In Search of a Theory of Everything Page 2
In the meantime, Thales is carefree and zestful, having the matter of water primarily under control, getting up but purposely jumping back in the river again, with novel, childlike, passionate, and playful curiosity. Off from the center of the action, revolving around a Central Fire, carefully preparing his food while singing in a harmonious but almost secretive whisper, is the legendary Pythagoras. Inspired by the moment, he stops the song and begins counting the proportionally spaced ripples of the water from each splash Thales makes. He is a prominent mathematician, able to face squarely all mathematical irrationalities, but he is also a cosmopolitan musician who enjoys master-like attention from orderly and exclusive gatherings of crowds. “Cosmic justice, conserve and save the phenomena,” thirstily shouts the infinitely abstract but also practical Anaximander, the genius of antitheses, feeling the heat of dry air and expecting that it will soon be neutralized by the opposite coolness of wet water.
It is really a beautiful and hot day, but imaginative Anaximenes, leaping over a stepping-stone, finds a creative and concrete way to moderate the heat and thereby cool down. With his lips nearly closed, he blows air out onto his body, noting that it emerges colder than when his mouth was wide open, causing his condensed sweat to rarefy and evaporate. Sitting at a distance, away from the many, boldly being where no one has been before, is the enigmatic Heraclitus, who skeptically observes the process of the constantly changing events, going through conspicuous but also subtle changes. He is quite certain he has previously taken a bath in this river’s fresh waters, but then again, strangely, everything looks new and changed. What is the Logos (cause) of all these eventful processes? To the contrary, judging all of the sense-perceived reality to be deceptive, there is the one and only Parmenides the ontologist, proud and relieved. For journeying during the darkness of night and into the light of day, through the unknown, from afar, he found the true way here by intentionally avoiding the known and opinionated way of all others.
Anaxagoras’s nous (or intellect) finds everything, in everything, to be a puzzle: “How is it that all these people from different eras of time and different places are here?” He wonders by skillfully placing his hands over his head. “Indeed a paradox, a paradox of space and time,” adds the argumentative and prolific Zeno, who, through dialectic (the method of reductio ad absurdum, or reducing to the absurd), is trying to prove that motion is an illusion of the senses, and so no one really moves, despite that all appears to so do. “Are you sure space and time are the only elements in the puzzle?” melancholy Empedocles challenges, while, in the name of episteme and his love for strife, holding tight onto his clepsydra (a water clock), he risks a dangerous experimental leap through the Air and over the flames of Fire but lands safely on Earth, in fact in the Water, just beside me.
“And who might you be, young fellow—the modern physicist?” he asks. As I respectfully nod in awe, I feel all eyes curiously staring at me as if I’d been expected. And immediately the brightness of the day surprisingly turns into a mysterious twilight. “I have been predicting an eclipse at your arrival,” Thales says, while nostalgically shaking off primarily the substance of water from his wet, muddy, ripped, and unfashionable clothes. “We have been longing to know your story,” he adds. Moments later, the bright daylight is pleasantly restored. It is now noon. “It is a beautiful day indeed,” I say humbly, “for I am learning yours. And I will tell you mine, too, but under your sunlight, for eclipses are ephemeral and pass, but your knowledge is timeless. You still bring fire to modern science.” The day is still young, and who knows of the morrow?
Everyone’s senses are keen, observing the changing sights, listening to curious sounds, smelling soul-awakening aromas, tasting the sweet air, touching the cosmic elements. But so is everyone’s intellect contemplating it all. What a beautiful day! What a beautiful nature! What is her nature?1
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1This chapter was inspired by chapter 2 of The God Particle, in which Leon Lederman imagines conversing with Democritus: Leon Lederman and Dick Teresi, The God Particle: If the Universe Is the Answer, What Is the Question? (Boston: Houghton Mifflin, 1993).
