The Rules of the Game: The New Rulebook
The comfortable, comprehensible, machine-like physical reality that was the received consensus of educated opinion in the 18th century rested on foundations that were not as secure as was believed. As discoveries about the nature of electricity accelerated, new ideas about the physical world began to emerge. And the advances of 19th century mathematics proved that there existed possible worlds that challenged our notions of “common sense”.
What follows is my unsophisticated, history major’s attempt to summarize the broad outlines of the discoveries of the modern physical sciences, and how these discoveries have utterly transformed our conceptions of physical reality. I do not pretend that I have any real grasp of the rather advanced mathematics that explain these phenomena in depth.
But to reiterate, I am convinced that any consideration of the emergence and nature of human history must incorporate this knowledge. I also believe, as do so many others, that the barrier between the natural sciences and the humanities must be removed, even though many of us who were trained in the humanities have long regarded the realm of the natural sciences as a strange and disquieting place. Such disquiet must now be set aside. We must attempt to acquire at least a general understanding of the forces which have brought us into being, even if we cannot grasp their mathematically-expressed quintessence.
Symmetry and Asymmetry
Symmetry can mean several different things. On the visible level an object is symmetrical, as Richard Feynman explains, when it can undergo some kind of change and retain its exact appearance. Feynman points out that spheres, among the most common of all objects in the Universe, are excellent examples of this kind of symmetry. No matter which way they are rotated, for example, they retain their basic appearance1. Nature seems to be filled with symmetrical objects and there appear to be many processes in the macroscopic world in which symmetries are preserved. This means that the function and appearance of certain objects are not altered by changes of location, changes of position, or progression through time.
On a deeper level, symmetries appear to govern the operations of the basic physical laws, and they appear to govern the smallest events, actions at the quantum level. (See below.) This is to say that the physical laws are consistent. In any conditions, the actions of the basic laws will always manifest themselves in the same manner, in other words, exhibit invariance. An object’s gravitational force, for example, will always be a function of the mass of the object and the inverse square of the distance between it and other objects. (Or put another way, an object will always curve space-time in a predictable manner.) No variance to this has ever been found.
As physicist Brian Greene has said, the symmetrical nature of the natural laws has been confirmed by every experiment scientists have ever run, and from our observations of space-time, no matter how far we look (which is, of course, looking back in time as well) the laws appear to apply. He concludes, “the symmetries of nature are not merely consequences of nature’s laws. From our modern perspective, symmetries are the foundation from which laws spring.” 2
Of course, if the fundamental nature of reality had permitted no changes or imbalances whatsoever to occur—had there been no asymmetries—nothing physical at all would exist. Physicist Frank Close points out that if, for example, there had been a perfect balance between matter and antimatter in the primordial Universe, both forms would have instantly annihilated each other and that would have been that. The Universe would have ceased to be immediately after it had come into being. Close explains that asymmetry—a lack of perfect balance, something found throughout the physical world—is what allows any number of vital phenomena to occur. Among these phenomena are the imbalance between two of the fundamental forces at work in the Sun, which has allowed the Sun to burn for billions rather than a mere few hundred thousands of years, and the structure of atomic elements, which Close describes as “lopsided”. As he puts it,
It is the journeying of the little electrons, the carriers of electrical charge, that determine everything we experience. The individual atom consists of these negatively charged electrons swarming around a static, bulky, positively charged nucleus. All but one of the two thousand parts of the mass of an atom reside in this central nucleus, while the tiny electrons flow from one atom to another…It is these negative charges that communicate and drive the biochemical processes in living things while the positives, too heavy to be easily stirred, tend to stay at home and form the templates of solidity. This asymmetry in mass is crucial for the structure of materials. 3
So the basic physical laws of nature are symmetrical, in that they are seemingly invariant throughout the known Universe, and yet the asymmetries in the structures and processes that emerge from or are embodied by them make possible the evolution of all things in the physical realm.
The Four Fundamental Forces
Mindful of the principles of symmetry, and the presence of asymmetry, scientists have traced the ultimate basis of physical reality to four forces that, between them, govern the operation of every single thing that exists in the physical Universe. In essence, a force is best understood by what it does rather than what it is. The word force seems to represent a reality that is so basic that it cannot be defined any more specifically. The fundamental forces of nature are the way things in the Universe interact with each other. Put another way, forces cause things to occur. The four of them that exist according to the human frame of reference are: gravity, the strong nuclear force, electromagnetism, and the weak force. This means that only four irreducibly basic things occur: physical bodies all over the Universe exert an influence on each other, the smallest building blocks of matter are held firmly in place so that other structures might be made, charged particles attract or repel each other, and the smallest building blocks of energy-matter can be converted from one form to another. Obviously, these are great oversimplifications, but they will serve for now. Everything we know of and experience is derived from these four varieties of fundamental event.
There are, by the way, many scientists who now speak of only 3 fundamental forces, pointing out that the weak nuclear force has been theoretically connected to electromagnetism, yielding a force they call electroweak which manifests itself at very high energies. But for the sake of clarity, we will stick to the four forces scheme, the one that is most widely used to explain the forces to non-specialists (like me).
In the first moments after the Big Bang which brought about the physical Universe (or at least its current manifestation) these forces began to peel off from the state of absolute unity that had existed for a fleeting instant. Paul Halpern gives us a good way to think about this:
The four forces certainly make odd brothers. Yet most physicists firmly believe that they share common parentage. At the time of their birth, in the fiery first instants of the universe, they all looked the same. Each force had the same range, strength, and ability to interact with particles. Somehow, though, in the changing environment that marked the passage of time, each force went its separate way and acquired its own characteristics. As the universe cooled, these distinct properties froze into place, like the varied shapes of ice crystals forming on a frigid window. 4
We do not yet know why this unity was broken, or even if the word “why” has any relevance in this case. But it was the splitting of the primordial unity that made possible the construction of physical reality.
The first of the four forces to diverge from the unified force that existed in the first instants after the Big Bang was, in the view of scientists, gravity. Gravity apparently emerged at 10-43 seconds after the initial events of the Universe’s history. Gravity is (usually) extraordinarily weak, but it is apparently infinite in range, and it pervades the Universe. Gravity is now understood to be a phenomenon associated with the warping of space by objects possessing mass, and the greater the mass, the greater the warping. Black holes are caused by objects of such incredible mass that gravitational fields of tremendous strength are created, ones which allow no light to escape from the objects at all. Less strong gravitational fields can still bend (but not contain) light, an effect called gravitational lensing. Objects generating gravitational fields exert influence on each other in proportion to the inverse square of their distance from each other. Gravitational effects are transmitted via a hypothesized particle called a graviton, but this particle has yet to be discovered. Gravity is what makes possible the very largest structures and systems we see. Galaxy clusters, galaxies themselves, and solar systems, among other phenomena, are constructed and held in place by it.
The Strong Force, or the Strong Nuclear Force
The strong force binds quarks, among the tiniest and most fundamental of all matter particles, together to form protons and neutrons, and binds protons and neutrons to each other, which in turn keeps atomic nuclei together. Although it is the strongest of the four forces, its range is extremely short—the diameter of a nucleus, a very small distance indeed. Currently, the strong force is thought to have broken from the initial unification at around 10-36 seconds after the Big Bang. Its force is carried by a particle called a gluon. By binding nuclei together, the strong nuclear force plays a major role in making the building of structures possible.
The Electromagnetic Force
The electromagnetic force is thought to have separated from force unity at about 10-12 seconds after the Big Bang, about the same time as the weak nuclear force with which it is now closely linked. Like gravity, its range is infinite and it obeys the inverse square law of effect. Its particle is the photon. Electromagnetism controls atoms and binds them together to create molecules. It is the force underlying visible light and all other electromagnetic phenomena, such as x-rays, radio waves, and gamma rays, among others. In a vacuum, electromagnetic rays and waves are the fastest things that exist. There are numerous electromagnetic fields in which humans are immersed (and a part of). The electromagnetic force is what made the emergence of chemistry possible, and it is the largest factor underlying chemical structures and reactions. Thus it is implicated in virtually every phenomenon and object that humans ordinarily encounter.
