The problem of flatness, the problem of the uniform 3-degree radiation, and several other problems of the Big Bang model were solved, at least theoretically, in 1980 by Alan Guth, an MIT particle theorist. His improvement is known as the Inflationary Big Bang model.
INFLATION AND THE SCALAR PARTICLE
In this brief history of the past 15 billion years I forgot to mention that the evolution of the universe is pretty much all contained in Einstein's equations of general relativity. Once the universe cools to a temperature of 1032 degrees Kelvin, classical (nonquantum) relativity prevails, and the subsequent events are indeed consequences of Einstein's theory. Unfortunately, the great power of the theory of relativity was discovered, not by the master but by his followers. In 1916, before Hubble and Knubble, the universe was thought to be a much more sedate, static object, and Einstein in his self-proclaimed "greatest blunder" added a term to his equation to prevent the expansion that the equation predicted. Since this is not a book on cosmology (and there are some excellent ones around), we will hardly do justice to the concepts, many of which are above my salary level.
What Guth discovered was a process, allowed by the Einstein equations, that generated an explosive force so huge as to produce a runaway expansion; the universe inflated from a size much smaller than that of a proton (10−15 meters) to the size of a golf ball in a time interval of 10−33 seconds or so. This inflationary phase arose through the influence of a new field, a nondirectional (scalar) field—a field that looks and acts and smells like ... Higgs!
It is Higgs! The astrophysicists have discovered a Higgs thing in a wholly new context. What is the role of the Higgs field in promoting this bizarre pre-expanding-universe event that we call inflation?
We have noted that the Higgs field is closely tied to the concept of mass. What induces the wild inflation is the assumption that the pre-inflationary universe is suffused with a Higgs field whose energy content is so large that it drives a very rapid expansion. So "In the beginning there was a Higgs field" may not be too far from the truth. The Higgs field, which is constant throughout space, changes over time—in accordance with the laws of physics. These laws (added to the Einstein equations) generate the inflationary phase, which occupies the enormous time interval of 10−35 seconds to 10−33 seconds after Creation. Theoretical cosmologists describe the initial state as a "false vacuum" because of the energy content of the Higgs field. The ultimate transition to a true vacuum releases this energy to create the particles and the radiation, all at the enormous temperature of the Beginning. Following this, the more familiar Big Bang phase of relatively serene expansion and cooling begins. The universe is confirmed at the age of 10−33 seconds. "Today I am a universe," one intones at this phase.
Having donated all of its energy to the creation of particles, the Higgs field retires temporarily, reappearing several times in various disguises in order to keep the mathematics consistent, suppress infinities, and supervise the increasing complexity as the forces and particles continue to differentiate. Here is the God Particle in all its splendor.
Now wait. I didn't make any of this up. The originator of the theory, Alan Guth, was a young particle physicist trying to solve what appeared to be a totally different problem: the standard Big Bang model predicted the existence of magnetic monopoles—isolated single poles. North and south would then be related as matter and antimatter are. Looking for monopoles was a favorite game of particle hunters, and every new machine had its monopole search. But all proved unsuccessful. So at least monopoles are very rare, in spite of the absurd cosmological prediction that there should be enormous numbers of them. Guth, an amateur cosmologist, hit on the idea of inflation as a way of modifying the Big Bang cosmology to eliminate monopoles; then he discovered that by improving his inflation idea, he could solve all the other defects of that cosmology. Guth later commented on how lucky he was to make this discovery because all the components were known—a comment on the virtue of innocence in the creative act. Wolfgang Pauli once complained about his loss of creativity, "Ach, I know too much."
To complete this final tribute to Higgs, I should briefly explain how this rapid expansion solves the isotropy, or causality, and flatness crises. The inflation, which takes place at speeds vastly greater than the speed of light (the theory of relativity sets no limit on how fast space can expand), is just what we need. In the beginning, small regions of the universe were in intimate contact. Inflation vastly expanded these regions, separating their parts into causally disconnected regions. After inflation the expansion was slow compared to light velocity, so we continually discover new regions of the universe as their light finally reaches us. "Ah," the cosmic voice says, "we meet again." Now it is not a shock to realize that they are just like us: isotropy!
Flatness? The inflationary universe makes a clear statement: the universe is at critical mass; the expansion will continue to slow forever, but it will never reverse. Flatness: in Einstein's general theory of relativity, all is geometry. The presence of mass causes space to be curved; the more the mass, the greater the curvature. A flat universe is a critical condition between two opposing types of curvature. Large mass generates inward curvature of space, like the surface of a sphere. This is attractive and tends to a closed universe. Small mass produces an outward curvature, like the surface of a saddle. This tends to an open universe. Flatness represents a universe with a critical mass, "in between" inward and outward curvature. Inflation has the effect of stretching a tiny amount of curved space to so huge a domain as to make it effectively flat—very flat. The prediction of exact flatness, a universe that is critically poised between expansion and contraction, can be tested by identifying the dark matter and continuing the process of measuring the mass density. This, we are assured by the astros, will be done.
