A message had arrived at the telegram office that morning. As the mailman approached the seaside apartment in Mumbai, India, that my grandfather Brij Kishore shared with my grandmother Chandrakanta and their four children, he felt his throat tighten as she pulled on his sleeve and said, “Taar aaya hai.” In Bombay in the 1960s, the arrival of a “taar”—a telegram—usually meant bad news. Few homes had telephones, so far-­flung family would send updates of their children, cooking, and cricket scores via the well-­named snail mail. Only if a matter was more pressing and urgent would they send the news via telegram.

Babuji, as we all called him, tore open the envelope and took out a sheet of pale blue paper. On it was glued a strip of white paper that contained three words: ANXIOUS TO RETURN. He looked at his wife, rolled his eyes, and reassured her that there was nothing to worry about.

After graduating college, Babuji’s son Shekhar had traveled to Italy to look for work. Evidently, he didn’t like it there and wanted to return, but Babuji was determined that Shekhar should give it a shot. So, he put on his chappals and walked down to the post office to send a telegram saying so, using as few words as possible, because telegrams weren’t cheap and were charged by length. Over the next few weeks, many more telegrams arrived from Italy, begging for a ticket back to Bombay. After ignoring many of them, Babuji finally relented. His son, my uncle, returned to Bombay, where he lived out his days.

Less than sixty years later, each week of pandemic lockdown was punctuated by the demanding squeaks of my toddler: “I want talk Nani right now!” The child of a pandemic, there were eighteen months of her life when she couldn’t see her grandparents in person, so her demands to speak to her grandma were swiftly obeyed. With the swish of a finger on a touchscreen, a call flew through the air to the other side of the planet, to which my mom responded. She saw my daughter crawl for the first time, and speak her early words, in color, live, on the screen of a smartphone. When I stop to think about the ease with which we were able to stay in touch through those tough times, I find myself not only in awe of how far we have come but also immensely grateful.

We have been through a radical shift in technology across just three generations of my family, and each step of the way has changed our lives dramatically, just as they did for society as a whole: allowing us to communicate with our loved ones, creating the world of instant news, changing the way we work, and altering the way we entertain and are entertained. But while a video call may seem a far cry from the telegram, all these forms of modern communication are based on the science of signals being sent from one distant point to another, almost instantaneously. And our ability to do that centers around magnets.

I find magnets magical. The magnetic fields that radiate from them are invisible, but they can be substantial, far-­reaching, and influential across large distances. The science is complex and wasn’t understood for thousands of years—­indeed, many physicists will tell you that magnetism, and especially electromagnetism, still isn’t fully understood. But once we had at least some understanding, we were able to create practical mechanisms. Humans harnessed the magic of magnets to create machines that could interact and exert forces on other machines, farther away than had ever been thought possible.

Unlike the inventions we’ve looked at so far, magnets—­or objects that exert magnetic forces—­exist in the very essence of our universe. You and I are magnets (very, very weak ones—­don’t worry, there’s no danger of us suddenly becoming attached to our refrigerators). Atoms, the minuscule building blocks of matter, are magnetic. The planet on which we live is a giant magnet. Magnets, unlike wheels and nails and springs, were discovered rather than invented by humans. Despite this, they nonetheless deserve their place in this book, because it was humans who figured out how to make them more useful than they were as supplied by Mother Nature. The magnets we found naturally in our surroundings a few thousand years ago were weak and hard to come by. They were formed of magnetite, which came to be known as lodestone, a natural mineral found in the earth that is a mix of iron and oxygen, plus other impurities. It’s a magnetic material, but only a small proportion of the magnetite that exists in nature is magnetic, because it needs both a specific combination of impurities inside it, and to have been exposed to specific conditions of heat and magnetic fields outside it.

The earliest references to this natural magnet date back to ancient Greece in the sixth century BCE. Around two hundred years later, the Chinese documented the phenomenon of a natural stone attracting iron, and in another four hundred years, they began using this material for geomancy (a form of divination). It took another thousand years, advancing into the Middle Ages, before it was used for navigation in the form of a compass. Navigators in the Song Dynasty in China shaped lodestone to look like a fish, and let it float freely in water, so it pointed south. This knowledge spread to Europe and the Middle East soon after. Even then, with over a thousand years of knowing about natural magnets, we couldn’t replicate them, and their use was restricted to navigation.

Magnets themselves come in two distinct forms: permanent magnets and electromagnets. Permanent magnets are the horseshoe-­ and bar-­shaped magnets we saw in school science demonstrations and those that decorate our refrigerators. They have two poles, north and south: bringing together the south poles or the north poles of two magnets creates a pushing or repulsion force, but bring a north and south pole together and the magnets will cling to each other.

It took millennia to come to grips with how magnetism works, because this requires an advanced understanding of atomic physics and material science. To become a magnet, a material requires many particles, at many different scales, behaving in a very particular way. Let’s start with the electrons that orbit the nucleus of an atom. Just as electrons have a negative electric charge, they also have what physicists call spin, which defines its magnetic characteristics. By “pointing” in different directions, the spin cancels out the magnetic forces of electrons entirely in some atoms, leaving them nonmagnetic. But in others, while some of the electrons are arranged so their spin cancels out, not all are, so there is a net magnetic force left over, creating a magnetic atom.

Then, if we zoom out from the electron scale to the atomic scale, the atoms in an element are naturally arranged at random, which means that the magnetic forces of the individual atoms cancel each other out. In some materials, however, little pockets of atoms—­called domains—­have atoms all arranged in the same direction, giving the domain a net magnetism. However, they are not yet magnets, because the domains themselves are usually arranged at random.

To make a material produce a net magnetism, then, the atoms in the majority of the domains need to be forced into magnetic alignment by a strong external magnetic field, or by large amounts of heat applied at particular temperatures in particular sequences. Once the domains point in the same direction, you have a magnet.

Even today, there is a debate as to how magnetite becomes magnetized in the first place, so artificially replicating this has been a challenge. Certain materials like iron, cobalt, and nickel have electrons favorably arranged to make their atoms magnetic, which in turn sit in well-­defined domains. Our ancestors tinkered with mixes of such metals, heating and cooling them in various combinations to try to figure out the best recipe for forming permanent magnets. They succeeded, to a degree, making somewhat weak magnets that didn’t hold their force for long.

The development of permanent magnets in a scientific way started in the seventeenth century, when Dr. William Gilbert published De Magnete, which outlined his experimentation with magnetic materials. In the eighteenth and nineteenth centuries, we developed more sophisticated methods for making iron and steel, and observed that certain combinations made much stronger or longer-­lasting magnets—­and sometimes even both. But we still didn’t really understand why. The nineteenth century also saw the advent of understanding electromagnetism, which we’ll come back to, but it took until the twentieth century and the conception of quantum physics before we were able to define and understand atoms and electrons well enough to create strong and long-­lasting permanent magnets ourselves.

This led to the use of three types of materials to make permanent magnets: metals, ceramics, and rare-­earth minerals. The first major improvement was the development of a metal mix of aluminum-­nickel-­cobalt, used to make “alnico” magnets, but these were complicated and expensive to make. Then in the 1940s, ceramic magnets were created from pressing together tiny balls of barium or strontium with iron. These were much cheaper, and today account for the vast majority of permanent magnets produced by weight. The third family of materials are the rare-­earth magnets, based on elements like samarium, cerium, yttrium, praseodymium, and others.

Within the space of the last century, these three types of permanent magnets have been refined to produce produced magnetic fields 200 times stronger than before. And this improved efficiency led to permanent magnets playing an important role in much of our modern lives: a car, for example, can have thirty separate applications for magnets, using over 100 individual magnets. Thermostats, door latches, speakers, motors, brakes, generators, body scanners, electric circuitry and components—­take any of these apart and you’ll find permanent magnets.

But as we saw, the stories of permanent magnets and electromagnets intertwine, and since the discovery of electromagnets around 200 years ago, each has swung in and out of favor as humanity learned more about how they worked and what they could be used for. The prevalence of permanent magnets in the past few decades is due not just to their increasing strength and compactness but also to the fact that, unlike electromagnets, they never need a source of power. But from the nineteenth century onward, and even today in situations where immense fields are needed, electromagnets dominated. We can control their strength, switching off or cranking up the magnetic field of an electromagnet when it suits.

The reason electromagnets took so long to make an appearance in the field is because we needed an understanding of the science of materials, electricity, and light—­and the mysterious force of electromagnetism. It’s only when we were able to move electrons in materials that we understood how to create and change this force and apply it to our technology.

Like gravity, electromagnetism is one of the fundamental forces in nature. It is the physical interaction that happens between particles, like electrons, that have an electric charge. In the late eighteenth and early nineteenth centuries, André-­Marie Ampère, Michael Faraday, and other scientists published numerous theories about electric and magnetic fields, which were eventually brought together and summarized by the mathematician James Clerk Maxwell in what are now known as “Maxwell’s equations.” These gave us crucial information that led to the invention of electric motors, and these equations are also the basis of our power grids, radios, telephones, printers, air conditioners, hard drives, and data-­storage devices; they are even used in the creation of powerful microscopes.

The key principle that led to such technological advancement was the realization that moving charges create magnetic fields. Without getting too deep into the complex science, this means that if an electric current is flowing through a coil of wire, it behaves like a magnet. If you change the strength of the current, you change the strength of the magnet. And the converse is also true: applying a variable magnetic field near a wire will create an electric current in the wire. Following on from this science, experiments proved that when a charge, like an electron, moves within a magnetic field (either freely or inside a wire), it feels a pushing force.