The Weak Force, or the Weak Nuclear Force
The weak force, which split off from unity at about the same moment as electromagnetism, operates at extremely short ranges, the shortest of any of the fundamental forces. It is conveyed through particles called W and Z bosons, with the W particles coming in two variations. Despite its name, it is actually much stronger than gravity, but gravity’s range is vastly greater. The weak force effects changes on quarks, altering their basic traits. The weak force underlies all radioactive decay. (The word “decay” should really be read as “transformation of elements”.) The weak force is utterly essential to the functioning of the Sun because it makes possible the fusion that produces the energy that washes over our Solar System. (Interestingly, if the weak force were much stronger, the Sun would have burned all its fuel in a relatively short time, which would have precluded the possibility of life forming and evolving on our planet.) The weak force allows stars to generate heat and light. The weak force’s role in solar fusion makes life on this planet possible.
When a particular region of space-time is controlled by a given fundamental force, we say that the force has established a field. Physicists tend to see physical reality, therefore, in terms of fields and their characteristics. The Universe, in one perspective, is an aggregation of fields, with electromagnetic and gravitational fields dominating the largest stretches of space-time.
So, how have the four forces acted to construct the physical Universe of which we are an intrinsic part and which we perceive in our uniquely human way? We will start with the world of the overwhelmingly huge and incomprehensibly fast, and then shift our view radically and examine the smallest phenomena known. In doing so, we will find that while the new way of examining the biggest and fastest things was the culmination of many centuries of research, the opening up of the world of the ultra-small challenged all traditional ways of defining reality.
For all of its startling impact and mind-challenging difficulty, relativity represents, in one respect, the culmination of classical physics. There was nothing in the original relativity theories that was inconsistent with the physical laws that had been discovered by physicists in the previous three centuries. It is revolutionary because Albert Einstein and those who worked with him, such as Arthur Eddington, pushed the boundaries of classical physics to their logical limits. It was not an overthrow of the Newtonian worldview. It was, rather, a modification of it, a correction of it. Relativity theory presupposes that there is a reality that humans can comprehend. To the end of his life, Albert Einstein considered himself a realist above all.
Relativity theory, as elucidated by Einstein, seems to have little relevance to the everyday life of humans. The world in which humans live still seems adequately represented by Newton’s equations (which in part were made possible, as we have seen, by the earlier work of many others) and the mechanistic, Euclidean, clockwork Universe they postulate. It is when humans stand back from the ordinary, applying relativistic ideas to the larger Universe, that a deeper, more mysterious, less comprehensible picture of physical reality emerges.
Einstein drew on the work of such figures as mathematicians Karl Friedrich Gauss (who worked on the possibility of non-Euclidean geometry) and Bernhard Riemann (who studied the geometry of curved space and the possibility of higher dimensions). He also drew on the work of physicist Hendrik Lorentz (who devised a way of calculating differences in perceived motion between different systems and explored changes that happen to a body in motion) and James Clerk Maxwell’s electromagnetic principles, among others. He added to their work his own profoundly insightful ideas, and explained them by means of his imaginative thought experiments. In doing so he created a new synthesis of classical ideas which altered the human perception of possibility.
Einstein was keen to explain his ideas to non-specialists, and to that end he published a popular work called Relativity: The Special and General Theory in 1916, which eventually went through many editions. In this work Einstein did his best to make the broad outlines of his ideas clear to educated laypeople. (It must be said that the mathematics in it is challenging, and my understanding of it is severely limited.) But in a mere 115 pages, Einstein was declaring that the traditional ways of measuring and thinking about the Universe were no longer adequate. His ideas were so radically new, and so removed from ordinary experience that when they are summarized, they seem vaguely disquieting to many, as if they were violations of “common sense”. But they describe a reality that although usually hidden has been verified by countless observations and experiments. Among Einstein’s key findings:
- The principle of addition of velocities does not apply to the speed of light. The speed of light in a vacuum does not vary.5 (This precept supersedes classical mechanical conceptions in which velocities must be added when two objects approach each other.)
- There is no such thing as universal simultaneity; the perception of an event’s occurrence in time is dependent on the motion of the observer.6
- The measurement of distance is dependent on the motion of the observer relative to another object.7
- The differences in the measurement of space-time events from one frame of reference to another can be explained mathematically (the Lorentz Transformation)8. If two different systems are moving at fixed rates in relationship to each other, the differences in the measurement of space-time events noted in each system will remain consistent and predictable. These principles are only observable or noticeable when relatively high velocities are involved.
- Clocks slow and objects contract in proportion to the percentage of the speed of light at which they are traveling.9
- The energy required to move an object possessing mass rises as the object moves toward the speed of light. An infinite amount of energy would be required to move it at the speed of light.10
- Space and time are essentially indistinguishable from each other; the world is a four-dimensional space-time continuum.11
- All motion is relative motion; there is no universal frame of reference by which all motion is measured.12
- Bodies in space do not directly draw other objects to them. Rather, bodies in space create gravitational fields which draw objects toward them. In other words, the Earth does not pull objects toward it; it creates a gravitational field that affects the objects that come under its influence. Bodies that come under the sway of a gravitational field will fall (in a vacuum) at exactly the same rate regardless of what they are made of.13
- Rays of light can be bent by gravitational fields.14
- In any gravitational field a clock’s rate of movement will depend on its resting position within it.15
- The Universe is not best described by means of Cartesian coordinates and Euclidean geometry. It is, rather, much better described by coordinates that describe a space-time continuum shaped by gravitational fields, and the geometry of curves.16
- Various entities in the Universe experience different passages of time and different perceptions of motion. All of these perceptions are valid; there is no fixed standard that exists.17
- The system of gravitation established by relativity theory is more accurate than Newton’s, and it therefore must replace the older system.18
- It is possible that the Universe is both finite and yet unbounded, just as the surface of a sphere is. The Universe, in fact, may be roughly spherical and it is that way because the density of matter in it bends space-time itself into such a shape.19
This was nothing less than a revolution in our understanding of the world. Many of us are familiar with the often colorful examples that have been used to clarify these propositions, but we may not have fully accepted the truth of them (in the human frame of reference). But it really would be true that a space voyager traveling near the speed of light would age markedly more slowly than those he or she left behind. It really is true that there is no such thing as a commonly agreed upon right now in the Universal sense. It really is true that gravitational fields have bent and warped the very fabric of space-time itself, and that time and space are simply different aspects of the same phenomenon. Gravity really can be strong enough to bend light itself, or even completely prevent it from emanating from a body in space. And the Universe itself indeed seems to be finite, albeit enormous in size. Einstein proved that energy and matter are interchangeable entities, and established the formula E=mc2 (although not explicitly mentioned in this text) that explains the amount of energy that can be derived from a given mass. (This formula opened many doors, some of them exceedingly dangerous to human survival, much to Einstein’s concern.)
Brian Greene gives us an excellent way to picture the inextricable bond between space and time which Einstein showed us. He reminds us of the following principle:
[T]he combined speed of any object’s motion through space and its motion through time is always precisely equal to the speed of light.
He then asks us to think about a car traveling northward, representing our progress through time. If we accelerate our motion, it’s as if we have started veering toward the northeast, away from due north. We begin to deduct from our movement through time, in other words, and add to our movement through space. If we accelerate to the speed light, it is as if we are now moving due east. We are no longer heading north—through time— at all. Since the combination of our motion through time and our motion through space can never be greater than light speed, time now stands still for us. (In truth, since our bodies have mass, it is impossible for us to be accelerated to the speed of light, since it would take an infinite amount of energy to do so. The best we can do is to be accelerated to near the speed of light.) This has been demonstrated empirically by pains-taking experimentation. As Greene says, “This is not dexterous wordplay, sleight of hand, or psychological illusion. This is how the universe works.”20
The examination of the very large and the very fast has had a major impact on our understanding of the Universe as it exists on the grandest possible scale. But there is another Universe, a microworld, which is even more fundamental to our understanding of what we are as physical entities, and our understanding of the other entities with which our lives are intertwined.
