A lively, accessible look at the Big Bang theory
This compelling book describes how the Big Bang theory arose, how it has evolved, and why it is the best theory so far to explain the current state of the universe. In addition to understanding the birth of the cosmos, readers will learn how the theory stands up to challenges and what it fails to explain. Karen Fox provides clear answers to some of the hardest questions including: Why was the Big Bang theory accepted to begin with? Will the Big Bang theory last into the next century or even the next decade? Is the theory at odds with new scientific findings? One of the most well-known theories in modern science, the Big Bang is the most accurate model yet devised in humanity's tireless serach for the ultimate moment of creation. The Big Bang Theory is the first title in a planned series on the major theories of modern science.
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About the Author
KAREN C. FOX is the author of Chain Reaction and a regular contributor to Discovery Channel Online, ABCNews.com, and Science and Hope magazines.
Read an Excerpt
The Big Bang TheoryWhat It Is, Where It Came From, and Why It Works
By Karen C. Fox
John Wiley & SonsISBN: 0-471-39452-1
Chapter OneThe First Cosmologies
In the beginning, there was nothing. Well, not quite nothing-more of a Nothing with Potential. A nothingness in which packets of energy fleeted in and out of existence, popping into oblivion as quickly as they appeared. One of these fluctuations had just enough energy to take off. It inflated wildly out of control-one moment infinitesimally small, moments later light-years across. All of space and time was created in that instant, and as that energy slowed, it cooled and froze into matter-protons and neutrons and photons. This baby universe kept expanding, over billions of years, and those particles coalesced into stars and planets and eventually humans.
And that's how the universe came to be.
Or at least that's the modern version. Descriptions of how the cosmos was born, from the dramatic to the lyrical, have proliferated throughout human history. Take the Enuma Elish, the creation myth recited in about 4000 B.C.E. on the fourth day of each new year by the Babylonians as they lay prostrate before a statue of their great god Marduk.
The epic begins:
When heaven was not named, and the earth beneath did not bear a name nor the primeval Apsu, who begat them, nor Tiamet, the mother of them.
Their waters, sweet and bitter, mingled together. And no field was formed, no marsh was to be seen. When none of the gods had been called into being, And none bore a name, and no destinies were ordained. Then in the midst of the waters, gods were created.
Lahmu and Lahamu, were called into being.
The non-Babylonians among us may need help understanding who these divine beings are. Apsu is the sweet river water; Tiamat, the salty ocean. They come together-just the way the Babylonians would have watched a river delta hit the sea-and they create the first gods: Lahmu and Lahamu represent silt and muddy slime, the earth itself.
A child hearing these two stories for the first time would have no way of choosing which one was correct. As stories, one simply chooses the prettier version-and most would probably want to go with the poetry. But there is a dramatic difference between the two: the big bang description is more than just a fable. Science prides itself on providing physically accurate descriptions of the observable universe; it seeks literal truths about what really happened. The methods of religion and science are vastly different.
So how does science decide on just one theory, the accurate one, the true one?
The way many people like to imagine the process is that everyone keeps an admirably open mind and changes his or her beliefs when enough contradictory proof collapses an old theory. Science is cumulative, they think, refining theories over time, always getting closer and closer to the "truth."
Thomas Kuhn explained the process a very different way. A historian of science who taught at Harvard, Kuhn advanced the notion of the "paradigm shift." He said that scientists worked within the confines of their theories long after there was enough factual proof to disprove them. A new theory was embraced only when someone finally overturned the whole shebang completely, as thoroughly as upsetting a dinner table of dishes and silverware to the floor. A new theory would arise in place of the old one, with a whole new language and set of assumptions to go with it. We believed new theories not because of the preponderance of evidence, but because they "made sense" to us, much the way a creation myth might.
And then there is a third view, bluntly expressed by Max Planck, who simply said that scientific theories don't change because scientists change their minds; they change because old scientists die.
Like most philosophical truths, the answer is probably some combination of all of the above. The story of how the big bang theory became accepted certainly contains a bit of each. There are geniuses who scoffed at all previous theories and devised brand-new, innovative solutions; and there are those who refused to reject their preconceived notions no matter how overwhelming the evidence. There are people who accepted cosmology theories based on the experiments only; and there are those who simply believed them with the same faith they might bring to a religion. There are those today who say they believe the big bang model because all the experiments support it; and there are those who say there are enough holes that we shouldn't believe it just yet.
