Imagine that on a nice summer night you look up and see hundreds of minuscule shimmering dots of light, immersed in the most absolute darkness. There seems to be no end to it, its vastness beyond anything you can comprehend. The word “infinity” springs to your mind. An unpleasant feeling of loneliness starts to creep in. You long for company, for a sense of closeness. But there is no one in sight. Just you, stars, and darkness. You shake off these thoughts by reasoning that it’s impossible to know for sure how vast it all is. For all you can see—even if you know this can’t be right—it seems equally reasonable that the stars are plastered in some kind of celestial sphere that slowly rotates westward with the night. Maybe the cosmos is bounded by some kind of celestial dome, like an all-encompassing womb. Why not? Much cozier this way, right? Infinity is a weird concept; you can’t put your hands on it. In fact, why not add spheres to carry each of the planets and the moon as well? Better make them out of crystal so you can still see through them. There, the night sky has some order now, the cosmos is finite and it all feels much better. It’s hard for us to tolerate the unknown.
Anaximenes, a Greek philosopher who lived around 540 BCE, was the first to propose this sort of cosmos of transparent spheres, like the rings of an onion. He also believed that stars and planets were made of exhalations that ascended from Earth and turned fiery in the heavens. Although he thought Earth floated on air, he assumed it was flat like a leaf. His cosmos was more like a half-onion, a hemispherical world. With these images, he was trying to explain the astronomical phenomena he observed with the tools available at the time, mostly his eyes and rudimentary geometry. His ideas seem far-fetched, after four hundred years of modern science, but much credit must be given to Anaximenes and Thales and Anaximander for being the first not to invoke gods or supernatural causes to explain what they couldn’t understand about the world. Instead, they used reasoning and common sense. They took the first baby steps toward science.
The night sky fills us with a deep sense of awe. Perhaps some of this sense has been taken away by the comforts and distractions of modern life, but hidden somewhere inside our minds is a primal connection with the unknown. To sense it you must be exposed to it, like a seed that needs water to germinate. The imaginary scene described above illustrates how the night sky inspires not only awe but also a disquieting uncertainty. The more you allow yourself to think about it, the more bizarre it all seems. If you let yourself go, your mind will be assaulted by questions that have been with us for as long as we know: Is there life elsewhere in the cosmos? Does the universe go on forever, or does it have an edge, like Anaximenes thought? If it does, what lies beyond? How did the universe come to be? What about us? Are we special? Do we have a “cosmic mission” or are we just here for the ride, a random accident among nature’s myriad creations?
Historical records dating back to the Babylonians—a thousand years before Anaximenes—show how deliberately they followed the motions of the constellations and planets across the sky, registering them in clay tablets. For example, the Venus tablets of Ammizaduga (c. 1580 BCE) detailed the risings and settings of Venus over a period of twenty-one years. The Babylonians viewed the heavens as holy; the relative positions between the constellations, sun, moon, and planets were a message from their gods, which could be translated by their priests. This interpretation of the heavens gave rise to the earliest forms of astrological forecasting and divination. The Babylonian fascination with the skies is in essence not so different from the need we have to understand our connection to this vast and unpredictable cosmos. Horoscopes are as popular as ever. At a more serious level, as modern-day astronomers point their telescopes to the sky, trying to uncover its mysteries, they are following in the footsteps of the ancient Babylonian priesthood, extracting meaning from methodical observations of natural phenomena. There is a road connecting our actions to theirs, a road starting well before the Babylonians, with the first hunter-gatherers that roamed the planet.
German philosopher Martin Heidegger once wrote that the essence of humanity is in the form of a question. No question is more fundamental than that of our origin. In attempting to answer this question, we define our age, values, and traditions. Different faiths clash with one another, and faith clashes with scientific reasoning. However, and this is a key point, even though the answers are distinct, the question remains the same. In what follows, we will visit a few of the milestones along this noble road, starting with a sample of the first answers to the question of creation, which are necessarily religious, and ending with the most recent ones, which are necessarily scientific. In doing so, we will be peering into humanity’s quest for coming to terms with existence.