The Building Blocks of the Universe and the Nature of Energy-Matter
Although, as we have seen, the atomic theory was first postulated and elaborated by Leucippus and Democritus in the fifth and fourth centuries BCE, the atom was still not definitively proved to exist (in our frame of reference) until around 1900, when the first reasonably accurate models of atomic structure were pieced together. Many scientists in the late 18th and early to mid-19th centuries helped lay the groundwork for the revolutionary discoveries of the late 19th and early 20th centuries, among them John Dalton (who strongly advocated the atomic theory of matter), Amedeo Avogadro (who developed a method for calculating molecular weights), Michael Faraday (who demonstrated that electricity and magnetism were connected), and James Clerk Maxwell (who devised the key equations that explain electromagnetism and who proved that all electromagnetic phenomena travel, in a vacuum, at the speed of light). The work which proved beyond all doubt that atoms were real and had substructures that could be examined empirically was done by such figures as Max Planck, Ernest Rutherford, Niels Bohr, J. J. Thomson, Marie and Pierre Curie, and Albert Einstein. And a whole array of scientists has built on these foundations, revealing an entire world within the atom of such minute size as to beggar the imagination, a world that operates under rules that challenge many of our notions of what is and is not possible. This is the world of particles, the fundamental units of physical reality by which and on which the four fundamental forces operate. Every tangible thing that we know of in the physical world is composed of them. And there may still be much more to be learned about them.
The term “particle” can be easily misinterpreted. When we think of small parts of something we often think of objects that have solidity, internal structure, definite dimensions, definite position and, if they are in motion, a measurable velocity. Many of the smallest particles have no mass or internal structure at all, and in size are really no more than geometrical points. Their positions can be determined, and their momentum can be ascertained, but their positions and their momentum cannot be determined at the same time, no matter how perfect the methods used to try to do so. And sometimes, neither their position nor their momentum can be measured.
Fundamental particles, those with no internal or sub-structures of any kind, are either matter particles, known as fermions, or energy (force carrying) particles called bosons. What defines a particle as either a matter particle or an energy particle? All subatomic particles possess a property known as spin, or in the case of photons, polarization. (For a layperson like me, this is a particularly forbidding subject, since not even trained physicists agree on how this should be explained to non-specialists.) Some experts contend that subatomic particle spin is not really analogous to the kind of spin that a sphere exhibits when it is rotating on an axis, while others explicitly explain it in such terms. In this context it means that particles have intrinsic angular momentum that is preserved. Spins occur in discrete, measurable units, ones which are used chiefly by quantum physicists, and these are expressed either as fractions or whole numbers. Matter particles, the fermions, have half-integer spins (such 1/2 or 3/2) and force carriers, the bosons, have integer spins (such as 0, 1, or 2). Additionally, the direction of a spin can be either clockwise or counterclockwise around any given hypothesized axis. It is the spin of particles that governs (in part) how they “look” to us and how they interact with other particles. And it should be understood that matter particles have mass; most energy particles don’t. (By the way, the mass of an object simply refers to the amount of material in it, not its weight. In different gravitational fields the same mass would have different weights.)
The building blocks of matter are the quarks and the leptons, the smallest and most fundamental of all particles. Neither possesses any internal structure. Six different kinds of quark have now been detected, and they have been given somewhat whimsical names: Up, Down, Charm, Strange, Top, and Bottom. Each kind of quark in turn comes in three different varieties, said to possess a quality called color (unrelated to the visual understanding of the term) which is an aspect of the strong force’s operation. Very, very early in the Universe’s existence quarks combined to form other particles, and they became confined to them. No free-roaming quark has ever been detected, nor do particle physicists think that one ever will be. Quarks are confined to particles called hadrons, which are bound together by the strong force. Some hadrons are matter particles, others are force carriers. The two most important matter particles that quarks construct are protons and neutrons, which reside in the nuclei of atoms. Protons and neutrons, being composed of three quarks apiece, are a kind of hadron called a baryon. (Another variety of hadron, the meson, very unstable and short-lived, consists of a quark and an antiquark.) The other basic units of matter, leptons, count among their number an exceptionally important basic matter particle, the electron, which is fantastically small and yet of supreme importance in nature. Many, many subatomic particles possess an electrical charge, either positive or negative, which governs the way in which they can interact with other particles. Particles possessing opposite charges attract each other; particles possessing identical charges repel each other. It is this absurdly simple rule that ultimately governs the building of all the physical structures we know of. Protons carry a positive charge and electrons a negative charge exactly equal in strength to the proton’s positive one. Neutrons, found in the nuclei of atoms, possess no charge (hence the name), and neutrinos, extremely fast particles with very little mass and very little interactivity with matter, are also electrically neutral.
All fundamental particles have both particle-like characteristics and wave-like characteristics. (In fact, as will see, this means everything physical is thought to be explicable in both wave and particle terms.) This property is known as duality. The best example of this is the behavior of photons, the carriers of the electromagnetic force. Visible light, for example, has the strange feature of being both a wave and a set of photons, depending on how it is observed. Understanding the duality of energy-matter is essential to understanding how physical reality works. Duality makes our study of nature the study of probabilities rather than certainties, as we will see.
All matter particles, including the smallest and most fundamental, have what are called antiparticles. If a matter particle is charged, its antiparticle has the exact opposite charge. Electrons, which are negatively charged, have an anti-electron called a positron, which is positively charged. When particles and antiparticles collide, they instantly annihilate each other, liberating energy.
As noted in the first section of this chapter, there was both matter and antimatter in the early Universe, but an asymmetry in the early Universe allowed matter to prevail and become dominant. The amount of anti-matter in the Universe is unknown, but everything that we can ordinarily detect seems to be matter. The search for traces of the primordial antimatter or evidence of its presence continues to be a difficult one.
To most of us, the most familiar unit of matter is the atom. An atom consists of a nucleus containing a specific number of positively charged protons and neutrally charged neutrons (except in the case of basic Hydrogen, H1, which has no neutron), surrounded by negatively charged electrons arranged in one to seven different orbitals (or periods). The old method of picturing an atom as electrons orbiting a nucleus in the same manner as planets orbiting a star has been superseded by a new view. It is now understood that electrons exist in a sort of “cloud” around the nucleus, and that in atoms that possess more than one orbital, or shell, electrons can “jump” from shell to shell, although I am using the term “jump” figuratively here. The nucleus of an atom is held together by the strong force. Electromagnetism in turn binds the nucleus and the electron cloud into a single, distinct entity. The number of electrons in atoms ranges from 1 in the basic type of hydrogen to 118 in a laboratory-discovered element called ununoctium. The number of electrons in an atom is equal to the number of protons in its nucleus.
Electromagnetism rules the world of the electrons, and in atoms that come close to one another it is the interaction of electrons that defines the processes of chemical bonding. It is the attraction of electrons to atomic nuclei other than those of their own atom that is at the heart of the bonding process. Only those electrons that occupy the outer orbital of an atom can be given, taken, or shared with other atoms, and are known as valence electrons. When atoms come close enough to other atoms, the natural repulsion of their outer electrons to each other can be overcome. When this happens, atoms with many electrons in their outer shells acquire the solitary electrons of atoms with just one in their outer shell. Sodium atoms surrender their lone outer shell electron to chlorine atoms, which have 7 in their outer shells. Thus salt comes to be. This type of bonding is called ionic bonding. Carbon atoms readily share electrons with other kinds of atoms, and can form an enormous number of chemical compounds. Carbon atoms can make long-chained molecules, rings, or three dimensional configurations. (The vast majority of molecules are three-dimensional.) One of the consequences of carbon’s “cooperative” nature was that it became the basis of all life forms on this planet—and by extension, us. The kind of bonding it and any other “cooperative” atoms do is called covalent bonding. In some bonds, two atoms share electrons, but the electrons tend to spend more time in proximity to one of the kinds of atom than the other. This is what happens when oxygen and hydrogen combine. The electrons stick around the oxygen a lot more than they do the hydrogen. Thus water is formed. This kind of linkage is called polar covalent bonding. Salt, life, water—all formed simply because electrons were taken or shared. From such simplicity did complexity arise.
