In scientific history, including that of the twenty-first century, discoveries are often made by parting company with established theories—despite a scientist’s best intentions not to. After all, breaking from the mainstream isn’t easy; established theories are what a scientist grows up with, is inspired by, and cannot do without. They are often a scientist’s lifelong partner and best friend. At the same time, discoveries are a scientist’s own brainchild; they are the enticement that attracted her to science in the first place and the legacy that survives her. The lucky ones have one or two breakthrough ideas during their lifetimes.
Often, though, the exaltation of a breakthrough idea is tested against the desire to maintain loyalty to established theories. This test happened to the founders of quantum theory, Planck, Einstein, Bohr, Heisenberg, and Schrödinger, and other great scientists of their generation. Confronted with this particular test, at least, many of these great minds failed—at first.
In such situations, scientists face a dilemma: they have to choose between their own theories and the theories that were the foundations on which their work was built. It is an impossible choice.
Difficult though that choice may be, however, any scientists worth their salt will choose the same way: they will select the path of investigation, of knowledge, of testability, no matter how steep the climb may be. It was no different for the founding fathers of quantum theory. At first, they resisted breaking away from the determinism of classical physics. But once convinced that they had the correct answer, they did the unthinkable. Scientific integrity overruled rigid austerity. They gave in and courageously stood tall against the might of classical physics. They bravely crossed over to the quantum realm and forever changed the way humans think about our world.
Perhaps the theory of the multiverse is poised to cause another, similar paradigm shift—forever altering how we conceive of our world and our place in it. We know that our universe is not eternal, and it is not infinitely large. It had a beginning 13.8 billion years ago, and it has grown to about 10^27 centimeters—its present size. These are big numbers but certainly not inconceivable for minds like ours. We have every right to wonder what existed in the cosmos fifteen billion years ago and what the cosmos looks like at 10^32 centimeters, beyond the horizon of our universe. We have every right to wonder—and investigate.
Cosmology is not a new field. In fact, it is among humanity’s oldest intellectual endeavors. All traditions of ancient mythology contain tales of the origin of the universe, sometimes based on gods and supernatural forces, other times on observations of the night sky combined with critical thinking. Human beings were asking probing questions about the cosmos long before telescopes, computers, Einstein’s equations, or quantum theory existed.
We cannot plot our future without a map of our past, and our past has some very surprising lessons for our present. Many of the models and theories of the universe in modern times can trace their roots to the wisdom and ideas of the ancients. And many of today’s battles over whether our universe is the center of the cosmos or just one in a vastness of universes have been fought before.
My introduction to the evolution of scientific thought came from my father. After reading Russian translations of English books, my father translated them and read them back to me in Albanian. Every Sunday that he was not in exile, my father shared his knowledge. My more practical mother sent her two intellectual dreamers to the National Library, which had a café and cake shop on the terrace and three floors of archives below.
To this day, I can still smell the green vinyl covering of the floors, see the spiral staircase rail I used to slide down, and hear my dad delivering seminars on the history of scientific thought to his devoted and attentive audience of one. I loved the stories he told about philosophers’ lives and work, great thinkers who debated and fought, sometimes even coming to blows, over cosmic issues. He was the person who introduced me to all the ways to see the proverbial forest despite the thousands of individual trees. My first exposure to prohibited Western literature and the evolution of ideas was through his translations.
The roots of Western cosmological thought can be traced all the way back to ancient Greece. No matter how far science believes it has advanced, the leading schools of Greek philosophy still echo in our present-day perceptions of the organization of our universe and what lies beyond. In many ways, our most modern ideas about the universe began there. Around 400 BCE, the philosopher Democritus, who was born into a wealthy and powerful family, used his wealth to travel to India, Egypt, and throughout the Mediterranean to absorb knowledge from other cultures and scholars. From his mentor Leucippus, he adopted the idea that the world was made up of indivisible clumps of matter (atoms) and empty space (voids) through which those atoms moved. Democritus also believed in a deterministic universe in which all events could be estimated and anticipated with 100 percent certainty. In Democritus’s world, the motion of atoms was mechanical. It followed a set of rules and was completely predictable.
