In my 2013 book God and the Atom, I traced the history of the ancient notion that the universe is nothing more than atoms and the void, with no role for gods, spirits, or the supernatural of any kind. I began the story 2,500 years ago with the Greek philosophers Leucippus (fifth century BCE) and Democritus (ca. 460–370 BCE), and wound up with the observation of the Higgs boson in 2012, which serendipitously happened just as I was finishing the manuscript. This provided the final verification for the standard model of elementary particles that had been in place since the 1970s and has agreed with all the data since.
That is not to say it's the final word. With the Large Hadron Collider now being doubled in energy, we can look forward to moving to the next level in our understanding of the nature of matter—what may lie beyond the standard model.
In this book I move from the very small to the very large and examine how humanity's view of the cosmos has dramatically changed over the last ten thousand years, from the primitive picture of a flat Earth with heaven above and an underworld below to the current majestic array of a hundred billion galaxies of stars lighting the night sky.
We will explore how the disciplines of particle physics and cosmology have collaborated to give a common picture of a boundless and eternal multiverse in which our universe is just one among countless others and has neither a beginning nor an end.
Of course, the existence of other universes besides our own has not been empirically established—at least not yet. We will see that the verification of the multiverse is not beyond the realm of possibility.
Given the current scientific respectability of the multiverse hypothesis, philosophers and theologians cannot simply sit back and ignore the implications of such a profound notion. All major religious traditions are likely to have great difficulty reconciling their concept of a creator god with a multiverse that is eternal and uncreated.
Even without the multiverse, there exist in our own, visible universe quadrillions of planets capable of supporting life. How will theists square that with their believe that humans are a special creation of God?
As we will learn in the early chapters, observations by ancient Greek astronomers led them, with one or two exceptions, to develop a picture of the sun, moon, planets, and stars circling a spherical Earth. In a remarkable feat of mathematics, in the second century of the Common Era, Alexandrian astronomer Claudius Ptolemy developed a complex geocentric model of the solar system. His model enabled the accurate prediction of the motions of the planets, which even the ancient saw did not follow exact circles but wandered around the sky.
This model stood until the sixteenth century when the Polish astronomer and Church canon Nicolaus Copernicus (1473–1543) proposed that Earth is just another planet that revolves around the sun.1 This revived the scheme that was originally put forward by Aristarchus of Samos (ca. 310–230 BCE) in the third century before the Common Era and was finally confirmed in the early seventeenth century when the Florentine physicist Galileo Galilei (1564–1642) turned the newly invented telescope on the heavens. We will cover these events in detail and show that their true implications are not exactly as commonly thought.
Galileo also founded the new science of particle mechanics that would be fully developed in England a generation later by perhaps the greatest scientific mind of all time, Isaac Newton (1642–1727).
Central to the success of the new science was the replacement of sacred authority by observation as the final arbiter of what was to be regarded as physical reality, at least among those scholars who were not bound by Church dogma. This doctrine of empiricism was first proposed by Francis Bacon (1561–1626) and seconded by John Locke (1632–1628), becoming the operating principle of the institution that set the standards for the scientific age that followed: the Royal Society of London for Improving Natural Knowledge, granted a charter by Charles II in 1660, shortly after he was restored to the throne.
Once the scientific revolution was underway, telescopes became steadily more powerful and it was realized that the sun is just another star in a galaxy of stars called the Milky Way. With large reflecting telescopes, originally invented by Newton, placed on mountaintops, the twentieth century saw incredible advances in our knowledge of the cosmos. The Milky Way in which we reside was discovered to be just one galaxy among others in the observable universe, now known to number on the order of 100 billion, each containing on the order of a 100 billion stars.
Equally startling was the discovery that the universe is expanding, with most galaxies receding from one another at speeds that increase with their distances from each other. This suggested that the universe is the remnant of an explosion called the big bang that occurred 13.8 billion years ago, by our current estimate.
The size of the observable universe calculated by astronomers went from around 1,000 light-years in 1900 to 46.5 billion light-years in 2000.2 Any signal traveling at the speed of light that we might receive from that distance would have come from the origin of the big bang. A signal from a lesser distance would have been emitted later. Any signal from a greater distance would not have reached us in the age of the universe. Such a signal would be beyond our light horizon. But note that this does not mean nothing exists beyond that distance.
As the twentieth century neared its close, cosmologists had accumulated convincing evidence that a tiny fraction of a second after the universe appeared, it briefly expanded exponentially by many orders of magnitude. As a result, the total universe that resulted from that original explosion is now far larger than that the portion within our horizon, perhaps hundreds of orders of magnitude larger.
As if that isn't sufficiently mind-boggling, as mentioned we now have strong indications that this vast universe in which we live is just one of an endless number of other universes within a multiverse that possibly extends indefinitely in space and endlessly in both the past and future. If it exists, it would have no beginning and no end.
These conclusions are not wild speculations but are based on vast amounts of ever-increasing and increasingly precise quantitative observations on mountaintops, in space, and underground. The main sources of information have been photons, the particles of electromagnetic radiation that are emitted from astronomical objects. They are observed not only in the spectrum to which our eyes are sensitive but also over a range of twenty or more orders of magnitude in energy that vastly exceeds the visible range.
