The Epic Quest to Understand the Quantum Nature of Cause and Effect


By Paul Halpern

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From Aristotle’s Physics to quantum teleportation, learn about the scientific pursuit of instantaneous connections in this insightful examination of our world.

For millennia, scientists have puzzled over a simple question: Does the universe have a speed limit? If not, some effects could happen at the same instant as the actions that caused them — and some effects, ludicrously, might even happen before their causes. By one hundred years ago, it seemed clear that the speed of light was the fastest possible speed. Causality was safe. And then quantum mechanics happened, introducing spooky connections that seemed to circumvent the law of cause and effect. Inspired by the new physics, psychologist Carl Jung and physicist Wolfgang Pauli explored a concept called synchronicity, a weird phenomenon they thought could link events without causes. Synchronicity tells that sprawling tale of insight and creativity, and asks where these ideas — some plain crazy, and others crazy powerful — are taking the human story next.




Ancient Views of the Celestial Realm

The Sun, seated in the middle of them, looked at the boy, who was fearful of the strangeness of it all, with eyes that see everything, and said “What reason brings you here?”

—OVID, Metamorphoses (translated by Anthony S. Kline)

MAPPING OUT THE WORKINGS OF THE COSMOS HAS BEEN HUmanity’s long-standing quest. The wheels within the wheels of astral motions—from the Moon to the Sun to the starry dome, each as seen from Earth—set our calendars, which, in turn, govern our lives in integral ways. From ancient times until the present, we’ve tried to find relationships between the behaviors of these bodies—first through speculation and then through science.

Understanding such interactions requires gauging their speeds. A connection involving a delay is fundamentally different than one that is instantaneous. Over the ages, as we’ve learned about the monumental scope of the universe, fathoming which interactions operate at various rates has become paramount. After all, swiftness is relative to size. Any lagging for a brief interval, presuming the rate stays the same, becomes increasingly significant for longer and longer spans.

To model how a city functions, an engineer would need to understand its networks of transportation and communication. A city restricted to pedestrians would have a wholly different character than one laced with multilane highways—especially in terms of how rapidly products would be delivered from place to place. A community in which mobile phones are banned or restricted would operate at a different pace than a locale in which everyone is carrying a phone at all times.

Similarly, deciphering the dynamics of the web of forces and other interactions in the universe requires a precise comprehension of their operating speeds. We now know that the speed of light in a vacuum serves as an important upper limit for causal interactions between objects in ordinary space. By causal, we mean obeying an order of events in which each effect (something being pulled, for example) is preceded by its cause (the thing doing the tugging).

The ancient Greeks understood the critical importance of light. Applying pure deduction, many philosophers of that era associated it with abstract qualities such as love and goodness, as well as physical properties such as brightness and warmth. Trying to fathom how light was conveyed, they debated whether or not it had a finite speed. Lacking modern instruments and methods, they were unable to resolve that question.

Indeed, because light is so swift, even during the time of the Renaissance, roughly two millennia later, scientists such as Galileo Galilei fared little better in ascertaining its speed. He proposed a method of two observers, separated miles from each other, flashing lanterns in succession and seeing if the timing of the light bursts depended on distance. Though his idea was clever, in practice it wasn’t precise enough to distinguish between instant and very slightly delayed (by a tiny fraction of a second) signals. Luckily, thanks to nineteenth-century innovators such as Albert Michelson and continued improvement in techniques and technology, we now know its velocity with great precision.

The speed of light is not just important for astronomy. It has turned out to be a critical component of modern theories of how forces work. Comprehending the forces of nature demands models of how they are conveyed through space. Not all forces involve contact. In fact, two of the four fundamental forces, electromagnetism and gravitation, can act over considerable distances. Do they somehow vault instantly from one point to another, or do they take some time? The electromagnetic interaction, as it turns out, involves the exchange of light. The gravitational interaction, though comprising a different mechanism, happens to occur at the same speed. Consequently, knowledge of the speed of light underpins the study of nature’s interactions.

