A good primer for particle physics, quantum physics, thermodynamics, evolution and entropy. In addition to the parts, this is a book about the universe and how it functions. The concept of quantum tunneling as it applies to the Higgs field is particularly riveting. Just like in The Alchemist, Brian Greene says at at the end, we have to manufacture our own purpose
| “I do mathematics because once you prove a theorem, it stands. Forever.” |
| We emerge from laws that, as far as we can tell, are timeless, and yet we exist for the briefest moment of time. We are guided by laws that operate without concern for destination, and yet we constantly ask ourselves where we are headed. We are shaped by laws that seem not to require an underlying rationale, and yet we persistently seek meaning and purpose. |
| The unfolding of any given life is beyond prediction. The final fate of any given life is a foregone conclusion. And yet this looming end, as inevitable as the setting sun, is something only we humans seem to notice. |
| To work and play, to yearn and strive, to long and love, all of it stitching us ever more tightly into the tapestry of the lives we share, and for it all then to be gone—well, to paraphrase Steven Wright, it’s enough to scare you half to death. Twice. |
| “Man is literally split in two: he has an awareness of his own splendid uniqueness in that he sticks out of nature with a towering majesty, and yet he goes back into the ground a few feet in order blindly and dumbly to rot and disappear forever.” |
| “We fly to Beauty,” said Emerson, “as an asylum from the terrors of finite nature.” |
| Eternity itself may forever lie beyond the reach of our equations, but our analyses have already revealed that the universe we have come to know is transitory. From planets to stars, solar systems to galaxies, black holes to swirling nebulae, nothing is everlasting. Indeed, as far as we can tell, not only is each individual life finite, but so too is life itself. |
| However much we’d prefer it otherwise, to achieve “I think, therefore I am” is to run headlong into the rejoinder “I am, therefore I will die.” |
| Eternity will be a long time coming. |
| A mist of particles drifting through a cold and quiet cosmos. |
| Nabokov’s description of a human life as a “brief crack of light between two eternities of darkness”6 may apply to the phenomenon of life itself. |
| “Death wipes you out…To be wiped out completely, traces and all, goes a long way toward destroying the meaning of one’s life.” |
| The universe will play host to life and mind only temporarily. |
| Emily Dickinson’s “Forever—is composed of Nows” |
| In the end, during our brief moment in the sun, we are tasked with the noble charge of finding our own meaning. |
| Large groups often display statistical regularities absent at the level of the individual. |
| You should expect to encounter high-entropy states. |
| You should seek an explanation beyond mere chance for any low-entropy configurations you encounter. |
| First law – law of energy conservation. |
| Unlike the first law, the second is not a law of conservation. It is a law of growth. |
| over time there is an overwhelming tendency of entropy to increase. |
| we associate low entropy with high-quality energy and high entropy with low-quality energy. |
| whereas the first law of thermodynamics declares that the quantity of energy is conserved over time, the second law declares that the quality of that energy deteriorates over time. |
| The future has higher entropy than the past. |
| Entropy can decrease. It’s just ridiculously unlikely. |
| We are all waging a relentless battle to resist the persistent accumulation of waste, the unstoppable rise of entropy. For us to survive, the environment must absorb and carry away all the waste, all the entropy, we generate. Which raises the question, Does the environment—by which we now mean the observable universe—provide a bottomless pit for absorbing such waste? Can life dance the entropic two-step indefinitely? |
| what ignited the big bang? |
| Unlike the electromagnetic force, which can push or pull, gravity seemed to be solely an attractive force. |
| According to the general theory of relativity, the gravitational force can be repulsive. |
| “afterglow of creation” (or, in technical jargon, the “cosmic microwave background radiation”), |
| It’s as if the classical tradition viewed the world through pristine, polished spectacles that brought all physical features into perfectly sharp focus, while the spectacles donned by the quantum perspective are inherently foggy. In the large, everyday world of common experience, the quantum fog is too thin to impact our vision, so the classical and quantum perspectives are barely distinguishable. But the smaller you probe, the foggier the quantum lenses become and the fuzzier the view. The metaphor might suggest that all we need do is clean the quantum lenses. But the uncertainty principle established that no matter how fastidious we are and regardless of the advanced equipment we use, there will always be a minimal amount of fogginess that cannot be wiped away. |
| As a particle transits from here to there, a classical physicist might draw its trajectory with a pointed quill, while a quantum physicist would run her finger along the wet ink, smearing out the path. |
| the question raised by Gottfried Leibniz—“Why is there something rather than nothing?”—than |
| A low-entropy configuration is special. |
| if you wait long enough even the most unlikely of things will happen. |
| When a tiny speck of space finally makes the statistically unlikely leap to low entropy, repulsive gravity jumps into action and propels it into a rapidly expanding universe—the big bang. |
| gravity spontaneously sculpts order from an ever-more-disordered cosmos. |
| Rocks and rabbits are different. But how? And why? Each is an enormous collection of protons, neutrons, and electrons, and all these particles—whether confined to rock or rabbit—are governed by the very same laws of physics. So what takes place within the body of a rabbit that renders its collection of particles so profoundly different from the collection of particles constituting a rock? It’s the kind of question a physicist would ask. More often than not, physicists are reductionists and so tend to look beneath complex phenomena for explanations that rely on properties and interactions of simpler constituents. |
| life is one more means the universe employs to release the entropy potential locked within matter. |
| By roughly ten minutes after creation, the temperature and density drop below the threshold required for nuclear processes.10 |
| British astronomer Sir Arthur Eddington (who when asked what it was like to be among only three people who understood Einstein’s general relativity, famously responded, “I’m trying to think who the third person is”) |
| the scorching interior of stars might provide cosmic Crock-Pots for slow-cooking more complex atomic species. |
| Stars that are sufficiently massive will continue to crush nuclei together, forcing them to fuse into the more complex atoms of the periodic table, while producing substantial heat and light in the process. For example, a star that’s twenty times the mass of the sun will spend its first eight million years fusing hydrogen into helium, then devote its next million years to fusing helium into carbon and oxygen. From there, with its core temperature getting ever higher, the conveyor belt continually revs up: it takes about a thousand years for the star to burn its storehouse of carbon, fusing it into sodium and neon; over the next six months, further fusion produces magnesium; within a month more sulfur and silicon; and then in a mere ten days fusion burns the remaining atoms, producing iron.13 We pause at iron, for good reason. Of all atomic species, iron’s protons and neutrons are bound together most tightly. This matters. If you try to build yet heavier atomic species by cramming in additional protons and neutrons, you’ll find that the iron nuclei have little interest in participating. The nuclear bear hug gripping together iron’s twenty-six protons and thirty neutrons has already squeezed out and released as much energy as is physically possible. To add protons and neutrons would require a net input—not output—of energy. As a result, when we reach iron, stellar fusion’s orderly production of larger and more complex atoms, with the accompanying release of heat and light, grinds to a halt. Like ash that’s fallen to the hearth of your fireplace, iron can’t be burned further. What then of all the atomic species with yet larger nuclei, including utilitarian elements like copper, mercury, and nickel; sentimental favorites like silver, gold, and platinum; and exotic heavyweights like radium, uranium, and plutonium? Scientists have identified two sources for these elements. When a star’s core is mostly iron, fusion reactions no longer generate the outward pushing energy and pressure necessary to counteract the inward pull of gravity. The star begins to collapse. If the star is massive enough, this collapse accelerates into an implosion so powerful that the core temperature rockets; the imploding material bounces off the core and triggers a spectacular shock wave that surges outward. And as the shock wave rumbles from the core toward the star’s surface, it compresses the nuclei it encounters with such fury that a slew of larger nuclear agglomerations form. In the maelstrom of chaotic particle motion, all of the periodic table’s heavier elements can be synthesized, and when the shock wave finally reaches the star’s surface, it blasts the rich atomic smorgasbord into space. A second source of heavy elements is the violent collisions between neutron stars, celestial bodies produced in the death throes of stars whose mass is roughly ten to thirty times that of the sun. That neutron stars are mostly made of neutrons—chameleonic particles that can transform into protons—bodes well for building atomic nuclei, as we have a profusion of the right raw materials. One obstacle, though, is that to form atomic nuclei the neutrons need to free themselves from the star’s powerful gravitational grip. That’s where a collision between neutron stars comes in handy. The impact can throw off plumes of neutrons, which, having no electric charge and thus experiencing no electromagnetic repulsion, more easily coalesce into groups. After some of these neutrons then flip the chameleonic switch and become protons (releasing electrons and anti-neutrinos in the process), we acquire a supply of complex atomic nuclei. |