The Beginning: Creation of Myths
The power of a myth is not measured by its reality but by its effectiveness. Myths give meaning to people’s lives, defining the most fundamental values of a given culture. Thus, when one hears a myth from a different culture, it is foolish to try to interpret it out of context. As fast-paced globalization erases native cultural values, it is easy to toss aside ancient mythical narratives about the origin of the cosmos as quaint or nonsensical. But these stories address themes we still debate, even if we are armed with the conceptual and technological sophistication of science.
Thinking about the origin of everything invariably leads to confusion. After all, if I tell you that everything came into existence some time in the distant past, you may legitimately ask “And what existed before that?” If I reply that nothing existed before, you might say “But how could something come out of nothing?” I might tell you that this is a very special kind of nothing. “Oh yeah?” you’d say, “And what kind of nothing is that?” What this “primordial nothingness” is depends on where and when you live, and if you are religious or not. Describing this primordial nothingness is the main goal of this essay.
Prescientific narratives dealt with the question of creation in two ways: either (1) the cosmos had an origin some time in the past, a birthday or moment of creation, or (2) the cosmos is eternal, its existence stretching from the infinite past to the infinite future. Within these two broad classes of myths— creation and no-creation—there are subclasses. Figure 35.1 summarizes the basic types of myths about the origin of the cosmos.
In the no-creation myths, those that do not assume a particular moment of creation, there are two possible approaches: (1) either the cosmos has existed forever, never beginning and never ending, or (2) the cosmos exists and is destroyed in cycles that succeed one another throughout eternity. The idea of an uncreated cosmos can be found in a text attributed to Jinasena, a teacher of Jainism who lived around 900 CE: “The doctrine that the world was created is ill-advised and should be rejected. . . . If God created the world, where was he before creation? . . . Know that the world is uncreated, as time itself is, without beginning or end. . . . Uncreated and indestructible, it endures under the compulsion of its own nature.”
An example of a cyclic cosmos is symbolized by the dance of Shiva, the Hindu god, who “rises from rapture and, dancing, sends through inert matter pulsing waves of awakening sound, and lo! matter also dances. . . . Dancing, He sustains its manifold phenomena. In the fullness of time, still dancing, He destroys all forms and names by fire and gives new rest.” Shiva repeats his choreography for all eternity, every cycle renewing the world and all material and living forms in it. No one cycle is more important than any other. Creation myths, those in which the world has a beginning, can be divided into three basic types: (1) creation by a supernatural being or beings, (2) cre ation out of nothing, and (3) creation out of chaos. Most creation myths fall
within the first group, myths where the world is created somehow by one or more supernatural beings. As the compilations by Sproul and Freund illustrate, there are hundreds of colorful variations, from the Old Testament narrative of Genesis—“In the Beginning God created the heavens and the earth”—to narratives in which a god sacrifices himself and the world sprouts from different parts of his body, or two gods copulate to create the world, or a mother goddess gives birth to the world, or gods decide to fashion the world out of clay. These narratives assume that the gods responsible for the creation of the world, and its living forms, exist in a timeless reality. In the realm of the gods, the concept of time is inexistent. Immortality renders time useless. It is only when the world comes into existence that time as we know it begins to exist. The origin of time heralds the beginning of history. The Bible opens without time and closes without it, at the end of Revelation, when evil is defeated. For myths assuming that supernatural beings created the world, “primordial nothingness’” signifies the realm of the gods before they engage themselves in creation. Time as we know it appears with the world.
The second type of creation myths assumes that the world came into being out of nothing. There were no gods, no supernatural deeds responsible for creation. The world just came into being out of a primal urge to exist, without any interference from an external agent. An example of this kind of myth can be found in chants by the Maori natives of New Zealand:
From nothing the begetting, From nothing the increase, From nothing the abundance, The power of increasing the living breath; It dwelt in empty space, And produced the atmosphere which is above us.