The Democritean model of a universe’s creation starts with a collection of atoms moving around the voids, then clumping together to form larger objects such as stars, planets, and the whole universe. Because there are an infinite number of atoms and voids, this process can be continuously repeated to form many universes, each of which meets its end when it collides with another and then is atomized back into individual particles. Thus, Democritus was the first recorded Western philosopher to imply that our world might be part of a multiverse.
Plato, a student of Socrates and perhaps the most influential thinker in Western science and philosophy, was a contemporary of Democritus, and it is not an exaggeration to say that Plato hated his fellow philosopher. It is alleged that Plato so loathed Democritean ideas that he wanted to burn all Democritus’s writings. I was astonished to read that Isaac Newton, two thousand years later, did the same with all the writings and portraits of fellow scientist and predecessor at the Royal Society Robert Hooke in an attempt to wipe out every trace of him. This is a recurring theme; many scientific conflicts have been repeated through three thousand years of history with the same viciousness, dedication, and passion as in our own modern times. (Though perhaps with a little less venom in the pre-internet era.)
While the Democritean model describes the material world in terms of atoms and voids, Plato took another position. He posited two levels of existence: the physical world that we see around us and an abstract, higher plane of existence, the form or demiurge, which fashions and maintains the physical universe.
Plato’s student Aristotle, the forefather of the natural sciences, argued for a different view; he believed that the cause of an event could be found in the physical world, that there was no need for a higher power or demiurge. In order to explain the motion of planets and stars without a demiurge, he embraced the view that the universe was a collection of etheric rotating celestial spheres to which planets and stars were “glued,” with the Earth fixed at the center of the spheres. Aristotle’s ether was an invisible, crystal-like material that filled space. His universe had no beginning and no end; it was eternal but limited (spatially) to about twenty thousand times the size of the Earth.
His model was supported by the geocentric Ptolemaic system developed by the Alexandrian astronomer Claudius Ptolemy in the second century CE. In the geocentric system, Earth sits at the center of the universe. This Ptolemaic view of planetary motion occurring through rotating celestial spheres dominated astronomy for almost two millennia, until the time of Galileo.
But Aristotle, Plato, and Democritus were not the only ones to have sweeping ideas about our universe. I think it is stunning that in the third century BCE, the Greek atomist philosopher Epicurus reasoned that there was a universal “uncertainty principle”—more than two thousand years before it was postulated by Heisenberg! Epicurus wanted to allow for human free will. He argued that if the course of atoms was predetermined and predictable, then people’s lifetime experiences had to be predetermined, since people were also made of atoms. But, he went on, if that were true, then people simply become bystanders to their own existence rather than participants in it. Which could not be.
Consequently, rather than a Democritean, predictable, deterministic world, Epicurus advocated for an unpredictable—indeterministic—universe. He postulated that nature allowed for random small deviations or the swerving of atoms in the voids, which moved them away from their predetermined course. Collectively, these deviations in groups of atoms, whether in humans or the whole universe, made their course undetermined, so they could be spoken of only in terms of chances. Two incredible facts about Epicurus’s life stand out. First, his reasoning in favor of an uncertainty principle and an indeterministic universe was reached through arguments for the existence of free will within human morality, yet it ultimately led him to establish the quantum uncertainty principle. Second, many of his original writings were preserved by a catastrophic accident—a library of papyri of his work was discovered inside the residence of a wealthy Roman senator during excavations of the town of Herculaneum in the eighteenth century. The papyri had been carbonized and preserved by volcanic ash from Mount Vesuvius’s eruption in 79 CE.
The importance of Epicurus’s work in physics and ethics cannot be overstressed. Thomas Jefferson considered himself an Epicurean, writing, “If I had time, I would add to my little book the Greek, Latin and French texts, in columns side by side, and I wish I could subjoin a translation of Gassendi’s Syntagma of the doctrines of Epicurus, which, notwithstanding the calumnies of the Stoics and caricatures of Cicero, is the most rational system remaining of the philosophy of the ancients, as frugal of vicious indulgence, and fruitful of virtue as the hyperbolical extravagances of his rival sects.”
