The Zoomable Universe Read online

  THE ZOOMABLE UNIVERSE

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

  CALEB SCHARF

  ILLUSTRATIONS BY RON MILLER

  AND 5W INFOGRAPHICS

  SCIENTIFIC AMERICAN / FARRAR, STRAUS AND GIROUX

  NEW YORK

  .Begin Reading

  Table of Contents

  About the Author

  Copyright Page

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  To all explorers. Of the past, present, and future.

  PREFACE

  Do you want to hear the most epic story ever?

  A long time ago the atoms in your body were spread across trillions of kilometers of otherwise empty space. Billions of years in the past there was no hint that they would eventually come to be configured as your eyes, your skin, your hair, your bones, or the eighty-six billion neurons of your brain.

  Many of these atoms came from deep inside a star—perhaps several stars, themselves separated by many trillions of kilometers. As these stars exploded, they hurled matter outward in a flood of scorching gas that filled a small part of one galaxy out of hundreds of billions of other galaxies, arrayed throughout a gaping maw of space and time almost a trillion trillion kilometers across.

  Despite being scattered in the cosmos, these atoms eventually became part of a world, our world, Earth. They cooled and condensed together, drawn by gravity, becoming new stuff, a billion trillion times denser than when they were just floating in space. For four and a half billion more years they shape-shifted into lots of different guises.

  Some of these atoms were part of the very first microscopic bubbles of living complexity in otherwise empty oceans and continents. And many of the very same atoms have been discarded and picked up a billion or more times as they’ve traveled through Earth’s environment.

  They’ve been in the shell of a trilobite, perhaps thousands of trilobites. They’ve been in tentacles, roots, feet, wings, blood, and trillions, quadrillions of bacteria in between. Some have floated in the eyes of creatures that once looked out across the landscapes of a hundred million years ago. Yet others have nestled in the yolks of dinosaur eggs, or hung in the exhaled breath of a panting creature in the depths of an ice age. For other atoms this is their first time settling into a living organism, having drifted through eons in oceans and clouds, part of a trillion raindrops or a billion snowflakes. Now, at this instant, they are all here, making you.

  Each atom is itself a composite that’s about a tenth of a billionth of a meter across—sitting on the precipitous edge of a universe between our perceived reality and the quantum world. Electrons hazily occupy much of the atom’s empty space. Protons and neutrons cluster in a nucleus, a hundred thousand times smaller than its atom, and are themselves composed of other stupendously small things, quarks and gluons. An electron may have no meaningful property of size but can be thought of as ten million times smaller than the nucleus. And, at some point, 13.8 billion years ago, all these components of all the atoms in the universe were squeezed into a far smaller, hugely energetic origin of space and time. Although that origin is now vastly expanded, we’re still inside its envelope, along with any being that may exist a billion light-years from here. We’re not truly disconnected, even now.

  It’s quite a tall tale. Except this is not fiction. It’s our current best shot at recounting what has really happened in the past 13.8 billion years.

  The purpose of The Zoomable Universe is to try to capture more of this story, to lead you through what we know (and what we don’t) about the entirety of nature. To do that we’ve turned to a tried-and-true approach: the simple premise of a tenfold zooming view to tour the universe, from the edge of the observable cosmos to the innermost knots of reality.

  The conceit of a journey through the scales of nature is not new, and doing it scientifically goes back at least as far as Micrographia, published by Robert Hooke in 1665. Works like the seminal 1957 book Cosmic View: The Universe in 40 Jumps, by Kees Boeke, and the short films Cosmic Zoom, 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 here in my hand are related to atoms over there, or on the next planet, or halfway across the cosmos. The physics that operates inside us is the same that operates on other scales, and at other cosmic times. And the patterns and emergent phenomena that infuse our day-to-day experiences share rules and properties in countless surprising ways throughout nature.

  From fingers and toes to modern mathematics and measurements, we can all grasp the notion of powers of ten, sizes that shift by ten times or by a tenth. Chain these sliding scales together and we have a language for expressing the continuities and relationships of nature that extend far outside our ordinary everyday experience. The powers of ten let us zoom from almost everything to nearly nothing.

