It is impossible for anyone to dispel his fear over the most important matters, if he does not know what is the nature of the universe but instead suspects something that happens in myth. Therefore, it is impossible to obtain unmitigated pleasure without natural science.
—Epicurus
Today every schoolchild knows that the world is made of atoms. They have been taught that even a solid rock is mostly empty space with tiny particles flitting about, occasionally colliding with one another or sticking together to form more organized masses. Some adults may also remember this from school.
Since the atomic theory of matter was not fully confirmed until the twentieth century, it is commonly thought that atoms are a recent discovery of modern physics and chemistry. However, the idea that everything is composed of infinitesimal, indivisible particles appeared in Greece 2,500 years ago and at about the same time in India.
According to Aristotle (384–322 BCE), who disputed atomism, Leucippus of Miletus (ca. fifth century BCE) invented the atomic theory of matter. However, none of Leucippus's writing has survived, and his collaborator Democritus (ca. 460–ca. 370 BCE) is credited with elaborating the theory. In the third century before the Common Era, philosopher Epicurus (341–270 CE) built a whole philosophy of life on the edifice of atomism.
Epicurus wrote extensively, but it was believed only a small portion of his works had survived until a major work was recently discovered in the ruins of Herculaneum, which was destroyed by the eruption of Mount Vesuvius that also destroyed Pompeii. Unfortunately, this newly found work has not yet been translated to English. We would know little of Epicurean philosophy were it not for a magnificent 7,400-word poem in Latin hexameter called De rerum natura (The Nature of Things) written during the time of Julius Caesar by a Roman citizen named Titus Lucretius Carus (ca. 99–ca. 55 BCE).
The atomists proposed that not only is the stuff we see around us in the world made of atoms, but so is the soul or mind, which is therefore mortal and so dies with the rest of the body. There is no life after death. The gods exist, but their nature and role are unclear. They did not create the universe, which always existed and is unlimited in extent and contains multiple worlds. Nor did the gods create life. Rather, nature generated all kinds of “freaks” out of which only those adapted to the environment survived. Sounds a bit like natural selection, doesn't it?
In contrast to the Greeks, atomists in India regarded the soul itself as a separate, eternal atom. So Indian atomism was still dualistic while Greek atomism was monistic and atheistic at its core.
No one until the twentieth century had direct empirical evidence for atoms as particulate bodies. No one knows exactly how the original atomists arrived at their intuition. But observation must have played a role. No fact about the world has ever been discovered by pure thought alone. What was for millennia nevertheless a remarkable feat of human perception became the primary picture we have today of the nature of matter and the universe. But, from the beginning, the notion that everything is simply atoms and the void, with no divine creation or purpose, was in massive conflict with conventional thinking. Today this heresy is still vigorously opposed by some influential intellectual and religious elements in society. It is not that these opponents deny the overwhelming evidence for atoms. They simply reject the notion that they are all there is. This book will make the case that atoms and the void indeed are all there is.
Aristotle was opposed to atomism because, among other reasons, he believed that empty space was impossible. Aristotle's mentor, Plato, viewed matter as an illusion. Plato had an atomic idea of his own, where the elementary objects of reality are idealized, immaterial geometrical forms. Still, the polytheism of the ancient world was pretty flexible and tolerant of most beliefs. As long as the atomists paid lip service to gods of some sort, they could avoid serious trouble. It is only with monotheism that we began to see the forceful elimination of even the slightest deviations from the official state religious dogma.
Most authors who write on the subject insist that the ancient atomists were not atheists because they still believed in gods. Yes, they said they believed, but that was probably to avoid having to drink hemlock. The atomist gods play no role in the universe or in human lives, unlike theism as we understand it today. Atomism is atheism.
Atomism is also not deism. Unlike theism, deism is the belief in a creator god who does not involve itself with the universe or human lives. The universe of the atomists is eternal and uncreated. As we will see, the atomism of 2,500 years ago was essentially, in principle if not in detail, the model of the universe that modern science brings to us today.