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The Quest for a Theory of Everything
Introduction
Thales (ca. 624–ca. 545 bce) was interested in how nature works. He was the first to ask what things are made of and what the properties of matter are. These are still the most fundamental and difficult questions of science. His answers were based on solely rational arguments, uncluttered by myths, superstition, rituals, or the actions of capricious gods. His approach was therefore the same as that of modern science.
He reasoned that in spite of the apparent diversity and complexity in nature, all things are made from the same stuff (water), and all things obey a common set of unchanging basic principles (water’s transformations, e.g., its solidification, liquefaction, and evaporation). Thus, for Thales, nature is characterized by a certain sameness or unity between all things, however diverse they may be, an overall intrinsic simplicity.1 Thales’s quest for sameness is modern physics’ search for a unified theory of everything. It tries to unify the four fundamental forces of nature—the electromagnetic, the nuclear strong, the nuclear weak, and gravity—and discover the one primary substance of matter from which everything is derived. A major challenge of this undertaking is to find a quantum version of gravity, a most difficult task.
What Are Things Made of?
We still don’t know what things are made of. Nonetheless, presently, according to the standard model of physics (introduced later in this chapter), things are not made from water but from microscopic particles called quarks (constituents of protons and neutrons) and leptons (particles including electrons). And the plethora of diverse things is partly due to their transformations (from one type of particle into another), not to the transformations of water.
Hence, both Thales and the modern physicist are wrong but right, too. They are wrong because neither water nor quarks and leptons are the primary substance of matter—what is, we are still in search of. But they are also right because all things in nature, evidence suggests, share a subtle underlying common law and are made from the transformations of one and the same substance, regardless of how different everything seems. His idea about the transformations of matter, in particular, not only describes a fundamental property of the modern concept of energy (or matter, since, as Einstein’s special relativity theory makes clear, they are equivalent and transmutable into each other), namely its ability to transform into various forms and cause change, but also employs causality (a relation between cause and effect), because for him the cause of all other things is the transformation of just one primary substance. But why was water the underlying principle/cause of such sameness and unity?
Why Water?
Several observations might have stimulated Thales in his speculation that all things are transient forms of water. Some ancient accounts such as Aristotle’s2 and Aëtius’s3 give us some insight. Water is required for the survival and development of all kinds of life. Primitive life exists in moist environments, and animal sperm is liquid. Also, since water transforms easily into the three forms of matter, the solid (as ice), the liquid, and the gaseous (as water vapor), and into a variety of shapes, it could, Thales might have thought, also transform into everything else, such as rocks or metals. Now, while all substances transform into the three states of matter (e.g., given enough heat, a solid piece of metal can melt and evaporate), water is the only substance of daily experience that does this before our eyes and on a regular basis through the changing seasons, something that observant Thales could not have missed. Furthermore, it transforms more easily: its evaporation temperature of about 100 degrees Celsius (at sea level) is smaller than that of, say, copper, bronze, or iron—materials that in antiquity were heated and melted to make tools—so one does not need a lot of heat to vaporize it; and in the cold winter, water is the only substance to turn to snowflakes and solid ice of all sorts of shapes. So its
choice as a primary substance over other things appears logical. Thales might have reinforced his water hypothesis, I speculate, from another everyday observation, namely, that when heated or burned, all things release (or so it seems, anyway) water vapor. One example that might have been an inspiring clue for his water doctrine might be observing the rising smoke from a burning piece of wood mixing with air and clouds, which in turn can be mixed with rain or snow and blend with the soil on earth. At first glance, smoke, air, and clouds, are like (or seem to be) water vapor; rain and snow are water, and soil contains the water and snow of the rain or snowstorm. Therefore, soil might be thought of as transformed water, and so might then be the plants (thus wood), since, starting as seeds, plants grow from the soil and “are nourished and bear fruit from moisture,”4 and so might also be the animals, since they eat plants or each other.
Since processes of this sort appear causal with water as the first cause, then it seemed logical to assume that everything is made from the same stuff—reconstructed from the same first principle—and that, in general, everything in nature is characterized by a certain subtle sameness.