Studying the electromagnetic force led us to define the phenomenon of electromagnetic waves. Think of these as waves of force that flow because of the interaction between electric and magnetic fields. Our understanding of light increased manifold when we were able to quantify it as an electromagnetic wave. And, in addition to visible light, we saw that a whole spectrum of electromagnetic waves—­from radio waves (with the longest wavelength) to gamma rays (with the shortest)—­exists, and that these waves can be used in different ways. It is electromagnetism and electromagnetic waves that form the basis of our long-­range communication technology: the technology used by countless people around the world to share news with their loved ones. People like my uncle, the prolific sender of telegrams.

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From Nuts and Bolts: Seven Small Inventions That Changed the World in a Big Way by Roma Agrawal. Copyright © 2023. Available from W.W. Norton & Company.

Writers know that every book has its own unique challenges. Sometimes a book has point of view issues. Or the timeline is tangled. Or the character’s motivation evaporates and you’re locked in a psychotic staring contest with your own delusion. When I sat down to write my latest thriller featuring an atmospheric physicist, the challenge was obvious: I didn’t know anything about physics.

I’ve always been a glutton for education. I have two bachelors and a master’s degree, and my book research is pure joy, whether I’m trekking through the Boundary Waters or learning the properties of rigor mortis. But the idea of tackling physics, even tangentially, intimidated me. Physics was the only class I took pass/fail in high school. I was never top of my class, but As and Bs were the norm and the idea of taking a class pass/fail, where you didn’t receive a grade at the end but only had to scrape by with something more than 60%, felt like flagrant cheating. I did it anyway because, to fifteen-year-old me, physics was elusive. I understood the world in terms of marching band and Methodism. Studying the science of matter and energy felt like ignoring the actors of the play to examine the joists of the set. Teenage me was not into joists.

Three decades later, things have shifted. Forty-four-year-old me is tired of the drama. I don’t know any of the actors’ names and the costumes seem like recycled outfits from my teenage closet. (I made the high-waisted light wash jeans mistake once and I won’t be doing it again. Also low rise, if they’re coming next, can fuck right off.) Now the joists beckon. I started reading popular science books by Carl Sagan and Stephen Hawking, cautiously curious about how the world around me actually works. Making the decision to writing a physicist character, while still intimidating to this pass/fail author, gave me the excuse to learn even more. Authors such as Michio Kaku, Carlo Rovelli, and Neil DeGrasse Tyson have given me a rudimentary understanding of the underlying support structures of the universe. For the following butchering of their theories and explanations, I am truly sorry. This is what happens when a murder writer swerves out of her lane.

Physics has always been a game of Russian dolls, a continual unmasking of the foundations of our reality to find something even more fundamental inside them. Aristotle believed the universe to be composed of Earth, Fire, Water, and Air, and he couldn’t throw shade fast enough at Democritus of Abdera, who developed the idea of “atomos,” the indivisible building blocks of all matter. Aristotle, via the later endorsement of the Catholic church, won the argument for over a millennium. Earth, Wind & Fire, baby. It was a certified Boogie Wonderland. The tides didn’t turn back toward atomic theory until experiments in the fifteenth and sixteenth centuries. By the 17^th century, Isaac Newton stepped up to the scientific stage to endorse Team Democritus and generations of Newtonian scientists made atomic theory canon.

One guy who definitely didn’t take physics pass/fail was J. J. Thomson. The son of a bookseller, he was a quiet man who liked to garden and was famously clumsy in the lab. He also invented the mass spectrometer, discovered the electron, and cracked open the subatomic world (no big deal). Thomson discovered that not only were atoms penetrable, but they consisted mostly of empty space. Rumor had it he was afraid to get out of bed the morning after his discovery. All the comforting bricks that built his world had turned into bubbles, and he was scared that if he stepped out of bed he might fall straight through the floor.

Thomson won the Nobel Prize in 1906 for discovering electrons and subatomic particles. Thirty years later, his son won the Nobel Prize for discovering that those particles were more like waves. So which is it, you ask. Particles or waves? Yes. The answer is yes. Welcome to quantum mechanics.

The technology developed from quantum mechanics gave us the world we know today—lasers, MRIs, cell phones, Bridgerton. In the physics of the subatomic world, probability replaces certainty. (Can Bridgerton season three top the Kanthony enemies-to-lovers storyline of season two? It’s entirely a game of chance.) The uncertainty of quantum mechanics blew everyone’s mind, Einstein included, because it contradicted everything we thought we knew. In crime fiction, we call that a twist.

And the twists keep coming. Carlo Rovelli, the Italian theoretical physicist, is one of the people rewriting our backstory. Remember the beginning of the universe and that single point of super dense matter that went bang? Rovelli explained in Seven Brief Lessons on Physics—honestly, the longest physics class this writer’s brain can handle—our origin story could have been the result of a previous collapsing universe. Instead of a big bang, it may have been the big bounce. The current expansion of the universe might just be one long exhale in a cycle of expansion and contraction, the ultimate recycling program. It could be the secret that hides all around us—in the ocean tides, the endless rise and fall of jean waistlines, the breath whispering inside our own chests.

To write Dr. Eve Roth, the atmospheric physicist in To Catch a Storm, I read books and took Masterclasses and listened to podcasts and I probably understood a tenth of it, but here’s what I learned: the universe is an unreliable narrator. It presents itself as a noun when it is fundamentally a verb. What appears to be a curio cabinet of fantastic objects suspended in darkness—planets, stars, and galaxies—is actually a network of vibrations and interactions where time curves and particles jump in and out of reality like this is all some spontaneous playground game. The universe does not exist. It happens.

And we happen. Humans, minute pulses within the grand symphony, mark our beats with brief and breathless insistence. We are desperate to be heard, to mean something, to be part of a whole we can feel but cannot fathom. We beat in a spectrum of ways, from the sublime to the horrific, while always gaslit by the universe’s story that what surrounds us is solid and stable. That we won’t fall straight through the floor.

We write stories with happy endings, with killers caught and a modicum of justice restored, and part of us recognizes the truth behind the fiction—we have to create our own certainties in a universe that offers none. In the end, I guess I didn’t learn much about physics. I learned how to tell a story from the first and greatest storyteller of all.

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To Catch a Storm by Mindy Mejia is available from Atlantic Monthly Press, an imprint of Grove Atlantic.

Quantum Mechanics is the science behind nuclear energy, smart phones, and particle collisions. Yet, almost a century after its discovery, there is still controversy over what the theory actually means. The problem is that its key element, the quantum-mechanical wave function describing atoms and subatomic particles, isn’t observable. As physics is an experimental science, physicists continue to argue over whether the wave function can be taken as real, or whether it is just a tool to make predictions about what can be measured—typically large, “classical” everyday objects.

The view of the antirealists, advocated by Niels Bohr, Werner Heisenberg, and an overwhelming majority of physicists, has become the orthodox mainstream interpretation. For Bohr especially, reality was like a movie shown without a film or projector creating it: “There is no quantum world,” Bohr reportedly affirmed, suggesting an imaginary border between the realms of microscopic, “unreal” quantum physics and “real,” macroscopic objects—a boundary that has received serious blows by experiments ever since. Albert Einstein was a fierce critic of this airy philosophy, although he didn’t come up with an alternative theory himself.

For many years only a small number of outcasts, including Erwin Schrödinger and Hugh Everett populated the camp of the realists. This renegade view, however, is getting increasingly popular—and of course triggers the question of what this quantum reality really is. This is a question that has occupied me for many years, until I arrived at the conclusion that quantum reality, deep down at the most fundamental level, is an all-encompassing, unified whole: “The One.”

The list below contains 12 books that I find particularly enlightening about why quantum reality makes sense, what the counter-arguments are, and what quantum reality is.

*

Manjit Kumar, Quantum: Einstein, Bohr and the Great Debate about the Nature of Reality

To understand how the controversy about quantum reality started, it makes sense to look back at the early history of quantum mechanics, and the quantum pioneers’ struggle to make sense out of the new theory. Manjit Kumar’s book tells this story as a captivating narrative, starting from Max Planck’s discovery that the electromagnetic radiation emitted by matter required that it was emitted or absorbed in bits, discrete units, or “quanta,” to the famous debate between Einstein and Bohr, always focusing on what quantum mechanics meant for our notion about what is real.

Jim Baggott, The Quantum Story: A History in 40 Moments

A wonderful alternative, companion or complement to Kumar’s book is Jim Baggott’s The Quantum Story. Whereas the former delivers a consistent story of the development of quantum mechanics in the first half of the twentieth century, the latter concentrates on the glorious moments of the most important discoveries and also includes topics such as modern particle physics, the Hawking radiation emitted by black holes, and the Wheeler-DeWitt equation for the quantum wave function of the universe.

Adam Becker, What Is Real?: The Unfinished Quest for the Meaning of Quantum Physics

In the years following the Einstein-Bohr debate, most physicists accepted that Einstein was wrong and Bohr was right. Moreover, after the outbreak of World War II and subsequent discoveries in nuclear, particle and solid state physics, research concentrated on applications of quantum mechanics rather than on the foundations of the theory. Adam Becker’s book zeroes in on the dissidents questioning Bohr’s orthodox view, and how they encountered a toxic blend of hostility and dogmatic pragmatism from their peers. It describes how these quantum dissidents, among them David Bohm, Hugh Everett, Heinz-Dieter Zeh and John Stewart Bell, saw their careers ruined or had to pursue their work on the meaning of quantum mechanics more or less secretly in their free time.

Olival Freire Junior, The Quantum Dissidents: Rebuilding the Foundations of Quantum Mechanics (1950-1990)

Olival Freire Junior’s Quantum Dissidents tells this story from a slightly different angle. It is a little more scholarly but still a great read, and it points out how the dissidents’ questions inspired the new research field of quantum information that is currently entering the stage where quantum computers are starting to outperform classical computers.