| neutron-star collisions produce heavier elements more efficiently and abundantly than supernova explosions, and so it may be that the majority of the universe’s heavy elements were produced through these astrophysical smashups. Fused in stars and ejected in supernova explosions, or jettisoned by stellar collisions and amalgamated in particle plumes, an assortment of atomic species float through space, where they swirl together and coalesce into large clouds of gas, which over yet more time clump anew into stars and planets, and ultimately into us. |
| the sun is a cosmic newcomer. It was not among the universe’s first generation of stars. We saw in chapter 3 that those stellar trailblazers originated from quantum variations in the density of matter and energy that were stretched across space by inflationary expansion. |
| The first stars were likely mammoth, hundreds or perhaps even thousands of times the mass of the sun, burning with such intensity that they quickly died out. The heaviest ended their lives in a gravitational implosion so emphatic that they collapsed all the way down to black holes, |
| Less massive early stars ended their lives with a fiery supernova explosion that, beyond seeding space with complex atoms, initiated the next round of stellar formation. Much as a supernova shock wave ripping through a star forcefully fuses its atomic constituents, a shock wave thundering through space compresses the clouds of molecular ingredients it encounters. And because compressed regions are denser, they exert a greater gravitational pull on their surroundings, drawing in yet more particulate constituents and setting off a new round of gravitational snowballing en route to the next generation of stars. |
| solar physicists believe the sun is a grandchild of the universe’s first stars, a third-generation arrival. |
| Early earth may have been a relatively calm water world, with small landmasses dotting a surface mostly covered by ocean. |
| Roughly fifty to one hundred million years after its birth, earth likely collided with a Mars-sized planet called Theia, which would have vaporized the earth’s crust, obliterated Theia, and blown a cloud of dust and gas thousands of kilometers into space. In time, that cloud would have clumped up gravitationally to form the moon, one of the larger planetary satellites in the solar system and a nightly reminder of that violent encounter. Another reminder is provided by the seasons. We experience hot summers and cold winters because earth’s tilted axis affects the angle of incoming sunlight, with summer being a period of direct rays and winter being a period of oblique ones. The smashup with Theia is the likely cause of earth’s cant. |
| Werner Heisenberg’s lament, muttered as he aimlessly walked through an empty park in Copenhagen after a grueling night of intense calculations with Niels Bohr, summed up the situation well: “Can nature possibly be as absurd as it seemed to us in these atomic experiments?”16 The answer, a resounding yes, came in 1926 from an unassuming German physicist, Max Born, who broke the conceptual logjam by introducing a radically new quantum paradigm. He argued that an electron (or any particle) can only be described in terms of the probability that it will be found at any given location. |
| When applied to atoms, the quantum perspective jettisons the old “solar-system model,” which pictured electrons in orbit around the nucleus much as planets orbit the sun. In its place, quantum mechanics envisions an electron as a fuzzy cloud surrounding the nucleus whose density at any given location indicates the probability that the electron will be found there. An electron is unlikely to be found where its probability cloud is thin, likely to be found where its probability cloud is thick. |
| think of an atom’s nucleus as a central stage and its electrons as an audience that watches the action from seats on surrounding tiers, arranged for theater in the round. In this “quantum theater,” Schrödinger’s math applied to atoms dictates how the electron audience fills in the seats. |
| Much as you’d expect from your experience climbing stairs in a real theater, the higher the tier the more energy an electron needs to reach it. |
| How many electrons can a given tier hold? Schrödinger’s math provides the answer, |
| The math also reveals one further peculiarity, a kind of atomic OCD that’s a primary driver of chemical reactions throughout the cosmos. Atoms have an aversion to tiers that are only partially filled. |
| for most atoms, the number of electrons needed to balance the number of protons does not fill a complete set of tiers.20 So what do they do? They barter with other atomic species. |
| Water provides an important case in point. Oxygen contains eight electrons, two on tier one and six on tier two. Oxygen thus strives for two more electrons, seeking to fill out its second tier to the maximum occupancy of eight. One readily available source is hydrogen. Every hydrogen atom has a single electron, hanging solo and twiddling its thumbs on tier one. If a hydrogen atom has the opportunity to fill this tier with one more electron it happily will. So hydrogen and oxygen agree to share a communal pair of electrons, fully satisfying hydrogen and bringing oxygen one electron closer to orbital bliss. Include a second hydrogen atom that similarly shares a pair of communal electrons with oxygen, and it is rapture all around. The sharing of these electrons binds the oxygen atom to the two hydrogen atoms, giving rise to a molecule of water, H2O. The geometry of this union has far-reaching implications. The interatomic pushes and pulls shape all water molecules into a wide V, with oxygen at the vertex and each hydrogen perched on one of the letter’s upper tips. Although H2O has no net electrical charge, because oxygen is so manic about filling its orbital tiers, it hoards the shared electrons, resulting in a distribution of charge across the molecule that is lopsided. The vertex of the molecule, oxygen’s home, has a net negative charge, while the two upper tips, where the hydrogens dwell, have a net positive charge. The distribution of electrical charge across a water molecule might seem like an esoteric detail. But it’s not. It proves essential to the emergence of life. Because of water’s skewed charge distribution, it can dissolve nearly everything. The negatively charged oxygen vertex grabs hold of anything with even a slight positive charge; the positively charged hydrogen tips grab hold of anything with even a slight negative charge. In tandem, the two ends of a water molecule act like charged claws that pull apart most anything that’s submerged for a sufficient time. Table salt is the most familiar example. Composed of an atom of sodium bonded to an atom of chlorine, a molecule of table salt has a slight positive charge near the sodium (which donates an electron to the chlorine) and a slight negative charge near the chlorine (which accepts an electron from the sodium). Drop salt into water, and the oxygen side of H2O (negatively charged) grabs hold of the sodium (positively charged), while the hydrogen side of H2O (positively charged) grabs hold of the chlorine (negatively charged), ripping salt molecules apart and dissolving them into solution. And what’s true for salt is true for a great many other substances too. The details vary, but water’s asymmetric charge arrangement makes it an uncanny solvent. Wash your hands, even without soap, and water’s electrical polarity will be hard at work, dissolving foreign matter and carrying it away. Well beyond its utility in personal hygiene, water’s capacity to grab hold of and ingest substances is indispensable to life. Cell interiors are miniature chemistry labs whose workings require the rapid movement of a vast collection of ingredients: nutrients in, waste out, comingling of chemicals to synthesize substances required for cellular function, and so on. Water makes this possible. Water, constituting some 70 percent of a cell’s mass, is life’s ferrying fluid. Nobel laureate Albert Szent-Györgyi summarized it eloquently: “Water is life’s matter and matrix, mother and medium. There is no life without water. Life could leave the ocean when it learned to grow a skin, a bag in which to take the water with it. We are still living in water, having the water now inside.” |
| Every molecule of DNA, whether from seaweed or Sophocles, encodes the information needed to build proteins in the same way. That is the unity of life’s information. |
| In living cells—let’s focus on animals to be definite—similar redox reactions take place but, importantly, the electrons stripped from atoms that you ingested at breakfast are not transferred directly to oxygen. If they were, the energy released would create something akin to a cellular fire, an outcome life has learned the benefit of avoiding. Instead, electrons donated by food pass through a series of intermediate redox reactions, rest stops on a trek that ultimately ends with oxygen but that allows smaller amounts of energy to be released at each step. Like a ball in the bleachers cascading down a stadium’s steps, electrons jump from one molecular receptor to another, with each receptor more electron crazed than the previous, ensuring that each jump results in the release of energy. Oxygen, the most electron-crazed receptor of all, waits for the electron at the bottom of the stairs, and when it finally arrives, the oxygen hugs the electron tight, squeezing out the marginal energy it can still provide, thus concluding the energy extraction process. The process for plants is largely the same. The main difference is the source of the electrons. For animals, they come from food. For plants, they come from water. Sunlight striking chlorophyll in the green leaves of plants strips electrons from water molecules, pumps up their energy, and sets them off on a similar energy-extracting redox cascade. And so the energy supporting all the actions of all living things can be traced to one and the same process, jumping electrons executing a series of cellular redox reactions. It’s why Albert Szent-Györgyi, continuing his poetic reflections, mused, “Life is nothing but an electron looking for a place to rest.” |
| Energy is the coin that pays for all comings and goings throughout the cosmos, a coin minted in a wide range of currencies and earned through an even wider range of callings. One currency is nuclear energy, generated by fission and fusion among a wealth of atomic species; electromagnetic energy is another, generated by pushes and pulls among a wealth of charged particles; gravitational energy is another still, generated by interactions among a wealth of massive bodies. And yet of all the innumerable processes, life on planet earth leverages one and only one energy mechanism: a specific sequence of electromagnetic chemical reactions in which electrons engage in a downward-directed sequence of jumps, starting with food or water and ending with the clutching embrace of oxygen. |
| a proton battery. |
