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CALEB SCHARF CALEB

ILLUSTRATIONS BY RON MILLER RON BY ILLUSTRATIONS

UNIVERSE

THE ZOOMABLE AN EPIC TOUR THROUGH COSMIC SCALE, NOTHING NEARLY TO EVERYTHING ALMOST FROM

SCIENTIFIC AMERICAN / FARRAR, STRAUS AND GIROUX AND STRAUS FARRAR, / AMERICAN SCIENTIFIC NEW YORK vii 5. Call We A World 93 10. . Fields Full of It’s 175 From Nearly to Nothing Almost Everything 191 Notes 195 205 Acknowledgments CONTENTS Preface ix Everything Almost 3 1. 2. and Darkness Light 23 3. and the Fantastic the Fast, The Slow, 49 Planets, 4. Planets, 69 6. Being in the Cosmos Conscious 115 7. One to Many From 129 Undergrowth 8. The 145 9. The Matter Emptiness of 159 ix A long time ago the in your body were spread across trillions of kilometers of other- of trillions kilometers of across spread were body in your atoms the time ago A long sep- themselves stars, several a star—perhaps deep inside came from these atoms of Many our part became a world, of eventually atoms these in being cosmos, the scattered Despite in living complexity of bubbles first microscopic part very the of were atoms these of Some

PREFACE ever? story epic hear the most to want Do you come eventually they would hint that no was there in the past years Billions of wise space. empty neurons billion eighty-six the or bones, your hair, skin, your your eyes, be configuredto as your of your brain. in a outward matter trillions they hurled many As these stars kilometers. exploded, by of arated other of billions of filled hundreds that a small galaxy part gas of scorching one flood of of out and a trillion time almost space of trillion maw kilome- a gaping throughout galaxies, arrayed ters across. billion half a and stuff, becoming a bil- new gravity, by drawn four Earth. together, and condensed For They cooled world, space. in floating just were they when than denser times trillion lion different guises. of lots into they shape-shifted years more been discarded have atoms same very the of otherwise And many oceans empty and continents. environment. through Earth’s traveled times as they’ve more or a billion up and picked They’ve been in the shell of a trilobite, perhaps thousands of trilobites. They’ve been in here in my hand are related to atoms over there, or on the next , or halfway across the cos- tentacles, roots, feet, wings, blood, and trillions, quadrillions of bacteria in between. Some have mos. The physics that operates inside us is the same that operates on other scales, and at other floated in the eyes of creatures that once looked out across the landscapes of a hundred million cosmic times. And the patterns and emergent phenomena that infuse our day-to-day experiences years ago. Yet others have nestled in the yolks of dinosaur eggs, or hung in the exhaled breath of share rules and properties in countless surprising ways throughout nature. a panting creature in the depths of an ice age. For other atoms this is their first time settling into From fingers and toes to modern mathematics and measurements, we can all grasp the a living organism, having drifted through eons in oceans and clouds, part of a trillion raindrops notion of powers of ten, sizes that shift by ten times or by a tenth. Chain these sliding scales or a billion snowflakes. Now, at this instant, they are all here, making you. together and we have a language for expressing the continuities and relationships of nature that Each is itself a composite that’s about a tenth of a of a meter across—sitting extend far outside our ordinary everyday experience. The powers of ten let us zoom from almost on the precipitous edge of a between our perceived reality and the quantum world. everything to nearly nothing. Electrons hazily occupy much of the atom’s empty space. Protons and neutrons cluster in a nu- This book is a synopsis, a cheat sheet if you will. It can’t recount every exact detail of the cleus, a hundred thousand times smaller than its atom, and are themselves composed of other contents and history of the universe. Instead, it treats the reality we know as a zoomable map stupendously small things, quarks and gluons. An electron may have no meaningful property with a preset path to follow. In video-game parlance, it’s a “rail shooter.” That rail follows the of size but can be thought of as ten million times smaller than the nucleus. And, at some point, physical scales of the cosmos—starting at the top and zooming on down. 13.8 billion years ago, all these components of all the atoms in the universe were squeezed into As we wrote and illustrated this journey, we agonized over how to build this rail. The cos- a far smaller, hugely energetic origin of space and time. Although that origin is now vastly ex- mos has three dimensions of space, and that tricky thing we call time. There are also trillions panded, we’re still inside its envelope, along with any being that may exist a billion light-years of interesting things to take a look at along the way. We’ve tried to balance the idea of a “grand from here. We’re not truly disconnected, even now. overview” with making sure we visited some very, very cool places en route. It’s quite a tall tale. Except this is not fiction. It’s our current best shot at recounting what Some of the waypoints are intellectually challenging—even in Chapter 1 you’ll have to con- has really happened in the past 13.8 billion years. tend with the strange concept of dark matter, an expanding universe, and even stranger things The purpose of The Zoomable Universe is to try to capture more of this story, to lead you like multiple and multiple versions of you. In Chapter 3 you’ll have to grapple with the through what we know (and what we don’t) about the entirety of nature. To do that we’ve turned majestic origins of the . By Chapter 6 you’ll be puzzling over the nature of conscious- to a tried-and-true approach: the simple premise of a tenfold zooming view to tour the universe, ness, and by Chapter 9 you’ll be tackling interpretations of quantum mechanics. Don’t worry— from the edge of the observable cosmos to the innermost knots of reality. the beautiful illustrations and infographics will help delight and inform you along the way. The conceit of a journey through the scales of nature is not new, and doing it scientifically We hope you enjoy finding your own connections among the gloriously varied pieces of data goes back at least as far as Micrographia, published by Robert Hooke in 1665. Works like the and knowledge that bring our vision of reality together. Remember, it’s your universe as much seminal 1957 book : The Universe in 40 Jumps, by , and the short films as anyone else’s. , by the National Film Board of Canada (1968), and Powers of Ten, by Charles and Ray Eames (1977), as well as many derivatives in subsequent years, demonstrate our universal love of cosmic journeys. It seemed that the time was ripe to make a contribution that not only brought the core material fully up to date but added focus on the intricate connectivity of the universe. Atoms