The most influential philosophers of ancient Greece—Plato, Aristotle, and the Stoics—rejected material atomism. It conflicted too much with their ingrained beliefs in the world of gods and myths that had been passed down through the ages. With the rise of Christianity, which embraced Plato and Aristotle philosophically if not theologically, the works of Epicurus and Lucretius were suppressed during the thousand-year period from roughly the fifth to the fifteenth centuries. Through these years, known as the Dark Ages, the Roman Catholic Church dominated western Europe. It was only by sheer luck that a copy of De rerum natura survived to be rediscovered in a German monastery in 1417 CE. After another copy was taken to Florence where more copies were made, it became a sensation that played an important role in the nascent Renaissance and the scientific revolution that was soon to follow.
Although atoms would not be directly observed until the twentieth century, most physicists, including Galileo Galilei (1564–1642), adopted the atomic theory as the basic model for the primary structure of matter. While there was little speculation about the actual nature of atoms for lack of empirical data, the notion that point-like corpuscles move through space, colliding with one another and sticking together to form structures, was given a theoretical foundation by Isaac Newton (1642–1727) and those who followed. With Newtonian physics based on atomism, or at least on particle mechanics, the scientific revolution exploded on the world.
Not that there weren't doubters. Even by the late nineteenth century, after the atomic theory had proved enormously successful in explaining many observed phenomena involving gases and other fluids, the philosopher and physicist Ernst Mach (1836–1916) was prominent among many who refused to accept the reality of atoms. Mach held to the philosophy called positivism, in which only observable entities should be treated as real. Perhaps he would have changed his mind about atoms had he lived in the late twentieth century when he would have witnessed them as imaged on the screen of a device called the scanning tunneling microscope. Today we include many directly unobservable objects, such as quarks and black holes, in our theories.
Besides, as we will see, deciding on what is real and what is not real is no easy task. My basic position as an experimental physicist is that all we know about is what we observe with our senses and instruments. We describe these with models, sometimes called theories, but we haven't the faintest idea what is “really” out there. But, does it matter? All we need to concern ourselves with is what we observe. If whatever is really out there produces no observable effect, then why should we worry about it?
When the Reformation and Renaissance undermined Roman Church authority, new avenues of thought were opened up and science came into its own. Atomism—as a useful model—became an important part of the scientific revolution and eventually both Catholic and Protestant churchmen no longer saw it as the atheist threat it once surely was when articulated by Epicurus and Lucretius. Their theology was simply ignored by churchmen. After all, the ancients did not know Christ.
This book chronicles the empirical confirmation of atomism, from Leucippus and Democritus to Peter Higgs (and others), which reached its current form in the field where I spent my forty-year research career—that is, elementary particle physics. I will argue that the reduction of all we observe to the interaction of tiny bits of matter moving about mostly randomly in empty space is irreconcilable with the common belief that there must be something more to the universe we live in, that human thoughts and emotions cannot be simply the result of particles bouncing around. We will see how attempts to uncover evidence for immaterial ingredients or holistic forces in nature that cannot be reduced to the interactions of elementary particles have been a complete failure.
Before we begin our story, a few clarifications are needed. The term atom arises from the Greek word for uncuttable. The original notion of the ancient atomists was that the ultimate particles that make up matter cannot be further divided into more elementary parts. Today, based on history, we take a more cautionary, empirical approach and simply call the elementary particles of matter in our models “conceptually indivisible.” So, for example, in the current so-called standard model of elementary particles and forces, electrons and quarks are uncuttable; but we can never say for sure they will always remain that way as science advances.
In the nineteenth century, the elements of the chemical periodic table seemed to be uncuttable and, indeed, are still called “atoms.” Chemists were unable to subdivide the elements simply because the energies involved in chemical reactions, produced by Bunsen burners and electric sparks, are too low. Once much higher energies became available with nuclear radiation and particle accelerators, it was discovered that the chemical elements were not elementary after all but that each element is composed of a tiny nucleus surrounded by a cloud of electrons.
