Echo of the Big Bang available in Hardcover
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- Princeton University Press
|Publisher:||Princeton University Press|
|Edition description:||With a New epilogue by the author|
|Product dimensions:||6.00(w) x 9.25(h) x (d)|
About the Author
Michael D. Lemonick is a senior science writer at Time magazine, where he has written more than forty cover stories on a wide range of science-related topics. He has also written for Discover, Playboy, and other publications. His books include The Light at the Edge of the Universe (Villard) and Other Worlds (Simon & Schuster).
Read an Excerpt
Echo of the Big Bang
By Michael D. Lemonick
Princeton University PressMichael D. Lemonick
All right reserved.
IS SOMETHING AMISS IN THE UNIVERSE?
Spring does not come subtly to Princeton University. It's early April 2002, and even after a mild winter, the brilliance of the campus in full bloom is almost overwhelming. The air is still uncomfortably cool, but vivid color is visible no matter where you look. Daffodils and hyacinths cover the ground; forsythia bushes burst with yellow flowers at eye level; cherry and magnolia trees are clouds of pink and white overhead. David Spergel doesn't notice any of this. He's much too distracted. A few weeks ago, he discovered evidence of something surprising and unsettling about the universe, evidence suggesting that its fundamental character is not what astrophysicists have believed for the past two decades or so. Papers published by other astrophysicists over recent months have declared that the cosmos is, at last, well understood. Modern cosmology, they say-the branch of astronomy that dares to address the ultimate questions about the birth and death of the universe-is essentially solved, only eighty years or so after it was founded. All that remains is to tidy up the last few decimal points. Newspapers and magazines have dutifully reported this comfortable conclusion, much as they reported a strangely similar comment made by the American physicist Albert Michelson in1894: "While it is never safe to say that the future of Physical Science has no marvels even more astonishing than those of the past, it seems probable that most of the grand underlying principles have been firmly established and that further advances are to be sought chiefly in the rigorous application of these principles to all the phenomena which come under our notice." Within a few years after that declaration, physicists would discover such previously unsuspected phenomena as radioactivity, subatomic particles, relativity, and quantum mechanics.
But David Spergel has reason to believe that cosmology is not solved. For a few hours he was the only one on Earth who had evidence to support this doubt. He may even have been the only one in the universe who had it. Now a small group of colleagues, fewer than twenty in all, have seen the evidence as well. They'll tell the rest of the world early the following year, most likely at a press conference at NASA headquarters. Their announcement will almost certainly be accompanied by the sort of public-relations blitz NASA has perfected in more than forty years of space exploration and discovery. The space agency puts on press conferences at different levels of breathlessness, from mild to hyper-ventilation, depending on what's being announced. The discovery of a new isotope of tin in the dust that floats between the stars doesn't generate much enthusiasm. The claim of evidence of life in a Martian meteorite gets the full treatment.
But for now, Spergel is focused on convincing himself and the others that what he's found is real rather than some glitch in the satellite that has been scanning deep space for the past nine months, or a bug in the computer code he uses to analyze its observations. Either of these is possible, for no matter how careful Spergel and his colleagues at Princeton and a handful of other institutions have been, the chance of a mechanical or electronic or software flaw, either new or too subtle to have been noticed over the past six years of careful work, may be making its presence known now, at the worst possible moment. The last thing these astronomers, physicists, and engineers want to do is make the shocking claim that much of the work of cosmology over the past two decades has been based on a faulty theoretical foundation-and then, a few months later to say, "Never mind."
This is looking increasingly unlikely, though. At first, when he told the others about what he'd found, they were appropriately skeptical. Spergel is one of the smartest, most talented theoretical astrophysicists around. That's why he was recruited for this project in the first place, and why, in the fall of 2001, the forty-year-old scientist had won a MacArthur Foundation "genius" grant. But even geniuses can make a mistake when they're writing hundreds of thousands of lines of computer code. Even geniuses can think they see patterns in data when the patterns aren't really there. Even geniuses are human enough to leap to world-shaking conclusions while overlooking a mundane explanation for what they've evidently found. Besides, the others on the team-all of them extraordinarily bright, even if the MacArthur committee hasn't formally certified them as such-have also looked at the data, and they can't think of any mundane explanation, either. The computer code is working fine. The satellite is performing as close to perfectly as anyone could wish. And it's simply not telling the story everyone expected.