x

xi 3 meters 23 , 10 24 kilometers. At a walking pace, it would take you twenty trillion years to trillion to twenty years you take would it a walking pace, At kilometers. stars, and at least that number of planets. These stars and planets span a These a span stars planets. and planets of number that least and at stars, , 10 25 , 10 trillion billion 26 Packed deep inside, hidden among these billions of other worlds, is one particular one is planet worlds, other of these billions among hidden deep inside, Packed family, Your life. and experience in think your know all the things about Now you that Looking up, you notice that tiny specks of glowing dust are caught in the beams of light in beams the are of caught dust glowing of specks tiny that notice you Looking up, observ- the size the of represent to were room if whole the yet areThe microscopic, specks more to home is It the Milky This a single sunlit Way. speck. galaxy, our is follow Now , 10 27 structure that is a hundred thousand light-years across—athousand distance of more than nine hundred this object. cross with a thin crystallized orb of rocky coating mineral crust call a modest is Earth.we This world we star that a lonesome orbits It and atmosphere. painted with lightly water interior, a hot atop galaxy. in a 10-billion-year-old old 4.5 only years billion call the Sun—one star, 1 EVERYTHING ALMOST 10 aboutFrom billion 93 light-years million to light-years 10 From the diameter of the cosmic horizon to the size of the of galaxies and this reading this page, book, holding sitting in a sunlit room morning. You’re a summer It’s start to scale. through a journey about cosmic and These swirl in loft streaming bright pinpoints the air through a the windows. like currents, creatures. mysterious of swarm an be the size of entire galaxy stars. of would motes these dusty of each universe, able 200 than friends, dogs, cats, small furry rodents, horses, houses, couches, beds, pizza, apples, oranges, trees, flowers, insects, dirt, clouds, water, snow, rain, mud, sunshine, and starry nights. Then think about all the people who have ever lived (a total of around 110 billion individual, biologically modern humans) and all that they knew in their lives. All these people, billions upon billions of them, experiencing their surroundings for centuries, decades, years, months, days, hours, seconds, and the blink of an eye. That’s a lot of special moments for human beings. But for 3.5 billion years before we came along, living things swarmed the Earth, from bacteria and archaea to multi- cellular clumps, from trilobites to insects, dinosaurs to cephalopods. Trillions of living entities slithered around every conceivable niche, compelled into existence by varying potentials of chemical energy and chance. During every passing moment of those many years, all these organisms were being sculpted and battered by natural selection, and driven by the restless engines of molecular mechanics. The sum total of that, every single last bit of it, has existed on this one world—a vanishingly small mineral dot among billions of mineral dots, all held within a single dust mote that you watch floating through a sunny room that is the universe as we know it. This one-mote galaxy that we call the is a microscopic part of a wrin- kly, web-like ocean of matter. That ocean sustains more than 200 billion other galaxies. These galaxies range from small to enormous, some isolated, some in the midst of messy collisions. And these are merely the galaxies from which light has had time to reach us in about thirteen billion years—they’re within our “horizon,” the horizon of light travel time, like the walls of your room. This cosmic sprawl is also awash in electromagnetic radiation, energy that exhib- its both wave- and particle-like behavior, packaged as massless units called photons racing to and fro across space. Some of this radiation is the product of the early and hot history of the place that we generally call the universe. Other photons are from specific, individual sources: stars, supernovas, warmly glowing young planets, cosmic crashes and shock waves, possibly even plaintive missives hurled between technological civilizations—or not. 10 27 4 The horizon of the 23 stars, fits neatly within the neatly fits stars, billion meters 18 , 10 19 , 10 20 , 10 21 Of course, physics wouldn’t actually let you do this, at least not without making a lot of mess. mess. making of without a lot not least this, at do actually you let wouldn’t physics Of course, their out- treat if density you low are actually rather holes black massive very because That’s two add example, with regular happens For objects. what different from very That’s , 10 22