Other successes of the inflationary model have given it wide acceptance. For example, one of the "minor" annoyances of Big Bang cosmology is that it doesn't explain the lumpiness of the universe—the existence of galaxies, stars, and the rest. Qualitatively that lumpiness seems okay. By chance fluctuation, some matter clumps together out of a smooth plasma. The slight extra gravitational attraction draws other stuff to it, making the gravity even stronger. The process continues, and sooner or later we have a galaxy. But the details show that the process is far too slow if it is dependent on "chance fluctuations," so the seeds of galaxy formation must have been implanted during the inflationary phase.
Theorists who have thought about these seeds imagine them as small (less than 0.1 percent) density variations in the initial distribution of matter. Where did these seeds come from? Guth's inflation provides a very attractive explanation. One has to go to the quantum phase of the universe's history, in which spooky quantum mechanical fluctuations during inflation can lead to the irregularities. Inflation enlarges these microscopic fluctuations to a scale commensurate with galaxies. Recent observations (announced in April 1992) by the COBE satellite of ever so small differences in the temperature of the microwave background radiation in different directions are delightfully consistent with the inflationary scenario.
What COBE saw reflects conditions when the universe was young—only 300,000 years old—and stamped with the imprint of the inflation-induced distributions that made the background radiation hotter where it was less dense, cooler where it was more dense. The observed temperature differences thus provide experimental evidence for the existence of the necessary seeds for galaxy formation. No wonder the news made headlines all over the world. The temperature differences were only a few millionths of a degree and required extraordinary experimental care, but what a payout! One could detect, in the homogenized goop, evidence of the dumpiness that presaged the galaxies, suns, planets, and us. "It was like seeing the face of God," said exuberant astronomer George Smoot.
Heinz Pagels stressed the philosophical point that the inflationary phase is the ultimate Tower of Babel device, effectively cutting us off from whatever went before. It stretched and diluted al
l the structures that preexisted. So although we have an exciting story about the beginning, from time 10−33 seconds to time 1017 seconds (now), there are still those pesky kids out there who say, Yes, but the universe exists and how did it start?
In 1987 we had a "face of God" sort of conference at Fermilab when a group of astro/cosmo/theorists gathered to discuss how the universe began. The official title of the conference was Quantum Cosmology, and it was called so that the experts could commiserate about the domain of ignorance. No satisfactory theory of quantum gravity exists, and until one does, there will be no way of coping with the physical situation of the universe at the earliest moments.
The conference roster was a Who's Who of this exotic discipline: Stephen Hawking, Murray Geli-Mann, Yakov Zeldovich, André Linde, Jim Hartle, Mike Turner, Rocky Kolb, and David Schramm, among others. The arguments were abstract, mathematical, and very lively. Most of it was over my head. What I enjoyed most was Hawking's summary talk on the origin of the universe, given Sunday morning at about the time when 16,427 other sermons on roughly the same subject were being delivered from 16,427 pulpits around the nation. Except. Except that Hawking's talk was delivered through a voice synthesizer, giving it just that extra authenticity. As usual, he had a lot of interesting and complicated things to say, but he expressed the most profound thought quite simply. "The universe is what it is because it was what it was," he intoned.
Hawking was saying that the application of quantum theory to cosmology has as a task the specifications of initial conditions that must have existed at the very moment of creation. His premise assumes that the proper laws of nature—which, we hope, will be formulated by some genius now in third grade—will then take over and describe the subsequent evolution. The new great theory must integrate a description of the universe's initial conditions with a perfect understanding of the laws of nature and so explain all cosmological observations. It must also have as a consequence the standard model of the 1990s. If, before this breakthrough, we have achieved, via data from the Super Collider, a new standard model with a much more concise accounting for all of the data since Pisa, so much the better. Our sarcastic Pauli once drew an empty rectangle and claimed he had replicated the finest work of Titian—only the details were missing. Indeed, our painting "The Birth and Evolution of the Universe" requires a few more brushstrokes. But the frame is beautiful.
BEFORE TIME BEGAN
Let's go back to the prenatal universe again. We live in a universe about which we know a great deal. Like the paleontologist who reconstructs a mastodon from a fragment of a shinbone, or an archeologist who can visualize a long-defunct city from a few ancient stones, we are aided by the laws of physics emerging from the laboratories of the world. We are convinced (though we cannot prove this) that only one sequence of events, played backward, can lead via the laws of nature from our observed universe to the beginning and "before." The laws of nature must have existed before even time began in order for the beginning to happen. We say this, we believe it, but can we prove it? No. And what about "before time began"? Now we have left physics and are in philosophy.