| In a living cell we encounter an analogous situation, with pent-up protons replacing pent-up electrons. But it’s a distinction that hardly makes a difference. Protons, like electrons, all carry the same electric charge, and so they also repel one another. When cellular redox reactions pack protons closely together, they too stand at the ready waiting for the chance to rush away from their enforced companions. |
| Your body contains tens of trillions of cells, which means that every second you consume on the order of one hundred million trillion (1020) ATP molecules. Each time an ATP is used, it splits up into the raw materials (ADP and a phosphate), which the proton battery-powered turbines then cram back together into freshly minted, fully rejuvenated ATP molecules. These ATP molecules then hit the road again, delivering energy throughout the cell. |
| the intricate and seemingly baroque collection of processes that power cells is universal across all life. That unity, together with the unity of DNA’s coding of cellular instructions, provides overwhelming evidence that all life emerged from a common ancestor. |
| With genteel restraint, Watson and Crick concluded their paper with an understatement ranking among the world’s most famous: “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” |
| To give a feel for just how rare such changes are, copying errors creep in at the rate of roughly one per every one hundred million DNA base pairs. That’s like a medieval scribe getting a single letter wrong per every thirty copies of the Bible. And even that tiny rate is an overestimate, because 99 percent of the misprints are repaired by chemical proofreading mechanisms operating within each cell, reducing the net error rate to about one per every ten billion base pairs. |
| Nature is not in a hurry and does not need to meet a bottom line. The cost of innovating by small random changes is a cost nature can bear. |
| molecular Darwinism. It shows how groups of jostling particles guided solely by the laws of physics can become ever more adept at reproduction—something we ordinarily associate with life. |
| RNA is an extraordinarily versatile molecule that is an essential component of all living systems. You can think of it as a shorter, one-sided version of DNA, comprising a single rail along which a sequence of bases is attached. Among its various cellular roles, RNA is a chemical mediator that takes imprints of various small sections of an “unzipped” strand of DNA, similar to the way a dentist can take a mold of your teeth when you separate your upper and lower jaws, and transports the information to other parts of the cell, where it directs the synthesis of specific proteins. |
| there’s an important difference between RNA and DNA: whereas DNA is content to be a cell’s oracle, a fount of wisdom directing cellular activity, RNA is willing to get its hands dirty with the manual labor of chemical processes. |
| RNA is thus both software and hardware. |
| Life is physics orchestrated. |
| Schrödinger explained that organisms resist the rise to higher entropy by “feeding upon negative entropy,” |
| The nuclear force, in tandem with gravity, is a fount of life-giving low-entropy fuel. |
| some of science’s most profound questions: Could life be such a long-shot possibility that it arose only once in a universe containing hundreds of billions of galaxies, each with hundreds of billions of stars, many of which have orbiting planets? Or is life the natural outcome, perhaps even the inevitable outcome, of certain basic and relatively common environmental conditions, suggesting a cosmos teeming with life? |
| “Everything begins with consciousness and nothing is worth anything except through it,” |
| Ambrose Bierce’s “I think that I think, therefore I think that I am,” |
| Science reacts to talk of realms beyond the reach of physical law with an exasperated grimace, a turning on its heels, and a swift return to the lab. Such scoffing represents a dominant scientific attitude but also highlights a critical gap in the scientific narrative. We have yet to articulate a robust scientific explanation of conscious experience. We lack a conclusive account of how consciousness manifests a private world of sights and sounds and sensations. |
| twenty-five-hundred-year-old sentiment of Democritus, “Sweet is sweet, bitter is bitter, hot is hot, cold is cold, color is color; but in truth there are only atoms and the void.” |
| Why would the particles that constitute the tangible elements of external reality and the physical laws that govern them have any relevance for explaining my inner world of conscious experience? Perhaps, then, we should expect an understanding of consciousness to not merely be a higher-level story, to not merely be a story that shifts its gaze from outward to inward, but to be a fundamentally different kind of story, one that requires a conceptual revolution on par with those of quantum physics and relativity. |
| Music is the hidden arithmetical exercise of a mind unconscious that it is calculating” |
| How can a collection of mindless, thoughtless, emotionless particles come together and yield inner sensations of color or sound, of elation or wonder, of confusion or surprise? |
| when it comes to conscious experience, physical processes are part of the story but not the full story. |
| Strategies for explaining consciousness fan out across an impressive terrain of ideas. At the extremes are positions that either dismiss consciousness as an illusion (eliminativism) or declare that consciousness is the only quality of the world that is real (idealism). |
| How can a swirl of mindless particles create mind? They can’t. To create a conscious mind you need a swirl of mindful particles. By pooling their proto-conscious qualities, a large collection of particles can yield familiar conscious experience. |
| Chalmers’s proposal is that there are two sides to information: There is the objective, third-party-accessible quality of information—the information that has, for hundreds of years, been the province of conventional physics. There is also a subjective, first-person-accessible quality of information that physics has so far not considered. |
| Carl Sagan’s famous dictum that extraordinary claims require extraordinary evidence is an apt guide. There is overwhelming evidence of something extraordinary—our inner experiences—but far less convincing evidence that these experiences are beyond the explanatory reach of conventional science. |
| conscious awareness is information that is highly integrated and highly differentiated. |
| Long ago, brains that may have become distracted by the billowing details of the physical world are brains that would have been swiftly eaten. Brains that survived are brains that avoided being consumed by details that lacked survival value. |
| When your attention is not directed at cars or avalanches or earthquakes, but is instead focused on animals or humans, you similarly create schematic mental representations. But beyond representations of their physical forms, you also create schematic mental representations of their minds. You try to assess what’s going on inside their heads—whether a given animal or human is friend or foe, offers safety or danger, is seeking mutual opportunity or selfish gain. Clearly, there is significant survival value in quickly sizing up the nature of our encounters with other life. Researchers call this capacity, refined over generations by natural selection, our theory of mind |
| As with the representation of the Ferrari, and as with your representation of the attention of others, the representation of your own attention leaves out vast swaths of details. It ignores the underlying neuronal firings, the information processing and complex signal exchanges that generate your focus and instead sketches the attention itself, what in common language we normally call our “awareness.” And this, according to Graziano, is the heart of why conscious experience seems to float unmoored in the mind. When the brain’s penchant for simplified schematic representations is applied to itself, to its own attention, the resulting description ignores the very physical processes responsible for that attention. That is why thoughts and sensations seem ethereal, as if they come from nowhere, as if they hover in our heads. If your schematic representation of your body were to leave out your arms, the motion of your hands would seem ethereal too. And that is why conscious experience seems utterly distinct from the physical processes carried out by our particulate and cellular constituents. The hard problem seems hard—consciousness seems to transcend the physical—only because our schematic mental models suppress cognizance of the very brain mechanics that connect our thoughts and sensations to their physical underpinnings. |
| Consciousness would be demystified without being diminished. |
| quantum mechanical calculations, based on Schrödinger’s equation, agree with experimental measurements to better than nine digits after the decimal point. |
| Nevertheless, there is a puzzle at the core of quantum theory. The primary new feature of quantum mechanics is that its predictions are probabilistic. The theory might assert that there is a 20 percent chance that an electron will be found here, a 35 percent chance that it will be found over there, and a 45 percent chance way over there. If you then measure the electron’s position in a great many identically prepared versions of the same experiment, you will find to impressive accuracy that in 20 percent of your measurements the electron is here, in 35 percent of them it is over there, and 45 percent of the time it is way over there. That is why we have confidence in quantum theory. Now, quantum theory’s reliance on probabilities may not sound particularly exotic. After all, when you flip a coin we also use probabilities to describe the possible outcome—there’s a 50 percent chance that the coin lands heads and a 50 percent chance that it lands tails. But here is the difference, familiar to many yet still deeply shocking: in the ordinary classical description, after you flip the coin but before you look, the coin is either heads or tails, you simply don’t know which. By contrast, in the quantum description, prior to examining the whereabouts of a particle like an electron that has a 50 percent chance of being here and a 50 percent chance of being there, the particle is not either here or there. Instead, quantum mechanics says the particle is hovering in a fuzzy mixture of being both here and there. And if the probabilities give the electron a nonzero chance to be at a variety of different locations, then according to quantum mechanics it would be hovering in a fuzzy mixture of being simultaneously situated at all of them. This is so fantastically strange, and so counter to experience, that you might be tempted to dismiss the theory out of hand. |