The philosophy of Epicurus was reintroduced to the Roman world and Western philosophy by the poet Lucretius in his epic poem De Rerum Natura (“On the Nature of Things”). Unlike Plato, Epicurus rejected the need for divine intervention in the formation and regulation of the universe. Like Democritus, he thought of the world as an infinite space and time containing many universes—a multiverse. But unlike Democritus, Epicurus believed the world had no certainty.
The fundamental argument between a Democritean deterministic versus an Epicurean indeterministic world is much the same one that continues to this day. The two sides have remained in a tug-of-war, with both camps for decades divided between an Einstein-inspired classical universe, where every event can be estimated and determined, and a competing quantum multiverse theory of an indeterministic cosmos that allows for many universes.
Before they reached our own era, these ancient Greek theories traveled across the intervening centuries. In the thirteenth century, the Aristotelean view of the cosmos fascinated the Western theologian and philosopher Thomas Aquinas. Aquinas tried to reconcile the Aristotelean paradigm with Christianity. While still respecting Aristotle’s view, Aquinas posited a universe that had a beginning and therefore required divine intervention to come into existence.
In early-sixteenth-century Poland, the astronomer Nicolaus Copernicus, in a paper published just before his death in 1543, formulated the heliocentric system, in which the Earth was one of a collection of planets orbiting the sun, even though for much of his lifetime, Copernicus was reluctant to break with Aristotelean authority and continued to subscribe to Aristotle’s celestial spheres.
A few decades later, in the 1570s and 1580s, the Danish astronomer Tycho Brahe found that the planets, including the Earth, were indeed orbiting the sun. Using detailed measurements, he showed that the paths of comets passed around the sun and therefore through the celestial spheres. For the first time, there was observational evidence to challenge Aristotle’s shell model of the universe. German mathematician and astronomer Johannes Kepler (1571–1630) drew upon Brahe’s calculations to produce the laws of planetary motion, confirming the sun’s central position in our solar system.
Final proof came from one man: Galileo Galilei, born in Pisa in 1564. Galileo learned of the newly invented telescopes produced by spectacle-makers in Holland. In 1608 and 1609, he built his own telescope to conduct astronomical observations. Applying his telescope and his genius, Galileo formally confirmed the existence of the heliocentric system, ensuring that the Earth would never again be viewed as the center of the universe. (Along with this new proof of how the universe was organized came efforts to calculate the age of the universe. In 1650, James Ussher, an erudite and influential Irish Anglican bishop, declared that the universe had started at 6:00 p.m. on October 22, 4004 BCE. This declaration may seem strange today, but his ideas were taken seriously until subsequent geological research in the nineteenth and twentieth centuries found that fossils of “terrible lizards,” or dinosaurs, that once walked the Earth were millions of years older.)
Aristotle’s views of the universe were finally laid to rest by Isaac Newton, an incontestable giant of physics and, as the astronomer royal Lord Martin Rees said, “the best student Cambridge University ever had.” In his book Philosophiae Naturalis Principia Mathematica (“Mathematical Principals of Natural Philosophy”), first published in 1687, Newton gave the world a theory of gravity and motion that showed that the heliocentric system was held together by gravity. To this day, Newton’s theory continues to provide explanations for the motion of most objects in the universe and on Earth.
But Newton firmly and, as Einstein was to demonstrate later, incorrectly, believed that space and time were the absolute building blocks of the fabric of the universe—that is, they were always there, like a permanent container, a sort of bucket inside which everything else moved and existed. Newton’s theory of gravity dominated physics until the late nineteenth century, when further discoveries in mathematics and physics led scientists to challenge that model.
Newton was convinced space and time were a structure that was always there, supporting the universe and the motion of celestial bodies within it. Newtonian space and time would appear like a rigid board, one that could not change its shape no matter how much weight was put on it. Einstein saw things differently—and it profoundly changed our understanding of the nature of our universe.
Einstein’s theory of relativity transcended Newton’s theory (just as Newton’s theory had transcended Aristotle’s—such is the history of science). It gives a universe where nothing exists before the singularity; that is, a universe without an absolute clockmaker. A universe where every event except creation can be calculated and predicted with certainty.