Finally, pinning down a finite speed for light has raised profound questions about the nature of communication and causality. In general, speed limits don’t seem very natural. As any hurried driver on a long, empty stretch of motorway would attest, on a day in which traffic police were on strike and nowhere to be seen, temptation to push past the barriers would reign over caution.

If the law of cause and effect is bounded by light-speed influences, as it seems to be, what would happen if that speed limit could somehow be circumvented? Might backward causality be possible? Quantum physics includes coherent states and long-distance correlations that operate faster than a causal chain of events, transpiring at light speed, would seem to permit. How does quantum entanglement, and other remote effects, mesh with the light-speed limit?

In short, the discovery of the finiteness of the speed of light sparked multiple chains of scientific inquiry that have continued until this day. Pure philosophy could not pluck that precious fruit. Rather, it needed to be cultivated and harvested through the development of precise scientific techniques.

Worshipping the Sun

The blazing light shone on our ancient ancestors stemmed from the same sources as the light that shines today. Yet back then, in stark contrast to our modern sense of the extraordinary remoteness of the astral dome, it seemed far more immediate. The ancient Greeks, for example, developed a detailed mythology about the Sun and the heavens that closely connected heavenly doings with terrestrial events.

In some parts of the Greek world, the Sun was worshipped as the god Helios, child of the titans Theia (goddess of sight) and Hyperion (god of celestial light). As Hesiod’s Theogony relates, Helios’s sisters were goddesses Selene (the Moon) and Eos (Dawn). Like siblings sharing a play space, the three immortals took turns dominating the sky.

More insight about the adoration of Helios derives from the Homeric hymns, a compendium of thirty-three poems of unknown authorship, similar in style to Homer’s works and likely written starting in the seventh century BC. One such hymn celebrates the Sun god as an exalted driver with a shining golden helmet, steering a quadriga (racing chariot driven by four horses) across the sky:

[Helios] rides in his chariot, he shines upon men and deathless gods, and piercingly he gazes with his eyes from his golden helmet. Bright rays beam dazzlingly from him, and his bright locks streaming from the temples of his head gracefully enclose his far-seen face: a rich, fine-spun garment glows upon his body and flutters in the wind: and stallions carry him. Then, when he has stayed his golden-yoked chariot and horses, he rests there upon the highest point of heaven, until he marvelously drives them down again through heaven to Ocean.

Personifying the Sun greatly restricted the ancients’ ability to study its properties. By purporting that Helios had volition, including the capacity to interact with mortals according to his will and whim, no one could study the body he represented as an actual, steady source of energy. Humans, after all, couldn’t fully grapple with the nature of a god’s power. Consequently, the road to understanding the Sun in a scientific way, including the process by which its light travels through space, began with the Greek rejection of Sun worship.

It would be in the cultural center of Akragas, near the coast of Sicily, where in the fifth century BC progress would be made in understanding the Sun and its illuminations. By then, although the image of Helios driving the quadriga was still widely known—appearing for example on a gold coin—historians surmise that Sun worship was no longer prevalent. While in Akragas there were prominent temples dedicated to Zeus, Hercules, and other gods, there were none specifically devoted to Helios.

In some parts of the Greek empire, the role of Helios was subsumed by Apollo, a widely worshipped, far more complex deity. A source of harmony, culture, and prophecy, Apollo was far more than just a light-bearer. Curiously, Akragas, unlike other, more central Greek cities such as Delphi, apparently did not have a temple dedicated to Apollo either.1

For Empedocles, a learned native of that city, the Sun was a source of philosophical speculation, rather than veneration. He wished to understand the ingredients of reality. The Sun, with its ceaseless fire, seemed an important part of the puzzle.

Dawn in the Valley of the Temples

Dawn comes to Akragas each day in the form of blanched pillars, blistering pavements, and a blinding glow. Far from Mount Olympus, but still part of the ancient Greek dominions, the disk of the Sun makes sure to announce its presence there on its daily rounds. The gleaming temples with their monumental Doric columns reflect an ancient truth. While they purportedly mirror the energy and wisdom of the gods, no one could guess that they actually scatter photons produced inside an unimaginably hot nuclear cauldron, before leaping millions of miles across empty space to reach terrestrial structures such as the temples. Reality is often stranger than myth.