| The problem is, the more we’ve worked, the weirder things have become. There is nothing in the quantum equations that shows how reality transitions from the fuzzy mixture of many possibilities to the single definite outcome you witness upon undertaking a measurement. In fact, if we assume—as seems utterly sensible—that the same successful quantum equations apply not just to the electrons (and other particles) you may be studying but also to the electrons (and other particles) that make up your equipment, and those making up you, and those making up your brain, then according to the mathematics the transition shouldn’t happen at all. If an electron is hovering both here and there, then your equipment should find that it is both here and there, and upon reading the equipment’s display, your brain should think the electron is both here and there. That is, after you perform a measurement, the quantum fuzziness of the particles you are studying should infect your equipment, your brain, and presumably your conscious awareness, causing your thoughts to hover in a fuzzy mixture of multiple outcomes. And yet, after each and every measurement, you report nothing of the sort. You report that you witnessed a single, definite result. The challenge, known as the quantum measurement problem, is to resolve the puzzling disparity between the fuzzy quantum reality described by the equations and the sharp familiar reality you consistently experience. |
| physicists Fritz London and Edmond Bauer,38 and a few decades later Nobel laureate Eugene Wigner,39 suggested that consciousness might be the key. |
| Imagine, then, that the rules of quantum mechanics apply all along the chain, from the electron that’s being measured, to the particles in the equipment performing the measurement, to the particles constituting the readout on the equipment’s display. But when you look at the readout and the sensory data flows into your brain something changes: the standard quantum laws cease to apply. Instead, when conscious awareness is brought to bear, some other process takes over—a process that ensures you become cognizant of a single definite result. Consciousness would thus be an intimate participant in quantum physics, dictating that as the world evolves all but one of the many possible futures are eliminated, either from reality itself or at least from our cognitive awareness. |
| Quantum mechanics is mysterious. Consciousness is mysterious. How fun to imagine that their mysteries are related, or are the same mystery, or that each mystery resolves that of the other. |
| when a quantum system is prodded—whether the prodder is a conscious being or a mindless probe—the system snaps out of the probabilistic quantum haze and assumes a definite reality. Interactions—not consciousness—coax the emergence of a definite reality. |
| Magnificent though it is, consciousness will be understood as another physical quality that arises in a quantum universe. |
| random outcomes are not freely willed choices. |
| Human freedom is not about willed choice. |
| Instead, human freedom is about being released from the bondage of an impoverished range of response that has long constrained the behavior of the inanimate world. |
| freedom is found in liberation from a restricted range of behaviors. |
| “I” is nothing but a shorthand that signifies my specific particulate configuration (which, although dynamic, maintains sufficiently stable patterns to provide a consistent sense of personal identity |
| The entropic two-step explains how orderly clumps can form in a world that is becoming ever more disordered, and how certain of these clumps, stars, can remain stable over billions of years as they produce a steady output of heat and light. Evolution explains how, in a favorable environment such as a planet bathed by a star’s steady warmth, collections of particles can coalesce in patterns that facilitate complex behaviors, from replication and repair, to energy extraction and metabolic processing, to locomotion and growth. Collections that acquire the further capacities to think and learn, to communicate and cooperate, to imagine and predict, are better equipped to survive and hence to produce similar collections with similar capacities. Evolution thus selects for these abilities and, generation upon generation, refines them. In time, some collections conclude that their cognitive powers are so remarkable that they transcend physical law. Some of the most thoughtful of these collections are then bewildered by the conflict between the freedom of will they experience and the unyielding control of physical law they recognize. But the fact is there is no conflict because there is no transcending of physical law. There can’t be. Instead, the collections of particles need to reassess their powers, focusing not on the laws that govern particles themselves but on the high-level, thoroughly complex, and extraordinarily rich behaviors each collection of particles—each individual—can exhibit and experience. And with that reorientation, the particle collections can tell an illuminating story of wondrous behaviors and experiences, suffused with wills that feel free and speak as though they have autonomous control, and yet are fully governed by the laws of physics. |
| Our sense of who we are, the capacities we have, and the freedom of will we seemingly exert all emerge from the particles moving through our heads. Fiddle with the particles, and those familiar qualities can fall away. |
| Pattern is central to human experience. We survive because we can sense and respond to the rhythms of the world. |
| Mathematics is the articulation of pattern. |
| Galileo summed it up by declaring that the book of nature, which he believed revealed God just as surely as the Bible, is written in the language of mathematics. |
| is mathematics the source of reality, rendering the world’s patterns the expression of mathematical truth? My romantic sensibilities lean toward the latter. |
| But my less sentimental assessment allows for mathematics to be a language of our own making, developed in part by overindulging our predilection for pattern. |
| Toni Morrison, “We die. That may be the meaning of life. But we do language. That may be the measure of our lives.” |
| As Bertrand Russell summarized it, “A dog cannot relate his autobiography; however eloquently he may bark, he cannot tell you that his parents were honest but poor.” |
| 60 percent of our conversation today is devoted to gossip, a staggering number (especially to those of us who’ve hardly mastered small talk) that some researchers argue reflects the primary purpose of language at its inception. |
| you can’t cherry-pick evolution.27 Evolution sometimes offers only package deals. |
| Storytelling is our most powerful means for inhabiting other minds. And as a deeply social species, the ability to momentarily move into the mind of another may have been essential to our survival and our dominance. |
| As intelligence matures, the very same impulse to explore and to understand manifests as an urge to infuse experience with significance. |
| questions that gnaw at our insides long after our stomachs are full. |
| Dreamtime, an eternal realm from which all life originates and to which all life will return. |
| If I do something for you, you’re going to have to do something for me, and make no mistake, I’m keeping a running tab. This reciprocal variety of altruism may be the source of the transactional nature of the relationship adherents typically have with the supernatural beings that populate religious traditions: I’ll sacrifice, I’ll pray, I’ll do good, but come tomorrow’s combat, you’ve got my back. |
| As Darwin himself put it, “When two tribes of primeval man, living in the same country, came into competition, if (other circumstances being equal) the one tribe included a great number of courageous, sympathetic and faithful members, who were always ready to warn each other of danger, to aid and defend each other, this tribe would succeed better and conquer the other.”17 Moreover, those whose service was inspired by devotion to departed ancestors or watchful deities would have been even more reliable and fervent in their commitment to the cause.18 And so to determine which genetic traits would have swum broadly through the gene pool, we must not only take account of within-group dynamics, favoring the selfish, but also between-group dynamics, favoring the cooperative. If we assume that across many thousands of generations between-group success dominated the calculus of survival, allegiance to the group would hold sway, and so religion’s social cohesion would triumph. |
| “I’ll do something good for you so long as you do something good for me in return, but you do something underhanded and I’ll quickly retaliate”—reliably trumps other variants, including those far more selfish. The theoretical analysis thus suggests that qualified cooperation of this sort aids survival.19 To the detractors, this demonstrates that cooperation can arise organically and spread via natural selection, with no need for participants to hold a common religious belief. |
| Ernest Becker, |
| Denial of Death |
| The terror of knowing we are going to die, these researchers argue, “would have rendered our ancestors quivering piles of biological protoplasm on the fast track to oblivion.”21 What may have saved us, they suggest, was the promise of life beyond physical death, either literal or symbolic. Becker himself made a persuasive case that addressing mortality awareness by invoking the supernatural was a wondrous human innovation. To alleviate the distress of transience requires a palliator with unqualified and unlimited durability, something impossible to achieve in the real world of material things. |
| as Stephen Jay Gould summarized it, “A large brain allowed us to learn…the inevitability of our personal mortality”26 and “all religion began with an awareness of death.”27 But whether religion then took hold because it transformed that awareness into an adaptive advantage is a wholly different question. |
| the Vedas seek something stable, some kind of constant quality underlying the shifting sands of familiar reality. |
| Deviating from its Vedic origins, Buddhism denies that there is an immutable substrate underlying existence and attributes the root of human suffering to the failure of recognizing the impermanence of everything. |
| the capacity for recognizing pattern is how we survive. |
| sometimes we go overboard. Sometimes, our naturally selected pattern detectors are so primed, so ready to announce that a signal has been found, that they see patterns and envision correlations that are not there. |