Here “primal nothingness” means the absence of everything, material or immaterial. One cannot fall into the trap of using dialectic logic here, and argue that “empty space” means the existence of something. When the Maori say “nothing,” they mean it in an absolute sense.
The third type of creation myths assumes that creation was the result of a primal tension between chaos and order. There were no supernatural agents to supervise creation. The cosmos emerged spontaneously as order finally broke loose from chaos and material forms coalesced into being. Complexity emerged from disorder as a spontaneous manifestation of self-organization. A Taoist myth from around 200 BCE describes it this way: “In the beginning there was chaos. Out of it came pure light and built the sky. The heavy dimness, however, moved and formed the earth from itself. Sky and earth brought forth the ten thousand creations, the beginning, having growth and increase, and all of them take the sky and earth as their mode. The roots of Yin and Yang—the male and female principle—also began in sky and earth. Yang and Yin became mixed, the five elements separated themselves from it and a man was formed.”
These basic types of creation and no-creation myths thus give us five answers to the question of how the world originated. Together, these five archetypes of creation exhaust all possible scenarios designed to explain cosmogenesis. Any attempt to explain creation, scientific or not, will necessarily borrow from one or more of the archetypes.
First Transition: From a Finite to an Infinite Cosmos We have seen that Anaximenes believed the cosmos was shaped like a halfonion, with stars carried by some sort of crystalline sphere in their orbs about Earth. Even if somewhat lopsided, his was a closed universe, bounded by the outmost sphere of the stars. Many Greek thinkers, from the Pythagoreans to Aristotle and others, refined the concept of a finite cosmos. Perhaps the bestknown rendering of the finite Aristotelian cosmos is found in Dante’s Divine Comedy (1321), although here it is infused by medieval Christian theology. Earth stood immobile at the center, surrounded by seven spheres carrying the moon, Mercury, Venus, the sun, and the three outer planets known then: Mars, Jupiter, and Saturn. An eighth sphere carried the fixed stars. A ninth sphere, known as the Primum Mobile, was responsible for generating the motions of the inner spheres. Aristotle (whose cosmos was more complicated, featuring over fifty spheres, several for each celestial body) referred to this as the Unmoved Mover, the one who moves for all eternity without ever stopping or needing to be moved by another cause. This is Aristotle’s solution to the problem of the first cause, that is, the first link in the world’s chain of causation. Clearly, even in Aristotle’s mechanistic cosmos of spheres within spheres, the first cause had theological undertones.
Aristotle’s claim that the cosmos was eternal and uncreated presented a dilemma for Christian theologians. The solution was to add a final tenth sphere, the Empyrean Sphere, “the dwelling place of God and the elect.” The Empyrean Sphere was immobile, as time played no role in God’s existence: motion was intrinsically related to change and God was unchangeable. Thus, according to Christian theology, God ruled the universe from the outside, as far from Earth and its citizens as possible. Much closer was Lucifer, who sat in Hell at the center of Earth.
The notion of a closed universe would survive through the Renaissance, even after the shift from an Earth-centered to a sun-centered cosmos perpetrated by Copernicus, Galileo, and Kepler. The shift of the cosmic center clashed with the basic precept of Aristotelian physics that objects always moved toward their places of origin. To Aristotle, earthy things fell because they were returning to where they came from. Fire rose because it had to float toward the upper parts of the sky, under the sphere of the moon. Since the sun and the other celestial luminaries were made of a fifth substance, the ether, placing the sun at the center disrupted the natural order of things: earthy objects such as stones could not fall toward something made of ether. Furthermore, Aristotle supposed that the natural motion of ethereal objects was circular, not linear like objects made of the four elements found on Earth: earth, water, wind, and fire. That being the case, how could the sun stand still and Earth circle around it?