The different kinds of atoms (which also includes their variations, called isotopes, which possess different numbers of neutrons in their nuclei) comprise the elements. It is the study of the characteristics and interactions of elements (and the compounds they produce) that comprises the subject matter of chemistry. Only a few types of atoms were created in the period immediately after the Big Bang; the rest are the product of stellar nucleosynthesis, which we will look at in the chapter entitled, The First Stars.
The number of naturally occurring elements is a matter of some dispute. Conventionally, 92 different elements are thought to occur naturally, but some of these are chemically quite unstable and brief in duration, so their status as “naturally occurring” has been qualified by some observers. Further, some of the elements that have been synthesized in laboratories may exist in very small quantities somewhere in the Universe, so their status is similarly uncertain. Be that as it may, the striking fact remains: every distinct solid, liquid, or gaseous thing we encounter in our daily lives is made out of a combination of atoms, atoms from which there are fewer than 100 different kinds to choose. The diversity and complexity in which we seem to be immersed is therefore somewhat of an illusion. They are the product of atoms arranged in different combinations and configurations, many of them quite simple. (And if it weren't for electromagnetism holding atoms and molecules together, nothing solid at all could exist.)
If measured by weight, the Universe is 74% hydrogen. If measured by the number of atoms, over 90% of the atoms in the visible Universe are hydrogen atoms. But the visible Universe may not be all there is to it. Most scientists believe that “ordinary” energy-matter only comprises about 5% of the Universe, that 25% of the Universe is composed of a hypothesized dark matter and a mind-boggling 70% is composed of a hypothesized dark energy. These percentages vary slightly depending on the source. For example, physicist Robert P. Kirshner of Harvard University in 2002 estimated the various forms of dark energy and dark matter to comprise approximately 99% of the Universe’s contents.21
There is substantial indirect evidence for the existence of dark matter, but as yet no direct observation of a particle of dark matter has been made. Scientists have had more success explaining what dark matter is not rather than what it is (if it is). Protons, neutrons, and electrons, for example, are ruled out because of their tendency to quickly form atoms and molecules.22 Dark matter is thought to take three different forms, according to Kirshner: a small amount of neutrino mass, dark baryons, and “mostly something else”.23
So what are (or have been) the “candidates” for the particles that comprise dark matter? Astrophysicist Dan Hooper, of the Fermi National Accelerator Laboratory in the United States, explains that at first the neutrino, with its infinitesimally small mass, lack of electrical charge, and general lack of interactivity, was considered a promising possibility, but recent observations and computer simulations have ruled it out. Dark matter must have been cold in order to help build the large structures that were formed relatively early in the Universe’s history, and neutrinos are a kind of hot dark matter.24 (And neutrinos simply have too little mass to do the job.) It appears that any particle which is likely to comprise dark matter came into existence very early in the Universe’s history, is electrically neutral, does not interact strongly with anything, and is a cold variety of dark matter. In fact, hypothesized entities known by the name WIMPS—Weakly Interacting Massive Particles—have been proposed, but as of this writing their existence had not been confirmed.25 In the mid-2000s, an entity known as a neutralino—a category of particle that includes the suspected partners of several force carriers—was thought to be a promising avenue of inquiry.26. Major experiments are underway to detect dark matter, and the great majority of physicists are confident that it will be proven to exist beyond a logical doubt.
Investigating dark energy is similarly problematic, but if real, it has an enormous impact on the physical Universe. Physicist Eric Linder:
The consequences of dark energy for fundamental physics will not be clear until its origin is discovered, but the effects on the universe are dramatic. Dark energy effectively contributes 70-75% of the current energy density of the universe, governing the expansion of space, causing it to accelerate over the last ~5 billion years, and will determine the fate of the universe. Such a phenomenon is not predicted within the standard model of particle physics nor within experimental experience of gravity as an attractive force.27
In fact, the acceleration of the Universe’s expansion, if dark energy is indeed at work, will cause all galaxies that are now visible to us to disappear from our view over the course of the next few hundred billion years. As Kirshner puts it, “The universe could become a lonely, dull, cold, dark place.”28
The action of dark energy is intimately connected with one of the methods by which physical reality is measured, the Hubble Constant. This is the rate at which the Universe is expanding in size. In 2009 the scientists who run the Hubble telescope published the most exact value of it yet presented:
Whatever dark energy is, explanations for it have less wiggle room following a Hubble Space Telescope observation that has refined the measurement of the universe's present expansion rate to a precision where the error is smaller than five percent. The new value for the expansion rate, known as the Hubble constant, or H0 (after Edwin Hubble who first measured the expansion of the universe nearly a century ago), is 74.2 kilometers per second per megaparsec (error margin of ± 3.6). The results agree closely with an earlier measurement gleaned from Hubble of 72 ± 8 km/sec/megaparsec, but are now more than twice as precise.29
This new, more accurate value of the Hubble constant was used to test and constrain the properties of dark energy, and is a measure of its impact, if it is indeed experimentally confirmed beyond doubt. Dark energy seems to have an effect that is counter-gravitational. If gravity is trying to collapse the Universe, dark energy is apparently trying to expand it. If there is a war between gravity and dark energy, therefore, dark energy is winning it. Dark energy, in fact, might possibly be the last thing left in the Universe of the deep future.
There are some physicists who question whether dark matter and dark energy actually exist. Physicist Mordehai Milgrom is a proponent of a hypothesis known as Modified Newtonian Dynamics or MOND. In the MOND hypothesis, a new constant has been proposed, one that alters our understanding of Newton’s descriptions of acceleration and force. The opponents of the dark matter and dark energy hypotheses are in the minority at present, but they believe that in MOND they have found a method which explains more simply all of the observational discrepancies seen in the examination of the Universe.30
The presence of dark matter and dark energy may end up reviving an idea of Albert Einstein’s that has lain dormant for many years—the idea of a cosmological constant, a force opposing gravity that keeps the Universe from contracting. For more than 70 years, the concept was considered unsupportable, because as originally calculated, it predicted a static Universe, which is obviously not the case. But when a different value is assigned to it, is has been found that it does appear to account for the expansion of the Universe, and it appears to be consistent with the existence of dark energy.31 However, as cosmologist and astronomer Evalyn Gates has pointed out, the cosmological constant still has issues and uncertainties attached to it, and the Universe may not necessarily be headed for a certain fate of darkness and cold.32 The fate of the Universe depends, ultimately, on what dark energy is—and that question is still open.
All of this is of the most intimate concern for humans. Physicist Lee Smolin has pointed out that the fundamental parameters of the physical particles are such that they make stars, and thus, nucleosynthesis, elements, and life possible, in that order. If stars had not formed in the early Universe, none of us would be thinking about these issues now. Because energy-matter behaved as it did, the possibility of life existed, and we are the result of that possibility. (Smolin has also put forth a controversial thesis: that the fundamental forces have, themselves, been shaped by a sort of cosmic natural selection, but this view remains a distinctly minority opinion .)33
And all of the fundamental particles live by the rules of the strangest, and probably most important realm of all…
It is now an accepted truth that there are levels of physical reality that contain objects which cannot be subdivided in any way. It is a further accepted truth that events at the subatomic level, such as spins and energy exchanges, occur in discrete units, and not as continuous events. It is also accepted that extremely small objects appear to be governed by rules which are not described by classical physics. The study of the smallest phenomena, the discrete ways in which they interact, and the seemingly strange rules under which they operate is called Quantum Mechanics, perhaps the most significant discovery about the world in human history. On it rests not only our understanding of the atomic and subatomic worlds, but our understanding of what reality (as humans are able to perceive it) actually is.