| James emphasized that while science cultivates an objective, impersonal approach it is only by considering our inner worlds—“the terror and beauty of phenomena, the ‘promise’ of the dawn and of the rainbow, the ‘voice’ of the thunder, the ‘gentleness’ of the summer rain, the ‘sublimity’ of the stars, and not the physical laws which these things follow”38—that we can ever hope to develop a full account of reality. |
| “Without music,” said Friedrich Nietzsche, “life would be a mistake.” |
| And, in the words of George Bernard Shaw’s Ecrasia, “Without art, the crudeness of reality would make the world unbearable.” |
| our artistic creations, as Keith Haring once said, are a “quest for immortality.” |
| through the creative use of language we have experienced perspectives familiar and foreign, allowing us to broaden and refine our responses to encounters in the real world. By telling stories and hearing stories and embellishing stories and repeating stories, we played with possibility without suffering consequences. We followed trail upon trail that began with “What if?” and, through reason and fantasy, explored a wealth of possible outcomes. Our minds freely roamed the landscape of imagined experience, giving us a newfound nimbleness of thought that, plausibly, proved valuable for survival. |
| To influence the biological makeup of subsequent generations, survival is necessary but not sufficient. |
| “Sexual selection has been an extra gear for art, not the engine itself.” |
| We like how the arts can make us feel, but neither creating nor experiencing them makes us more fit or appealing. From the standpoint of survival, the arts are junk food. |
| “Art has been about stirring up and shaping the emotions in a way that binds and inculcates those under its sway as participants in a culture.” |
| A mind that assiduously sticks to what’s true is a mind that explores a wholly limited realm of possibility. But a mind that becomes accustomed to freely crossing the boundary between what’s real and what’s imagined—all the while keeping clear tabs on which is which—is a mind that becomes adept at breaking the bonds of conventional thinking. Such a mind is primed for innovation and ingenuity. |
| Einstein’s essential step toward relativity was not driven by new experiments or data. He was working with facts—to do with electricity, magnetism, and light—that were already well-known. Instead, Einstein’s bold move was to break free from the widely held assumption that space and time were constant, which required the speed of light to vary, and in its place envision that the speed of light is constant, which required space and time to vary. |
| the discovery relied on imagining a simple but fundamental rearrangement of the Lego pieces of reality, an inversion of symbolic patterns so familiar that most minds glided over the possibility entirely. It is a variety of creative maneuver that resonates with the highest levels of artistic composition. In the assessment of illustrious pianist Glenn Gould, the genius of Bach is demonstrated by his ability to devise melodic lines “which when transposed, inverted, made retrograde, or transformed rhythmically will yet exhibit…some entirely new but completely harmonious profile.”17 Einstein’s genius rested on a similar, and similarly uncanny, ability to reconfigure the building blocks of understanding, looking anew upon concepts that had been scrutinized for decades, if not centuries, and combining them according to a novel blueprint. That Einstein described his intellectual process as thinking with music and that he frequently relied on visual explorations free of equations and words perhaps isn’t all that surprising. Einstein’s art was to hear rhythms and see patterns that revealed deep unity in the workings of reality. |
| An examined life need not be an articulated life. |
| The lyricist Yip Harburg, |
| “Words make you think a thought. Music makes you feel a feeling. But a song makes you feel a thought.” |
| thinking is intellectual, feeling is emotional, but “to feel a thought is an artistic process.” |
| We are all bags of particles—both mind and body—and the physical facts about the particles can fully address how they interact and behave. But such facts, the particulate narrative, shed only monochrome light on the richly colored stories of how we humans navigate the complex worlds of thought, perception, and emotion. |
| “The only true voyage of discovery,” he once said, “would be not to visit strange lands but to possess other eyes, to see the universe through the eyes of another, of a hundred others.” |
| the pursuit of symbolic immortality is a primary driver of human behavior. |
| coping with mortality through creating art is a pathway to sanity. |
| Tennessee Williams, through the fictional patriarch Big Daddy Pollitt, noted that “ignorance—of mortality—is a comfort. A man don’t have that comfort, he’s the only living thing that conceives of death,” and in consequence, “if he’s got money he buys and buys and buys and I think the reason he buys everything he can buy is that in the back of his mind he has the crazy hope that one of his purchases will be life everlasting!” |
| Sylvia Plath, “O God, I am not like you / In your vacuous black / Stars stuck all over, bright stupid confetti / Eternity bores me, I never wanted it,” |
| When I asked why he chose music, my dad answered, “To keep away the loneliness.” |
| permanence is something we humans covet but never attain. The closest we come—a sense of time having dropped away, whether the result of a euphoric or tragic encounter, a meditative or chemical inducement, an exalted religious or artistic experience—can provide life’s most formative experiences. |
| Wolfgang Pauli, a famously caustic quantum pioneer (“I don’t mind your thinking slowly; I mind your publishing faster than you think”8), |
| Being clumps of matter, the galaxies exert attractive gravity, mutually pulling inward and thus slowing the cosmic exodus. Being spread uniformly, the dark energy exerts repulsive gravity, pushing outward and thus quickening the cosmic exodus. To explain the accelerated expansion the astronomers observe, dark energy’s push simply needs to exceed the galaxies’ collective pull. And not by much. Compared with the blistering outward swelling of space during the big bang, today’s expansion is gentle, and so a diminutive dark energy is all that is needed. Indeed, in a typical cubic meter of space, the amount of dark energy required to power the observed galactic speedup would keep a hundred-watt bulb running for about five trillionths of a second—almost comically tiny.13 But space contains a lot of cubic meters. The repulsive push contributed by each and every one combines to yield an outward force able to drive the accelerated expansion measured by the astronomers. |
| But simplicity, while favored conceptually, has no fundamental claim on truth. |
| we are hurtling toward a violent reckoning that physicists call the big rip. |
| it is possible that repulsive gravity will shred the very fabric of spacetime itself. Reality started with a bang, and sometime before we reach the eleventh floor, one hundred billion years since the big bang, it may end with a rip. |
| Much as specks of white paint stuck to a black swatch of spandex move apart when the spandex stretches, galaxies are, for the most part, stuck to the fabric of space and move apart because space swells. |
| The light each galaxy emits does travel through space. And much as a kayaker will be stymied if she’s paddling upstream at a speed that’s less than that of the stream itself, the light emitted by a galaxy that is sprinting away at superluminal speed will fight a losing battle as it tries to reach us. Traversing space at light speed, the light cannot overcome the faster-than-light-speed increase in the distance to earth. As a result, when future astronomers look past nearby stars and focus their telescopes on the deepest parts of the night sky, all they will see is velvety black darkness. The distant galaxies will have slipped beyond the bounds of what astronomers call our cosmic horizon. It will be as if the distant galaxies have dropped off a cliff at the edge of space. |
| by the eleventh floor, the Local Group, dominated by the Milky Way and Andromeda galaxies, will likely have merged, an anticipated future union astronomers have christened Milkomeda (I would have lobbied for Andromilky). |
| assuming that the data we’ve gathered, establishing that the universe is expanding, were to somehow be preserved and delivered to the hands of astronomers a trillion years from now, would they believe it? Using their state-of-the-art equipment, a trillion years in the making, they will see a universe that on the largest of distances is black, about as eternal and unchanging as it gets. You can well imagine that they’d wave aside quaint results handed down from an ancient and primitive era—ours—and instead accept the erroneous conclusion that, overall, the universe is static. |
| Even in a world subject to a relentless rise in entropy, we have grown accustomed to measurements always improving, data sets always growing, understanding always refining. The accelerated expansion of space can subvert these expectations. Accelerated expansion can cause essential information to race away so quickly that it becomes inaccessible. Deep truths may silently beckon to our descendants from just beyond the horizon. |
| Stars will be fading away. The more massive a star, the more its heft crushes its core and the hotter its central temperature. In turn, the hotter temperature spurs a more rapid rate of nuclear fusion and thus a more rapid burn-down of the star’s nuclear reserves. While the sun will burn brightly for about ten billion years, stars that are much heavier will have exhausted their nuclear fuel well before that time. By contrast, flyweight stars, down to roughly a tenth of the sun’s mass, burn more gently and so live far longer. Astronomers use the catchall name red dwarf to label an assortment of such low-mass stars, |
| Like a game of tag played by widely dispersed slugs, only rarely will stars collide or even have a near miss. |
| At the center of most galaxies is an enormous black hole, millions or even billions of times the mass of the sun. |
| the only stars remaining in galaxies will be burnt-out embers that, having avoided ejection, will slowly orbit the galaxy’s central black hole. And much as planets slowly spiral inward as their orbital energy is funneled into gravitational waves, so too for stars around a galactic black hole. |
| central black holes will sweep most galaxies clean of stars by the thirtieth floor, 1030 years since the big bang, if not sooner. By this era, a tour through the cosmos will not exactly be a riotous affair. Punctuated here and there by cold planets, burnt-out stars, and monstrous black holes, space will be dark and desolate. |