The “Valley of the Temples” at the heart of Akragas is, in truth, situated on a plateau, nestled between a ridge and hills; its location chosen for protection against invaders. In most ancient Greek cities, the orientation of each temple aligns specifically with the direction of the rising Sun during times of ritual importance, such as equinoxes—permitting the greatest illumination of its façade during religious ceremonies. In Akragas, however, the situation is more complicated. With a regular grid pattern of streets, oriented to the plateau’s topography, the city is an emblem of functionality. Rather than aligning all the temples according to ritual calendars, at least some of them seem to be arranged for practicality—aligned with the city’s lattice, rather than with the Sun’s arc.2 Those alignments further suggest a diminished role for the Sun in worship, offering a greater opening to secular analysis of its properties, including the influential speculations of Empedocles.

Born in Akragas around 492 BC, when the city was less than a century old, Empedocles grew up in a family blessed with great wealth. As with other aristocratic Greek youth of his day, numerous servants waited on him hand and foot. He took to wearing flamboyant clothes, including a flowing purple robe, bronze sandals, and a laurel wreath on his head. The extravagant outfit gave him a regal air, with divine pretentions. Not wanting to be seen as a mere mortal, he presented himself as a mystic and healer. Surprisingly, however, rather than scorning the less fortunate, he did the opposite. Politically, he became a strong advocate of equality and democracy (within the context, that is, of his own hierarchical society that discriminated against women). He worked in his community to pass ordinances guaranteeing equality for free citizens. How could someone profess equality while acting like a holy sage? To paraphrase Walt Whitman, his personal contradictions reflected that he “contained multitudes.”

The young Empedocles had a ravenous appetite for poetry and philosophy, ingesting the best works of his day, including the philosophical poem “On Nature” by Parmenides, which had a profound influence on his ideas and style, the natural speculations of Anaxagoras, and the musings of the school of Pythagoras. His readings motivated him to scribe his own meditations about the natural world.

Cosmic Ingredients

As in the case of many pre-Socratic Greek philosophers, much of what we know about the views of Empedocles derives from fragments of his writings and secondhand sources that reference his works. One of his works, “On Nature,” directly addresses, and in certain ways rebuts, the monist (single substance) worldview of his mentor Parmenides. It also draws a marked contrast with the numerological views of the Pythagoreans, followers of the philosopher Pythagoras. Parmenides had characterized the cosmos as essentially static—composed of one eternal substance that morphs into various guises but remains fundamentally the same over time. Change, therefore, is a complete illusion. Empedocles, in contrast, argued for a dynamic universe composed of multiple interacting elements.

The Pythagoreans contended that numbers and geometry were the fundamental building blocks of the universe. The integers from one to ten and the regular shapes, such as circles and spheres, had a particular significance as the key components of a hallowed natural order. They ascribed to “one,” the “Monad,” the property of unity, and “two,” the embodiment of divisiveness. In general, odd numbers, connected in their mind with masculinity, brought harmony (the Pythagoreans were an all-male group and thereby biased), and even numbers, linked with femininity, led to clashes of opposites. However, “ten,” the “Decad,” despite being even, represented the sum of the first four numbers, and thus represented inclusiveness and totality.

One of the most sacred symbols of the Pythagoreans was the Tetractys, a representation of the first ten numbers as an equilateral triangle of points arranged in four rows, with one point on the first row, two points on the second, three points on the third, and four points on the fourth. It wonderfully connects the first four numbers, symbolizing various components of nature, with the cosmic wholeness denoted by the number ten.

Ratios of those first four numbers came into play when the Pythagoreans promoted the idea of harmonious musical scales. Simple ratios of tones, they argued, sounded best. They based their cosmic models, involving concentric spheres of celestial orbits surrounding a “central fire” (not the Sun, but an unseen power source, called “Guard,” Zeus’s watchtower), on such pleasing combinations of musical notes: dubbed “harmony of the spheres.”

The Pythagoreans spoke of eight celestial orbs: the Sun, the Moon, Mercury, Venus, Mars, Jupiter, Saturn, and the dome of the stars. Earth’s orbit around the central fire was the ninth sphere. To complete the sacred Decad they also lumped in a tenth body, called the “counter-Earth,” which orbits the central fire on the opposite side and thus remains forever invisible.