The Process of Discovery
The world of late-19th century physics had already undergone several major shocks. The ether, the substance that supposedly acted as the medium over which all energies in the Universe were propagated, was definitively shown not to exist in 1887. In 1895, Wilhelm Röntgen discovered the existence of x-rays, an utterly unexpected development. And in 1896, Henri Becquerel discovered naturally-occurring radioactivity. But the real revolution lay just ahead.
Max Planck, in 1900, was the first physicist to postulate that light traveled in distinct packets of energy. He named these packets quanta, even though he simply thought of them as a convenient mathematical trick, without actual physical substance. Assuming the existence of these packets simply helped explain what is known as black body radiation. Planck devised a method for measuring the energy emitted by a radiating object. He determined that the energy in a photon was in proportion to a mathematical constant multiplied by the frequency at which the photon was being radiated. The constant came to be known as Planck’s Constant, and it was to become a major part of the foundation of quantum mechanics. The formula is E=hv, where E is energy, h is Planck’s Constant, approximately 6.63 x 10-34 joule-seconds, and v is the frequency. Planck had uncovered one of nature’s hidden realities, an incredibly tiny but distinct unit of energy that had an impact on the smallest of all objects.
Albert Einstein, intrigued by Planck’s ideas, set about to explain the photoelectric effect, the ability of light to stimulate an electric current in metal, causing it to emit electrons. Einstein found that different colors of light had different abilities to stimulate current in metal (and move electrons), demonstrating that the these colors of light were composed of particles—later to be named photons—with energy levels specific to that frequency of light. If light were purely a wave, than the brightness of the lights, regardless of color, should have determined the number of electrons that were stimulated—but it didn’t. Dim blue lights stimulated more electrons than bright red ones. Einstein therefore proved that these quanta, these little packets of energy, were real, and not just mathematical constructs.
Physicist Niels Bohr, working with another scientist, Ernest Rutherford, began to apply quantum ideas to the internal structure and workings of the atom. Bohr ascertained that electrons could not emit radiation constantly, but rather did so in discrete packets. (It was Bohr and Rutherford who devised the planetary orbit picture of the atom that prevailed for so many years.) Bohr demonstrated that when electrons “jumped” from one level to another, there were distinct, quantized packets of energy either released or absorbed by their atoms. It was a major discovery.
The 1920s saw huge developments in quantum mechanics. In 1924, Louis de Broglie proposed that all matter particles could be described as waves as well as particles. This proposition was later overwhelmingly confirmed, reinforcing the idea of the duality of nature. (See above.) Also in 1924 the Indian physicist S. N. Bose sent Einstein a paper Bose had written entitled, “Planck’s Law and the Hypothesis of Light Quanta”. Einstein was tremendously impressed by it, and he realized Bose had come up with a statistical method for counting both photons and atoms alike, a genuine breakthrough.
In 1925 Wolfgang Pauli formulated what is now known as Pauli’s exclusion principle, which says that two similar matter particles cannot have the same position and velocity, i.e., exist in the same state at the same time (within the limits of uncertainty). Stephen Hawking explains the significance of this feature of physical reality:
If the world had been created without the exclusion principle, quarks would not form separate, well-defined protons and neutrons. Nor would these, together with electrons, form separate, well-defined atoms. They would all collapse to form a roughly uniform, dense “soup.”34
Erwin Schrödinger, the Austrian-born physicist, contributed a major theory of wave function to quantum mechanics in 1926, and his wave function equation is at the beginning of most textbooks on quantum mechanics. (He disliked the concept of duality, however, and spent much of his life attempting to prove that the wave interpretation of matter was the only possible one.)
In the period 1927-28 Paul Dirac effectively invented quantum field theory, an offshoot of quantum mechanics that allows us to resolve the difficulties involved in the analysis of infinitely variable particle behavior. Dirac formulated an equation which describes how electrons interact with electromagnetic fields, which eventually led to yet another offshoot of quantum theory known as quantum electrodynamics, or QED. (See below.) (The original equations of QED were used inaccurately, and for around 20 years little progress was made in the area.) Dirac also predicted that an anti-electron, unknown at the time, would be discovered. In 1932 the anti-electron, the positron, was indeed discovered.
In 1927, Werner Heisenberg published his revolutionary Uncertainty Principle, which established the fact that a particle’s position and momentum cannot be established simultaneously. The very act of measuring one changes the other. The implications of this were vast. In some respects, it meant that reality itself could not be fully known at any given moment, if by knowing reality we mean keeping tabs on what electrons are doing. Moreover, it overthrew one of the great ideas of 19th century science: that if we could know the position and momentum of every particle in the Universe, we would have the power to predict what was going to happen in the physical realm. Heisenberg is telling us that such a hope is utterly without foundation.
By 1928, Bohr had formulated a full-fledged version of his complementarity principle, which basically was the argument that atomic and subatomic particles behaved both as waves and particles, that they looked like one or the other depending on the way they were measured, that the two ways could never be perceived simultaneously, and that both had to be understood in order to gain the fullest possible description of the particle being studied. Bohr’s picture of the reality that resulted from this principle, and the discoveries of other quantum physicists, chiefly Heisenberg and Max Born, is known as the Copenhagen Interpretation (although in fact Bohr did not refer to it as such). In this view, the world described by classical physics, the ordinary world of our human-based perception, is assumed to be a given, a benchmark so to speak. The quantum world does not spring into existence until an attempt is made, by use of classical measuring devices, to ascertain its qualities. Only when they are being examined, according to this view, do the smallest objects in physical reality “choose” a state from among infinite possibilities. Observation causes the quantum probability waves to collapse, so to speak, into a single state. This became the dominant view in quantum physics and remained so for several decades. Its implications were sobering: fundamental reality has no definite features until someone attempts to measure it. Albert Einstein, among others, balked at this idea. In a letter to Max Born, he wrote the following famous lines:
You believe in a God who plays dice, and I in complete law and order in a world which objectively exists, and which I, in a wildly speculative way, am trying to capture. I firmly believe, but I hope that someone will discover a more realistic way, or rather a more tangible basis than it has been my lot to do. Even the great initial success of the quantum theory does not make me believe in the fundamental dice game, although I am well aware that your younger colleagues interpret this as a consequence of senility.35
Einstein remained a determined critic of the Copenhagen Interpretation, and never fully reconciled himself to the findings of quantum physics, even though he himself had been instrumental in establishing the field.
Einstein remained a determined critic of the Copenhagen Interpretation, and never fully reconciled himself to the findings of quantum physics, even though he himself had been instrumental in establishing the field.
In the 1930s, physicist John von Neumann applied the mathematics of David Hilbert to the description of the quantum world, making quantum mechanics more mathematically rigorous. Two decades earlier Hilbert, the brilliant German mathematician, had done work that made it possible to study vector spaces possessing infinite dimensions, which are now known as Hilbert Spaces. Hilbert Spaces are a way of representing problems that involve an unlimited number of possibilities The study of Hilbert Spaces is critically important to quantum mechanics and the indeterminacy it is trying to portray. (See below.) It is within the parameters of Hilbert Spaces that quantum events are described. (And no, I pretend no grasp of the exotic mathematics embodied by them.)
The study of quantum mechanics was interrupted by the onset of the Second World War, but after the war Richard Feynman, Julian Schwinger, Sin-Itiro Tomonaga, and Freeman Dyson revived quantum electrodynamics, rectifying the old mistakes of others, and exploring new ground. QED describes the interaction of photons and electrons. It cannot, of course, predict what an individual electron will do, but it can, with very great accuracy, predict what groups of electrons will do when they encounter groups of photons. QED, therefore, like all other aspects of quantum mechanics, deals in probabilities rather than definite certainties. Feynman, for example, demonstrated that light will “investigate” every possible path as it travels from Point A to Point B. The probabilities of where light can go add up in such a way that it appears that light is going in a straight line. But it has sampled every possibility.