Copernicus did not try to seriously address the physical consequences of this new sun-centered astronomy. Kepler was the first to propose a way out, suggesting that a force emanating from the sun was responsible for the motions of the planets. This was a groundbreaking insight, the precursor of a theory of gravity, which Newton would take up a few decades after Kepler’s death. Before Kepler, no physical causes were sought to explain planetary motions.
Kepler still believed in a closed cosmos, as did Galileo. Only with Newton was there a clear break, triggered by his theory of gravity. Five years after he published his masterful Mathematical Principles of Natural Philosophy, where he laid down the foundations of mechanics and gravitation, Newton exchanged a few letters with Richard Bentley, the chaplain to the Bishop of Worcester. Bentley was writing a set of lectures in which he attempted to use Newton’s new science to argue for the existence of God. If the universe was finite, reasoned Bentley, and the attractive force of gravity governs every bit of matter, how come matter had not collapsed into a great big lump in the middle? Newton replied that the universe was not finite but infinite, and that all cosmic bodies were kept in equilibrium, being equally attracted in all directions. He conceded this to be a very unstable type of equilibrium, comparing it to balancing infinitely many needles vertically. “Yet,” Newton wrote, “I grant it possible, at least by a divine power.” So, to Newton, an infinite universe was only possible if regularly kept in check by God. His new theory of gravity compelled him to propose an infinite universe where God was ever present.
Newton’s successors did away with the notion that God was a sort of everpresent cosmic mechanic, keeping the orbits of celestial bodies in check. The increased sophistication of Newtonian mechanics and its successful applications to widespread phenomena led to a more materialist approach to science, which left little room for spiritual speculations. A famous aphorism by Pierre Simon de Laplace summarizes this change of attitude. When Napoleon, after reading a copy of Laplace’s Celestial Mechanics, asked him where was God in his universe, Laplace replied, “Sir, I have no need for that hypothesis.” God gradually disappeared from scientific rhetoric. There was no need to mention religious or spiritual beliefs in scientific manuscripts. Many scientists are religious, but their beliefs are usually kept away from discussions with their scientific colleagues and from their technical publications.
Second Transition: From an Infinite Cosmos to and Expanding Universe
The next great step in our understanding of the physical nature of the universe came with Einstein’s general theory of relativity. For Newton’s mysterious action at a distance, Einstein substituted the concept of a gravitational field that acts on the geometry of space and the flow of time. According to Newtonian gravitation, any two massive bodies attract each other with a force proportional to the product of their masses and inversely proportional to the square of their distance. When pressed (also by Bentley) to explain what was it in the bodies that caused them to attract each other, Newton replied that he “feigned no hypothesis.” He argued that his theory described very well the observational data, even if at the cost of supposing the existence of a force that emanated mysteriously from massive bodies. That, by the way, is an excellent example of how science progresses: not by supplying all answers at once, but by providing workable models that describe observed phenomena. Einstein proposed that the presence of a massive body bends the geometry
of space around it. More precisely, given that the theory of relativity describes space and time as joined in a four-dimensional space-time, masses also affect the flow of time. The confirmation of this theory has been one of the great triumphs of the human imagination. And yet, here too there is an unexplained hypothesis, that masses (or better, energy) can affect the geometry of spacetime. Once again, the success of the theory justifies its acceptance. We can describe how masses affect geometry, but we don’t know why they do it. It is a matter of personal opinion whether one should care about this.
In the limit of small masses or weak gravitational fields, Einstein’s theory reproduces Newtonian gravitation. Thus, it can be regarded as a generalization of Newton’s gravity, albeit with a very different conceptual structure. Just as Newton wondered about the implications of his theory to the structure of the universe as a whole, so did Einstein, who proposed applying his theory to cosmology, pioneering the study of what is now known as relativistic cosmology. His basic idea was simple: since matter determines geometry, if we knew how much matter there is in the universe, we could apply the theory to obtain its geometry: its shape and size.