David Kaiser, How the Hippies Saved Physics: Science, Counterculture and the Quantum Revival

Kaiser’s book focuses on a small group among the quantum dissidents, especially a gang of freewheeling physicists in Berkeley that called themselves “Fundamental Fysiks Group”. While the group explored some quite outlandish topics such as parapsychology, they also for some time included John Clauser who conducted the first experiment demonstrating what Einstein had called “Spooky Action at a Distance,” puzzling correlations between entangled particles that may be separated by large distances, and who received the 2022 Nobel prize.

Nick Herbert, Quantum Reality: Beyond the New Physics 

Another member of this group was Nick Herbert, whose wrong claim that such “Spooky Action” allows for faster-than-light signaling inspired the “No-Cloning-Theorem” in quantum information science, that is prohibiting to copy arbitrary, unknown quantum states. Herbert also wrote a book that actually was titled Quantum Reality. It offered one of the first discussions of various conflicting interpretations of quantum mechanics. And while the book doesn’t do full justice to the Everett interpretation, it contains one of the rare discussions of what quantum entanglement implies when being applied to the universe: “The world is an undivided wholeness”.

Jim Baggott, Quantum Reality: The Quest for the Real Meaning of Quantum Mechanics- A Game of Theories

Quantum Reality is also the title of a more recent book by Jim Baggott. Similar to Herbert’s book, Baggott’s more modern counterpart discusses many interpretations of quantum mechanics, and the respective notions of reality they infer, and reviews the arguments both in favor and against these interpretations. At the end Baggott isn’t convinced and remains skeptical about a realistic interpretation of quantum mechanics.

George Musser, Spooky Action at a Distance: The Phenomenon That Reimagines Space and Time – and What It Means for Black Holes, the Big Bang, and Theories of Everything

Coming back to “Spooky Action at a Distance,” George Musser is opening an entirely new can of worms: What does the strange correlation of faraway things imply for our notion of space? Musser’s journey leads him to the most cutting-edge research in string theory and quantum gravity, that aims to show how space and time may be stitched together from quantum entanglement. His conclusion: “spacetime is doomed.”

Peter Byrne, The Many Worlds of Hugh Everett III: Multiple Universes, Mutual Assured Destruction, And The Meltdown Of A Nuclear Family

The most obvious and straightforward but equally bizarre and controversial approach to adopt the quantum-mechanical wave function as reality is Hugh Everett’s “Many Worlds Interpretation”: If the quantum-mechanical wave function allows for two or more alternative events, all of them happen, albeit in parallel realities. Everett was an exceptional person, both unconventional and ingenious, and this is beautifully illustrated in Peter Byrne’s biography.

David Deutsch, The Fabric of Reality

David Deutsch is one of the pioneers of quantum information science, and his book is an unadorned plea for a realistic wave function in the shape of Everett’s many worlds interpretation. According to Deutsch, “It is the explanation—the only one that is tenable—of a remarkable and counter-intuitive reality.” Deutsch goes on and relates this view to interesting and passionate discussions about philosophy of science, quantum computing, the unreality of the flow of time and the significance of life.

Sean Carroll, Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime

Carroll’s book starts with a credo: Quantum mechanics should be understandable, even if it suggests a distinction between what we see and what really is. He continues with an advocacy of Everett’s Many-Worlds-Interpretation, and finishes with a line of argument on why an understanding of quantum reality is important: it helps us to make sense of the exciting new approaches to quantum gravity and an emergent spacetime as a consequence of quantum entanglement.

David Wallace, The Emergent Multiverse: Quantum Theory According to the Everett Interpretation

Explaining what reality is isn’t a job exclusively for physicists. Philosophers have at least as much to say about the topic, and David Wallace does so. “The Emergent Multiverse” surveys Everett’s interpretation from the perspective of philosophy, and does not shy away from rather abstract topics such as the lessons to be learnt from Everett about statistics and probability. Most importantly, it conveys an important message: The “many worlds” of the Everett interpretation aren’t fundamental, they emerge from a more fundamental, unique quantum world.

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The One: How an Ancient Idea Holds the Future of Physics by Heinrich Päs is available from Basic Books, a division of Hachette Book Group.

The aim of physics is to understand how the Universe and everything in it behaves. One of the ways we try to do this is to ask questions, and as I studied more physics the question that seemed to lie at the core of it all was: “What is matter, and how does it interact to create everything around us—including ourselves?” I suppose I was trying to figure out the meaning of my own existence. Rather than study philosophy, I went about it in a more indirect way: I set about trying to understand the entire Universe.

People have asked questions about the nature of matter for millennia, but only in the last 120 years has this curiosity finally led us to some answers. Today our understanding of the tiniest constituents in nature and the forces that govern them is described by the field of particle physics, one of the most awe-inspiring, intricate and creative adventures that humans have ever embarked on. Today we have intimate knowledge of the physical matter of the Universe and how it all fits together.

We’ve found that reality has a richness and complexity that humans just a few generations ago could never have imagined. We’ve overthrown the idea of atoms as the smallest bits of our world and discovered fundamental particles that play no role in ordinary matter, but appear necessary based on the mathematics that—somewhat miraculously—describes our reality. In just a few decades we have learned how to fit all of those pieces together, from the blast of energy at the start of the Universe to the most precise measurements in nature.

Our view of the smallest constituents in nature has changed rapidly throughout the last 120 years: from radioactivity and the electron, to the atomic nucleus and the field of nuclear physics, together with the development of quantum mechanics (which describes nature on the smallest scales). Some way into the twentieth century this work became known as “high- energy physics,” as new particles were found and the focus shifted away from the atomic nucleus. Today the study of all the many particles and how they are formed, behave and transform is simply called particle physics.

The Standard Model of particle physics classifies all the known particles in nature and the forces through which they interact. It was developed by many different physicists over decades and our current version came about in the 1970s. This theory is an absolute triumph: it is mathematically elegant and unbelievably precise, yet fits on the side of a mug. As a student, I was drawn in by how completely the Standard Model seemed to describe how nature works at a fundamental level.

The Standard Model tells us that all the matter that makes up our everyday existence is composed of just three particles. We consist of two types of quark called “up” and “down” which form our protons and neutrons. These two quark types together with electrons make up atoms, held together by forces: electromagnetism and the strong and weak nuclear forces. That’s it. That’s us and everything around us. Yet despite being composed of nothing more than quarks and electrons, we—humans—have somehow figured out that there is much more to nature than this.

Our triumph of knowledge has not come about purely through conceptual and theoretical leaps. The stereotype of a lone genius theorizing at a desk is largely incorrect. For over a century, questions like “What is inside the atom?”, “What is the nature of light?” and “How did our Universe evolve?” have been addressed by physicists in an entirely practical way. The reason we can say today that we know all this stuff, that we think our theoretical models represent reality, is not because we have pretty mathematics but because we have done experiments.

While many of us come across the idea that protons, neutrons and electrons make up the world around us as children, very little is said about how it is that we learned about matter and forces and, well, everything. A proton is a million million times smaller than a grain of sand and it is far from obvious how we actually go about working with matter on so small a scale. This is the art of experimental physics: to follow our curiosity from a seed of an idea, to a real physical piece of equipment, to the accumulation of new knowledge. That evening at the dark sky site, that understanding that I enjoyed physics more when I got to experience it firsthand, led me towards the idea of being an experimental physicist.

While theoretical physicists can revel in mathematical possibility, experiments take us to that frightening frontier of vulnerability: the real world. This is the difference between theory and experiment. While a theoretical physicist’s ideas must take into account the results of experiments, an experimental physicist has a more nuanced job. She is not simply testing out the ideas of theoretical physicists; she is asking her own questions and designing and physically building equipment which she can use to test those ideas.

The experimentalist must understand and be able to use theory, but she must not be constrained by it. She must stay open to finding something unexpected and unknown. She also has to understand many other things: her practical knowledge ranges from electronics to chemistry, from welding to handling liquid nitrogen. She must then combine these things together to allow her to manipulate matter that she cannot see. The truth is that experiments are hard, and the process involves many false starts and failures. It takes a certain kind of curiosity and personality to want to do this. Yet throughout history, many have had the passion and persistence to do so.

Over the last century the experiments that scientists have used in particle physics have gone from single-room setups led by one person to the largest machines on Earth. The era of “Big Science,” which began in the 1950s, has now grown to produce experiments that involve collaborations of over a hundred countries and tens of thousands of scientists. We build underground particle colliders consisting of many kilometers of high-precision electromagnetic equipment in projects that span more than twenty-five years and cost billions of dollars. We have reached a point where no individual country can achieve these feats alone.

At the same time, our everyday lives have gone through a similarly dramatic transformation. In 1900, most homes were twenty years away from having electricity, horses were the main form of transport and the average lifespan in the UK or United States was less than fifty years. Today we are living longer, in part because when we get sick the hospital has MRI, CT and PET scanners to help diagnose illnesses and a range of medicines, vaccines and high-tech gadgets to treat us. We have computers, the World Wide Web and smartphones to connect us, which have created entirely new industries and ways of working. Even the goods around us are designed, augmented and enhanced using new technology, from the tires on our cars to the gemstones in our jewelry.

When we think about the ideas and technologies that make up the modern world, we rarely associate this with the parallel trajectory of experimental physics, but they are intimately connected. All the examples above came about from experiments designed to learn more about matter and the forces of nature—and this list is only scratching the surface. Within just two generations, we have learned to control individual atoms to build computing devices so small that even a microscope struggles to see them; to use the unstable nature of matter to diagnose and treat disease; and to see inside ancient pyramids using high-energy particles from space. It’s all possible because of our ability to manipulate matter at the level of atoms and particles, knowledge which came from curiosity-driven research.