| life of any sort will need to harness suitable energy to power its life-sustaining functions—metabolic, reproductive, whatever. As stars burn down, are ejected into deep space, or spiral into omnivorous black holes, that task will become increasingly difficult. There are creative ideas, like harnessing particles of dark matter that we believe waft across space, which can produce energy as pairs collide and transform into photons.26 But here’s the thing: even if some form of life is able to tap a novel source of useful energy, as we continue our climb another challenge, more significant than all others, will likely emerge. Matter itself may disintegrate. |
| as we have continued developing our mathematical understanding of the cosmos, proton decay has reared its head at almost every turn. |
| On lower floors, life’s dominant challenge is to harness suitable high-quality, low-entropy energy to power the processes of animate matter. |
| With the dissolution of atoms and molecules, the very scaffolding of life and most structure in the cosmos will have crumbled. So if life has made it this far, will it now hit the final wall? Perhaps. But, perhaps too, over the timescales we’re considering—more than a billion billion billion times the current age of the universe—life will have evolved into a form that has long discarded any need for the biological architecture it currently requires. |
| Underlying such speculation is the assumption that life and mind are not dependent on any particular physical substrate, |
| can thought persist indefinitely? |
| information processing, the function of thought, can also be described as entropy processing. |
| to power its thinking, the Thinker must extract energy from its surroundings. |
| as stars burn out, solar systems unravel, galaxies disperse, matter disintegrates, and the universe expands and cools, the Thinker will face the increasingly difficult task of gathering the concentrated, high-quality, low-entropy energy it needs to continue cogitating. |
| as time goes by, the Thinker should continually lower its temperature, slow down its thinking, and decrease the rate at which it consumes the universe’s diminishing supply of quality energy. |
| “Although thinking at ever lower temperatures is essential for prolonging thought as well as for needing only a finite supply of energy, there will come a point when your entropy will build up more quickly than you can expel it. And from there on, if you try to think further, you will burn up in your own thoughts.” |
| The Thinker needs periodically to give thinking a rest—turn off its mind and go to sleep—pausing entropy production while continuing to clear out all of its waste heat. |
| The Thinker can think without the need to purge heat so long as the Thinker never erases a memory. But assuming the Thinker is of finite extent, it will have a finite memory capacity that will sooner or later fill to its limit. Once it does, all the Thinker can do internally is reshuffle the fixed information it has in memory, endlessly ruminating on old thoughts—not a version of immortality many of us would choose. If the Thinker wants the creative capacity to think new thoughts, to lay down new memories, to explore new intellectual terrain, then it will have to allow for erasures, thereby producing heat and taking us right back to the situation discussed in the previous section and the hibernation strategy recommended there. |
| As the Thinker continues to decrease its temperature (which, remember, is what allows it to continue thinking indefinitely on a finite energy budget), sooner or later it will reach the tiny value of 10−30 kelvin. At that point, game over. The universe won’t accept its waste. One more thought (or, more precisely, one more erasure) and the Thinker fries. |
| of course, if the universe is eternal, any duration, however long, registers as infinitesimal. Narrated from the perspective of these longer scales, the cosmological accounting would go like this: a moment after the big bang, life arose, briefly contemplated its existence within an indifferent cosmos, and dissolved away. |
| The black hole eats and its spherical waist widens. |
| The surface area of the black hole’s event horizon thus seems to keep track of the entropy the black hole has ingested. |
| the total entropy of a black hole is given by the total area of its event horizon |
| black holes are black only if you ignore quantum physics. |
| When a particle-antiparticle pair pops into this environment, sometimes the two particles will annihilate quickly, just as they would anywhere else. But, and this is the point, Hawking realized that on occasion they will not annihilate. Sometimes one member of the pair will get sucked into the black hole. The surviving particle, now bereft of a partner with which to annihilate (and tasked with conserving total momentum), turns tail and rushes outward. With this happening repeatedly in every tiny region of space all along the surface of the black hole’s spherical horizon, the black hole will appear to radiate particles in all directions, what we now call Hawking radiation. What’s more, according to the calculations, each such particle that falls into the black hole has negative energy (perhaps not surprising, given that the partner particle escaping the hole has positive energy, and total energy must be conserved). As the black hole consumes these negative mass particles, it’s as if it is eating negative calories, resulting in its mass going down, not up. Viewed from the outside, the black hole thus appears to steadily shrink as it radiates particles. Were it not that the source of the radiation is exotic—a black hole immersed in the quantum bath of fluctuating particles inherent in empty space—the process would appear thoroughly pedestrian, like a glowing chunk of charcoal radiating photons as it slowly wastes away. |
| Much as mature Great Danes are large and mild while shih tzu puppies are small and manic, large black holes are calm and cool while small black holes are frenzied and hot. |
| A black hole whose mass is larger than the moon’s has a temperature that is lower than that of the 2.7 degree microwave background radiation currently suffusing the cosmos. Handy for erudite cocktail party chatter, this is a numerical factoid of cosmological significance. Because heat spontaneously flows from higher to lower temperatures, heat will flow from the frigid microwave-filled environment surrounding such a black hole to the yet more frigid black hole itself. Although the black hole emits Hawking radiation, on balance it will take in more energy than it releases, slowly increasing its heft. Because even the smallest black holes so far discovered by astronomical observations are much more massive than the moon, they are all in the process of plumping up. However, as the universe continues to expand, the microwave background radiation will continue to dilute and its temperature will continue to cool. In the far future when the background temperature of space drops below that of any given black hole, the energy seesaw will pivot, the black hole will emit more than it receives, and it will start shrinking as a result. In the fullness of time, black holes will waste away too. |
| What happens when the black hole is almost gone, when its mass nears zero and its temperature soars toward infinity? Does it explode? Does it fizzle? Something else? We don’t know. |
| the recipe for building a black hole is dead simple: gather any amount of mass and form it into a ball of a sufficiently small size. |
| To turn a grapefruit into a black hole, you’d need to squeeze it down to about 10−25 centimeters across; to turn the earth into a black hole you’d need to squeeze it down to about two centimeters across; and for the sun, you’d need to squeeze it to about six kilometers across. |
| As the amount of matter used to create a black hole increases, the required density to which that matter must be crushed decreases. |
| To build a black hole like the one in the center of the Milky Way, whose mass is about four million times that of the sun, you need matter whose density is about one hundred times that of lead, so you’ve still got some serious crushing ahead of you. To build one with mass one hundred million times that of the sun, the necessary density drops all the way to that of water. And to build one that’s four billion times the mass of the sun, the density you need is on par with that of the air you’re now breathing. Gather together four billion times the mass of the sun in air, and unlike the case with a grapefruit, or the earth, or the sun, to create a black hole you would not need to squeeze the air at all. Gravity acting on the air would form a black hole on its own. |
| the more massive the black hole, the lower its temperature and the more subdued its glow. |
| Higgs envisioned that space is filled with an invisible substance, now called the Higgs field, and that particles pushed through the field experience a drag force somewhat like that experienced by a Wiffle ball flying through air. Even though a Wiffle ball weighs next to nothing, if you hold it outside the window of a car revving up to ever-higher speeds, your hand and arm will get quite a workout: the Wiffle ball feels massive because it is plowing through the resistance exerted by the air. Similarly, Higgs proposed, when you push on a particle it feels massive because it is plowing through the resistance exerted by the Higgs field. The more hefty a particle the more it resists your push, which according to Higgs means the particle experiences a stronger resistance from his space-permeating field. |
| Higgs was suggesting that if space were truly empty in the conventional and intuitive sense, particles would have no mass at all. |
| the masses of the fundamental particles would change if the value of the Higgs field they encountered was different. For all but the most minuscule of shifts, such a change would almost certainly destroy reality as we know it. |
| A wealth of laboratory experiments and astronomical observations have established that for most if not all of the past 13.8 billion years, the masses of the fundamental particles have been constant and thus the value of the Higgs field has been stable. Yet, even if there is only a minute probability that in the future the Higgs field can jump to a different value, that probability will be amplified into a near certainty by the enormous durations we are now considering. |
| quantum tunneling, |