The Quest for Sameness
Sameness is a core concept in modern physics, not only because it emphasizes a universal, underlying, simple principle as a characteristic of all things in nature, but also because it points to a commonality in their ultimate origin. Unity (in the sense that everything can be derived from one and the same principle), Thales reasoned, is a subtle, intrinsic property of nature.5 This idea inspired all natural philosophers (each creating his own special theory on unity, as we’ll see in subsequent chapters), and, in turn, they have inspired scientists of recent times in their own searches for a theory of everything.
A Brief History of Recent Times
James Clerk Maxwell (1831–1879) unified successfully the electric and magnetic forces by proving mathematically that they are really two manifestations of the same force, the electromagnetic. The electric force is caused by the electric charge: the positive and negative. Objects of opposite electric charge attract one another while objects of the same type of charge repel. The magnetic force is caused by an electric charge in motion. A permanent magnet has two poles, the north and the south. Opposite magnetic poles attract, and similar magnetic poles repel. He also unified electromagnetism with light. An electron oscillating up and down produces an electromagnetic wave, light, just as a floating cork oscillating in and out of water produces a water wave.
Albert Einstein (1879–1955) from 1925 until 1955 attempted unsuccessfully to unify the electromagnetic force with gravity. Gravity is still the most puzzling of the forces, although it was the first force to be described mathematically, with the law of universal gravitation of Isaac Newton (1642–1726), and advanced significantly through Einstein’s theory of general relativity.
Nonetheless, success struck another physics front with the combined efforts of Sheldon Glashow (1932–), Steven Weinberg (1933–), and Abdus Salam (1926–1996). In the 1960s, the three physicists managed the unification of the electromagnetic force with the nuclear weak force in what is known as the electroweak force.6 The nuclear weak force is responsible for the radioactive decay of unstable nuclei such as that of uranium, and the transformation from one type of material particle into another—Thales’s notion on the transformation of matter is a significant process in modern science. The experimentally confirmed unification of the electromagnetic force with the weak force occurs at high energies and temperatures—where the two forces have the same strength and are indistinguishable; thus, they are considered as one force. However, at lower energies/temperatures (generally those of everyday experiences), these two forces are two expressions of the same force: the electroweak.
The standard model of physics is the theory that combines the knowledge of the electroweak force and the nuclear strong force—which binds the quarks in the protons and neutrons and also the protons and neutrons in the nucleus of an atom. It is the best model so far because it combines successfully several theories to explain how particles interact and how the universe works. Quarks and leptons are among several experimentally confirmed predictions of the standard model. In fact, even more important with respect to Thales’s view, according to the standard model, the materialness of quarks and leptons—in particular the source of their mass—is one and the same type of particle, the famous Higgs boson. It was discovered in 2012 at the Large Hadron Collider, the most powerful atom smasher in the world. Although successful, the standard model has a few major challenges: it doesn’t include gravity and can’t explain dark matter, dark energy, and why there is more matter than antimatter in the observable universe—topics to be discussed later.
Through a grand unified theory (GUT) physicists hope to extend the standard model by creating an experimentally verifiable theory in which the electroweak force and the nuclear strong force are unified. Several good candidates for a GUT do exist, making concrete testable predictions (such as the decay of a proton, not yet observed), though none has so far been experimentally verified. It is hypothesized that these forces were indistinguishable only for a miniscule moment, 10–35 seconds after the big bang, when the universe was superhot. According to the big bang cosmological model, about 13.8 billion years ago the entire universe was unimaginably small, possibly a mere point, infinitely dense and hot. It then exploded in the absolutely most extraordinary event called the big bang and has ever since been expanding, cooling, rarefying, and creating the eventful universe we live in. The idea of the big bang originated with Georges Lemaître (1894–1966), a Belgian priest trained in physics who used Einstein’s relativity to predict it.