I chose to be an experimental physicist in the field of accelerator physics: I specialize in inventing real-world equipment that manipulates matter on this tiny scale. Accelerator physicists constantly discover new ways of creating beams to help learn more about particle physics, but increasingly our work contributes to other parts of society. It still surprises students, friends and audiences when I tell them that their nearest hospital almost certainly houses a particle accelerator, that their smartphone relies on quantum mechanics and that their ability to browse the web is only possible because of particle physicists. We build particle accelerators to study viruses, chocolate and ancient scrolls. Our detailed understanding of the geology and ancient history of our planet is the outcome of research in particle physics.

Curiosity-driven research takes us past the limits of what we know and what we expect, leading us to ideas, frontiers and solutions that change the course of history. Through this search for new knowledge, we bridge the gap between what we know to be possible and what we believe to be impossible. That is where curiosity leads to truly groundbreaking innovation. Physics, in particular particle physics, offers perhaps the most striking examples of this phenomenon. So how did a series of physics experiments lead to all of these aspects of our modern world?

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Excerpted from The Matter of Everything: How Curiosity, Physics, and Improbable Experiments Changed the World by Suzie Sheehy. Copyright © 2023. Excerpted by permission of Alfred A. Knopf, a division of Penguin Random House LLC. All rights reserved. 

In 1945 Peter Higgs was in the science sixth form, at age sixteen. Politically, he was still very much following his parents’ example. As the 1945 UK general election happened, the school staged a mock election and Higgs took the side of the Conservatives, which was the family tradition.

Once the Clement Attlee government was elected and he saw how it was transforming the country, he was very rapidly converted. “The NHS [National Health Service] was part of it but the whole program was quite inspiring. It was clear that it would transform the country in a way I was sympathetic to”, he explained. He went on to support socialist ideals for the rest of his life.

Higgs’ teenage search for self-identity was settling around a love for physics when suddenly news broke that atomic bombs had been dropped over Hiroshima and Nagasaki. He was distraught. His father’s experiences in World War I had already imprinted a hatred of warfare, and now tens of thousands of Japanese civilians had been extinguished by the result of the physics which drew him. For a time, he even “contemplated a change of career”.

Bristol University physics professor Neville Mott spoke about the bomb at a Bristol Rotary lunch on 20 August, in a talk titled “The Bomb Which Might End Wars—or Civilisation”. He told the audience, “The centre of the atomic bomb explosion is very like the core of the sun—hotter if anything”. Mott warned that “the bomb dropped on Hiroshima was a Mark 1. In 10 years, these things will be bigger and better. We must improve the Charter of the United Nations to the point where there is only one armed-force in the world.”

Mott’s remarks to this small gathering were reported in the press and piqued public interest. He and his physics colleague, Professor Cecil Powell, decided it was their duty to stage a public lecture and inform Bristolians of the background to the bombs, insofar as it was possible for them to do so. The US War Department had issued 250 pages of information about the weapon’s development in the Smyth Report on 12 August, just three days after the bombing of Nagasaki, but many technical details of the project remained highly secret. The university was near to Cotham School but a long way from his home, so after school was ended for the afternoon, Higgs remained and then walked over to the university to listen.

The event took place in early October. Powell gave an account of the basic nuclear physics involved, followed by Mott’s assessment of the political and practical implications. Higgs recalled that the hall in the university was full, “the audience packed tightly on the benches”.

In atomic nuclei, the neutrons and protons adjust themselves to make the most stable configuration. This is an example of nature’s golden rule: the most stable structure is the one that will survive the longest. Just as a pile of stones stabilizes by collapsing to rubble, for an atomic nucleus to achieve stability the effects of the electrical forces disrupting the cluster of protons must be minimized. Atomic nuclei adjust naturally from configurations of higher to lower energy, emitting the excess energy in what we call radioactivity, until stability is reached. Radioactivity typically emits a million times more energy, atom for atom, than that liberated in a chemical reaction, and it was chemical reactions that formed all processes known from primitive times until the early twentieth century.

Powell told the audience what physicists had known since around the start of the war before secrecy took over atomic science. The breakthrough that led to the atomic bomb was the discovery in 1938 of nuclear fission, which releases nuclear energy on a scale previously unimagined. The key is a rare form of uranium known as U-235.

Nuclei of these atypical uranium atoms are so fragile that a mere touch by a slow neutron can be enough to split the pack. When the nucleus of a uranium atom splits this way, the total energy released is over one hundred times greater even than in radioactivity. Comparison to chemical reactions is stark: fission frees nearly a billion times the energy. This, the audience learned, was the first step towards the newly arrived atomic age.

The discovery that opened the route to the atomic bomb had come early in 1939 when scientists found that the fission of a uranium nucleus also liberates neutrons. If these secondary neutrons hit other atoms within the lump of uranium and cause them to divide with the release of both energy and further neutrons, a self-sustaining nuclear chain reaction is possible. This causes an immense release of energy and in extremis a nuclear explosion.

Higgs now heard Powell explain that this was the basic idea behind the bomb that had been dropped over Hiroshima. The horror didn’t end there as Powell then announced that the newly released information revealed there was another way of making an atomic explosion, which was used at Nagasaki. Scientists had discovered that when neutrons hit uranium, it is possible to make an entirely new element, one not found naturally on Earth and existing beyond uranium in the periodic table: plutonium.

Mott’s vision of the implications was depressing. No one yet knew for sure, because much was still highly secret, but he suspected—correctly—that nations would build arsenals of these new atomic weapons. He conjectured that a United Kingdom of big cities would be vulnerable to attack by atomic bombs, and he portrayed a dystopian society readjusting to a form of existence more familiar in the days of Henry V, when the population was scattered among many small towns.

He also warned that if an atomic bomb exploded on the ground instead of in the air, the place where it fell “might remain radioactive for weeks or even years.” Humans visiting the site would sustain internal burns which would develop later. “You would go and do rescue work on an atom-bomb site at your peril”, he warned the audience. He added more optimistically that there was vast potential for atomic energy to be used for peaceful means such as power, though he tempered this vision with an observation about the vast cost: “At the moment it is not an economical alternative to coal petrol and other existing fuels.”

The effect on the young Higgs was a lifelong abhorrence of nuclear weapons.

The experience convinced Powell that there was an audience for popular science lectures, so the following year, 1946, he gave a series of talks about his own research. These lectures, in which he described photographic emulsions and demonstrated their ability to reveal the passage of particles smaller than atoms, were Higgs’ first exposure to the experimental side of a new field of science: particle physics.

Whereas the first public lecture in Bristol had presented Higgs with a hellish picture of nuclear physics, this time he learned there was a more optimistic vision of what it could offer in understanding the workings of nature. Powell’s talk also implicitly pointed at a profound puzzle: the fact that atomic nuclei exist at all. The audience were familiar with the force of gravity, which controlled the motion of the planets, and the effects of electrical discharges and magnets, which were manifestations of the electromagnetic force.

But if gravity and electromagnetic forces were everything, then atomic nuclei could not exist. The electrical disruption among electrically charged protons is huge and their mutual gravitational attraction trifling by comparison. That atomic nuclei manage to survive implies the existence of a strong attractive force between protons and neutrons, at least when they are in close proximity. One of the questions puzzling Powell and other scientists was the nature of this strong force. One means of finding out could be to see how easily nuclei could be disrupted by violent impacts, and what happens when they are.

Although atoms are very small—typically 100,000 of them could span the width of a single human hair—they are nonetheless vast compared to the atomic nucleus. In relative size, the nucleus is like a fly in the atomic cathedral. The atomic nucleus may appear inaccessible, but Powell began with the exciting announcement that nature has gifted us a way of smashing it apart. He told his audience about cosmic rays.

Thousands of meters above the Earth’s surface, the outer atmosphere experiences a continuous bombardment of atomic particles, known as cosmic radiation. The particles—which are mainly the nuclei of atoms—have been whisked to very high energy by magnetic fields deep in space. The Earth’s own magnetic field reaches out for tens of thousands of miles and attracts some of these extraterrestrials. They smash into atoms in the upper atmosphere and break them up, their energy spawning showers of novel particles.

At ground level, the overlying atmosphere protects us from the full force of cosmic rays, so to study their full power Powell planned to send photographic emulsions to high altitude in balloons. Collisions between cosmic rays and nuclei of atoms in the emulsion would disrupt these nuclei, and the results would energize the emulsion, enabling their trails to be revealed once the images were returned to Earth and developed. He had great hopes for this new venture, not least as cosmic rays had already revealed hints of unusual varieties of stuff hitherto unknown on Earth.

Powell speculated that cosmic rays would reveal many surprises. Even as he spoke, this prediction was being fulfilled with the imminent discovery in cosmic rays of strange particles. Within a few years, earthly analogues of the collisions of cosmic rays in the form of experiments at particle accelerators would become feasible. As Higgs prepared to move on to university, in 1947, a new field of research—high-energy particle physics—was about to flower.

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Excerpted from Elusive: How Peter Higgs Solved the Mystery of Mass by Frank Close. Copyright © 2022. Available from Basic Books, an imprint of Hachette Book Group, Inc.

The greatness of literature lies in its capacity to communicate the experiences and feelings of human beings in all their variety, affording us glimpses of the boundless vastness of humanity. Literature has told us about war, adventure, love, the monotony of everyday life, political intrigues, the life of different social classes, murderers, banal individuals, artists, ecstasy, the mysterious allure of the world. Can it also tell us anything about the real and profound emotions connected with great science?