| Place a small marble in an empty champagne flute, and if no one disturbs it, you would expect the marble to remain there. After all, the marble is hemmed in by barriers on all sides and doesn’t have enough energy to climb the walls of glass and escape through the top. Nor does it have enough energy to penetrate directly through the glass. Similarly, if you place an electron in a trap shaped like a tiny champagne flute, hemming in its position with barriers on all sides, you would expect that it too would remain in place. Indeed, most of the time the electron does. But sometimes it doesn’t. Sometimes the electron disappears from the trap and rematerializes outside it. Surprising as such a Houdini-like move may be for us, in quantum mechanics it is business as usual. Using Schrödinger’s equation, we can calculate the probability that an electron will be found in this or that location, such as on the inside or on the outside of the fluted trap. The math shows that the more formidable the trap—the taller and thicker the sides—the smaller the likelihood that the electron will escape. But, and this is key, for the probability to be zero, the trap would need to be infinitely wide or infinitely high, and in the real world that just doesn’t happen. And a nonzero probability, however small, means that by waiting long enough, sooner or later the electron will make it to the other side. Observations confirm that it does. Such a transit through a barrier is what we mean by “quantum tunneling.” I’ve described quantum tunneling in terms of a particle penetrating a barrier, changing its location from here to there, but it can also involve a field penetrating a barrier, changing its value from this to that. Such a process, involving the Higgs field, may determine the long-term fate of the universe. In the units physicists conventionally use, the current value of the Higgs field is 246.16 Why 246? No one knows. But the drag force mustered by a Higgs field with this value (together with the precise manner in which each particle interacts with it) successfully explains the masses of the fundamental particles. But why has the Higgs value been stable for billions of years? The answer, we believe, is that the Higgs value, like the marble in the flute or the electron in the trap, is hemmed in on all sides by formidable barriers: if the Higgs field was to try migrating from 246 to a larger or smaller number, the barrier would forcefully drive it back to its original value, much like the marble would be driven back to the bottom of the flute should someone momentarily shake the glass. And were it not for quantum considerations, the Higgs value would permanently remain at 246. But as Sidney Coleman discovered in the mid-1970s, quantum tunneling changes the story. |
| Just as quantum mechanics allows an electron occasionally to tunnel out of a trap, so too does it allow for the value of the Higgs field to tunnel through a barrier. Were this to occur, the Higgs field would not change its value across all of space simultaneously. Instead, in some tiny region singled out by the random nature of quantum events, the Higgs would make its move, tunneling through the barrier to a different value. Then, much as a marble that tunnels through a champagne flute will drop to a lower height, the Higgs field’s value would drop to a lower energy. The lure of lower energy would then coax the Higgs field at nearby locations to make the transition too, a domino-like effect that would yield an ever-growing sphere within which the Higgs value would have changed. Inside this sphere, the new Higgs value would cause particle masses to change, so the familiar features of physics, chemistry, and biology would no longer hold. Outside the sphere, where the Higgs value had yet to shift, particles would retain their usual properties, and so all would seem normal. Coleman’s analysis revealed that the boundary of the sphere, marking the transition from old Higgs value to new, would spread outward at very nearly the speed of light.18 Which means that for those of us on the outside it would be virtually impossible to see the wall of doom approaching. By the time we saw it, it would be upon us. One moment it would be life as usual. The next moment we would cease to be. |
| Current data suggest that the Higgs is likely to tunnel to a different value somewhere between 10102 and 10359 years from now— |
| While the timescale for such change, such disintegration, gives little cause for anxiety, note that there is a chance that the tunneling event could happen today. Or tomorrow. That is the burden of living in a quantum universe in which future events are governed by probability. |
| everything you know reflects thoughts, memories, and sensations that currently reside in your brain. |
| all of that is in your head right now because of the particular arrangement of the particles that are in your head right now. Which means that if a random spray of particles flitting through the void of a structureless, high-entropy universe should, by chance, spontaneously dip to a lower-entropy configuration that just happens to match that of the particles currently constituting your brain, that collection of particles would have the same memories, thoughts, and sensations that you do. |
| Boltzmann brains. |
| a solitary Boltzmann brain is the minimal and hence most likely random formation of particles that can briefly cerebrate and thus wonder how in the world it came to |
| there’s a reasonable chance that a Boltzmann brain will form within 101068 years. |
| Which raises an interesting, somewhat personal concern. Where did your brain come from? |
| Some conclude that Boltzmann brains are much ado about nothing. Sure, this perspective acknowledges, Boltzmann brains can form. But ease your mind. You are definitely not one of them. Here’s how to prove it: Look out on the world and take in all you see. If you are a Boltzmann brain, the odds are overwhelming that a moment later you won’t exist. A brain that can last longer is a brain that’s part of a larger and more ordered support system and thus requires a yet rarer fluctuation to even lower entropy, making its formation that much more unlikely. So if your second glance at the world seems much like your first, your confidence that you are not a Boltzmann brain increases. |
| Notice, though, that the argument assumes each of the moments in such a sequence is, in the conventional sense, real. If right now you have a memory of looking out at the world a dozen times during the past minute, repeatedly assuring yourself that you are not a Boltzmann brain, that memory reflects the state of your brain right now and is thus compatible with your brain having turned on just now imprinted with those very memories. By taking the scenario fully to heart, you realize that the empirical observations you used to argue that you are not a Boltzmann brain may themselves be part of the fiction. I may have memories of saying to myself “I think, therefore I am,” but viewed from any given moment, an accurate accounting requires that I say instead, “I think I thought, therefore I think I was.” In reality, the memory of such thoughts does not ensure that the thoughts ever happened. |
| quantum leap in which the value of the dark energy would suddenly change. Currently, the accelerated expansion of the cosmos is driven by a positive dark energy suffusing every region of space. But just as positive dark energy yields an outward-thrusting repulsive gravity, negative dark energy yields an inward pulling attractive gravity. Consequently, a quantum tunneling event in which the dark energy leaped to a negative value would mark a transition from the universe’s swelling outward to its collapsing inward. Such an about-face would result in everything—matter, energy, space, time—being squeezed to extraordinary density and temperature, a kind of reverse big bang that physicists call the big crunch. |
| physicist Paul Steinhardt and collaborators Neil Turok and Anna Ijjas imagine parlaying such a potential universe-ending crunch into a more upbeat universe-producing bounce.31 According to this theory, regions of space like ours go through phases of expansion followed by contraction, with the cycles repeating indefinitely. The big bang becomes the big bounce—a rebound from the previous period of contraction. The idea itself is not entirely new. Shortly after Einstein completed the general theory of relativity, a cyclic version of cosmology was proposed by Alexander Friedmann and subsequently developed by Richard Tolman.32 Tolman’s aim, in particular, was to dodge the question of how the universe began. If the cycles extend infinitely far to the past, there was no beginning. The universe always existed. Tolman found, however, that the second law of thermodynamics thwarts this vision. The continual buildup of entropy from one cycle to the next implies that the universe we currently inhabit could be preceded only by a finite number of cycles, thus requiring a beginning after all. In their new version of the cyclic approach, Steinhardt and Ijjas argue that they can surmount this problem. They have established that during each cycle a given region of space stretches far more than it contracts, ensuring the entropy it contains is thoroughly diluted. Cycle upon cycle, the total entropy across the entirety of space increases, as per the second law of thermodynamics. But in any finite region, such as the one giving rise to our observable realm, the entropic buildup that stymied Tolman is no longer a concern. Expansion dilutes away all matter and radiation, while the subsequent contraction harnesses the power of gravity to replenish just enough high-quality energy to start the cycle anew. The duration of each cycle is determined by the value of the dark energy which, based on today’s measurements, sets the duration on the order of hundreds of billions of years. As this is far less than the typical time required for Boltzmann brains to form, cyclic cosmology provides another potential solution for preserving rationality. While there would be ample time during a given cycle to produce brains in the ordinary manner, the cycle would conclude well before there would be time to produce brains in the Boltzmannian manner. With reasonable confidence we could all then declare that our memories were laid down by events that really happened. |
| cyclic cosmology has emerged as a main competitor to the inflationary theory. |
| The burst of inflationary expansion at the big bang would likely have so vigorously disturbed the fabric of space that the gravitational waves produced might still be detectable. The more gentle expansion of the cyclic model results in gravitational waves too mild to be observed. In the not-too-distant future, observations may thus have the capacity to tip the balance between the two cosmological approaches. |
| the other worlds—the other regions—are not a matter of interpretation. If space is infinite, the other regions are out there. |
| even though we can contemplate eternity, and even though we can reach for eternity, apparently we cannot touch eternity. |