2 DARKNESS LIGHT AND 10 million aboutFrom 1.06 light-years light-years to 106 From about Milky 8 to 10 diameters Way to the size of a giant molecular cloud all scrunch up to stars the decides in alien the being are who an all-powerful you Imagine that getting in all between, rid of space the By another. one to next are they packed that so Milky Way times the radius fifty-four (or kilometers 8 billion about can a cube only these stars fit into you containing 200 That cube, side. some each on orbit) Earth’s of surplus of galaxy the plenty has words, In other system. in Neptune solar our diameter of orbital stars. its between room hole. making wind up a black you’d that is place in one mass with putting this much The problem Weirdly, be irresistible. would another pull all stars of one on those the gravitational Because Why? Milky the stars 200 the containing of of mass the more hole or billion black the size the of though, 146. about than of imaginary our bigger a factor stars be much by of cube would Way a black the size of but counterintuitive, their feel size. of This as the measure may extent ermost from mass surrounding hole’s the return, no radius the of point (the horizon hole—the event if words, In other mass. with hole’s the in lockstep within nothing can escape)—increases which horizon. event the of radius the double you mass, hole black the double you Black holes tear up matter and make light. identical balls of dough together, and the new radius of the combined ball is not twice what it was; it’s only about 26 percent larger. Why? Because for ordinary materials in a sphere the radius grows as the cube root of the mass—double the mass and you only increase the size by 26 percent. So if we treat the event horizon of a black hole as a measure of its physical size, the average density of matter within its bounds can end up being very low. A black hole with a mass three billion times that of the Sun would appear to be only as dense as the air we breathe! But this is a bit of cosmic misdirection, because our formal understanding of these objects tells us that all of a black hole’s mass is actually concentrated in a tiny, hidden, infinitely dense region at its center. Where such giant singularities exist, in the cores of most large galaxies, they also often look like the precise opposite of what we might expect. Yes, black holes are black, but you might not think so, because they can generate enormous amounts of light. Gas, dust, stars, planets, and who knows what else gets accelerated, shredded to bits, and heated if close enough to a black hole. In the process, energy spews outward, from above the event horizon and before the point of no return. With enough infalling matter, a spinning black hole can convert mass to energy with higher efficiency than even nuclear fusion. The most luminous cases across the universe shine with the power of hundreds of trillions of suns. Matter at its most compact, like in a black hole, can surprise even the most scientific among us. At the other extreme, all that empty space in a galaxy like the Milky Way is also surprising.

NECESSARY EMPTINESS

Most of us experience physical loneliness at some point in our lives: lost in an unfamiliar city, alone in a house, or abandoned in a deep, dark wood by scheming relatives. But intergalactic space and interstellar space—between the galaxies or between the stars in the typical parts of a galaxy—are actually the two loneliest places you might ever wind up in. In these “inter-zone” environments it can be a very, very long distance between safe havens, devoid of much of anything at all. If you were a hapless cosmic hitchhiker stranded between the stars of the Milky Way, your

Compact matter in black holes strongly warps space and time. body would represent a concentration of matter a hundred million trillion times greater than the

25 Inside the Local Group of galaxies

Birth of a Solar System

Stars and planets condense out of interstellar space—when material collects Proto-stellar jet High- Maker of Suns and Worlds speed outflow of hot, and compacts itself. It’s not an easy process. Gravity is pitted against thermal A proto-planetary disk is full of structure, flow, and activity. Its flared shape and accelerated matter energy and electromagnetic energy, and no two systems are identical. luminous central star create zones of temperature, evaporation, and chemistry that influence composition and the growth of planetary building blocks.