Up to this point, geometry had been based on the work of the Greek mathematician Euclid, who published his Elements around 300 BCE. Euclid had deduced the principles of his geometry from a small set of axioms, starting with “The shortest distance between two points is a straight line,” an axiom we can easily grasp. Indeed, we know that if we were to walk from, say, the Art Institute to the Wrigley Building in Chicago, the shortest path would not be a zigzag or a circle but a straight line along Michigan Avenue.
The problem is that Euclidean geometry breaks down when applied in a curved space-time, such as the space-time of our universe. To see why, imagine for a moment that the universe looks like the surface of a sphere, roughly like planet Earth. On this sphere universe, we want to travel from Chicago to Tokyo. We can see on the globe that the shortest path joining Chicago and Tokyo is part of a circle that goes over the North Pole. It is definitely not a straight line. The reason that the shortest path is an arc is due to the curvature of the sphere. If we had applied Euclid’s straight-line geometry to the curved space-time of our example, we would have been misled.
In the late nineteenth century, mathematical breakthroughs, notably with the work of Riemann, Lobachevsky, and Minkowski in non-Euclidean geometry, began to transform physics and established the foundation on which a new theory of the universe could be built. The beginning of the twentieth century witnessed the greatest revolution thus far in the history of physics. Not unlike Plato’s ancient view of two levels of existence, twentieth-century physics also found two levels of existence: the macroscopic, visible world, a single, deterministic universe governed by Einstein’s theory of relativity; and the microscopic, unseen world, inhabited by atoms, electrons, particles, and waves, whose workings were captured by quantum mechanics. But the most disruptive element of a quantum universe is not its small size; it is its indeterminism, which means that every event in it, including its own creation, is uncertain and based on probabilities.
And that is where we began our story in this book. We have seen how a quantum universe based on probabilities allows for the existence of many worlds—in other words, the multiverse.
The journey from antiquity to the third millennium may seem long. But put in perspective, it took about 3.8 billion years for life to emerge on Earth. In another four billion years, our Milky Way galaxy is set to collide with Andromeda, a nearby galaxy, an event that will likely wipe out our planet. Even before that event, our planet will be too hot from the increase in the sun’s luminosity, and life as we know it will be extinct in about one billion years.
Viewed at this scale, five thousand years are a mere blink of an eye. Yet in that blink of an eye, humanity, through imagination, observation, and courage, has journeyed to the very edge of the universe and the first millisecond of its conception 13.8 billion years ago and to a theory of the creation of our universe—an achievement of astounding proportions. Today, through the power of physics, observation, supposition, and mathematical proof, we can now reach back to the moment before our universe was conceived.
Truly, today we have gained the ability to travel beyond the confines of our own universe, if only in our minds. But perhaps in the process, we have discovered something more important: that our universe and our very existence arose from a bizarre quantum-probability game and that our universe is but a humble member in an intricate, vast, and breathtakingly beautiful cosmic family.
When I was growing up, for two weeks every summer, my parents rented a holiday apartment by the beach in their hometown of Vlora, an ancient coastal city along the Adriatic Sea. Known as Aulona in Greek and Roman times, it remained a special place to visit even during 1980s Communist Albania. Aulona’s spirit, imprinted on the traditions, superstitions, and landscape of the place, floats outside of time. The town is guarded by a rugged terrain of high mountains, turquoise waters, and black rocks that blend into silence at sunset. It is a place to dream.
My favorite evening activity during these family vacations was to sit on the sand alone. I would watch the waves linger at the soundless horizon and then break rhythmically onto the shore. As night fell, I waited until the line dividing sky and sea blurred away and all boundaries vanished. Of course, everybody knew that the world beyond the horizon was strictly forbidden to those of us behind the Iron Curtain. But sitting in the dark, I was free to imagine. Were the kids who lived on the other side of the Adriatic, in Italy, equally enchanted by the edge of the sky and sea we shared?
Eventually my dad would come over and, without reprimand, sit on the sand next to me. Then it was the two of us in a hushed conversation with the sky. Before long, he would tell me it was time to leave, and the gentle spell of the sea and the sky would break.
