take us only so far because it is so nearly impossible to envision a dimension comprising three parts space to one part time, all interwoven like the threads in a plaid fabric. At all events, I think we can agree that this was an awfully big thought for a young man staring out the window of a patent office in the capital of Switzerland.

Among much else, Einstein’s general theory of relativity suggested that the universe must be either expanding or contracting. But Einstein was not a cosmologist, and he accepted the prevailing wisdom that the universe was fixed and eternal. More or less reflexively, he dropped into his equations something called the cosmological constant, which arbitrarily counterbalanced the effects of gravity, serving as a kind of mathematical pause button. Books on the history of science always forgive Einstein this lapse, but it was actually a fairly appalling piece of science and he knew it. He called it “the biggest blunder of my life.”

Coincidentally, at about the time that Einstein was affixing a cosmological constant to his theory, at the Lowell Observatory in Arizona, an astronomer with the cheerily intergalactic name of Vesto Slipher (who was in fact from Indiana) was taking spectrographic readings of distant stars and discovering that they appeared to be moving away from us. The universe wasn’t static. The stars Slipher looked at showed unmistakable signs of a Doppler shift[19]—the same mechanism behind that distinctive stretched-outyee-yummm sound cars make as they flash past on a racetrack. The phenomenon also applies to light, and in the case of receding galaxies it is known as a red shift (because light moving away from us shifts toward the red end of the spectrum; approaching light shifts to blue).

Slipher was the first to notice this effect with light and to realize its potential importance for understanding the motions of the cosmos. Unfortunately no one much noticed him. The Lowell Observatory, as you will recall, was a bit of an oddity thanks to Percival Lowell’s obsession with Martian canals, which in the 1910s made it, in every sense, an outpost of astronomical endeavor. Slipher was unaware of Einstein’s theory of relativity, and the world was equally unaware of Slipher. So his finding had no impact.

Glory instead would pass to a large mass of ego named Edwin Hubble. Hubble was born in 1889, ten years after Einstein, in a small Missouri town on the edge of the Ozarks and grew up there and in Wheaton, Illinois, a suburb of Chicago. His father was a successful insurance executive, so life was always comfortable, and Edwin enjoyed a wealth of physical endowments, too. He was a strong and gifted athlete, charming, smart, and immensely good-looking—“handsome almost to a fault,” in the description of William H. Cropper, “an Adonis” in the words of another admirer. According to his own accounts, he also managed to fit into his life more or less constant acts of valor—rescuing drowning swimmers, leading frightened men to safety across the battlefields of France, embarrassing world-champion boxers with knockdown punches in exhibition bouts. It all seemed too good to be true. It was. For all his gifts, Hubble was also an inveterate liar.