Mathematics is indeed the language of nature. However, by postulating that “all is number,” composed of simple integers and shapes, the Pythagoreans boxed themselves in to an abstract, unrealistic accounting of the universe’s ingredients. They used mathematics to proscribe, rather than describe, the cosmos—leading to severe limitations. For example, the Pythagoreans detested irrational numbers, such as pi or the square root of two, because such abnormalities didn’t fit into their scheme. Science depends on embracing all numbers—as tools, rather than ingredients.

Eschewing Pythagorean numerology and musicology, Empedocles advocated more tangible cosmic ingredients. His cosmogony consisted of four main substances: earth, air, fire, and water. He called these “roots,” like the roots of a plant. Two opposing fundamental forces, love and strife, acted on those elements to generate nature’s dynamo.

Love, according to Empedocles, is the universal force of attraction. It brings like substances together and eventually merges them with dissimilar elements. If allowed to act on its own, however, it would lead to absolute uniformity: a bland, inert mixture of earth, air, fire, and water. While perfect harmony sounds idyllic, it doesn’t allow for change, and thereby doesn’t permit life.

Luckily, strife serves to counterbalance love, by cajoling elements to separate from each other. Over time, strife drives the various substances increasingly apart until they are as distinctive as the bands of a layer cake. Ultimately, if strife were to prevail, it would divide everything absolutely. In that opposite extreme, life would also be impossible. However, each time strife reaches its upper limit, love kicks in, and the cycle of opposites begins anew. Steered by those disparate forces, the elements mix in various combinations, recycling the stuff of the world over and over again.

Empedocles used an artist’s palette analogy to help explain his system. Just as artists mix primary colors together to form secondary hues, to decorate, for instance, a painted vase, nature’s force of love brings elements together to create its own masterpieces. With a primitive pointillist perspective, he imagined the varied elements to be tiny dots of material, placed side by side, so finely meshed as to appear to be something new, but were actually a pattern of distinct elemental substances.

By including in his vision the possibility of endless cycles, along with many options for change within the course of each cycle, Empedocles produced a very flexible cosmology. He advanced the study of nature by modeling it with pliable components subject to a variety of interactions. While the elements and forces he listed are far from those scientists consider today to be basic components, the essence of his classification scheme was revolutionary and profound for his time. Look hard, and we see in Empedocles vague premonitions of the current notion of fundamental constituents of matter being quarks and leptons, galvanized by four basic interactions: gravitation, electromagnetism, and the strong and weak nuclear forces.

Empedocles was not just interested in modeling the behavior of inanimate substances. He also ventured into the rudiments of biology, as well as the intersection of those sciences, in his study of the senses. He developed a theory of vision, based on the idea that fire (light) attracts more fire. Vision, he proposed, is an affinity between the fire in one’s eyes and the fire in another object.

In what is called the “emission theory of light,” Empedocles postulated that the eyes emit beams of light, which make contact with other bodies to illuminate them and perceive them. His theory stood in stark contrast to the “reception theory of light,” advanced by the Pythagoreans and other Greek philosophers, which held that the human eye picks up rays transmitted by everything that it observes. Given the dearth of empirical observation in that era, neither camp had the tools to prove its vision of vision. Nevertheless, the philosophical debate between the advocates of the emission and reception theories persisted for years.

In a variety of the reception theory, Democritus, a pre-Socratic Greek philosopher born in 460 BC, proposed each object in the world manufactures unlimited replicas of itself, called eidola, which are transmitted through space and taken in by the body, including the eyes as well as the brain. When soaked in by the eyes, eidola form visual images. When directly absorbed by the brain, eidola offer evocative dreams that allow for premonitions about worldly events. Thus, in his view, seeing and soothsaying are simply different manifestations of how we perceive eidola.

One of the founders of atomism, Democritus believed that everything was made of tiny constituents of various shapes and sizes, which could easily be replicated and released. Therefore, eidola from all parts of the world are all around us, awaiting our notice. Why they arrive exactly in the same order that events transpire, rather than being a jumble of past, present, and future transmissions, Democritus didn’t explain.