The Trigger DARK CLOUD GRAVITATIONAL COLLAPSE PROTO-PLANETARY DISK Part of a great nebula 12Time: 0 3100,000 to 3 million years becomes gravitationally Star will be Gas-and-dust structure unstable, possibly due born in center may exist for as long as several million years. to a passing supernova Hot ionized region shock wave, and falls in on itself to form Planets will a disk of matter. form in disk Warm molecular region 10,000 AU

Solar nebula contracts Outer disk (mass reservoir) 200,000 AU Cold midplane (planet-forming region)

100 AU Dust inner rim

Proto-star Pure Gas and dust gas disk 10 AU Warm temperatures concentrate in a allow only metal/rock growing spherical material to condense region at the center. in the inner system.

0.1 AU Terrestrial planets form Planetary from metal and rock. debris disk

Distance to star (AU*) 0.03 AU Cold temperatures 0 AU allow water ice, Giant, carbon dioxide ice, mostly gaseous and more to form Our Planetary GIANT PLANETS in outer system. 25 AU planets System 4 3 to 50 million years Most gas is either evaporated or condensed into planets. Orbiting dust and solid chunks keep merging, colliding, and perturbing Solar wind helps blow one another’s motions. YOUNG SOLAR SYSTEM remaining gas into Planetary systems are 5 interstellar space. 50 million years *AU = Astronomical Unit: the distance from Earth to the Sun (roughly 150 million kilometers). always a work in progress. 25 AAUU

These creatures show complicated, and apparently altruistic, social behavior. They are almost cer- tainly conscious. They are clearly intelligent, even if their smarts are not exactly like ours. At the same time, the elephant’s feathery symbiotic companion has a different lineage, one that had a last common ancestor with mammals 300 million years ago. The oxpecker, like all modern birds, is a descendant of a particular group of “great lizards”—the egg-laying dinosaurs. Between 65 million and 260 million years ago, the oxpecker’s raptor ancestors scooted about this very same continental landscape. It was a world where dinosaurs had the evolutionary upper hand, or at least hogged the evolutionary limelight. The oxpecker is certainly aware and intelligent by standards that we recognize. Many birds show signs of self-awareness, numeracy, and tool use. Yet a bird’s brain is physically much smaller than that of either the elephant or a human, and contains (only) about 100 million neurons. The parasitic louse in the bird’s beak has an ancestry that goes even further into the past. It is part of the group of wingless insects, at least 480 million years old, that evolved from a group of invertebrates. In that sense the louse is the most alien organism in the picture, and also the most successful, despite its present predicament. Is the louse conscious or intelligent? Some insects, like bees, show behaviors that can be construed as signs of cognition, of intelligence, and can have upwards of a million neural cells. The louse is no bee, but we don’t know what’s really going on in its nervous system. This one brief slice of life (a snapshot out of hundreds of millions of years of photo op- portunities) contains another critical story. A mammal hosts a bird and an insect. The Role reversal: Once, some dinosaurs succeeded as apex species, while mammals did not. bird consumes the parasitic insect, helping the 1 122 Brains of the World Brain capabilities Much is still a mystery Brains are built out of neurons—specialized cells that form about the inner electrically sensitive networks capable of receiving, processing, workings of brains. Homo erectus and transmitting electrochemical signals. Brains are the YES UNKNOWN 1.9 million to most complex biological structures we know of. 70,000 years ago Abstraction 1,000 cm3 Invention/creativity Social behavior Altruism Associative learning Fear/pain Language Consciousness

Sperm whale A sperm whale’s Western gorilla Physeter macrocephalus cerebral cortex is far Gorilla gorilla ~250 billion neurons more convoluted than

33 billion neurons B/B mass ratio: 1:5,260 a human’s. Brain/Body (B/B) mass ratio: 1:266 Modern human Autralopithecus Homo sapiens afarensis 86 billion neurons 3.9 million to B/B mass ratio: 1:50 3 million years ago 438 cm3

Modern human brains have 16 billion neurons in the cerebral cortex— a number exceeded Dog African gray parrot only by the long-finned Canis lupus familiaris pilot whale. Psittacus erithacus 1.5 billion neurons 160 million neurons B/B mass ratio: B/B mass ratio: 1:51 1:125

House mouse Mus musculus 71 million neurons B/B mass ratio: 1:40 Cats have more Cat neurons devoted to Felis catus visual processing than humans. 300 million neurons Fish brains can Atlantic herring B/B mass ratio: 1:110 African elephant 97.5% of elephant neurons Clupea harengus generate new Loxodonta africana are in the cerebellum. Only ~10 million neurons neurons after 257 billion neurons 5.6 billion neurons are in B/B mass ratio: 1:1,000 damage. B/B mass ratio: 1:1,000 the cerebral cortex.