And now, the budding field of neutrino astronomy is joining photon astronomy to produce yet another window on the universe. Neutrinos interact very weakly and are able to pass through a great thickness of matter as if it were not there. They promise to reveal processes and details about the cosmos that are inaccessible to photons.
While all these observational methods have contributed to a spectacular enrichment of our knowledge of the universe, perhaps the most significant has been the incredible wealth of information gained by measurements of small anisotropies across the sky in the cosmic microwave background (CMB), the radiation left over from the big bang. These reveal the spectrum of sound waves produced in the very early universe by the quantum fluctuations in space that ultimately led to the complex structure of matter that formed the galaxies we see today. The big bang really made a bang. The CMB data, which exhibit the fundamental tones and harmonics of a crude musical instrument being played in a hall with poor acoustics, have enabled cosmologists to determine not only characteristics of that instrument but also something of the structure of the hall itself.
From these and other observations, it has been determined that luminous matter—the stars and hot gas we see in the sky by eye and instrument—constitutes a mere 0.5 percent of the total mass of our universe. Another 4.5 percent is nonluminous matter, such as planets and dead stars, made of the same familiar atoms. In addition, 26 percent is composed of something different than atoms or their constituent elementary particles. Dubbed dark matter, it remains unidentified. The remaining, dominant 69 percent of the universe is an even more mysterious dark energy that has resulted in an accelerating expansion of the universe that will continue indefinitely into the future, making the universe increasingly dilute.
Today the term atom conventionally refers to the elements of the chemical periodic table. However, if we take the term as defined by the ancient Greeks to refer to the basic irreducible (“uncuttable”) material stuff of the universe, whatever it is, then we can retain their description of the natural world as “atoms and the void.” Void, then, identifies the empty space between atoms.
Note that the existence of dark “energy” does not imply anything immaterial, since it still exhibits the qualities of inertia and gravitation that characterize matter. Energy is one of the properties of matter and is not separate stuff.
But this book is more than a particle physicist's presentation of the history of cosmology. From the earliest days when humans contemplated the world around them, they have sought explanations for what they saw. Until very recently, they lacked the tools, both physical and mental, that were needed to provide a reliable picture free of magic and superstition. Not seeing the actual forces behind many events, they mythologized those events in terms that were familiar but simply invisible and more powerful than those forces that they did see or, such as the wind, that they could feel.
When it came to the cosmos, the sky was the “heavens” and the precise motions of the heavenly bodies contrasted sharply with the unpredictability of events on Earth, suggesting they were gods or under the control of gods. For most of history, astronomy and astrology were related activities. Astronomy provided an accurate clock by which events such as the Nile flood could be usefully predicted. Astrology provided useless predictions such as when to go to war.
Copernicus, Galileo, and Newton gave us a less human-centered model of the world. But for the centuries that followed until very recently, most scientists still saw the need for a divine providence behind everything.
In this book I describe the events that led to the remarkable success of current cosmology and the picture it now paints of our universe, including the marvelous prospect that many other universes exist as well. The vast majority of humanity does not appreciate most of these findings. I hope I can make an incremental addition to their accessibility.
I will show how the universe that presents itself to our senses and instruments can be described without any need for the introduction of forces other than those that are purely natural. This conclusion is disputed by those who declare that they cannot understand how all the complexity we see around us, in life on Earth and in the vast galactic structures in the sky, can have happened except by the hand of some supreme power. So they conclude that a creator God must exist.
As we will see in many examples throughout the book, this argument from complexity is nothing more than the God-of-the-gaps argument—often less politely called the “argument from ignorance.” Just because a particular author cannot personally understand how some phenomenon can be explained naturally, it does not follow that no explanation is possible other than a supernatural one.
On the other hand, science is in the business of finding natural explanations for events because those explanations often prove useful to human life. Where would today's teenager be without the smartphone, which is an application of electromagnetic theory? Indeed, imagine life without electricity. In fact, you don't have to imagine it—just look at history.
Perhaps more important than practical applications, the more science is able to demonstrate the bankruptcy of the magical thinking inherent in all religion, moderate as well as extreme, the less humans will rely on this worthless and dangerous way to rule their lives. The future survival of humanity depends on it ridding itself of magical thinking.
Our current picture of the physical world is well described by the standard model of elementary particle physics and various cosmological models. Of course, not every phenomenon has a proven explanation within that framework. We still don't know everything, and we never will. And you can be sure that much that is in this book eventually will be outdated in the future. All we can do is provide plausible models for the observations made to date. Because these natural models are more parsimonious, that is, require fewer assumptions than supernatural alternatives, their very viability suffices to refute any claims that science provides support for gods or spirits of any kind.
Throughout this book, the primary emphasis is on science and, within science, more on observation and experiment than theory. My own background is that of a retired professor of physics who spent forty years teaching and doing research in experimental elementary particle physics and astrophysics.