Philosophers of the ancient world crafted their arguments through logic and elegance. Empirical data were largely absent, except for obvious facts such as that water quenches fire. Therefore, Empedocles and his contemporaries were driven by instinct, rather than experiment. And we’ve seen how gut feelings can often mislead.

According to some accounts,3 Empedocles’s own demise in 433 BC, at around the age of sixty, may have been a case of fire seeking fire: a blazing personality meeting a scorching demise. As dramatized by Matthew Arnold in his poem “Empedocles on Etna,” legend has it that in his final act Empedocles climbed Mt. Etna, the highest European volcano, situated in Sicily. Once he ascended to its rim, he flung himself into its sea of fire, as if to signal his godlike bravery and aspirations of life beyond the grave—attempting to prove, perhaps, the immortality of his own soul. Did Empedocles think the fateful influences that would merge his vital essence with the hellish flames would eventually reverse themselves in a renewed cycle of existence? One might only speculate about the manner and reasons for the death of the great philosopher.

As Arnold imagined Empedocles’s final cry:

[T]his heart will glow no more! thou art

A living man no more, Empedocles!

Nothing but a devouring flame of thought—

But a naked, eternally restless mind!

To the elements it came from

Everything will return.

Our bodies to earth,

Our blood to water,

Heat to fire,

Breath to air.

They were well born, they will be well entomb’d!4

Regardless of the corporeal fate, Empedocles did achieve immortality in his scholarly legacy. Many subsequent philosophers have referred to his writings and ideas, which, along with the works of Pythagoreans and the atomists, had a lasting impact on the shaping of science. That pivotal era was the starting gate in a race over more than two millennia to identify the essential components of nature and how they interact via its fundamental forces.

Among the most influential of the “theories of everything” put forth in the ancient world were presented in the works of Plato, a renowned scholar and teacher, who lived from 429 BC until 347 BC. Founder of the Academy in Athens, he was an avid amalgamator of earlier philosophical views, which he brilliantly shaped into original conceptions of the world, described in writings such as the Timaeus.

Following the path of the Pythagoreans, Plato had embraced an idealistic view of the cosmos based on a search for perfection. He proposed that the observed universe, with its obvious flaws, was purely an echo of a harmonious eternal domain. Rather than trying to understand the mundane world by analyzing it directly, he suggested peering beyond its blemishes and trying to fathom its pristine blueprints: the realm of what he called “forms.”

A form is the ideal, eternal prototype of all realistic, ephemeral objects in the world. Imagine an immaculate grandfather clock ticking endlessly, free from all sources of friction and resistance, its pendulum swinging beautifully back and forth for all eternity. Compared to a cheap watch, bought in a dollar store, that needs to be reset virtually every day, the majestic clock would be far more representative of time. But even better would be an absolutely perfect timepiece, an archetype of the clock, that didn’t even present the possibility of ever missing a beat. That would be the form of “time,” from which the best clocks could be crafted and the worst watches graded poorly in comparison. Similarly, the symmetry and elegance of the grandfather clock’s pristine exterior could be matched against the form of “beauty,” and a child’s prodigious admiration for the clock’s mechanisms matched against the ideal of “wisdom.” The mortal child herself would be a reflection of the idyllic essence of a person—an echo of her perfect “soul.”

In short, for every object or quality in the world, the tangible has emerged from the ethereal. Individual human souls themselves have emerged from divine perfection—like a grand, austere cherry tree scattering gorgeous blossoms onto a field below. Those blossoms might be muddied or frayed. Yet any vestige of their beauty that distinguishes them from the base soil offers evidence of their supreme origin.

Such emergence lacks the clockwork precision of causality in the modern sense. There are no obvious, indelible chains that link the realm of forms to the everyday world. Rather, the linkage is an amorphous kind of flow that picks up impurities as it touches coarse reality, like a pristine mountain stream winding its way through secret crevices, slipping past isolated hamlets, darkening as it picks up the needles shed by pine tree groves on its banks, and eventually ceding its waters into a murky municipal basin. Hence, Plato’s vision allows for more esoteric modes of connections, such as acausal linkages, associations based on numerology, symmetry, and other mathematical principles, and all manner of supernatural influences. Not surprisingly, in the centuries that followed Plato’s passing, it would be subject to a vast range of mystical and occult interpretations.