In principle, of course, scientists aren't supposed to expect anything when they go into an experiment. They're simply supposed to observe, as objectively as if they were robots, aware of, but unprejudiced by, what their predecessors have seen. But they aren't robots. Science is an intensely human enterprise. Observers go into a new experiment with both expectation and hope. Unless it's the first time an experiment is being done, they generally expect that existing theories or assumptions are probably correct, that this latest attempt to observe and measure will expand or refine what we already know. This is true often enough that it can prove dangerous: people tend to see what they're expecting to see. When that happens, says Tod Lauer, an astronomer at Kitt Peak National Observatory in Arizona, "you're not likely to double-check it very carefully. Whereas if you see something unexpected, you recheck it over and over to figure out where you might have been fooling yourself." Yet the "correct" observation could be equally wrong. An observer can be too quick, in other words, to dismiss a crucial, telltale anomaly as nothing more than experimental error.
Scientists can also be tempted to err in precisely the opposite direction. It's important and satisfying to confirm or refine an existing theory with higher precision than anyone's ever achieved before. But most scientists agree that it's even more satisfying to prove the conventional wisdom utterly wrong. Showing yet again that Einstein's general theory of relativity is correct is certainly a good thing; refuting it would be a much bigger deal (that's one reason Einstein refutations are the number-one choice of cranks who send their handwritten "manuscripts" to physicists and science journalists).
So if a scientist discovers something dramatically new and important-cold fusion, say, or the first evidence of a planet orbiting a star other than the sun-it can be tempting to shout the news before you've thought it through. In the former case, two chemists from the University of Utah coined a new shorthand for "discovery that really isn't." But even when you have thought it through, you can overlook something. In 1991, a radio astronomer named Andrew Lyne thought he'd discovered planets orbiting a pulsar, the dense, burned-out remnant of an exploded star. He knew this was an audacious, even a preposterous claim, so he did every test he could think of to explain it away as a glitch. Eventually, he went public, only to realize to his horror that he'd failed to think of the one test that actually could-and in fact did-prove that the planets weren't there after all. Lyne's public apology to the astronomical community was deemed by John Bahcall, then president of the American Astronomical Society, to be "the most honorable act I've ever witnessed." But that didn't make Lyne feel much better.
Finally, there's a more subtle source of confusion in presenting new data. It's common that the first studies or experiments to explore a scientific question are inconclusive, but suggestive. The instruments in question-the telescopes, or particle detectors, or seismographs-are pushed to their limits of sensitivity, and find evidence that's not quite definitive. Depending on their confidence, researchers might play up or play down what they've found-label it a tentative discovery, or merely an interesting result. A long-sought particle known as the Higgs boson may have turned up in 2000, for example, in experiments at the Large Electron-Positron Collider in Europe. Or it may not; because of a scheduled major upgrade of the equipment, the experiment couldn't be run long enough to make a definitive measurement-although the physicists pleaded for a few more months. These scientists opted for caution, and didn't claim a discovery.
In medicine, by contrast, the public demands to hear about every result, preliminary or not, and often acts on it. When doctors found a relationship between fresh vegetables and reduced risk of cancer, they deduced that beta carotene, a chemical found in many vegetables, was a likely reason. Beta carotene supplements, they said, might be a good idea. So people began swallowing beta carotene pills by the handful. Later studies showed that taking these supplements actually raised the risk of cancer in some people. Something similar happened when doctors first established a link between saturated fats and heart disease. They suggested it might be wise to switch from butter to margarine. Then, a few years later, they discovered that the processed, or hydrogenated, vegetable oil in margarine was actually worse for the heart than ordinary saturated fat. So the recommendation swung back. People were indignant and assumed that medical scientists didn't know what they were talking about. But the earlier recommendations were as good as the data permitted them to be. The mistake, largely the fault of health experts and journalists, was that the provisional nature of the research was downplayed in the interest of making a good story.