The story of how the big bang theory was accepted incorporates all these scientific styles, and it begins in ancient Greece.
Imagine looking at the sky for the first time-as if you knew nothing about its workings. Every day you'd see the sun rise and then set as the moon rose up to replace it. By and large you'd think they were similar bodies, both traveling around the globe in exactly the same way.
At first, all those other bright stars in the night sky would seem to be entirely different. They could be as small as fire-flies hovering just a mile or so up in the air for all you knew. The fact that the moon passes in front of them in her nightly journey will tell you they're at least farther away than the moon, but that's about all. In time you'd see the night sky move around the earth, too, all the stars moving in unison, and assume it was some two-dimensional backdrop twirling around a fixed earth at the center.
Eventually you'd notice that six of those stars didn't move in sync with the others. Each has its own erratic path. Each moves across the sky in one direction until suddenly it slows down, stops completely, and begins moving in the opposite direction for a while before finally resuming its course. Sometimes these six would even get larger, as if they were coming closer. You'd know these were different somehow, and your first guess might be that they were like the sun, just much, much farther away, circling the earth as the sun does.
And that would be about as far as you'd get. You could record daily movements of these wandering planets (the very word "planet" means "wanderer" in Greek), but your predictions about why they moved and how they were created would be based only on what you saw with the naked eye-and would be highly inaccurate.
Sure, you might realize that the sun moving around the earth would make the sky look just the same as if the earth twirled on its own axis, but relying on nothing more than your unaided vision, you really couldn't prove anything one way or the other. And the idea of the world twirling wouldn't make too much sense, because wouldn't you expect to feel the wind rushing past?
It's into this world, with just this much knowledge and this much observation, that the Greek philosophers arrived. They could map the night sky, they could predict eclipses, they could geometer their way into beautiful drawings of planetary motions, and they used all of this to devise theories about the universe, but they didn't have the tools to prove any of it.
The Greek philosophers didn't rely on experiments the way modern scientists do, but they took a giant step in that direction by rejecting religious explanations and denying that gods caused daily phenomena. Lightning bolts weren't hurled to the ground by the angry arm of Zeus, but born of natural processes, processes that could be rationally explained. Lucretius, for example, writing in the first century B.C.E., said: "Nature is free and uncontrolled by proud masters and runs the universe by herself without the aid of gods. For who-by the sacred hearts of the gods who pass their unruffled lives, their placid aeon, in calm and peace!-who can rule the sum total of the measureless?"
Notice how just as Lucretius denies divine intervention he invokes the existence of gods. He's our very first example of someone who embraced a new theory yet couldn't quite let go of what he'd been taught all his life. His whole philosophy was based on the idea that nature-made of little atoms-ran independently of the divine. But jettisoning the gods altogether? That would be going too far.
The Greek philosophers came up with numerous versions of how the universe worked. (A personal favorite: Anaximander's proposal that we live inside a huge sphere with fire along the outside rim-the sun is nothing but a hole in the sphere through which we can see the fire.) But one model truly captured the imagination of the Western world well into the 1600s. This was the version described by Aristotle; his would be the unquestioned assumptions that philosophers and scientists embraced for centuries. And Aristotle got the assumptions from his teacher Plato.
Aristotle and Plato
Plato lived in tumultuous times. Born in 427 B.C.E., he grew up during the Peloponnesian War and learned his philosophy in the marketplace where Socrates preached to the young men, telling them to question the morals they'd been taught. The community elders-who'd done all that moral teaching-weren't pleased, and Socrates was soon tried and sentenced to death.
Perhaps it was his friend's death and the chaos of a war-torn nation that led Plato to seek solid truths to put order and calm into his world. Plato lived in the world of ideals. The physical world, he claimed, was merely a facsimile of the perfection created in some divine mind. Plato referred to this divinity as the Demiurge. We, too, could experience true reality only in our own minds: a circle can only be perfect in our thoughts, after all-draw one and it's invariably slightly off-kilter.
Plato's universe depended on these "perfections." He picked five ideal shapes and claimed that the "elements" matched them: fire was a tetrahedron (a three-sided pyramid), the sharp sides of which could cut the connection between other elements; earth was a solid cube; air, an octahedron (a solid with eight sides that look like pentagons); and water was a slippery twenty-sided icosahedron (each side is an equilateral triangle). The planets, he believed, must travel in circles with uniform motion.