It did not end there. Nuclei were found to be composed of protons and neutrons and these, in turn, were discovered to be made of more elementary particles we identify as quarks. At this writing, the set of elementary particles in the standard model includes quarks, electrons, and other particles such as neutrinos and photons for which no substructures have yet been identified in experiments. This model has been in existence since the 1970s, agreeing with all observations, and only now are experiments reaching sufficiently high energy where further substructure might be revealed. This book is being written just as the final gap in the standard model, the Higgs boson, seems to have been filled at the Large Hadron Collider (LHC) in Geneva, Switzerland. No one is stopping there. More data from the collider will surely, even necessarily, point us in the direction of new physics beyond the standard model.
It is felt by most physicists that ultimately we will have to reach the point where the ultimate uncuttable constituents of matter will be established. I will generally call them elementary particles rather than “atoms” and, to further avoid confusion, the structures that constitute the chemical elements will be referred to as chemical atoms, unless the distinction is clear from context.
The ancient atomists introduced the notion that atoms move around in otherwise empty space—a vacuum or a void. As mentioned, Aristotle attempted to prove that such a void was impossible, but when Evangelista Torricelli (1608–1647) and other seventeenth-century scientists began producing vacuums in the laboratory, Aristotle's views fell out of favor. Of course, these laboratory vacuums, then and now, are hardly empty space. But at least the notion was established that a chamber empty of particles is conceivable.
Today we often hear it said that, according to quantum mechanics, we can never have completely empty space, as particle-antiparticle pairs flit in and out of existence. While this is true, at any given instant a volume will contain these particle pairs with empty space in between. The basic atomic model remains part of quantum physics. The matter we observe on all scales is mostly empty space with tiny particles mostly randomly moving about constituting the visible universe and perhaps its invisible parts as well.
Yet another clarification is needed because of the use of “particles” in the preceding paragraphs. It remains possible that in some future, successful theory, the ultimate constituents or atoms of matter may not be treated as point-like (zero-dimensional) particles but strings (one-dimensional) or multidimensional “branes” (from “membranes”). Even if these models ultimately succeed (they haven't so far), the elementary structures will be so small that they will remain particulate in the eyes and instruments of experimenters for the foreseeable future. For my purposes, I have no need to bring in these speculations and will stick to what is already well established.
Some confusion may also arise when we discuss the issue of reductionism. I will claim that the atomic model exemplifies the notion that we can reduce everything to its parts. Despite desperate opposition from those wedded to holistic philosophies, reductionism has triumphed.
However, you might wonder, if an atom were “uncuttable,” then that would seem to mean that it is irreducible. If that is the case, then how can atomism be reducible?
The reducibility of the atomic model refers to the fact that the observations we make about matter, such as the wetness of water or the color of copper, and perhaps even human intelligence, can be reduced to the motions and interactions of elementary particles that themselves do not possess such properties. The anti-reductionists have always objected that this is impossible. We will give examples showing that it does indeed happen. And, as I said, nothing is stopping us from considering the current elementary particles as ultimately reducible to even smaller parts. This is physics, not philosophy. What matters is data, not words.
Finally, we will find that the expedient of describing an observed phenomenon in terms of the behavior of constituent particles of the material bodies involved not only greatly simplifies the understanding of these phenomena but also removes much of the mystery that confounds much of modern life in the physical world.
A note to the reader: This book starts out mostly historical and philosophical, but as it progresses chronologically, it becomes increasingly scientific. Some of the latter material is somewhat technical with a few equations at the level of high-school algebra, but it still should be accessible to nonscientists who have at least some familiarity with the subjects from reading popular books and articles. I feel that a minimum amount of technical detail is necessary to establish the validity of my thesis, that modern science has fully confirmed the model of the world first proposed 2,500 years ago.