At the time, there was no compelling evidence to suppose the universe was changing in time. So Einstein proposed a static universe with the closed geometry of a sphere: it should be visualized as a three-dimensional generalization of the surface of a ball, which is two-dimensional. Its geometry is called closed because, just as with a ball, if you mo
ve in one direction you will end up coming back to your starting point. Einstein implicitly assumed that his universe was eternal and uncreated, curiously reminding us of Aristotle’s model. The choice of spherical symmetry had the added advantage of providing a finite cosmos without a boundary: on the surface of a sphere, no point is more important than any other. This was reflected in Einstein’s “cosmological principle,” which stated that on average (and the average here is taken over very large distances, of millions of lightyears) the universe looks the same everywhere.
A flurry of activity followed Einstein’s first cosmological model. By 1930, several models had been proposed, each with its own predictions about the geometry and behavior of the universe as a whole. These were the “desktop universes,” cosmological solutions to Einstein’s equations obtained by varying the assumptions about the material content of the universe. The most notable were those found by the Russian scientist Alexander Friedmann in 1922, which have the distinction of being the first to suggest that the universe expanded in time.
Friedmann suggested that the fate of the universe depends on the amount of energy (matter is a form of energy, but not the only one) it contains: if above a certain critical value, the universe would eventually cease its expansion and recollapse into a point of infinite energy and density. This cycle of expansion and contraction could in principle repeat itself throughout eter nity, an image reminiscent of the Hindu creation myth based on the rhythmic dance of Shiva. If, on the other hand, the amount of energy were equal or smaller than the critical value, the universe would keep expanding forever. So Friedmann turned the universe into a dynamical entity, endowed with its own history.
When the American astronomer Edwin Hubble proposed in 1929 that distant galaxies were receding from each other with velocities proportional to their distances, cosmology entered a new era, driven not only by theoretical speculation but also by astronomical observation. Although Hubble did not subscribe to the interpretation that the recession of galaxies implied an expanding universe, the evidence quickly became compelling, if not yet conclusive.
The Belgian cosmologist and priest Georges Henri Lemaître, a pioneer of the desktop universes period, took the idea of an expanding universe to its logical consequence: if the universe is expanding now, it must have had a beginning some time in the distant past. In 1931, he suggested that the cosmos was initially like a giant atomic nucleus, the “primeval atom.” Just as large nuclei are radioactively unstable, Lemaître’s primeval atom spontaneously decayed, emitting different kinds of radiation. As it did so, it also generated the space where it existed: “The disintegration of the atom was thus accompanied by a rapid increase in the radius of space which the fragments of the primeval atom filled, always uniformly.” Lemaître never speculated on how the primeval atom appeared in the first place, trying to avoid mixing his physics with his Christianity. He did, however, suggest that the decay of the atom resulted in the creation of “fossil rays,” a sort of radiation left over from the first moment after the beginning. His vision was amazingly prescient.
The notion of a universe with a beginning rapidly generated friends and foes. During the late 1940s, two rival cosmological models pitched for dominance. Their key difference was how they handled the question of the beginning.
Herman Bondi and Thomas Gold, and, independently, Fred Hoyle, all from Cambridge University in England, proposed a cosmological model without a beginning. They generalized Einstein’s cosmological principle to a “perfect cosmological principle,” wherein not only all points in the universe were alike, but also all moments in time. As no moment in time is more important than any other, they proposed a cosmos without a history, which reminds us of the Jain creation narrative of an eternal, uncreated universe.
In order to accommodate the recession of galaxies observed by Hubble, the trio suggested that as the universe expanded and the density of matter decreased, more matter would be created to maintain its average density constant. To the critics who said that matter creation violated the law of conservation of energy, the trio responded that in order to keep things as they are, only about an atom of hydrogen would need to be created in a cubic of half-meter size per century. Clearly, such a minuscule amount of energy violation would be impossible to test in the laboratory. What we know of nature is based on the accuracy of our observational tools; if we cannot measure a small violation, we cannot state with certainty that energy is perfectly conserved. Due to the balance between dilution of matter and its creation, this model became known as the “Steady State” model.