No matter that there was no proof of any of this, or even that the planets zigzagged across the sky in a way that looked distinctly noncircular. Because it was a beautiful theory, Plato believed it must be true. Those who thought they could understand the stars by, gasp, observation were as empty-headed as birds, as he wrote in his Timaeus: "But the race of birds was created out of innocent light-minded men, who, although their minds were directed toward heaven, imagined, in their simplicity, that the clearest demonstration of the things above was to be obtained by sight."
Plato's blindness did not, therefore, come from an inability to see but from his disdain for what he saw. He chose to ignore what he observed. He created a theory of the universe with everything moving in these perfect circles-even though it certainly doesn't look like this from earth as the planets wander backward and forward through the night sky-and then asked others to produce a mathematical model that would fit it.
Yes, those planets obviously traveled back and forth through the sky, so how do you create a universe run only by perfect solids and circles? Eudoxus, born in Sparta in 408 B.C.E., and one of Plato's pupils, rose to the challenge. To "save the appearances," Eudoxus described a set of planets sitting on a series of moving spheres with the earth at their center. The sun, for example, had three spheres: one to move around the earth daily; another, slower sphere, which on an annual basis moved to account for the way the sun appears to move higher in the sky throughout the seasons; and a third sphere to explain some incorrect observations of the time that had the sun changing position on the horizon from equinox to equinox. Eudoxus described each planet this way, adding on spheres moving at different speeds and in different directions, until there were twenty-seven spheres in total.
The model was totally wrong, of course, but the concept itself was mind-boggling. For the first time, someone hammered out a mathematical model correlated to what he saw. Eudoxus didn't think it was a description of what was actually happening in the heavens, and his model didn't perfectly fit the data, but you could use it to predict where a planet should be with reasonable accuracy. Math corresponded to reality.
Math corresponding to reality is seductive. It makes you believe the model is correct. In fact, using a theory to successfully predict an outcome in the physical world is exactly the kind of thing that gives modern-day scientists confidence in their models. If a theory doesn't fit reality, that's easy-you discount it immediately. The theory is wrong, and it's time to move on. When a theory fits the data, however, one doesn't quite know what to think. Sure, there's a chance it's right, but what about Eudoxus's rings, a theory we now know to be hogwash? Scientists must always remember how false theories have been emphatically believed in the past. This one, with the help of Aristotle, would be believed for centuries as insistently as we believe today that the earth goes around the sun-all because it by and large fit the data.
Aristotle added a twist to Eudoxus's model: he turned those ephemeral spheres into something solid. If the math worked, why couldn't it be a valid physical description? Aristotle studied under Plato for some twenty years before founding his own academy, but he wasn't as afraid of observation as his mentor was. Perhaps Aristotle's world simply seemed more stable. Aristotle was born in northern Greece in Macedon in 384 B.C.E. His father served as personal physician to the ruler, Amyntas II. Aristotle's life in Athens was largely good, as he was originally tapped to be Plato's successor.
Aristotle eventually stepped far enough away from the master that he wasn't chosen to lead the academy, but Plato's influence over his philosophy would be the rut that kept Aristotle's theories from being accurate. Aristotle inherited Plato's incorrect assumptions: Aristotle trusts so implicitly in the obvious perfection of a sphere that he never bothers to offer detailed proofs, as he does for other ideas, that the planets move in circles. In "On the Heavens" he writes: "The shape of the heaven must be spherical. That is most suitable to its substance, and is the primary shape in nature." So there.
The spheres in Aristotle's cosmology stemmed from Eudoxus's, but they needed some jury-rigging to become a physical reality. Aristotle devised a system whereby each sphere forced the spheres inside to rotate with it. Consequently he had to add spheres not only to account for the oddities of each planet's rotation but also to negate movement from the sphere above it.
Excerpted from The Big Bang Theory by Karen C. Fox Excerpted by permission.
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Table of Contents
PART I: HOW WE CAME TO BELIEVE THE BIG BANG THEORY.
1. The First Cosmologies.
2. The Birth of the Big Bang.
3. The Search for Proof.
Interlude: Popular Reactions.
PART II: HOW GOOD A THEORY IS IT?
4. Scientific Reactions.
6. Current and Future Research.
7. The Edge of the Unknown.
A Big Bang Timeline.