Among the sciences, cosmology is especially prone to the danger of premature conclusions. One reason is that it's not an experimental science. There is only one universe, and it's physically inaccessible. You can't deduce its underlying structure or behavior or laws by taking one apart in the lab, or by varying the growth medium and cultivating a new one to see what happens. It's hard, moreover, to gather information about the cosmos; the photons of electromagnetic radiation that carry information about the stars and galaxies are sparse, and they overlap with each other in a tangle of data that must be untangled. As a result, astronomers have always been forced to build their models of the universe, initially at least, on meager information. A century ago it wasn't even clear that a universe existed beyond the Milky Way. Eighty years ago, nobody imagined that the universe was expanding. Forty years ago, the Big Bang was a somewhat crackpot theory.
Time after time, astronomers have been startled to realize how much less they understood about the universe than they'd thought. Confident statements about its basic nature have been proven not just wrong, but deeply, profoundly and sometimes embarrassingly wrong. In almost every case, the mistakes have been based on incomplete information, which in turn has been the fault not of sloppy observers but of primitive technology. In the 1920s, when the modern picture of the cosmos began to emerge, the largest and most powerful telescope on Earth had a light-gathering mirror just 100 inches across; the largest today spans nearly 400. The most sensitive medium for recording that light was the photographic plate, which was much better than the human eye but still very inefficient and inconsistent; today's charge-coupled devices, or CCDs, are a hundred times better.
And that just covers visible light. Nobody suspected a century ago that it would be useful to explore the full range of the electromagnetic spectrum, of which visible light is only a small subset. As the wavelength of light becomes shorter and shorter, visible light shades into ultraviolet, which humans can't detect (but which causes sunburn nonetheless). As the wavelength shrinks further, ultraviolet gives way to X-rays, then gamma rays. All three are part of the electromagnetic concerto broadcast by the universe, by individual stars and black holes and knots of superheated gases; all three carry telltale messages about the nature of these phenomena; yet none of them was part of astronomers' observing programs, nor even contemplated.
The same applied to the region of the spectrum with wavelengths longer than those of visible light. If short-wavelength radiation corresponds to the right-hand keys, the high-pitched notes, on a cosmic piano, then infrared radiation, microwaves, and radio waves are the bass notes to the left. By the 1920s, physicists understood something about radio waves, and broadcasters had begun to exploit them, first to send Morse code across the oceans and then to send news, and music, and jingles for selling detergent. In the early part of the twentieth century, Guglielmo Marconi even aimed his primitive wireless antenna toward the planet Mars, to try and pick up any broadcasts the Martians might be directing toward their sister planet.
But Marconi never tried to listen for natural radio emissions from the heavens. Nobody did. And so the deepest tones of the cosmic electromagnetic concerto, like the high notes, went unheard. Astronomers tuned in only to the few notes they could get to at the center of the keyboard. What they learned was true, as far as it went. But the bass and treble notes they couldn't hear would, time and again, alter the melody beyond recognition. Quasars, black holes, neutron stars, dark clouds of organic chemicals between the stars were all invisible, and in many cases unimagined, until astronomers learned to probe the high- and low-pitched frequencies of light.
So it was as well with the experiment David Spergel and his colleagues are now engaged in. Anyone who watched television before the days of cable, or who still gets a TV signal out of the air, remembers "snow"-the salt-and-peppery visual static that filled the screen when a set was tuned to a weak or nonbroad-casting channel. Nobody ever gave it much thought, except to curse at it; those who did figured it was some electronic noise in the picture tube, or maybe a distant station, coming through so feebly that the picture had disintegrated.
But at least some of those electronic crackles were and are something much more important than that. They're a message from the birth of the universe-a detailed record of the beginnings of space and time, and of the subsequent evolution of the cosmos. Every minute of every day, the Earth is bombarded with a barrage of photons, the particle-like building blocks of electromagnetic radiation. Most of these come from the Sun and the stars; they were emitted anywhere from today to a few thousand years ago. The photons that help wash out the Today Show and Sesame Street, though, are thousands of times older. They are by far the oldest radiation in the universe-the electromagnetic echo of the Big Bang itself.
Excerpted from Echo of the Big Bang by Michael D. Lemonick Excerpted by permission.
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Table of Contents
Is Something Amiss in the Universe? 1
The Birth of Cosmology 15
A Whisper of Microwaves 37
Bad Blood 63
Now What? 73
Forming a Team 83
How to Design a Satellite 100
The Build 128
Horse Race 142
Deepening Mystery 168
The Answer 190