The competing model was proposed by the Russian-American George Gamow in 1946, and refined through several works with Ralph Alpher and Robert Herman. It assumed the universe had a very hot and dense infancy and has been expanding and cooling ever since. Although Gamow and his collaborators did not speculate on the very early stages of the cosmic evolution, their model was compatible with a universe with a beginning some time in the distant past. Their interest was not to solve the question of creation, but to understand the physical processes responsible for generating the chemical elements that make up the matter in stars, galaxies, and people. Gamow believed that the nuclei of the chemical elements were formed by a continuous aggregation of protons to neutrons as the universe expanded and cooled. In this sense, the matter we are made of is a fossil from the earlier stages of the universe’s history.
Their main idea is that, early on, the universe was too hot for protons and neutrons to bind to each other and form atomic nuclei. However, as the universe expanded and cooled, the strong attraction between protons and neutrons eventually prevailed, and the first chemical elements formed, starting with hydrogen (one proton and no neutron) and its isotopes (deuterium with one neutron, and tritium with two), and helium (two protons and two neutrons) and its isotope (with one neutron). This process, known as nucleosynthesis, started roughly when the universe was one second old and ended when it was three minutes old. Although Gamow originally proposed that all chemical elements were forged in the primeval furnace, we now know that only the lightest elements—hydrogen, helium, and lithium—and their isotopes are primordial. All heavier elements are made in the interior of stars in a process known as nuclear fusion. Still, nucleosynthesis predicted the cosmic abundances of the lightest elements to be 75 percent for hydrogen and 24 percent for helium, which are in excellent agreement with observations. Most of the matter in the universe consists of its two lightest chemical elements.
During a 1949 debate with Gamow, Fred Hoyle referred to this concept derisively as the “Big Bang.” The name stuck, and that is how the model is now widely known. The distinctive prediction that finally determined the advantage of the Big Bang over the Steady State model was the existence of a background radiation, a fossil left over when electrons finally bound to protons to form the first hydrogen atoms. Present-day calculation sets the time of hydrogen synthesis at about 400,000 years after the “bang.” Gamow and his collaborators not only proposed the existence of these fossil rays (as suggested in Lemaître’s primeval atom) but also computed what its present-day temperature should be. Their numbers varied between three and ten degrees above absolute zero (-273 Celsius), or Kelvin. The present-day value is of 2.75 degrees Kelvin. The dis covery of this cosmic background radiation in 1965 by Arno Penzias and Robert
Wilson resolved, in the minds of most but not all cosmologists, the dispute between the two rival models. The Big Bang model is now accepted as the best description we have for the early history of the universe.
Third Transition: From a Classical to a Quantum Universe
Any physical theory has a range of applicability, determined by certain parameters. For example, Newtonian mechanics works well for speeds sufficiently below the speed of light, and for distances sufficiently larger than atomic and subatomic scales. High-speed motion needs Einstein’s relativity theory. But Einstein’s theory doesn’t let us describe the very first moments of cosmic history. Nor does it explain the motion of atomic and subatomic entities; for that, we need quantum mechanics.
Classical (Newtonian) physics describes the transfer of energy between two systems (e.g., an ice cube melting in a glass of water) or the motion of objects as continuous. But in quantum physics, the world of the very small, energy is transferred in little bits called quanta. We are familiar with several quantized systems in our everyday life. The most common is the monetary system: the quantum of the American monetary system, for example, is the cent. In this system, no denomination can be smaller than a cent, and all financial transactions proceed in multiples of this fundamental quantity.
If energy is quantized, how come we don’t perceive this? Imagine a very large number of small objects piled up on each other: individual ones are imperceptible. If you look at a beach from afar, the sand appears continuous, a frozen light brown substance. But if you sit on a sandy beach and focus on the small patch around you, you begin to differentiate the individual grains. In the classical physical world, transactions involve so many quanta of energy that they appear continuous, even though they aren’t.