In 2013, twenty years after our family’s last trip to Vlora and the year the Planck satellite was launched, I returned to my favorite spot in Vlora with my three-year-old daughter. She was excited to be there, completely carefree, happy to splash sand and water in every direction. How stunning, I thought—how far we’d come in just a generation, politically and scientifically. My daughter belongs to a generation and a country that does not have to accept limits on imagination and discovery. She can live by the motto that my father taught me: “Without knowledge, existence is in vain.”
And how much further we have come in the brief time since this trip. Consider for a moment the possibility of a far more complex and richer cosmos made up of many universes—a multiverse in which our universe is but a single, humble member in a far-flung corner of this vastness. That possibility allows for the mathematical calculation of a range of values for habitation; it allows us to objectively compare chances of existence of different universes, rather than the logically flawed comparison of a single universe to itself, and it allows us to derive and explain our origins, not postulate them on anthropic grounds. It offers a glimpse of the cosmos beyond our horizon and before the Big Bang. And rather than shutting the door on scientific inquiry, it pushes us to think more broadly and boldly.
The scientific knowledge that the human race has accumulated so far is a glorious chapter in the book of our species’ endeavors. But the next frontier in the relationship of humans with nature—laws above and the multiverse below—is waiting to be written. When we take up the pen, we will be bound by nothing—nothing, that is, save for the limits of our own imagination.
Acknowledgments
This is it. I have crossed the finish line, written the book, and I haven’t done it alone. I would like to thank the many friends, colleagues, and family members who contributed to the completion of this project.
First, thank you to my scientific collaborators, some of whom I have already mentioned, for sharing the ups and downs of this journey of discovery. I am also grateful to Professor Christian Iliadis, my colleague and friend at UNC, for his enthusiastic support.
A special acknowledgment goes to Peter and Amy Bernstein, my dear friends and agents at the Bernstein Literary Agency. Peter and Amy, thank you for your guidance, encouragement, and direct help with editing the whole manuscript multiple times, something very few people would do. And thank you for your continuous trust in me throughout the years.
I am grateful to Alexander Littlefield, executive editor of Mariner Books at HarperCollins, who mentored me through the writing process and managed to make me do something I haven’t done before—talk about myself! His high professional standards are demanding, but at the same time the incredible care, scrutiny, and thoroughness he invested in every line of the book have been very helpful and motivational during the crucial final editing stages. I would also like to express my gratitude to Stuart Williams, executive editor, and his deputy Will Hammond at Bodley Head, Vintage Penguin, who worked closely with Alex to provide invaluable editorial support.
Many thanks go to Lyric Winik, who patiently helped me edit many versions of the book as it evolved into its final form.
I would like to acknowledge the help of many friends who read earlier drafts and provided feedback and support: Phil Doran and Nick Ward in Cambridge, England; Rob Westermann and David Ballinger in the United States; and Dhurata Sinani in Canada.
The support of my family has been incredible. I appreciate the help of my husband and companion on my journey, Jeff Houghton, who was the first person to read, candidly criticize when called for, and edit every line I wrote while providing backup on all the family fronts when I was busy writing. Special thanks also to my brother, Aurel Mersini; his son (my nephew), Dominic; and my mother, Stela Mersini, for their unwavering and uplifting support and their honest comments.
Last but not least, I would like to thank the two most influential people in my life, the ones to whom this book is dedicated and who, through their unconditional love and support, do not ever allow me to grow old:
My exceptional daughter, Grace Houghton, fills every day of my life with pride and happiness. Although she is still a child, her infectious optimism and maturity beyond her years, her love, and her encouragement are my inspiration. Grace, as you used to tell me when you were younger, I love you from here to infinity, with a love bigger than the multiverse!
Anyone reading my book will not be surprised to hear that the biggest influence on my earlier years was my wonderful father, best friend, and confidant, Nexhat Mersini, who died in 2011. Dad, I miss your quiet strength, your wisdom, kindness, integrity, friendship. I most of all miss our long conversations over triple espressos about any interesting topic, be it in science, math, arts, poetry, philosophy, evolution of ideas, or music. I hope I have done justice to your memory through our stories. Thanks, Dad.