| We all are collections of particles, beneficiaries of innumerable evolutionary battles that have unshackled our behaviors and given us the capacity to delay entropic decay. |
| Longevity varies widely. Yet the fact that we will all die, and the fact that the human species will die, and the fact that life and mind, at least in this universe, are virtually certain to die are expected, run-of-the mill, long-term outcomes of physical law. The only novelty is that we notice. |
| Living in an endless world absent death, writes the protagonist in Jorge Luis Borges’s “The Immortal,” “no one is anyone, one single immortal man is all men…I am god, I am hero, I am philosopher, I am demon and I am world, which is a tedious way of saying that I do not exist.” |
| Williams argues that with endless time each of us would satiate every objective that drives us onward, leaving us listless in the face of a mind-numbingly monotonous eternity. |
| Aaron Smuts, inspired in part by Borges’s story, contend that immortality would drain the decisions that shape a human life—how to spend one’s time and with whom—of the consequences essential to their significance. Make the wrong choice? No problem. You’ve got eternity to make it right. The satisfaction of achievement would also fall victim to immortality. Those with limited abilities would reach their potential and then experience eternal frustration; those with abilities capable of deepening without limit would be guaranteed to improve continually, deflating the sense of accomplishment that comes from outperforming expectations. |
| thinking about life that never ends clarifies the relevance of life that does. |
| “Which news would affect you more,” she asked, “being told you have a year to live or that in a year earth will be destroyed?” At the time I said something facile about it depending on whether either outcome would entail physical pain, but later, as I mulled the question over, I found it unexpectedly illuminating. A terminal prognosis affects people in different ways—focusing attention, providing perspective, stoking regret, fueling panic, delivering composure, inspiring epiphany. I anticipated that my own reaction would lie somewhere among these. But the prospect that earth and all of humankind would be wiped out triggered a different kind of reaction. The news would make everything seem rather pointless. Whereas my own impending end would heighten intensity, endowing with significance moments that might have otherwise receded into the daily humdrum, contemplating the end of the entire species seemed to do the opposite, yielding a sense of futility. |
| our equations and theorems and laws, even if they tap into fundamental truths, have no intrinsic value. They are, after all, a collection of lines and squiggles drawn on blackboards and printed in journals and textbooks. Their value derives from those who understand and appreciate them. Their worth derives from the minds they inhabit. |
| While immortality of the individual may sap significance, immortality of the species seems necessary to secure it. |
| There is no need to chant, and a lotus position is optional, but if you find a quiet place and let your mind slowly and freely float along the cosmic timeline, moving through and then past our epoch, past the era of distant receding galaxies, past the era of stately solar systems, past the era of graceful swirling galaxies, past the era of burnt-out stars and wandering planets, past the era of glowing and disintegrating black holes, and onward to a cold, dark, nearly empty but potentially limitless expanse—in which the evidence that we once existed amounts to an isolated particle located here instead of there or another isolated particle moving this way instead of that—and if you are at all like me and let that reality fully settle in, the fact that we’ve traveled fantastically far into the future hardly diminishes the shuddering yet awestruck feeling that wells up inside. Indeed, in one essential way, the enormous sweep of time only adds weight to the nearly unbearable lightness of being; compared to the timescale we’ve reached, the epoch of life and mind is infinitesimal. By today’s scales, its entire span, from the earliest microbes to the final thought, would be less than the duration required for light to traverse an atomic nucleus. The entire duration of human activity—whether we annihilate ourselves in the next few centuries, are wiped out by a natural disaster in the next few millennia, or somehow find a way to carry on until the death of the sun, the end of the Milky Way, or even the demise of complex matter—would be more fleeting still. We are ephemeral. We are evanescent. Yet our moment is rare and extraordinary, a recognition that allows us to make life’s impermanence and the scarcity of self-reflective awareness the basis for value and a foundation for gratitude. While we may long for a perdurable legacy, the clarity we gain from exploring the cosmic timeline reveals that this is out of reach. But that very same clarity underscores how utterly wondrous it is that a small collection of the universe’s particles can rise up, examine themselves and the reality they inhabit, determine just how transitory they are, and with a flitting burst of activity create beauty, establish connection, and illuminate mystery. |
| Most of us deal quietly with the need to lift ourselves beyond the everyday. Most of us allow civilization to shield us from the realization that we are part of a world that, when we’re gone, will hum along, barely missing a beat. We focus our energy on what we can control. We build community. We participate. We care. We laugh. We cherish. We comfort. We grieve. We love. We celebrate. We consecrate. We regret. We thrill to achievement, sometimes our own, sometimes of those we respect or idolize. Through it all, we grow accustomed to looking out to the world to find something to excite or soothe, to hold our attention or whisk us to someplace new. Yet the scientific journey we’ve taken suggests strongly that the universe does not exist to provide an arena for life and mind to flourish. Life and mind are simply a couple of things that happen to happen. Until they don’t. I used to imagine that by studying the universe, by peeling it apart figuratively and literally, we would answer enough of the how questions to catch a glimpse of the answers to the whys. But the more we learn, the more that stance seems to face in the wrong direction. Looking for the universe to hug us, its transient conscious squatters, is understandable, but that’s just not what the universe does. |
| Even so, to see our moment in context is to realize that our existence is astonishing. Rerun the big bang but slightly shift this particle’s position or that field’s value, and for virtually any fiddling the new cosmic unfolding will not include you or me or the human species or planet earth or anything else we value deeply. If a super intelligence were to look at the new universe as a whole, much as we look at a collection of tossed pennies as a whole or the air we’re now breathing as a whole, it would conclude that the new universe pretty much looks the same as the original. For us, it would be vastly different. There wouldn’t be an “us” to notice. By shifting our attention away from fine details, entropy has provided an essential organizing principle for grasping the large-scale trends in how things transform. But whereas we generally don’t care if this penny is heads or that tails, or if one particular oxygen molecule happens to be here or there, there are certain fine details that we do care about. Profoundly so. We exist because our specific particulate arrangements won the battle against an astounding assortment of other arrangements all vying to be realized. By the grace of random chance, funneled through nature’s laws, we are here. It is a realization that echoes across each stage of human and cosmic development. Think of what Richard Dawkins described as the nearly infinite collection of potential people, would-be carriers of the nearly infinite collection of base pair sequences in DNA, none of whom will ever be born. Or think of the moments constituting cosmic history, from the big bang through your birth and on to today, filled with quantum processes whose relentless probabilistic progression at each of a nearly limitless collection of junctures could have yielded that outcome instead of this, resulting in an equally sensible universe but one that would not include you or me.10 And yet, with this astronomical number of possibilities, against astonishing odds, your sequence of base pairs and mine, your molecular combination and mine now exist. How spectacularly unlikely. How thrillingly magnificent. |
| And the gift is greater still: our particular molecular combinations, our specific chemical and biological and neurological arrangements, give us the enviable powers that have occupied much of our attention in earlier chapters. Whereas most life, miraculous in its own right, is tethered to the immediate, we can step outside of time. We can think about the past, we can imagine the future. We can take in the universe, we can process it, we can explore it with mind and body, with reason and emotion. From our lonely corner of the cosmos we have used creativity and imagination to shape words and images and structures and sounds to express our longings and frustrations, our confusions and revelations, our failures and triumphs. We have used ingenuity and perseverance to touch the very limits of outer and inner space, determining fundamental laws that govern how stars shine and light travels, how time elapses and space expands—laws that allow us to peer back to the briefest moment after the universe began and then shift our gaze and contemplate its end. |
| As we hurtle toward a cold and barren cosmos, we must accept that there is no grand design. Particles are not endowed with purpose. There is no final answer hovering in the depths of space awaiting discovery. Instead, certain special collections of particles can think and feel and reflect, and within these subjective worlds they can create purpose. And so, in our quest to fathom the human condition, the only direction to look is inward. That is the noble direction to look. It is a direction that forgoes ready-made answers and turns to the highly personal journey of constructing our own meaning. It is a direction that leads to the very heart of creative expression and the source of our most resonant narratives. Science is a powerful, exquisite tool for grasping an external reality. But within that rubric, within that understanding, everything else is the human species contemplating itself, grasping what it needs to carry on, and telling a story that reverberates into the darkness, a story carved of sound and etched into silence, a story that, at its best, stirs the soul. |