  This book is a synopsis, a cheat sheet if you will. It can’t recount every exact detail of the contents and history of the universe. Instead, it treats the reality we know as a zoomable map with a preset path to follow. In video-game parlance, it’s a “rail shooter.” That rail follows the physical scales of the cosmos—starting at the top and zooming on down.

  As we wrote and illustrated this journey, we agonized over how to build this rail. The cosmos has three dimensions of space, and that tricky thing we call time. There are also trillions of interesting things to take a look at along the way. We’ve tried to balance the idea of a “grand overview” with making sure we visited some very, very cool places en route.

  Some of the waypoints are intellectually challenging—even in Chapter 1 you’ll have to contend with the strange concept of dark matter, an expanding universe, and even stranger things like multiple universes and multiple versions of you. In Chapter 3 you’ll have to grapple with the majestic origins of the solar system. By Chapter 6 you’ll be puzzling over the nature of consciousness, and by Chapter 9 you’ll be tackling interpretations of quantum mechanics. Don’t worry—the beautiful illustrations and infographics will help delight and inform you along the way.

  We hope you enjoy finding your own connections among the gloriously varied pieces of data and knowledge that bring our vision of reality together. Remember, it’s your universe as much as anyone else’s.

  1

  ALMOST EVERYTHING

  1027, 1026, 1025, 1024, 1023 meters

  From about 93 billion light-years to 10 million light-years

  From the diameter of the cosmic horizon to the size of the Local Group of galaxies

  It’s a summer morning. You’re sitting in a sunlit room holding this book, reading this page, and about to start a journey through cosmic scale.

  Looking up, you notice that tiny specks of glowing dust are caught in the beams of light streaming through the windows. These bright pinp
oints loft and swirl in the air currents, like a swarm of mysterious creatures.

  The specks are microscopic, yet if the whole room were to represent the size of the observable universe, each of these dusty motes would be the size of an entire galaxy of stars.

  Now follow a single sunlit speck. This is our galaxy, the Milky Way. It is home to more than 200 billion stars, and at least that number of planets. These stars and planets span a structure that is a hundred thousand light-years across—a distance of more than nine hundred thousand trillion kilometers. At a walking pace, it would take you twenty trillion years to cross this object.

  Packed deep inside, hidden among these billions of other worlds, is one particular planet we call Earth. This world is a modest rocky orb with a thin coating of crystallized mineral crust atop a hot interior, lightly painted with water and atmosphere. It orbits a lonesome star that we call the Sun—one star, only 4.5 billion years old in a 10-billion-year-old galaxy.

  Now think about all the things that you know and experience in your life. Your family, 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 multicellular 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 Milky Way is a microscopic part of a wrinkly, 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 exhibits 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.

  The horizon of the observable universe

  Add up all the recognizable matter and there may be 1080 particles, like protons, neutrons, electrons, and other subatomic items, inside our cosmic horizon. Although that’s a very big number, it’s also really just peanuts, because there are probably a billion times more photons zinging around, making a beastly total of 100,000,000,000,000,000,000,000,000,000,000,000,000,000,

  000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 of these electromagnetic-energy carriers in the observable cosmos.

  Yet this atomic and subatomic stuff is barely 16 percent of what we think is the total matter content of space. It’s the part that our eyes and instruments can see. Astronomical evidence suggests that there is an invisible shadow universe of still-mysterious subatomic particles that constitute the bulk of matter in the cosmos, some 84 percent of the mass. Here’s an underworld of dark matter, dominating entire galaxies with its gravitational pull, but unseen by us.

  Even stranger is that all the normal and dark matter is swimming in a space-time fabric that is seething with submicroscopic quantum phenomena. These ethereal quantum manifestations are too small, too brief, and too strange to be readily noticeable—except in a cumulative and quite terrifying effect that we now call dark energy. Astronomers think that dark energy is the prime suspect behind the accelerating expansion of the cosmos. Space-time itself—the underlying fabric of the universe as a whole—is swelling more and more with every passing hour.

  That is, in essence, what Everything really is.