Of course it can: literature is full of science. An entire genre, science fiction, is fed by it. Playwrights have engaged with it, not the least of them Brecht in his Galileo, a play that goes to the heart of the critical attitude upon which scientific thought is based:

We put everything, everything in doubt…What we find today, tomorrow we will erase from the blackboard and we will not write any more, at least until we find it again the day after that. If some discoveries follow our predictions, we will look on them with particular distrust…And only when we have failed, when beaten and without hope we are reduced to licking our wounds, then with iron in our souls we will begin to ask ourselves if we might not be right after all.

This is how, at the end of the play, Brecht has Galileo respond to his young assistant Andrea, when the latter is impatient to immediately find evidence to corroborate a brilliant idea. Many great scientists, and Galileo himself with his Dialogue Concerning the Two Chief World Systems, have written works that indisputably figure as classics of literature as well as of science.

But it is the greatest literature that has sought to come to terms directly with the scientific vision of the world. The striking opening of one of the most intelligent novels of the early 20th century, Robert Musil’s The Man without Qualities, is a dry list of meteorological data that opens out, at the end of the paragraph, with their translation into vernacular and everyday terms: “…it was, in other words, a beautiful August day.” Here, and filigreed throughout the novel, Musil attempts to incorporate and come to terms with a vision of the world revealed by the great successes of 19th-century science: a world of data and numbers.

The same challenge, if very differently inflected, was faced by the Milton of Paradise Lost. The poem includes these tremendous lines in which he wonders about the Copernican model that was still hypothetical at the time:

What if the Sun
Be Centre to the World, and other Stars
By his attractive virtue and their own
Incited, dance about him various rounds?
Their wandering course now high, now low, then hid,
Progressive, retrograde, or standing still,
In six thou seest, and what if sev’nth to these
The Planet Earth, so stedfast though she seem,
Insensibly three different Motions move?

The passage brims with the excitement of an immense step forward in science, a radical remapping of the universe that was in the process of being accomplished. All of Milton is secretly oxygenated by the new science: the immensity of the cosmos, the harmonious yet complex nature of the universe and of its movements, interstellar space and the possibility of traveling through it, the dominant role of the sun, the probability of extraterrestrial life… Throughout Milton’s writings, there is the impetus of the great conceptual revolution that in the 17th century was being brought about by science.

But to find a pure singer of science we need to go back further, until we get to the great poet who was able to devise a way of thoroughly uniting poetry and science, demonstrating how intimately linked they really are, to the point of almost becoming the same thing. I am talking about Lucretius, in whose work the most rational of deductions acquires the power of poetry:

And now if we accept that the number of atoms is so
endless
That an entire human era would not be sufficient to
count them,
And that if there exists the same force and nature
that may
Bring these atoms together anywhere, in the same
fashion
That they have converged here, then it is necessary to
acknowledge
That there must be other terrestrial globes elsewhere in
the void
And different races of men, and different species of
beasts.

Naturalism, which animates science, not only was the source of Leopardi’s anguish, but filled Lucretius with a kind of serenity: “Sometimes, like children who are afraid of the dark, we fear in the light of day things as inconsistent as those that the child is afraid of at night.” And it is this thoroughgoing naturalism that allows Lucretius, the anti-​religious classical writer par excellence (“How many afflictions have been brought about by religion…”), to turn to the goddess Venus with such luminous sentiments:

Mother of Aeneas and all his race, delight of men and
of gods,
Alma Venus, who beneath the wandering stars of the
heavens
Populates with living creatures the sea furrowed by
ships, the earth
Fecund with fruits; through you every living species
forms,
And once it has blossomed can come out to see the
light:
Before you, O Goddess, the winds run—at your first
appearance
The clouds leave the sky—for you the ever industrious
earth
Brings forth sweet-​smelling flowers; for you expanses
of the seas
laugh, and the becalmed sky is radiant with light.

Twenty centuries have elapsed since Lucretius, during which abysses of new knowledge—and alongside it new, boundless mysteries—have gradually opened up before us. Will we be able to find someone capable today of singing, with as much lucidity, about the complexity and mystery, as well as the strange comprehensibility and profound beauty of nature, as revealed by the lights of science?

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Excerpted from There Are Places in the World Where Rules Are Less Important Than Kindness: And Other Thoughts on Physics, Philosophy and the World by Carlo Rovelli. Copyright © 2022. Available from Riverhead Books, an imprint of Penguin Group, a division of Penguin Random House, LLC.

Call me Johnny, he urged the Americans invited to the wild parties he threw at his grand house in Princeton. Though he never shed his thick Hungarian accent, von Neumann felt that János—his real name—sounded altogether too foreign in his new home. Beneath the bonhomie and the sharp suit was a mind of unimaginable brilliance.

During a life cut short by cancer, von Neumann laid the foundations of quantum mechanics, founded modern game theory, helped design the atom bomb, drafted the blueprint for every modern computer from smartphone to laptop, and with Klári Dan, his second wife, wrote the first truly useful, complex programs ever to have been executed.

Von Neumann’s machine at the Institute for Advanced Study in Princeton would spawn the first generation of modern computers worldwide including the IBM 701, the company’s first commercial model, and his refusal to patent anything helped birth the open source movement. But not content with computers that merely calculated, he proved during a lecture in 1948 that these information-processing machines could, under certain circumstances, reproduce, grow, and evolve. Even on his deathbed, he wrote lectures comparing computers and brains that built a bridge between neuroscience and computer science for the first time.

Fearing a catastrophic third world war, von Neumann supported a pre-emptive strike against Stalin’s Soviet Union. He changed his mind  but not before becoming one of a handful of scientists who inspired Stanley Kubrick’s Dr Strangelove. The caricature has overshadowed his astonishing achievements, prescience and impact, which have been all but forgotten.

“He died so prematurely,” his friend, the mathematician Stanisław Ulam, said, “seeing the promised land but hardly entering it.” Some sixty-five years after von Neumann’s death, we are just beginning to glimpse his promised land ourselves.

*

Over lunch in Los Alamos in 1950, Enrico Fermi suddenly asked his friends, “But where is everybody?” Everyone burst out laughing. Fermi had been thumbing through a copy of the New Yorker and come across a cartoon blaming the recent disappearances of dustbins on extraterrestrials. The “Fermi Paradox” is the name now given to the conundrum of why the human race has not made contact with any alien species despite some estimates suggesting they should be legion in our galaxy. Thirty years later, Frank Tipler “solved” this paradox. Given that at least some intelligent beings would be expected to develop self-replicating machines, Tipler asks, and the billions of years such von Neumann probes would have to crisscross the galaxy, why has there been no trace of one detected in our solar system? His conclusion is that human beings are the only intelligent species in the cosmos.

Von Neumann thought we were alone too. Shortly after Hiroshima, he had remarked semiseriously that supernovae, the brilliant explosions caused by massive stars collapsing in on themselves, were advanced civilizations that “having failed to solve the problem of living together, had at least succeeded in achieving togetherness by cosmic suicide.” He was keenly aware of the various ways in which his work might ultimately contribute to humanity’s undoing. In coining the term “singularity,” in conversation with Ulam, von Neumann imagined a point ‘in the history of the race beyond which human affairs, as we know them, could not continue’. Whether that would be in a negative or positive sense remains a matter of debate: thinkers have variously speculated that an artificial superintelligence might end up fulfilling all human desires, or cosseting us like pets, or eradicating us altogether.

The cynical side of von Neumann’s personality, shaped by his scrapes with totalitarianism and made famous by his transitory enthusiasm for preemptive war with the Soviets, often yielded to a softer face in private. “For Johnny von Neumann I have the highest admiration in all regards,” said neurophysiologist Ralph Gerard, a contemporary of his. “He was always gentle, always kind, always penetrating and always magnificently lucid.” Shy of revealing too much of himself, his good deeds were quietly done behind people’s backs. When a Hungarian-speaking factory worker in Tennessee wrote to him in 1939 asking how he could learn secondary school mathematics, von Neumann asked his friend Ortvay to send school books.

Benoît Mandelbrot, whose stay at the IAS had been sponsored by von Neumann, unexpectedly found himself in his debt again many years later. Sometime after von Neumann’s death, prompted by a clash of personalities with his manager at IBM, Mandelbrot went looking for a new job—and found that the way had been made easier for him. Von Neumann had spread the word widely that his research could be of great significance—but was very risky. “He may really sink,” von Neumann warned them, says Mandelbrot. “If he’s in trouble, please help him.”

Which of these was the real von Neumann? “Both were real,” Marina says. But the dissonance between them confused even her, she admits. Beneath the surface the two facets of his personality were at war. Von Neumann hoped the best in people would triumph and tried to be as magnanimous and honorable as possible. But experience and reason taught him to avoid placing too much faith in human virtue.

Nowhere is the tug-of-war between the cool rationalist and kind philanthropist more evident than in von Neumann’s remarkable meditation on the existential threats facing humanity in the decades to come. Published in June 1955 in Fortune magazine, “Can We Survive Technology?” begins with a dire warning: “literally and figuratively, we are running out of room.” Advances in domains such as weaponry and telecommunications have greatly increased the speed with which conflicts can escalate and magnified their scope. Regional disputes can quickly engulf the whole planet. “At long last,” he continues, “we begin to feel the effects of the finite, actual size of the earth in a critical way.”

Long before climate change became a widely discussed concern, the essay shows von Neumann was alert to the idea that carbon dioxide emissions from burning coal and oil were warming the planet. He favored the idea of coming up with new geoengineering technologies to control the climate by, for example, painting surfaces to change how much sunlight they reflect—quite likely the first time that anyone had talked about deliberately warming or cooling the earth in this way. Interventions such as these, he predicts, “will merge each nation’s affairs with those of every other, more thoroughly than the threat of a nuclear or any other war may already have done.”