Plato used a famous thought experiment, the “allegory of the cave,” to demonstrate how real life could be an illusory shadow of the realm of forms. He imagined prisoners shacked to an interior wall of a cavern, not too far from its entrance, in which they viewed silhouettes on the opposite wall of people and things that passed by outside—soldiers and their weapons, merchants and their wares, and so forth. If they’d never been free (or had somehow forgotten what the outside world was like) the prisoners might mistake the shadows for actuality. Similarly, our mundane experiences comprise merely an illusory shadow play that bears limited resemblance to omnipresent truths.

Like Pythagoras, Plato was enamored with ideal geometries. The orbits of the planets, Sun, Moon, and stars, he likewise argued, must be circular, at least in the ideal realm. Any perceived deviations in astral behavior must stem from an improper reflection of perfect reality, like a visage in a smudged mirror. One key difference between his model and that of the Pythagoreans is that his vision was geocentric: all orbits centered on Earth, rather than around a central fire.

In the Timaeus, Plato presented a curiously Pythagorean take on the elements of Empedocles, connecting them with regular polyhedra (three-dimensional shapes with polygon sides, such as triangles and squares). Such elements behave differently, Plato surmised, because of their unique geometric compositions. Mathematicians note a profound distinction between regular two-dimensional polygons, for which there are an infinite number, and regular polyhedra, for which there are only five types: tetrahedra (four-sided pyramids), cubes, octahedra, dodecahedra, and icosahedra. In other words, those five are the only polyhedra in which all sides are identical and equilateral. The Pythagoreans likely discovered that fact, which the Greek mathematicians Theaetetus and Euclid also described. Nonetheless, given that Plato called special attention to those regular polyhedra, they are usually called the five “Platonic solids.”

Nature’s Hidden Light

After Plato’s death, his Academy in Athens stood for many centuries, even into the fledgling era of the Roman Empire, and his philosophy persisted well beyond that. Throughout the ages, Platonism would resonate in the works of many eminent thinkers. In tandem with the Pythagorean belief in numerology, Plato’s focus on forms, rather than the physical world, suggested that nature possesses a hidden code and a transcendental perfection. Platonism, in its various incarnations, thereby challenged savants to try to solve that code.