  Are you tempted to ask what comes next? What is beyond the phenomenon we call Universe, beyond the Everything? What might be “outside” the sunlit room of our observable reality? These are great questions, and in a very real sense anything “outside” our universe must for now be simply not universe.

  The start of your journey through this book and through all known scales of reality is at that edge between known and unknown. This is a place hovering at our cosmic horizon, the scale set by the distance light travels during the age of the universe, the threshold of the doorway into your room. Within is the observable universe. Just outside is a still-mysterious labyrinth.

  The dark side of the universe’s web of matter

  UNIVERSE TO MULTIVERSE

  In truth, we think that our universe must continue on for a while beyond that horizon of the known. The universe from which light has not yet had time to reach us may be far, far larger than the part we can see. Some estimates, based on analyses of the known geometry of space-time, suggest that the “full” universe could extend at least 250 cosmic horizons farther. Other estimates, based on the very rapid expansion—or inflation—of the universe in its very early youth, suggest that the universe may be on the order of 1023 times larger than the part we will ever see, or ever access.

  If this is correct, the universe might contain places that are, in effect, repeats of where we find ourselves. Those repeats could even include solar systems, planets, and life-forms that bear an uncanny resemblance to the ones we know.

  It’s an unsettling thought, that the roll of cosmic dice might have happened enough times to reproduce Earth and its history. But lurking in our hypotheses about the fundamental nature of the universe and its physical origins are ideas that are even stranger.

  Another world, beyond the observable universe?

  To produce the cosmos that we observe, including the “shape” of its space-time and its relative uniformity on the largest scales, scientists have invoked the phenomenon of cosmic inflation. Very early in time, a mind-bogglingly brief 10−36 seconds after the Big Bang, there was likely an episode of enormously rapid expansion of space-time—where the universe grew by more than a trillion trillion times until the cosmic clock hit 10−32 seconds. That’s like a small pore on your skin inflating to the size of the Milky Way galaxy over a period that is a hundred quadrillion times less than some of the shortest intervals of time human devices have ever registered (about ten-quintillionths of a second).

  Pocket universes

  One outcome that physicists have proposed for this inflation produces an array of “pocket” universes, so many in number that it makes your eyes water; possibly 10-to-the-10-to-the-10-to-the-7 universes. Not only would there be a spectacular number of universes just like ours—there would be a spectacular number of universes not like ours. If true, this “multiverse” would contain other versions of all of us as well as all our evil twins.

  There are, to say the least, some disturbing aspects to this possibility. It would mean that any decision you make—good or bad—would be made many times elsewhere, and in many different ways. So does it really matter if I pick up that piece of litter when a trillion other versions of me will pick it up a tr
illion other times somewhere else in the multiverse? Should we bother discovering the secrets of the universe when it’s only one among many, and not as unique as we once thought?

  We’re left to wonder for now, and to go and make a strong cup of tea.

  VIEW FROM A FAR HORIZON

  In this book our journey begins at the place that matches the reach of our current knowledge: we’ll start our deep dive into powers of ten at a scale of 1027 meters (an octillion meters). We choose this scale because if we could measure the physical diameter, the extent, of the universe between the bounds of the cosmic horizon at this instant in time, we would find it to be about ninety-one billion light-years, or 860,951,000,000,000,000,000,000 kilometers, across—roughly 1027 meters.

  If you’re quick-witted you might query that number—since the universe is only 13.8 billion years old, how can it be physically larger than the distance light would travel in that time? The answer is universal expansion—that swelling of space-time. As a consequence, at this very instant, you’d measure it to be larger than you might expect.

  We can actually map aspects of the cosmic horizon. As the universe expands, it cools, since the photons racing through space get their wavelengths stretched out and lose energy. If we could go back in time, we’d find that the universe gets hotter and hotter. Until the universe was around 379,000 years old, its average temperature was above 3,000 Kelvin (4,940˚F)—too hot for electrons to be bonded in atoms. The photons racing through space were continually scattered by these free electrons. This made the young cosmos a “fog” impenetrable by electromagnetic radiation.