In this regard, I differ from the preponderance of professional physicists and cosmologists who write popular books, most of them quite excellent and to which I often refer, who are mostly theorists. I generally try to avoid the numerous theoretical speculations you will find in their books, entertaining as they are, and stick as much as possible to what the data say.
Of course, I can't avoid some theoretical interpreting, since there is a close tie between theory and experiment. But where I do this, I try to choose the simplest proposals that are consistent with all observations and make the fewest hypotheses not required by the data. In particular, I do not worry myself when some theory has a logical or mathematical problem requiring its proponents to generate paper after paper proposing solutions. That's their business, not mine. If one of their equations goes to infinity, then the equation is wrong since, as we will see, there are no infinities in the empirical world. And this includes the so-called singularity that so many people still think spawned our universe.
Theoretical physicists and mathematicians understandably marvel at the wonders of mathematics and how surprisingly, even “unreasonably,” successful it is when put to practical use. This leads them—with several notable exceptions I will mention—to view their equations and the other mathematical objects in their theories as the actual elements of ultimate reality. They adopt the concept, first proposed by Plato (438–427 BCE), in which our observations are simply shadows or distortions of the true reality that exists in ideal “forms.”
I disagree. The approach I take throughout is that observation is our only source of information about the world. The models we then formulate are attempts to rationalize our observations and put them to practical use. These models may contain mathematical abstractions, but it is a mistake to assume that these abstractions relate in any direct way to whatever may be the elements of an ultimate reality that lies beyond what we detect with our senses and scientific instruments. Of course, for the models to be successful they must have some relation to reality. But we have no way of knowing what that relation may be. Furthermore, they are constantly being replaced by new and better models, so how can they possibly represent absolute reality?
We must make a careful distinction, which unfortunately the majority of scientists do not make, between the objects in their models and the quantities they measure. This includes our most basic notions, such as space, time, mass, and energy. In actual scientific practice, these are all defined operationally, that is, in terms of carefully prescribed, repeatable measuring procedures. And so time is what you read on a clock. Temperature is what you read on a thermometer. All these notions are human contrivances introduced to quantify our observations. An alien species might make different definitions. And neither theirs nor ours are likely to bear a one-to-one correspondence with the elements of reality.
Short of divine revelation, for which no evidence exists, I know of no method by which we can determine what is ultimately real. The best we can do is make ever-improving observations and describe them with ever more accurate models.
Although they are human inventions, the models of physics are not subjective. They are discarded if they do not agree with objective observations. In this regard, physics models are not socially constructed, as the now largely defunct philosophy of social-constructivist postmodernism once tried to tell us.3 I am often misquoted, without any citation, as having said, “There is no connection between models and reality.” Allow me to make it as clear as I can: If a model agrees with the data, then it has something to do with reality. We simply have no way of knowing if the elements of that model correspond to any elements of reality.
Many of the arguments you will hear for the existence of a world beyond the senses, whether from theologians or secular academics, rest on the notion that pure reason, absent of any empirical data, is capable of gaining knowledge of reality. Reason often is associated with deductive logic, but it also includes other methods such as induction.
However, nothing new can be learned by logical deduction that is not already embedded in its original premises. At best, the process provides only a check on whether a statement is consistent with its premises.
As for other forms of “pure thought,” over the centuries not a single verifiable fact has ever been discovered by either pure reason or by mystical experience. This is sufficient to rule it out, along with divine revelation, which has been equally unproductive.
In this book I will be treading on the territories of many experts who know more than I do about the precise terrain. Their domains include history, philosophy, theology, theoretical physics, astronomy, and cosmology. These experts are bound to complain, as experts always do, that the actual facts are more complicated and I have oversimplified their subjects. Of course, no one can be expert in everything. At the same time, I think all of these subjects are simpler, or at least less arcane, than the experts often claim when we just limit ourselves to observational implications. What today's theorists call “deep problems” are usually associated with their own current theories, not with observable facts. Quantum mechanics is the prime example, where we have a theory that has agreed with all observations for almost a century and people still argue over “what it means” without ever coming to a consensus.
Let me say a few words about the technical level of the book. The early chapters should provide no problem for the general reader, but as we get into modern physics and cosmology I will necessarily have to use some technical language that I will try to define as I go along and that can be easily searched on the web. However, the mathematically challenged need not freak out. When I write an equation, it will be no more than shorthand for a statement that can be also put in words. Why write, “Energy equals mass times the speed of light squared” when E = mc2 says the same thing far more compactly? Also, why write “a hundred thousand million million” (as Stephen Hawking was forced to do by his publisher in order to sell more books) when 1017 will do?
While I will not use any higher mathematics, I do present many graphs that are crucial for demonstrating quantitative results. I suspect that anyone picking this book up in the first place will have no trouble understanding these illustrations, nor the meaning of 1017.
Finally, to fend off the often-repeated charge that my ideas and those of other scientists are just as “dogmatic” as those of any religion, allow me to state unequivocally: if in the future convincing empirical evidence shows that any result or conclusion presented here is wrong, I will be perfectly happy to make the necessary corrections.