The concept of time is tied to the appearance of events. A happening marks a point in time. Two happenings define an interval. A regular sequence of happenings can define a "clock"—a heartbeat, the swing of a pendulum, sunrise/sunset. Now imagine a situation where nothing ever happens. No tick-tock, no meals, no happening. The very concept of time in this sterile world has no meaning. Such may have been the state of the universe "before." The Great Event, the Big Bang, was a formidable happening that created, among other things, time.
What I am saying is that if we cannot define a clock, we cannot give a meaning to time. Consider the quantum idea of the decay of a particle, say our old friend the pion. Until it decays, there is no way of determining time in the universe of the pion. Nothing about it changes. Its structure, if we understand anything, is identical and unchanging until it decays in its own personal version of the Big Bang. Contrast this with our human experience of the decay of a homo sapiens. Believe me, there are plenty of signs that the decay is progressing or even imminent! In the quantum world, however, there is no meaning to the questions "When will the pion decay?" or "When did the Big Bang take place?" We can, on the other hand, ask the question "How long ago did the Big Bang take place?"
We can try to imagine the pre-Big Bang universe: timeless, featureless, but in some unimaginable way beholden to the laws of physics. These give the universe, like a doomed pion, a finite probability of exploding, changing, undergoing a transition, a change of state. Here we can improve on the metaphor used to start the book. Again we compare the universe in the Very Beginning to a huge boulder on top of a towering cliff, but now it is sitting in a trough. This would make it stable according to classical physics. Quantum physics, however, permits tunneling—one of the weird effects we examined in Chapter 5—and the first event is that the boulder appears outside of the trough and, oops, goes over the edge of the cliff, falling to release its potential energy and create the universe as we know it. In very speculative models, our dear dear Higgs field plays the role of the metaphoric cliff.
It is comforting to visualize the disappearance of space and time as we run the universe backward toward the beginning. What happens as space and time tend toward zero is that the equations we use to explain the universe break down and become meaningless. At this point we are just plumb out of science. Perhaps it is just as well that space and time cease to have meaning; it gives us the possibility that the vanishing of the concept takes place smoothly. What remains? What remains must be the laws of physics.
When dealing with all the elegant new theories about space, time, and the beginning, an obvious frustration sets in. As opposed to almost all other periods in science—certainly since the 1500s—there seems to be no way for experiments and observations to help out, at least not in the next few days. Even in Aristotle's time, one could (at risk) count the teeth in a horse's mouth in order to enter the debate on the number of teeth the horse has. Now our colleagues are debating a subject that has only one piece of data: the existence of a universe. This of course brings us to the whimsical subtitle of our book: the universe is the answer but damned if we know the question.
RETURN OF THE GREEK
It was almost 5 A.M. I had dozed over the last pages of Chapter 9. My deadline was (long) past, and I had no inspiration. Suddenly I heard a commotion outside our old farmhouse in Batavia. The horses in the stable were milling around and kicking. I walked out to see this guy in a toga and a pair of brand-new sandals coming out of the barn.
LEDERMAN: Democritus! What are you doing here? DEMOCRITUS: Call those horses? You should see the Egyptian chariot horses I raised in Abdera. Seventeen hands and up. They could fly!
LEDERMAN: Yes, well, how are you?
DEMOCRITUS: Do you have an hour? I've been invited to the control room of the Wake Field Accelerator that just turned on in Teheran on January 12, 2020.
LEDERMAN: Yeow! Can I come?
DEMOCRITUS: Sure, if you behave. Here, hold my hand and say Πλανχκ Mασσ. [Planck mass]
LEDERMAN: Πλανχκ Mασσ
DEMOCRITUS: Louder! LEDERMAN: Πλανχκ Mασσ!
Suddenly we were in a surprisingly small room that looked totally different from what I had expected— the command deck of Star Ship Enterprise. There were a few multicolored screens with very sharp images (high-definition TV). But the banks of oscilloscopes and dials were gone. Over in one corner a group of young men and women were engaged in an animated discussion. A technician standing next to me was punching buttons on a palm-sized box and watching one of the screens. Another technician was speaking Persian into a microphone.
LEDERMAN: Why Teheran?
DEMOCRITUS: Oh, some years after world peace, the UN decided to locate the New World Accelerator at the ancient crossroads of the world. The government here is one of the most stable, and they also made the best case for good geology, proximity
to cheap power, water, and skilled labor and the best shishkebab south of Abdera.
LEDERMAN: What's going on?
DEMOCRITUS: The machine is colliding 500 TeV protons against 500 TeV antiprotons. Ever since 2005, when the Super Collider discovered the Higgs at a mass of 422 GeV, there was this urgent need to explore the "Higgs sector" to see if there are more kinds of Higgs.
LEDERMAN: They found the Higgs?
DEMOCRITUS: One of them. They think there is a whole family of Higgses.
The God Particle Page 51