Finally, a community of ambitious physicists is currently on the quest for the ultimate principle of sameness, that is, for the absolute unification of all four aforementioned fundamental forces of nature in what is termed the theory of everything (TOE). A TOE hopes to establish that everything in nature is explainable by a single overarching timeless principle and its associated equation, that everything is truly a consequence of just one primary substance, as Thales initially envisioned, and one force—why four forces? Oneness, it appears, has been evolving to be a simpler, more preferred philosophy, for both our science and our religion (i.e., monotheism).
The Challenge for a Theory of Everything
Through a TOE we hope to reduce all of nature into one fundamental force and one fundamental substance with its transformations, an utter simplicity and sameness of Thalesian grandness. The paramount challenge in finding a TOE is rooted in our inability so far to find a quantum version of gravity, commonly called “quantum gravity.” That is, to combine the rules of quantum theory (also known as quantum mechanics or physics, and which includes the standard model) with the rules of Einstein’s theory of general relativity—or find new rules completely. Since nature is one and beautiful, one and beautiful should also be the theory that would explain Her. But the two theories we have for Her are mutually exclusive, a very displeasing situation in science. Probability reigns in quantum mechanics, determinism in relativity. Nature is granular in the first theory, smooth in the second. Space is a “mute” immutable container in quantum (and Newtonian) physics for things to just be in, but a dynamic malleable fabric in relativity that “tells matter how to move.”7 A cosmic clock tells the same exact time for everyone everywhere, objects have a fixed size, and time travel is impossible in the former theory; but in the latter theory, time is relative (it slows down or speeds up depending on how you move or where you are), moving objects contract, and you can travel into the future. Quantum theory describes successfully the world of the tiny, of atoms, electrons, protons, neutrons, quarks, and so on. Relativity describes successfully the world of the large, of planets, stars, galaxies, and generally the large-scale universe by explaining how space, time, matter, and energy are all inextricably intertwined and how gravity works. (Aspects of both of these theories will be discussed in later chapters.) Quantum theory and general relativity are sig
nificant improvements over Newton’s and Maxwell’s physics. Nevertheless, as special cases of the former two, the latter two are still abundantly practical.
String Theory
A possible TOE is string theory. It is highly speculative and without yet any experimental support for its claims. It seeks to describe nature in terms of vibrating strings of energy in eleven dimensions. According to string theory and in agreement with the essence of Thales’s idea, everything is made from the same stuff: absolutely identical strings, theorized to be the primary substance of the universe. These strings, like violin strings, have different modes of vibrations that are speculated to manifest as different types of particles, which include the quarks and leptons.8 Now, we are aware of the three dimensions of space (think of them as three edges of a cube meeting at a vertex) and the one of time—thus with respect to what we can readily experience, we live in a four-dimensional universe. The other spatial dimensions predicted by string theory are hypothesized to be curled up into unimaginably small, ball-like geometrical shapes of size 10–35 meters, known as Planck length, as big as the vibrating strings themselves, and thus not easily detectable.
Loop Quantum Gravity
Like string theory, loop quantum gravity is a theory of quantum gravity—it attempts to combine the rules of quantum physics with those of relativity. Although loop quantum gravity is not a TOE (for it doesn’t try to unify the four forces as string theory does), its findings might still help to find one. But like string theory, loop quantum gravity too is very speculative without experimental backing. Loop quantum gravity seeks to describe nature by radically reimagining space.9 Space is not composed of points—it’s not infinitely divisible into ever-smaller regions. Space is composed of magnitudes: indivisible, interlinked, finite space expanses—“atoms” of space—shaping like loops, or rings, roughly of Planck length. The word atom means “indivisible” in Greek, implying that there is a smallest “cut” of something; thus, that cut cannot be divided further. The notion of an atom is of central importance to all of science. Atoms of matter have first been hypothesized by Leucippus and his student Democritus (chapter 12). And atoms of space and of time have been the innovation of Epicurus (chapter 13), a student of their atomic school of thought. Atoms of matter have of course been experimentally verified, but not the atoms of space and time.