Von Neumann speculates that nuclear reactors will rapidly become more efficient and held out hope that mankind would harness fusion too in the long term. Automation would continue, he predicted, accelerated by advances in solid-state electronics that will bring much faster computing machines. But all technological progress, he warns, will also inevitably be harnessed for military use. Sophisticated forms of climate control, for example, could “lend themselves to forms of climatic warfare as yet unimagined.”

Preventing disaster will require the invention of “new political forms and procedures” (and the Intergovernmental Panel on Climate Change, established in 1988, arguably embodies one attempt to do exactly that). But what we cannot do, he says, is stop the march of ideas. “The very techniques that create the dangers and the instabilities are in themselves useful, or closely related to the useful,” he argues. Under the ominous heading “Survival—A Possibility,” he continues: “For progress there is no cure. Any attempt to find automatically safe channels for the present explosive variety of progress must lead to frustration. The only safety possible is relative, and it lies in an intelligent exercise of day-to-day judgment.”

There is, as he puts it, no “complete recipe”—no panacea—for avoiding extinction at the hands of technology. “We can specify only the human qualities required: patience, flexibility, intelligence.”

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Adapted from The Man from the Future: The Visionary Life of John von Neumann by Ananyo Bhattacharya. Used with permission of the publisher, W. W. Norton. Copyright 2022 by Ananyo Bhattacharya.

In 1905, physicists understood something of the laws governing two types of forces: those of electricity and magnetism and of gravity. We’ve seen that the laws of electricity and magnetism, encoded in Maxwell’s equations, forced a rethinking of the most basic concepts of space and time. But what about Newton’s law of gravity? How might it be purged of the notions of absolute space and absolute time?

In 1907, two years after putting forward his special relativity, Einstein was asked to write a review of the subject. In the course of this project, he confronted the question: How does Newton’s theory of gravity fit in with his principles? The simple answer: It doesn’t. This was actually related to a deficiency of Newton’s law of gravitation that was clear from the moment he promulgated it.

Newton—and perhaps more importantly his critics—were very troubled by a feature of his theory called action at a distance. In Newton’s laws, if, say, the sun were suddenly to “jump” (for the moment, take the far-fetched possibility of some space invader attaching rockets to it), the effect on the planets in the solar system would be instantaneous. This despite the fact that the planets are far away. Neptune, for example, is so far away that it takes light from the sun four hours to reach it, but it would move immediately in response to the sun’s sudden motion.

Newton was criticized for this—was he suggesting that some higher being was responsible for the force between stars and planets? But his law was extremely successful, and, for almost two centuries, this question was largely put aside. Indeed, it was only in the early 20th century that it was possible to seriously test this disturbing feature.

But with special relativity, one could no longer look away. It didn’t make sense that this principle should apply to electro-magnetism but not to the force of gravity. It was hard to see how Einstein’s assertion, that events at one place and time can affect events at another only after at least enough time has passed for light to travel from one to the other, would not have to apply to any law of nature. This was not a crisis in the sense of an obvious experimental or observational problem. Newton’s theory works so well because the speed of light is so large. Light moves so fast that in most of the situations that astronomers encountered in the two centuries after Newton put forward his law, the effects of the finite (as opposed to infinite!) speed of the propagation of information and interactions were impossible to see.

Still, Einstein began to consider how one might modify Newton’s theory so as to retain its enormous successes while accommodating the relativity principle. In other words, the new laws, in situations where the objects under study are moving much more slowly than the speed of light, or in which the force of gravity is not too strong, should reduce to Newton’s.

The process of arriving at what Einstein called his general theory of relativity involved a struggle of eight years and a combination of extraordinary scientific insight and sheer hard work. Along the way, there were many missteps. But the theory even more fully revealed Einstein’s genius than did his accomplishments of 1905. Einstein might have gone at the problem by observing that Newton’s gravitational force law is almost the same as Coulomb’s force law for charged particles. Just replace electric charges by masses, and they look alike. The electric force is described by Maxwell’s equations. So he might have tried to write equations like Maxwell’s, but for the gravitational force.

This is how I would likely have proceeded, and the result would have been failure. But Einstein thought much more deeply before starting his struggle. He was struck by the fact that planets, stars, and other celestial objects all pull on each other; they never push each other apart. This is different from electric forces, where while a proton attracts an electron—pulls the electron toward itself—two protons repel each other. The force of gravity always seems to be attractive, never repulsive. This is hard to mimic with Coulomb’s law. Einstein instead took his cue from observations that predated Newton.

Among Galileo’s most famous experiments were his studies of falling objects. Archimedes, the ancient Greek philosopher, had asserted that heavy objects fall faster than lighter ones.

This was a plausible guess, but not a statement based on careful observations. Galileo was skeptical and studied the question experimentally. Whether he actually dropped objects of different mass from the Leaning Tower of Pisa is a subject of scholarly debate, but he did perform experiments in which he established that objects of different mass fall to earth at the same rate, neglecting the fact that the air tends to slow everything down. (On the surface of the earth, a piece of paper falls much more slowly than a brick, due to the resistance of the air, but you can easily do a version of this experiment dropping two heavy objects, of different weight, from the same height.)

These observations had been improved over the intervening centuries by various investigators, including Newton. Very sensitive experiments were conducted in the late 19th century by Baron Loránd Eötvös, a Hungarian physicist, who used a different strategy, attaching various objects to a rod. The device was set up so that it would move if objects of different types responded differently to gravity, but not otherwise. Eötvös established that, for a range of substances, these responses were the same to better than a part in a million; present experiments do thousands of times better.

In Newton’s laws, mass has to do with inertia, the rate at which things accelerate in response to a force. But it also has to do with the strength of the force of gravity between two objects. Newton, presumably under the influence of Galileo, assumed that these two kinds of mass were the same. But as far as Newton was concerned, this was simply a fact; no deep principle forced this relationship. Eötvös (and others) established that the inertial mass is the same as the gravitational mass to a high degree of accuracy.

Einstein started with this observation and assumed that the equivalence is exact. He then performed a very simple but very ingenious thought experiment, in a setting from daily life. In developing special relativity, Einstein had reasoned by analogy with experiences of one important technology of his day—railroads. He now reasoned by invoking another, newer technology—elevators.

He imagined cutting an elevator cable so that the elevator would fall freely (a rather scary prospect). He noted that due to this assumed equivalence of inertial and gravitational mass, observers in an elevator in free fall would experience what we now call weightlessness. They could, for example, float around in the elevator, or pass a ball back and forth with no sense of gravity. It would be as if no gravitational force acted on the objects in the elevators. For the passengers, unfortunately, this would last only until the elevator hit the bottom of the shaft.

But nowadays we routinely achieve weightlessness in space travel. The International Space Station, when it orbits the earth, is in free fall. It falls due to the earth’s gravity. It stays in orbit because the downward pull of gravity competes with the energy of motion provided by the initial launch, to keep the spacecraft constantly circling around the earth. The effects of free fall can also be achieved with aircraft by shutting off the engines for a period. This is routinely done as part of astronaut training. Famously, Stephen Hawking, one of the great gravity theorists, was treated to such a flight in 2007.

Einstein didn’t have the advantage of this experience, and the tallest buildings of his day would have allowed a fall of only 4 or 5 seconds. But he realized the phenomenon of weightlessness would follow from the observations of Galileo and Eötvös. Einstein called his realization “the happiest thought of my life” and elevated this to a principle: No experiment can distinguish free fall in a gravitational field from motion with uniform acceleration (as in the elevator). He put forward the hypothesis, his “Principle of Equivalence,” that this should apply to all laws of nature: gravity, electromagnetism, and laws yet to be discovered.

From here to mathematical equations was a long struggle. Einstein knew roughly what he was looking for, but when he set out on his journey he did not possess a suitable mathematics for achieving it. David Hilbert, a professor in Gottingen, Germany, and one of the greatest mathematicians of the day, did know the required mathematics and was also in a quest for a theory of gravity; it is likely that had he fully understood the physics issues, he would have gotten to general relativity first, and indeed he almost did.

In 1915, however, Einstein completed and published his general theory. The theory met his basic requirements. First, it was consistent with the principles of special relativity. For example, the gravitational interaction propagated at the speed of light; there was no action at a distance. Second, it incorporated the principle of equivalence. Finally, it reduced to Newton’s laws except in very exceptional circumstances. Around typical stars and planets, the corrections would be very tiny.

Einstein’s theory presented a radical new conception of space and time. No longer were they fixed eternally, but they responded to the presence of matter. Space might be curved, time might run faster or slower near larger or smaller concentrations of matter. Most physicists and mathematicians familiar with the theory would describe it as beautiful, but while the principles are simple, the mathematics is rather complicated, and calculations can be challenging. Einstein, however, focused not only on the great principles and the beautiful mathematics but on the observational consequences of the theory. Because in most circumstances the corrections to Newton’s laws are extremely tiny, he had to look for situations where these effects, though small, would be sufficiently prominent to be detectable. He made three predictions that one could realistically hope to test with the technologies then available.

One of these predictions might be more properly described as a “postdiction,” an explanation of an already known puzzle in the motion of the planet Mercury. The sun exerts the dominant force on each of the planets; the planets also pull on each other, but these effects are relatively small. Taking into account, first, only the force due to the sun, Newton had shown that the planets would move in orbits the shape of ellipses, just as Kepler observed. According to Newton, these orbits should retain their shape and orientation for all time, ignoring the pull of the other planets.