QED explains how chemistry at the deepest level works since, as we have seen, chemical bonding occurs between two atoms when electrons are lost, gained, or shared. QED’s predictions about this process are fantastically precise. It has been tested repeatedly, and it has passed every test. QED has been described as the most successful set of scientific theories ever developed. But, somewhat shockingly, QED states that electrons, however briefly, actually go back in time when they are struck by photons, reversing their time trajectory when struck by another photon. It seems impossible—and yet, there it is. QED has not been “finished”, so to speak, but no refinement of it can remove its more bizarre characteristics.36
Discontent with the Copenhagen Interpretation of reality led a team of physicists in the 1950s to begin the construction of a new paradigm known as The Many-Worlds Interpretation, which has gained a great deal of support among physicists, but which is also still being studied intensively. Essentially, Many-Worlds theorists postulate that what happens when we observe an event at the quantum level is not a collapse of the wave function, i.e., the collapse of all probabilities and the selection of just one. In this paradigm the Universe explores every possible outcome of the act of observation, and all of these outcomes occur in some context, although we perceive only one of them. The term “Many Worlds” is somewhat misleading—it implies that a new Universe, a new “world” is created during an observation, for every possible event that occurs. Gell-Mann, who helped develop the theory (which was first proposed by Hugh Everett III in 1957) says that it is best understood by the term “many alternative histories of the universe”. It is not really about parallel universes, he says, and it is not necessary or even accurate to assert that these alternate histories are all “equally real”.37 But there are adherents of this idea who say that these alternate histories, these alternate outcomes, do retain their own separate reality. (See below.)
In 1964, John Bell, an Irish physicist, decided to investigate a phenomenon called quantum non-locality. Non-locality is the ability of two objects to influence and respond to each other without any mediation of any sort, however widely separated—what Einstein called “spooky action at a distance”. In 1935 Einstein, Boris Podolsky, and Nathan Rosen had demonstrated, to their satisfaction at least, that objects in space-time had to be connected by some sort of field or other, more direct contact, in order to influence other objects. Bell was seeking to confirm this hypothesis, but he was taken aback by what he uncovered. His research led him to conclude that all reality is non-local. In practical terms, his theorem appeared to demonstrate that once two particles interact with each other, they become entangled (or more strictly speaking, they undergo a phase entanglement) which is to say that they respond instantaneously to each other across any distance, however large. Numerous experiments in the 1970s and 1980s confirmed Bell’s findings. Reality itself was non-local, it appeared.
To say that Bell’s Theorem had a major impact would be to understate the case. The Einstein-Podolsky-Rosen conjecture was shown to be incorrect. More challengingly, if Bell was correct, it would mean that particles that were entangled were “communicating” with each other at superluminal speed—that is, faster than the speed of light. That this presents relativistic problems would be to say the least. It would mean that events were, in effect, going backward in time, something that violates all of our rules. It was another in a series of jolting discoveries by quantum physicists that challenged our conceptions of reality.
By the mid-1980s, quantum physicist Nick Herbert counted no fewer than eight major versions of quantum reality, all of which had to take into account the seeming presence of non-locality. These versions asserted, variously, that there is no deep reality; that the world is created by the act of observation; that the world is an undivided whole, which allows things to instantaneously affect other things; every possible world than can exist does exist; that the world is put together by the rules of quantum logic, which does not fully specify a thing’s attributes; that the world is made of ordinary objects; that consciousness creates reality; and that the Universe is, in the deepest sense, tendencies, potentialities, and possibilities.38 It seemed as if no ultimate answers could be gleaned from such an array.
In the 1990s, string theory emerged as the dominant conception of ultimate physical reality, and it is still the most widely adhered to view among physicists. String theory is predicated on the assumption that quarks and electrons are not truly fundamental, and that there are one-dimensional entities in them simply called strings, of incredible minuteness. (John Gribbin points out that a typical string would only be 10-35 meters long, and that it would take 1020 of them to cross the diameter of a proton!)39 These strings are thought to vibrate at different frequencies, creating all the various subatomic particles. Hypothetically, these strings can divide or recombine with other strings, and can act in such a way that gravitons—the hypothesized force carrier particle of gravity—would act. Strings are also thought to possess an utterly counter-intuitive property: they are thought to encompass within themselves not four dimensions (three of space and one of time) but eleven dimensions, ten of space and one of time. These extra spatial dimensions would, in effect, be incredibly small in size, and they would interact with each other in an intricately complex geometry. String theorists are hoping that strings can provide the mathematical framework in which the four forces of nature can be unified, and that string theory can resolve the questions surrounding quantum phenomena.
The Picture Today
Quantum mechanics and its offshoots form the most significant theory about the physical world ever devised. Mathematically, they appear to work with beautiful effectiveness, and all electronic devices are based on quantum principles, which has in turn made a major impact on the world’s technological, social, and economic growth. But the key questions are these: what can our investigation of the quantum realm tell us about the ultimate nature of reality? What is even meant by the term reality? On these questions there is profound disagreement, even among those who understand the quantum world most deeply.
So what, in very general terms, is understood in the present day about the quantum mechanical world? What aspects of quantum theory have gained the widest acceptance? What seems to be true about the fundamental physical reality as humans are capable of perceiving it? And what are the chief currents of thought?
First, it should be made clear once again that quantum mechanics is above all the study of how things at the smallest level of reality behave. It is the fundamental premise of quantum mechanics and its various offshoots that electromagnetic, strong force, and weak force phenomena are transmitted in quantized form, in other words, in discrete little packets of force. It is considered likely that gravity is transmitted in the same manner, but this has yet to be empirically demonstrated.
Every physical thing that exists is made of the same kind of substance, what Nick Herbert calls “quantumstuff”. It may said, then, that “quantumstuff” forms the foundation from which everything in the Universe has emerged. Since the smallest entities comprise the physical foundation of the Universe itself, it means that the entire Universe behaves in a quantum fashion. Scientists are endeavoring to determine the original conditions of the early Universe, but they have abandoned the idea of a deterministic Universe. The most that can be said, ultimately, is that fundamental reality is guided and shaped by indeterminacy, and that when we observe that fundamental reality, it seems to have effects that go beyond our frame of reference.
Physical things at the most elementary level display both particle and wave-like qualities. Particles at the quantum level exhibit a phenomenon called superposition. This means that a particle’s state, the description of all its characteristic behaviors, is composed of all its possible states, one of which will be displayed when it is observed. We cannot predict which state will be displayed by an individual particle. We can only know the probability that it will display a given state.
The behavior of particles in the quantum world is describable only collectively; we cannot know for sure what an individual photon, for example, will do when confronted by a barrier of some sort with limited access points, or an environment, like a crystal, in which its path will be altered but not completely blocked. We do know that a photon’s attempt to pass through a barrier will be either completely successful or completely unsuccessful. There will be no half-way. At the individual level a quantum event exhibits what J. C. Polkinghorne called “radical unpredictability”.40 Murray Gell-Mann has pointed out that in radioactive decay, for example, we cannot know the exact moment when a given atomic nucleus will decay, but we can plot the decay of a specified quantity of a radioactive substance, like plutonium, on a graph, with a high degree of accuracy.41
Not only is it impossible to determine a particle’s position and momentum simultaneously, as Gell-Mann states, “[t]here is also an infinite variety of other possible quantum states for a single particle, in which neither position nor momentum is exactly specified, only a smeared-out probability distribution for each.”42
There are numerous possible ways in which the entities that comprise the foundation of the Universe can behave. To quote Colin Bruce, mathematical physicist:
Whenever we test a small piece of our universe experimentally, we find that up until that moment it has been behaving as a chunk of Hilbert space, developing not as a single history, but as a nest of interacting probability waves. This description of nature is by far the most accurate that has ever been achieved.43
Quantum mechanical laws underlie the quasi-classical domain (as Gell-Mann put it). The world we see and experience emerges from the quantum realm and rests on it completely, and yet we don’t seem to see objects in the macroscopic sphere behaving like subatomic particles. So where is the “boundary”, so to speak, between the quantum world and the world in which the rules of classical physics seem to apply? When do quantum effects seem to yield to classical ones? The famous double-slit experiment may help us here.