Nile crocodile Common frog Crocodylus niloticus Rana temporaria B/B mass ratio: 1:2,000 16 million neurons but alters with age B/B mass ratio: 1:172

Honeybee Neurons in a bee brain Crocodile Apis mellifera are 10 times more brain mass 960,000 neurons densely packed than grows with B/B mass ratio: 1:100 in a human brain. body mass, but more slowly. 129 meters −5 , 10 −4 , 10 −3 , 10 Complexity is a central part of the currency of the universe. We’ve already encountered it it encountered already We’ve part a central currency the universe. is the of of Complexity If really is. it what for see this world us quite let senses don’t our of limitations The built-in painfully years thousand hundred past the of most spent we’ve this limitation, of Because −2

7 FROM MANY TO ONE 10 1 centimeterFrom micrometers to 10 From the size of a human fingertip to the size a of cloud-water droplet or an animal cell The planet we call home is fading into the background times than larger a billion scope the that’s a blur as just we and drama now is color zoomscale. All Earth’s of ever further down the cosmic magnitude within of are far from it orders this scale few and But the next waypoint. new our of are beautiful both that The and concepts strange. by here be challenged to going boring. You’re call complexity. we what is these first of The structure infuses very it too. daily our existence but galaxies the among and nebulas, out that. of with are proof live we that species of populations bodies our and multilayered the of granularity. biological complicated of in a world live we notice, seldom we Although can distinguish, only eyes our faces, our distance from a comfortable at objects tiny two hold we separation that Cut a human hair. the width of least at by separated the pair if they’re resolve, or objects. two or one looking at we’re tell whether us can’t of eagle-eyed the most in and half, even and skin. our under fingernails, drool, our noses, in beneath our blood, the universe of unaware pack- wrapped as tightly creatures, and other selves, physical our about thought mostly We’ve and self-contained. solid appears equally bugs lowly to beasts great Everything from ages. −2 10 A mouse and a whale contemplate each other across two orders of magnitude in scale. Prochlorococcus is possibly A bacterium, with a flagellum (tail) and a peppering of viral invaders the most plentiful species on Earth: a single milliliter of cells surface seawater may contain or more

Prokaryotes may have a global biomass of

of the Earth’s dry biomass

Antarctic krill form one of The length of all DNA the largest biomasses in your body’s cells of any individual animal species

The length of all human DNA on planet Earth is

* Some studies indicate this biomass may be a smaller 50 billion to 250 billion tons of carbon. extensions called pili. Inside the capsule is a mess of genetic material: a lengthy DNA strand, small loops of double-strand DNA known as plasmids, and a crowd of smaller compounds and molecular structures. This bacterium is a fully fledged biological entity. It’s a busy chemical factory, with com- pounds endlessly filtering in and out of its membrane covering. As alien as it appears, the bac- 10 −6 146 175 a single proton. inside orders of magnitude away. That’s a That’s magnitude away. of orders nineteen meters, or the approximate scale of a proton, we hop hop we a proton, scale of the approximate or meters, −16 meters −35 , and . 10 −18 , 10 −17 , 10 Our ultimate destination is an astonishing an is astonishing Our destination ultimate expected. might have than and inelegant we messy are far more The proton innards that of and gluons of particle a stew is the structure find that this of composite and we Look closer all virtual the set aside complement could that and anti-quarks an quarks you instant, for If, modify sense to makes ideas earlier our it an alien and in scales, these such environment, At −16 10 From a tenth of a femtometer to the Planck length From approximate proton radius to nearly nothing 10 at Starting descent. final our is This Farther into the composite proton 10 IT’S FULL . FIELDS OF hole. rabbit the of bottom very the to down us all take to way the going is that a trajectory onto the to universe observable the entire the scale of from earlier passage our to equivalent journey all And it’s parochial familiarity system. Earth- the of contains two simply as if it world outside the by experienced is object thisAlthough composite part story. the only is of that quark, down and one quarks up of withinvirtual existence allowances the of pairs—popping in and anti-quark and out quark the uncertainty and stuff balanced; Energy appears principle. and disap- and time are borrowed can angry. bookkeepers get universal the pears before be all remain. These that three are would quark down and one quarks up the two another, one senses—the asymmetry in the stew. world the outside what still is a waves of mathematics the (although and “waves” “particles” of a reality composed about −16 10