The quantized nature of quantum processes has several amazing consequences. In classical physics, once a ball is at rest, it will stay at rest unless disturbed. In quantum mechanics, there is no such thing as absolute rest. In the world of the very small, everything jiggles. As a consequence, the values of physical quantities are fuzzy. We don’t really understand why this is so, but we know that it is so. The uncertainty principle, proposed by Werner Heisenberg in 1926, refers to this jiggling. The principle encapsulates the unavoidable clash between the way we picture the world classically and the abstruse reality of the quantum world. We describe reality and objects in terms of images, such as a particle (a small, localized object) or a wave (a widespread, regularly patterned object). What experiments have shown is that quantum objects such as electrons or atoms can manifest themselves as either particles or waves, depending on how we look at them. The point is, a quantum object is neither particle nor wave. It is neither localized nor widespread. And yet, it is both at once. In the absence of an ideal picture, it is best to imagine quantum objects as perpetually jittering things. And if they are always jittering, their energies can never be zero, since they are never truly at rest.
At very short distances, gravity must also be quantized. And since Einstein’s relativity theory describes gravity as the curvature of space-time, the fourdimensional continuum where physical events take place, quantizing gravity means quantizing space and time. No more treating space as an inert, smooth arena where events take place, or time as a river resolutely flowing forward always at the same rate. In quantum gravity, the geometry of space and the flow of time can fluctuate. If gravity is fuzzy, there are no more well-defined points in space.
For cosmology, this means that considering the universe as having started from a singular point in space with infinite energy density is too simplistic a view. It seems better to say that, in the beginning, there was a quantum era of cosmology, when quantum effects dominated the scene and space-time was fuzzy. Our cosmos emerged from this quantum cosmological realm as a bubble in a boiling soup, so to speak. This does away with the issue of “But what happened before the Big Bang?” After all, if a streaming time is a classical concept, one can only talk about the flow of time within the framework of Einstein’s theory, which is applicable only up to when quantum effects dominate. It is best to describe the cosmos as having a transition from a quantum era, where no single time-flow really exists, to a classical era, where time flows as we are used to. The remaining question, then, is what is this quantum cosmological era? Our present answers, at least within quantum cosmology, are compelling, but still incomplete.
Rethinking the Cosmic Origin
Much of the modern rethinking of cosmic origins happened during the 1980s. Influenced by Edward Tryon’s ideas dating back to 1973, James Hartle and Stephen Hawking, and, independently, Alexander Vilenkin and Andrei Linde, assumed that the initial state of the universe was a pure quantum state. Therefore, it had to obey the rules of quantum mechanics as they applied to the gravitational field. The same way that an electron orbiting an atom obeys an equation that predicts the probability of finding the electron in this or that energy level (the Schrödinger equation), it should be possible to write an equivalent equation determining the probability that the universe will have this or that geometry. This program, known as quantum cosmology, treats the whole universe as a quantum system. And, as in any quantum system, a quantum universe would have counter-intuitive behavior. The most important for cosmology is the concept of “tunneling.” Quantum systems that are constrained by a certain obstacle (a force, an energy barrier) can traverse it and emerge on the other side. Some refer to this as “barrier penetration.” An equivalent phenomenon would be water that leaks spontaneously through glass, or, more dramatically, a person going through a wall, like a ghost.