Even in Newton’s day, astronomers studied the motion of the planets with precision. They carefully calculated the orbits on paper, making corrections for all sorts of small effects, such as the pull of the planets on each other. They compared these calculations with equally careful observations. They concluded that small corrections due to the other planets and other effects would lead to a slow deviation from Newton’s results; the ellipse would gradually rotate over time. This is referred to (by those with a better memory than mine of their high school analytic geometry) as the precession of the perihelion. Already in the 1850s, astronomers noted that the precession of Mercury was not quite at the speeds predicted by Newton’s laws; there was a tiny deviation. They proposed a variety of explanations, such as a small, unseen planet or dust, but none was compelling.

Einstein was aware of the discrepancy in Mercury’s motion. He realized that Mercury, being the planet closest to the sun, experiences the strongest force of gravity and was thus a promising testing ground for his theory. Einstein set out to calculate the correction to Newton’s result. He found it was exactly what was needed to account for the observed precession. I can only begin to imagine how he felt. For a physicist, discovery of a new law of nature is the supreme accomplishment. I have speculated as to several, but the likelihood that anyone is true is, typically, not high. Einstein indeed recalled that he was enormously excited—he said he had palpitations—and with the correct result for Mercury’s perihelion, he became convinced that his theory was correct.

But inventing theories to explain possible observational discrepancies is still within the realm of more “routine” science. Even better was to come. The second prediction was a real prediction in the sense that he proposed a measurement that had not yet been performed and predicted the outcome. In Newton’s theory, one describes the force of gravity as acting on mass. The path of a satellite passing near the sun would be bent by the pull of the sun’s gravity. But in special relativity, mass is just a form of energy, and in the general theory, gravity acts on all forms of energy. Light has no mass, but it does carry energy. So the paths of light rays should be altered from simple straight lines as they pass near objects with strong gravity. In 1911, before the theory was fully developed, Einstein tried to calculate the effect. He found that one should be able to see a slight alteration in the position of stars lined up with the sun during a solar eclipse.

Einstein was a genius—and he was also lucky. As I said, the mathematics of general relativity is complicated and was, at that time, also rather unfamiliar. It turned out that in his first calculation of the bending of light by the sun, before he had his theory in its final form, Einstein had made a mistake. He actually obtained the value that Newton would have obtained if the energy of the light was treated as equivalent to mass, through E=mc2.

Already in 1912, and again in 1914, expeditions to observe the bending of light during eclipses failed to obtain results, the first time due to rain, the second when it was canceled due to the outbreak of the First World War. In 1915, the year in which he published the final version of the general theory, he got the correct result for the bending of light, finding double the Newton value. The war prevented further measurements until 1919.

In that year, two expeditions, one to Príncipe island led by the English astronomer Arthur Eddington, and one to Brazil by Andrew Crommelin of the Greenwich observatory, succeeded in observing the effect. The results were announced in a joint meeting of the Royal Society and the Royal Astronomical Society: Einstein’s prediction was confirmed. By this time, Einstein was already well known in the scientific community, and occasional articles about him had appeared in the popular press, but now his name became a household word.

The headline of the London Times of November 17, 1919, was typical: “Revolution in Science. New Theory of the Universe. Newtonian Ideas Overthrown.”

When I was a student, Einstein’s theory of general relativity was a subject of fascination—something any self-described theoretical physicist should know something about. At the same time, actually saying that you might work on it would lead to rolling of eyes. There was, in those days, only very limited evidence that the theory was correct—beyond the perihelion and the bending of light, only a phenomenon called the redshift—and it seemed that only dreamers imagined there would be new tests.

Perhaps even worse, the theory, when combined with quantum mechanics, the subject of the next chapter, did not seem to make sense. Attacking that problem put you even more on the fringe. Still, most of the great theorists of the era had taken a stab at these issues, including Richard Feynman and Lev Landau (one of the greatest of 20th century Russian theoretical physicists). In the 1980s, perhaps more famously, Stephen Hawking raised issues that challenged the notion that general relativity and quantum mechanics could be reconciled and argued that a reformulation of quantum mechanics would be necessary.

Over the course of my career, all that has changed dramatically. Einstein’s theory is now a well-tested theory. Our understanding of general relativity is an important tool in our explorations of the universe. Observation of black holes is almost routine. General relativity is a crucial tool in determining the composition of the present universe, and essential, as we’ll see, to our understanding of the big bang. Recently, the discovery of the gravitational waves predicted by the theory over a century ago has opened up a new window on astrophysical phenomena. General relativity even plays a role in our navigation apps (through the Global Positioning System, or GPS). On the quantum mechanical side, we have learned a great deal as well, although experimental verification of what we do understand (and clues as to what we don’t) is probably not around the corner.

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Excerpted from This Way to the Universe by Michael Dine. Copyright © 2022. Available from Dutton Books.

Imagine a point. A very small point.

Imagine it expanding, inflating, fragmenting as it stretches, giving rise to distortions, attractions, repulsions, connections, fields, bodies, lives, with an open horizon yet still ahead. A limitless horizon of change, in which more potential exists as more variables are born, complicating the network of relations, of possibilities.

That was how our universe was born. That is how writing is born. Both carry within them the massive cone of a preceding history condensed in a point that is the present; words fix themselves on a page in a certain constellation, carrying all history within them.

*

“Within each is a universe.” That cliché, yet expressive, phrase does not take an abstract form in writing: it takes on a material existence.

To capture that idea in words, I started writing a story, “Vodka at the Seaside.” Its last three paragraphs move at tremendous speed from the Big Bang, 13.7 billion years ago, to the present day, following a woman as she carelessly walks on the beach in Aqaba, Jordan. Like a pelican riding the wind, freely floating, then dipping fast towards an exact point for a particular fish, I closed in on one character from that distant expanse of history

She, a mere particle of sand in the vast shoreline of existence, is also holding a future history-in-the-making within her. Another flap of a butterfly’s wing. A new fetal universe in the making.

When the comics artist Mahmoud Hafiz Eissa worked on the story, he created a parallel fast-forward, or rather a fast-rewind: a new existence in three pages, in which the character gulps down the universe, and with it galaxies, stars, planets, visible matter, and dark matter, all amassing within her glass.

I decided to publish the comics version of the story, including both timelines—the written and the drawn—as well as both histories on opposing pages, bearing witness that a text diverges, expands, and takes on new meaning from the interaction of two.

*

Luma was her name. She played the piano and studied Greek and I was in love.

Love is a quantum experience, full of potentialities and possibilities. Love is uncertainty embodied. Passion is anxiety, restlessness, the tension of a possible spark, the crackle of embers catching air, glowing as they are consumed.

With impressive vocal control, the iconic Mayada El Hennawy sings Baligh Hamdi’s semi-cheesy words, giving them a different existence: “You’re honey and bitterness, faithfulness and betrayal; you’re tenderness, but also thorns and tears, a sea of sorrow,” yet concluding “you’re the love of a lifetime,” the love.

Love, like a thrust of a single particle in the double-slit experiment, can exist in two places at the same time, producing an interference pattern in its wake. Love is like quantum foam; it multiplies and expands like fractals, and the freedom it creates, its entropy, tends to a maximum. Yet, the ultimate state of entropy is homogeneity: a highly organized drop of ink, if added to a cup of water, will randomly diffuse in a chaotic, free behavior all until the color is uniform.

Two people are in love. They want to be inside each other—to combine, blend, fuse, to the maximum possible. As the homogeneous mix emerges, the flicker subsides, the catalyst is consumed, and entropy has reached its maximum. The movement continues, but the appearance is the same in every direction. Love becomes uniform, bland; has an end, sometimes.

Thus was born my story “Orchestra,” which takes a genre-breaking freeform in its first part, a semi-guided narrative path in its second, and concludes in a metered third section as the lovers get entangled with themselves and with the subject; we no longer know if the lovers are creating poetry or if poetry is creating them.

But Luma left before “we” ever reached that point. The embers are still there, dormant, under a layer of ash, but very much alive, and they burn. Like the ever-present echo of that distant primordial explosion, she’s always present in me and I in her.

*

She often had nightmares, and she would recite them to me in her low, soft, perfervid voice. She was convinced that it “felt real”—that a hand did touch her shoulder, that footsteps had a muffled sound inside her room. I gave her explanations, mainly extracted from the troubles of her everyday life, her overdramatic family, her annoying friends—I drew parallels, inventing relations and representations. She would show me that what I had said was reasonable. I could see, deep down in her black eyes, she was still afraid.

In his book The Grand Design, theoretical physicist and cosmologist Stephen Hawking tells us how the city council in Monza, Italy banned pet owners from keeping goldfish in round bowls because curved surface of the glass presented a distorted lens on reality. Hawking expounds on this, explaining that our view of the universe is not any more real than that of the fish in the bowl, and that both perspectives are equally as “real,” especially if we are able to develop a theory to describe the world—from the inside of the fishbowl.

Was I looking at her from outside the fishbowl? Was she trapped inside? Was I trapped outside?

Our two existences form a continuum—when seen together, they appear distorted, and one collapses almost completely when the other is cornered into observation. In “City Nightmares,” the borders between dream and reality, past and present, are removed. They are not just explored on the personal, psychological level, but also in the transformations of a physical urban space (that of my hometown, Amman) as it is sucked into commercialized neoliberal pseudo-cosmopolitanism. The duality is further explored along internal-external personal-societal conflict.

In my writing, all events are part of a field, interactions of disturbances within a field of fluctuations—and while physics is yet to come with a theory that unifies all observations, in a literary text, once we involve the reader, that might happen.

*

If mathematics is the invisible foundation of music, then quantum physics is the undetectable substance of literary writing.

As the observer plays a key role in a physical event, changing it by their mere observation, so does the reader—investing meaning in words and sentences, involving emotions and perceptions, changing viewing angles.

A text does not exist purely, supernaturally; it exists only through reading, and reading is necessarily an act of interpretation, extension, comparison, construction. It is an act of active engagement; of coauthoring; of creation.