The double-slit experiment consists of firing a beam of photons (in the form of ordinary light) in the direction of a barrier with two slits in it. Behind the barrier is a highly sensitive photographic plate. We would expect to see two distinct patterns of photons on the photographic plate, corresponding to the two openings in the barrier. But that is not the case. If there is no attempt to measure them, the photons in such experiments appear to go through both slits and cross their own trajectories (!), making all kinds of different lines on the photographic plate, consistent with waves that have interfered with each other. Even a single photon will appear to do this and interfere with itself after it does so. This is an illustration of a principle of quantum mechanics called (unsurprisingly) interference. When entities in a quantum state are interacting with themselves in such a way that they are not “forced” to choose among their probabilities, we cannot ascertain what their exhibited behavior will be. But when things at the quantum level are forced to interact with other particles, especially those that comprise objects in the macroscopic sphere of existence, they are forced to “choose”. They undergo what is called decoherence, and from that point, the probabilities of their group behavior can be calculated with great accuracy. If photons are given only one slit to go through in the barrier against which they are flung, they obediently go through it and behave in a “classical” manner. If they are measured by means of macroscopic devices, even when given two slits, they make two distinct patterns on the photographic plate.
There is a group centered at Oxford University that adheres strongly to the Many-Worlds Interpretation, although its individual members differ on certain key points. They believe that the principles of interference and decoherence can be interpreted in no other way. They are convinced that in any situation there are countless probabilities, ones that end up occurring in alternative worlds or histories, and that these alternative worlds have as much reality as the one we perceive. These worlds are parallel to our own, in their view, and as yet it is impossible for us to make any contact with them. Further, those who believe the Many-Worlds Interpretation to be the best explanation of physical reality are convinced that it solves the locality problem: there is no faster-than-light communication taking place between particles. There are simply worlds in which such particles are correlated. And while the Copenhagen Interpretation still has its adherents, and while there are other schools of thought still in contention with the Many-World supporters, the believers in the multiplicity of parallel worlds appear to be in the ascendant.
The nature and interactions of the basic particles, and the findings of the various fields within quantum mechanics that describe them comprise what physicists call The Standard Model, which has proven tremendously successful in almost every respect. But there still remains the issue of reconciling the quantum world with gravitation. The problem is this: electromagnetism, the strong force, and the weak force are all described in quantum terms. Gravity, as explained by relativity theory, is described in classical terms. It does not appear that gravitational force is quantized, in other words, it does not seem to be conveyed in discrete packets. QED is fantastically successful as a predictive method, but so is relativity, and the two describe the Universe in fundamentally different ways. The attempts by physicists to unite the seemingly incompatible worlds of gravity and the quantum realm are aimed at the formulation of what is called a Grand Unified Theory, sometimes called a Theory of Everything, a set of equations that will describe every aspect of physical reality from the smallest to the largest in a fully integrated and consistent manner. This has often been called The Holy Grail of Physics. There are some scientists who don’t believe that it will be discovered. Astronomer and physicist David Lindley has challenged the notion of a unified theory itself, contending that its existence is taken more as an article of faith than a demonstrated reality. But in the main the world’s physicists believe that the principles of quantum gravity will eventually be discovered, along with the graviton, and the grand unification will become a reality.
A major step toward completion of the grand unification was announced in July of 2012. A piece of the Standard Model that had been missing, a force carrying particle called the Higgs Boson, was finally discovered at the CERN facility near Geneva, Switzerland. Higgs Bosons comprise the Higgs Field, which gives all matter its mass. A Higgs Field pervades the Universe and all particles interact with it to varying degrees. The extent of the interaction determines the mass of the particle, and what particles are interacting with are Higgs Bosons. Higgs Bosons both mediate the field and are a product of it. They are both tremendously energetic and of extremely short duration. The discovery of the particle confirmed the existence of the field, and gave us new insight into how the Universe itself was constructed.
Six Essential Numbers ( According to Martin Rees)
British astronomer and Cambridge professor Martin Rees has identified what he believes to be the six most significant numbers that form the basis of physical reality itself. They are (with Rees’s explanations):
1. N equal to the number
“This is the strength of the electrical forces that hold atoms together, divided by the force of gravity between them.” If this number were just a few zeroes shorter, the Universe would have been very small in size, and very short-lived, precluding the possibility of life evolving.
“This is the strength of the electrical forces that hold atoms together, divided by the force of gravity between them.” If this number were just a few zeroes shorter, the Universe would have been very small in size, and very short-lived, precluding the possibility of life evolving.
2. ε, “whose value is 0.007, defines how firmly atomic nuclei bind together and how all the atoms on Earth were made.” This was crucial for the stellar nucleosynthesis that created the elements, and this nuclear binding controls the Sun’s power. If it were 0.006 or 0.008, humans could not exist.
3. Ω or omega, which “measures the amount of material in our universe—galaxies, diffuse gas, and ‘dark matter’. Ω tells us the relative importance of gravity and expansion energy in the universe.” Too much variance in this ratio and the universe would have either collapsed long ago or failed to have formed stars—and us—at all.
4. λ (lambda), which represents a cosmic “antigravity”. “It is destined to become ever more dominant over gravity and other forces as our universe becomes even darker and emptier.” It is, fortunately for our existence, still very small.
5. Q, the ratio of two fundamental energies, the strength of gravity in relation to the rest mass of stars, galaxies, and galaxy clusters. It is about 1/100,000. If Q were an even smaller value, no structures would have arisen, and if it were much larger the universe would be so violent that no stars could survive.44
6. D, the number of spatial dimensions in which we live—three. Rees contends that humans could live in neither two nor four spatial dimensions. This, according to Rees, does not preclude the existence of ten-dimensional strings.45
In examining Rees’s numbers, we might be tempted to see them as confirmation of the anthropic viewpoint—that the Universe was created for us. I see them as reflections of factors that permitted the evolution of life on this planet, but did not ordain it. The assertion that our existence is some sort of universally significant phenomenon is one I believe to be unsupportable. (See A Species Lost in Both Space and Time for my view of this matter.) I would contend that the existence of life in the Universe is a matter of supreme indifference to the Universe, as it is an entity incapable of caring one way or the other. Moreover, if we assume that our Universe is not a sentient being of some sort, it stands to reason that it is similarly unconcerned with its own size, density, energy content, general structure, dimensions, or duration. Yes, Rees’s numbers, if true, were fortuitous for the emergence of life. But that is a matter of concern only to a rather small percentage of the Universe’s energy-matter. If no life had ever evolved anywhere in the Universe, the Universe would simply keep grinding away without it. There would be no human perception of the Universe, of course, and that unique vantage point would never be experienced. But the entity we call the Universe would still be here—and it would have no need of us whatsoever.
Complications and Dissenters
Although string theorists are hopeful that empirical evidence for the existence of strings will be discovered in the 21st century, at the time of this writing such evidence had yet to be produced. The hope is that the Large Hadron Collider, at CERN, will provide this evidence. The mathematics behind string theory, according to its adherents, seems to be compelling, but some physicists (such as Lee Smolin) question whether string theory has any basis in reality at all, however beautiful its mathematics.
Roger Penrose, one of the giants of modern physics, is severely critical of both the Many-Worlds interpretation of quantum reality and string theory. He dismisses the Many Worlds interpretation, saying:
You want a physical theory that describes the world that we see around us. That’s what physics has always been: Explain what the world that we see does, and why or how it does it. Many worlds quantum mechanics doesn’t do that. Either you accept it and try to make sense of it, which is what a lot of people do, or, like me, you say no—that’s beyond the limits of what quantum mechanics can tell us.