A quantum universe is a hard thing to fathom. A useful image is that of a boiling liquid. Bubbles emerge and disappear in rapid succession, some of them living long enough to escape into the air. Picture the primordial universe as a quantum soup of geometries, possible space-times of different geometries popping randomly in and out of existence. The Big Bang model, our classical universe described by the general theory of relativity, corresponds to a specific fluctuation, that is, a specific space-time geometry. It is the one bubble that managed to escape the quantum soup, tunneling into existence like the bubble that reaches the surface of the boiling pot. This quantum soup of space-time geometries is the modern version of “primordial nothingness.” (But Barrow and Cole describe other kinds of nothingness as well.) According to this picture, our universe is just one of a multitude, or perhaps infinitely many universes out there, which may pop out of the eternally boiling quantum geometry soup. Some call this entity a multiverse or a metaverse, and each of the bubbly attempts at existence is called a cosmoid. Most cosmoids live an ephemeral existence, reverting back to the primordial soup before they can grow into anything noticeable. We happen to live in a cosmoid that is somewhat special. It had the right combination of physical parameters to have survived for 14 billion years and to have allowed for complex structures to emerge, from stars and galaxies to lobsters and philosophers. Many questions are probably bubbling in your mind, just as cosmoids do in the quantum soup. If there are other universes out there, can we ever find out about them? Why is our cosmoid so special? Are we somehow related to its existence, perhaps even being its purpose? Is the universe purposeful?
If there is indeed a multiverse, we may never be able to communicate with its other parts. We live within a bubble with a radius of 14 billion lightyears, the distance traveled by light since the beginning of (classical) time. Hence, we cannot receive or send signals beyond our bubble. True, as our bubble grows, it may brush against other cosmic patches. But we are talking of billions or even trillions of years. Could we tunnel into another universe through objects called wormholes, hypothetical shortcuts across the cosmic geometry? This situation calls into question how scientific the idea of a multiverse really is. After all, physics must be empirically validated; ideas must be confirmed by observations to be accepted as valid descriptions of nature. Without a specific test, such notions may as well be relegated to metaphysics. We need to be able to prove what theories are wrong in order to improve those that are right.
To think that our cosmoid is special in some way is also a very difficult concept to swallow. By special it is meant that only a very small subset of all possible universes could have evolved to become this way. But if our universe is special, so must we be, since we are the ones here thinking about it. This general line of reasoning is referred to as the anthropic principle. Its main idea is to use what we know about the universe (that it is old, that it has complex structures, that it has life) to learn about its fundamental properties,
such as how much and what kind of matter it has, and what sort of infancy it had. But the anthropic principle is burdened by a posteriori reasoning: it works backward. It does not explain what physical mechanisms determined the universe’s age or parameters; it simply affirms that it could not have been otherwise. We need to be more ambitious with our theories, even at the risk of having fewer satisfactory answers.
So, What Can We Say?
Some people get frustrated when they hear that scientists still don’t have an accepted explanation for the origin of the universe. They want to know, and they want to know in simple, comprehensible terms. This expectation is derivative of religious zeal; for those who believe in the mythic explanations of religious texts, faith is enough to settle the question. Anyone who takes an interest in the history of religion, however, knows that religious texts are open to multiple interpretations. In any case, the mechanisms of religious and scientific enquiry are very different. Science will never have all the answers. It is a continuous process of discovery, based on the acquisition of empirical data and the subsequent organization of that information into explanatory and predictive mathematical models. As we develop new tools, we will also probe into new unknowns for which new science will be needed. Thinking about the origin of the universe, for example, forces us to deal with the nature of time.
The origin of the universe may never be fully explained within science. For science is built on sets of rules and only functions within these rules. If in the future someone develops a flawless model of quantum cosmology that is perfectly in accordance with observations, even to the point of predicting new phenomena that are subsequently observed, can we then claim to have understood the origin of the universe? Not really. After all, we can always ask where the set of rules used to build the model came from. Why should the universe obey the rules of general relativity and quantum mechanics? To say that other universes may not and we are one in infinitely many possibilities doesn’t help at all. (Proving convincingly that this is true, however, may.) Science, as it is presently conceived, cannot explain itself. Unless some new kind of conceptual framework is developed for science, and that is always a possibility, we must be content with what we can do with the one we have, trying to change it here and there as we go along. And this is not so bad.
The most important lesson to be learned from science is that ignorance is a key to progress, that only by not knowing can we know more. To not have all the answers is a good thing. So, even if we may never fully explain the origin of the universe with our present scientific framework, the road leading to the answer will be full of wonders. We have only gotten started on a very long trek.
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