I have attempted to capture this plenitude of perspectives, and encourage the creative part of reading, by involving different elements and techniques: films, laws of physics, photographs, letters, shifting narrator types within a single story, footnotes, an extended contextualizing text, and one lie (the Arabic saying goes: “the most pleasurable of poetry is its falsest”). Each additional hint is a different reading, each infused object is a new layer of meaning, a new lens in an infinite set through which all observations are true.

*

In his book S/Z, Roland Barthes categorized texts into two types depending on their engagement of the reader: the “readerly” text that leaves the reader “with no more than the poor freedom either to accept or reject the text,” and the “writerly” text that transforms the reader into “a producer of the text.” For Barthes, the ideal writerly text is what he calls a “plural text,” in which:

the networks are many and interact, without anyone of them being able to surpass the rest; this text is a galaxy of signifiers, not a structure of signifieds; it has no beginning; it is reversible; we gain access to it by several entrances, none of which can be authoritatively declared to be the main one; the codes it mobilizes extend as far as the eye can reach, they are indeterminable.

Stephen Hawking concludes his contemplation of reality by referring to a fundamental formulation of quantum physics, multiple histories or sum over histories of the physical event, describing how the Universe (or any event within it) does not possess one existence or history as such, but rather every state or possible history exists simultaneously. This links directly to Barthes’ two different types of texts. The “readerly” text is the fishbowl perspective on the world; the “writerly text” involving many possible interpretations related to each reader, to the depth of each reading; it accepts other realities.

The Monotonous Chaos of Existence is one attempt to create, or capture, a plural text as it manifests itself in the current sociopolitical situation in the Arab region; a region with multiple histories, living in many epochs as it carries the heavy inheritance of colonialism, bears the continuing overpowering slaps of interventionism. Leaning towards openness, towards the writerly, The Monotonous Chaos of Existence tends “not to know,” not to have final answers or truths; opening up spaces instead of confiscating them. It is one attempt to prove that language is a sum over histories, that fiction is infested with reality, that imagination is an acrobat walking a high-wire while juggling the objects of the world, completely altering them as she proceeds.

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The Monotonous Chaos of Existence by Hisham Bustani, translated by Maia Tabet, is available via Mason Jar Press.

A lot of people seem to have this question.

It’s a common conundrum that gets covered in many science books, and it’s a question that our listeners and readers often ask us. But why is that? Are there black holes popping up everywhere in backyards across America? Are there people out there who are planning to have a picnic near one and are worried about letting their kids run around it unsupervised?

Probably not. More likely, the fascination with falling into a black hole has less to do with the chances of it actually happening, and more to do with our basic curiosity about these intriguing space objects. And we get it: black holes are mysterious. They are weird regions of space out of which nothing can escape—voids in the fabric of space-time itself that are completely disconnected from the rest of reality.

But what would it be like to fall into one? Would you necessarily die? Would it feel different from falling into a regular hole? Would you discover deep secrets of the universe inside, or see time and space unfold before your very eyes? Would your eyes (or your brain) even work inside of a black hole?

There’s only one way to find out, and that is to jump in. So grab your picnic blanket, say good-bye to your kids (maybe forever), and hang on, because we are about to take a dive into the ultimate backyard hazard.

Approaching the Black Hole

The first thing you might notice as you approach a black hole is that black holes do indeed look like… black holes. They are definitely black: black holes give off absolutely no light, and any light that hits them gets trapped inside. So when you look at one, your eyes don’t see any photons, and your brain interprets that as black.

They are also definitely holes. You can think of them as spheres of space where anything that goes into them stays there forever. What keeps things inside is the gravity of the things already in them: mass is compacted so densely in a black hole that the effects of gravity are enormous. Why? Because gravity gets stronger the closer you are to something with mass, and having mass compacted means you can get really close to it.

Typically, things with a lot of mass are fairly spread out. Take, for example, the Earth. The Earth has about as much mass as a black hole that’s half an inch wide (about the size of a marble). If you were to stand a distance of one Earth radius away from the center of Earth and one Earth radius from a marble-size black hole, you’d feel the same amount of gravity.

But as you get closer to each object, two very different things would happen. As you get close to the center of Earth, you will actually start to feel no gravity. That’s because Earth is now all around you, so you’re being pulled equally in all directions. But as you get close to the small black hole, you’d feel an enormous amount of gravity. You’d feel the entire mass of Earth, all of it really close to you. That’s what a black hole is: it’s super-compacted mass, which makes it extremely powerful to the things immediately around it.

A really compacted mass creates extreme gravity around itself, and at some distance, space gets so distorted (remember that gravity doesn’t just pull on things; it distorts space) that not even light can escape. The point at which light can no longer escape is called the “event horizon,” and it (more or less) defines where the black hole starts. It’s the radius of the black sphere we call a black hole.

The size of a black hole can change, depending on how much mass you squeeze inside. If you compress Earth enough, you’ll get a black hole the size of a marble because, at a distance of about a centimeter, light can no longer escape. But if you add more mass, that distance is larger. For example, if you compress the sun, the distortion of space is higher and the event horizon happens farther out, at three kilometers, giving you a black hole six kilometers wide. The more mass, the bigger the black hole.

In fact, there is theoretically no limit to how big a black hole can be. The smallest black hole we’ve detected in space is about 20 kilometers wide, and the largest is tens of billions of kilometers wide. Really, the only limitation is how much stuff is around to make the black hole and how much time you allow for the black hole to form.

The second thing you might notice as you approach a black hole is that black holes are often not alone. You would sometimes see stuff surrounding them, falling into the black hole. Or, more precisely, you would see the stuff swirling around waiting to fall into the black hole.

This stuff is called the “accretion disk.” It’s made of gas, dust, and other matter that didn’t get sucked straight into the black hole but is instead circling in orbit, waiting for its turn to spiral in. With a small black hole it may not be very impressive, but with a supermassive black hole it can be a sight to behold. The sheer friction of all that gas and dust whipping around at ultrahigh speeds can be so intense that the matter gets ripped apart. This emits a lot of energy, creating some of the most powerful sources of light in the universe. These quasi-stars, or quasars, can sometimes be thousands of times brighter than all the stars in a single galaxy combined.

Fortunately, not all black holes, even supermassive ones, form quasars (or blazars for that matter, which are like quasars on steroids). Most of the time, the accretion disk doesn’t have the right amount of stuff or the right conditions to create such a dramatic scene. This is a good thing because being close to a quasar would probably vaporize you instantly, way before you even get a glimpse of the black hole. Hopefully, the black hole that you picked to fall into has a nice, relatively calm accretion disk around it, and you actually have a chance at getting near it.

Getting Closer

After you’ve confirmed that the black hole you’re falling into doesn’t have a swirling toilet bowl of burning gas and dust spraying more energy than billions of stars combined, the next thing you might want to worry about is death by gravity itself.

Usually when you hear the words “death by gravity,” you think of falling to your death from something high, like a building or an airplane. But in those cases gravity isn’t the one to blame. It’s the landing that kills you, not the falling. In space near a black hole, however, it actually is the falling that can kill you.

You see, gravity doesn’t just pull on you; it also tries to tear you apart. Remember that gravity depends on the distance to the object that has mass. When you stand here on Earth, your feet are closer to Earth than your head, which means your feet feel a stronger gravitational pull than your head. If you were to pull on one end of a rubber band harder than you are pulling the other end, the rubber band would stretch, even if you’re pulling both ends in the same direction. That’s what’s happening to you right now: the parts of you closer to the ground feel more gravity and Earth is trying to stretch you like a rubber band.

Of course, you probably don’t feel stretched out, and that’s because (a) our bodies are squishy, but not that squishy (i.e., we hold together pretty well); and (b) the difference in gravity between your head and your feet is not that strong. Gravity on Earth is fairly weak, which means your head and your feet pretty much feel the same amount of gravity.

But if the gravity overall was much stronger, then you might be in trouble. If you were in free fall moving toward a really massive object, then the gravity might be strong enough for you to feel the difference in pull between your head and your feet. It’s kind of like a playground slide: the taller the slide, the steeper it is on the way down. At some point, the difference in gravity between both ends of you might be enough to actually tear you apart.

This is where a lot of science books will tell you that surviving entering a black hole is impossible. They’ll typically say that gravity around a black hole is so strong that you’d be “spaghettified” (aka pulled apart) before you even went in. But actually, this is not necessarily true! It’s totally possible to enter a black hole. It turns out that the point at which gravity would tear you apart (we’ll call it the “spaghettification point”) and the point at which light can’t escape the black hole (i.e., the edge of the black hole) are not the same, and are actually in different places relative to each other depending on the mass of the black hole. The spaghettification point changes proportionally to the cubic root of the mass of the black hole, whereas the edge of the black hole changes linearly with the mass.

What this means is that for small black holes, the spaghettification point is bigger than the event horizon, which means it sits outside the edge of the black hole. But for large black holes, the spaghettification point is smaller and sits inside the black hole. For example, a black hole with the mass of a million suns has a radius of 3,000,000 kilometers, but its gravity won’t pull you apart until you are deep inside, 24,000 kilometers from its center. On the other hand, a small black hole with a radius of 30 kilometers would pull you apart at a distance of 440 kilometers, way before you get to its edge.

It might be strange to think that smaller black holes are actually more dangerous to approach than bigger black holes, but that’s just how the math of black holes works out. Bigger black holes cover such an enormous area that they don’t need to be that powerful at their edges to suck things in and keep them inside.

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Excerpted from Frequently Asked Questions About the Universe. Used with the permission of the publisher, Riverhead Books, an imprint of Penguin Random House LLC. Copyright © 2021 by Jorge Cham and Daniel Whiteson.