Penrose also points out that no evidence for string theory exists at all, and he characterizes adherence to it as a “fashion”. He is of the opinion that the core of quantum mechanics has yet to be elucidated, and that the study of quantum reality has produced assertions which cannot be substantiated. Coming from anyone else, such opinions could be dismissed, but Penrose is in the same rank, in the view of many, as Einstein and Hawking. I do not wish to use the Argument from Authority here, but Penrose is still an active investigator, with a half-century of experience, and I believe his views merit consideration. Have we gone too far in trying to make quantum theory a comprehensive explanation of reality? Perhaps we have.46
Naïve Responses and Layman’s Conjectures
So what can those of us who, like me, are not specialists, not scientists, and not mathematically gifted, make of all this? Obviously, people like me cannot study these matters in any sort of rigorous way. But I am convinced that we who study history must at least have a general knowledge of these topics, because from such stuff did the world—and us, and the whole experience of the genus Homo over the last 25,000 centuries—emerge. If human social and cultural reality is the product of a series of emergences, the process began with the tendency of physical reality to self-organize, and the first things that did so were the fundamental forces and the infinitesimally small objects that emerged in the earliest moments after the break-up of the initial unity. Trying to grasp something about the rules by which these forces and objects function is to try to trace our history back to the very foundation of (human-perceivable) reality itself.
My own questions, perhaps unsurprisingly, center on quantum mechanics. I take some comfort in the Feynman quotation,
I think it is safe to say that no one understands quantum mechanics. Do not keep saying to yourself, if you can possibly avoid it, “But how can it possibly be like that?” because you will go down the drain into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.
But when I am confronted with the hypothesis that every observed variable in the world creates an alternate history, or even in its most radical form, an entire new Universe, how can I not question this? There are tremendous intellects, such as the physicist David Deutsch of Oxford University who are convinced of the reality of parallel universes. Who am I to question such intellects? In one sense, I am not entitled to even participate in a discussion of such matters. But I have no choice! I have questions I must have answered:
- When the Many Worlds advocates speak of a “world” or a “universe”, are they postulating an entity with its own history stretching back to the Big Bang? When a new world is supposedly created, is its entire past created along with it?
- What constitutes a variable? Suppose we consider a tire on a car traveling at 50 kilometers per hour. The treads on the tire flex in a complex pattern. If a section of the tread flexes in a given way, does that constitute a variable from which a new universe might arise, since it is possible that it could have flexed in a slightly different fashion? If so, how many universes are being created by a single tire on a single car going on a five kilometer trip? Or are there none at all created, because the flexing of the tread was not observed?
- What constitutes an observer? Does an observation have to be made by a human? Can an observer be another sentient being, such as a chimpanzee, a dolphin, a dog, a cat, or a squirrel? Can anything capable of noticing some kind of change in its environment qualify as an observer?
- If a new universe is created every time an observer notices a variable in action, does that mean, as Nick Herbert asked, that some sentient being in the Andromeda galaxy is creating new versions of me every time he, she, or it observes something?
- Defenders of the Many Worlds interpretation praise it for its mathematical economy, while granting that it is lavishly extravagant in its creation of worlds. One defender of the MW interpretation has argued that it is less lavish than the assumption that every particle in the known Universe is entangled in some way with every other particle, and that these particles are sending innumerable “messages” to each other at faster-than-light speed. But I must ask: how many worlds, how many parallel universes, are the people of the Earth creating at every moment? In these parallel universes, are the parallel selves of these people in turn creating parallel universes and parallel selves, who will in turn create new universes, and so on and so on? Where does this process stop? Is the MW interpretation assuming that infinities of worlds will be created? If the sentient beings of the entire Universe are creating parallel universes at every moment, how quickly will the number of such universes equal the estimated number of subatomic particles in the Universe in which we live, perhaps 1085? If the sentient beings of the Universe have been doing this since sentient beings evolved in various corners of the Universe, how many parallel universes are now existing in what David Deutsch calls the multiverse? Is it possible that quantum entanglement is actually more economical in its creation of phenomena than is the MW interpretation?
- Are all possibilities equally likely? Are there events that, while they do not violate the tenets of logical impossibility, are so utterly unlikely that their occurrence even once in any conceivable universe can be ruled out? For example, it is possible that an object at rest in a gravitational system can spontaneously jump a meter in height, if its constituent particles are in the proper quantum state to do so (or so I am given to understand). But in all the universes that can exist, has it happened even once?
- Do all universes follow the same fundamental rules ours does? In how many hypothesized worlds does the Earth not exist at all?
- Is what we call our Universe and its deep history the result of a quantum wave function in some other world?
- But if some form of entanglement (or whatever we wish to call non-local reality) is taking place, how is it possible that particles separated from each other by distances too vast to comprehend can act synchronously instantaneously? Aren’t the rules of relativity being violated? If such violations are taking place, does that mean that time itself, classically thought to go in a single direction, is subject to reversals? If such reversals occur, are the paradoxes resulting from them resolved immediately?
- Finally, is it possible, as some scientists have speculated, that the entanglement of particles follows special rules which have either not yet been discovered, or which operate only at the quantum scale of size and which do not carry over to the macroscopic world?
It is certainly possible that there are untold, parallel histories or even whole parallel universes, which exist along with ours. Our concern, naturally, is the extent to which such parallel worlds might have an impact on our own Earth-bound reality. If parallel worlds theorists are correct, then no contact with other worlds is possible at all, and hence they can have no effect whatsoever. As physicist and philosopher Roland Omnes points out, this means that the Many-Worlds hypothesis is non-falsifiable. It may work mathematically, but no empirical test of it can ever, by definition, be made. Interestingly, Omnes says that in one sense the MW interpretation is insane—his word—and yet he can’t fully refute it.47
And so, we are left to wonder: Is reality simply the sum of all possible perspectives? Is there no ultimate standard for “real” reality, just relative perceptions of it? It appears that classical realism—the doctrine that objects are distinct and facts are definite—is on the wane. But how are we to build on the nebulous and amorphous foundation that has replaced realism? It is possible in my view that in trying to elucidate the quintessence of physical reality, we may, as a species, have run up against the limits of what our consciousness can comprehend.
If we accept the implications of quantum mechanics, it means that, in a sense, human history is the sum of all the outcomes of all the quantum events that have ever occurred in this world, and the human future could conceivably affect any number of worlds, even though this can never be known with certainty. Yet, there is enough decoherence in the microscopic world to allow the world of visible and tangible objects in the macroscopic sphere to emerge. The chasm, as Omnes puts it, between the quantum world and the world with which we are familiar, is almost incomprehensible.
In facing the future, are we dealing with entities, processes, realities, which by their very indeterminacy preclude any sort of prediction? Are the odds and statistical chances of things we see in the macroscopic world driven by the quantum world that is their fundament? Are our own brains, our own minds, shaped, as Penrose suggests, by quantum principles which have yet to be ascertained?
We are ruled by the four forces which set the boundaries of physical reality. We live in a Universe in which all perspectives on speed and motion are valid, however different. We ourselves are composed of objects that follow rules remote in the extreme from ordinary experience. Humans are, as Daniel Dennett said, essentially persistent patterns. And it may be true, as one physicist said, that there are no “things” that actually exist—only waves. Of such is our world made.
Humans are unimaginably tiny in comparison to a galaxy. But there are multitudes of particles that, were they conscious, would consider us to be the size of a galaxy. In that world, smaller than our unaided sight can perceive, emergence has asserted itself dramatically. The quarks, leptons, and force carrier particles have constructed the atomic nuclei and created mediums of energy exchange, making atoms and allowing them to interact, bond with each other, and break from each other in endless procession. The 92 or so varieties of atom and their interactions have brought forth the chemical world and the molecules out of which the macroscopic world has been created, including life forms. The earliest kinds of life forms ultimately, after the branching-off and emergence of countless other life forms interacting with the ever-changing environment of the Earth, brought forth the beings capable of studying the subatomic world that is the foundation of their existence.
The unconscious brought forth the conscious. That alone may be the most remarkable event that has ever occurred.