  • "An elegant and smoothly written account of how fundamental physics has informed our view of the cosmos from ancient times to the present. An engaging and informative blend of the scientific advances and the lives of the people who made them. A great read!"
    IanStewart, author of Do Dice Play God?
  • "Writing beautifully, Halpern describes with lucidity and great verve the whole story of how physics has led us to rethink what synchronicity means and ultimately to examine what Einstein once called "spooky action at a distance."—Gino Segre, author of The Pope ofPhysics
  • "A masterful account of the developments of fundamental physics over the past century."—Marcus Chown, author of Solar System
  • "Synchronicity is a very informative and thought-provoking account of humankind's efforts from antiquity to the present to understand the causal structure of the everyday world and, during the past century, to unite that understanding with the apparently acausal nature of the quantum world of atoms and particles. Paul Halpern writes with remarkable clarity and insight in a very accessible and engaging style."—David C. Cassidy, author of Beyond Uncertainty
  • "Paul Halpern, a gifted expositor of science, takes the reader on an exciting ride through history, showing how physicists and their antecedent philosophers have sought to understand nature through its connections-through synchronicity."—Kenneth W. Ford, author of Building the H Bomb
  • "Paul Halpern has zeroed in on one of the biggest mysteries in physics: objects with no mechanical linkage somehow act in harmony. He gives it a human face by digging into the Pauli-Jung collaboration-there is nothing else quite like it in the history of science."—George Musser, author of Spooky Action at a Distance
  • "In this beautifully written page-turner, physicist Paul Halpern reveals as much about the secrets of the universe as he does about his own masterful ability to uncover hidden patterns in the history of ideas. With elegance, clarity, and penetrating insight, Synchronicity takes its readers on a sweeping journey through a dazzling array of intellectual traditions in search of what connects everything around us and beyond. A superb intellectual achievement."—Julien Musolino, author of The Soul Fallacy
  • "A roller coaster of a ride that covers more than 2,000 years of philosophy and physics, culminating in a fascinating brain-bender of what we have to give up if we want to reconcile ideas like 'cause and effect' with the bizarreness of our fundamental reality. Every possible interpretation, including those of the 20th century's greatest physicists, dissatisfies us in some way. In Halpern's capable hands, our uncertainties about the quantum Universe transform from frustration to wonder as various ideas are at last put to the test, deepening our appreciation of our mysterious quantum Universe."—Ethan Siegel, author of Beyond the Galaxy
  • "Synchronicity is a sweeping account of humanity's understanding of the nature of causality. With great virtuosity, Paul Halpern weaves together all of the threads of this important story from the ancient Greeks to modern physics while entertaining the reader with insightful character studies and colorful anecdotes. A delightful book that anyone interested in the history of ideas will enjoy."
    John Kounios, coauthor of The Eureka Factor
  • "Paul Halpern engagingly explores the many kinds of connection in the universe, from cause and effect to coincidence, and on to the weirdness of entanglement. After reading Synchronicity, you'll think twice the next time someone says everything happens for a reason."—Steven Strogatz, author of Infinite Powers
  • "The development of scientific knowledge is often portrayed as some kind of superhighway - as a fast route to complete understanding of the world. This is far from the truth. Real science meanders, it twists and turns, runs this way and then that, and sometimes gets hopelessly lost. Synchronicity takes us on a delightful journey along the pathways of real science, and Halpern is a most genial guide."—Jim Baggott, author of Quantum Reality
  • "From what primeval pattern was the fabric of the universe formed? What determined its warp and its woof? In this wonderfully readable book, which somehow never skimps on the science, Paul Halpern explores the mystery of causality through the ever-intriguing collaboration between Wolfgang Pauli and Carl Jung. Masterfully written, it is at once an inspiring story of how quirks and creativity drive breakthroughs in science and a cautionary tale of how our all-too-human desire to seek meaningful patterns can lead even the brightest minds astray."—AmandaGefter, author of Trespassing on Einstein's Lawn
  • "Synchronicity is an extraordinarily accessible and deeply engaging introduction to one of the most provocative issues in physics today: the instantaneous, acausal connections between indefinitely remote entities, exhibited in phenomena such as quantum coherence and entanglement. The ideas Halpern discusses are quite complex, but his flair for crisp and elegant descriptions, delightfully original metaphors, and judicious sprinkling of amusing historical anecdotes, keep the reader both grounded and enthralled. Synchronicity is an insightful, thought-provoking book, and compelling reminder that science does not progress along a purely logical, deterministic path but one that is curved and warped by the passions, predilections, and prejudices of its practitioners.—Tasneem Zehra Husain, author of Only the Longest Threads
  • "As always, Halpern's writing is engaging and accessible, and he readily identifies inconsistencies and problems still needing solutions. Readers will appreciate his thoughtful approach and his consideration of coincidence, synchronicity, and the mysteries of physics."—Kathleen McBroom, Booklist
  • "Synchronicity is an entertaining read and provides a valuable service... The book invites nonspecialists to widen their appreciation of the range of what explanation in science could amount to."

    Science Magazine
  • "Halpern is a fun and engaging writer... Readers who aren't familiar with the stories will likely find this a fun and eye-opening read."—Forbes

On Sale
Aug 18, 2020
Page Count
304 pages
Basic Books

Paul Halpern

About the Author

Paul Halpern is a professor of physics at Saint Joseph’s University and the author of eighteen popular science books, including Flashes of Creation, The Quantum Labyrinth, Einstein's Dice and Schrodinger's Cat, and Synchronicity. He is the recipient of a Guggenheim Fellowship and is a Fellow of the American Physical Society. He lives near Philadelphia, Pennsylvania.  

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