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  Copyright

  Copyright © 2017 by Bob Berman

  Cover design by Allison J. Warner

  Cover art by Shutterstock

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  ISBN 978-0-316-31131-1

  E3-20170817-JV-PC

  Contents

  Cover

  Title Page

  Copyright

  Epigraph

  Introduction

  CHAPTER 1: Light Fantastic

  CHAPTER 2: Now You See It, Now You Don’t

  CHAPTER 3: The Green Planet and the Red Heat

  CHAPTER 4: Hot Rays

  CHAPTER 5: Ultraviolet Brings the Blues

  CHAPTER 6: Danger Beyond the Violet

  CHAPTER 7: Energy Rhythms

  CHAPTER 8: The Exploding Sun

  CHAPTER 9: No Soap

  CHAPTER 10: Turning On and Tuning In

  CHAPTER 11: The Speed That Destroyed Space and Time

  CHAPTER 12: Microwaves Everywhere

  CHAPTER 13: The Man with the X-ray Vision

  CHAPTER 14: Röntgen Rays for Everyone

  CHAPTER 15: What’s in Your Basement?

  CHAPTER 16: The Atomic Quartet

  CHAPTER 17: Gamma Rays: The Impossible Light

  CHAPTER 18: Cell-Phone Radiation

  CHAPTER 19: Cosmic Rays

  CHAPTER 20: Beams from the Universe’s Birth

  CHAPTER 21: Energy from Our Minds

  CHAPTER 22: Ray Guns

  CHAPTER 23: The Next Frontier: Zero-Point and Dark Energies

  CHAPTER 24: Total Solar Eclipse: When the Rays Stop

  CHAPTER 25: ETs May Be Broadcasting, but What’s Their Number?

  CHAPTER 26: Does Light Have a Bright Future?

  Discover More Bob Berman

  About the Author

  Also by Bob Berman

  It is obvious that we must attach a deeper and much wider meaning to the word light than has hitherto been ordinarily understood.

  —EDITORIAL IN THE LANCET, FEBRUARY 22, 1896

  INTRODUCTION

  It’s everywhere.

  At this moment, as you sit quietly reading this book, you are awash in it. At work, it’s emanating from your electronic devices; step outside for lunch, and the sun bathes you in it. You may receive an extra dose of it when you visit your doctor, pass through security at the airport, or drive through city streets, but minuscule amounts of it are with you always. You cannot see, hear, smell, or feel it, but there is never a single second when it is not flying through your body. Too much of it will kill you, but without it you wouldn’t live a year.

  “Invisible light” seems like a contradiction. Like Simon and Garfunkel’s “The Sound of Silence,” it’s an oxymoron. We think of light, by definition, as something seen, something that enables our seeing, illuminating the darkness. Unlike dogs, who sniff in order to “get” what an object is, we depend on vision above all our other senses. We rely on light to tell us about our surroundings.

  But just as there are frequencies of sound audible to other animals that we cannot hear, there is a whole world of light outside our range of vision, a world that is humming with activity. Though we rarely think about this invisible world, our way of life depends on it. It’s because of invisible light that you can do things such as send a text message, use GPS to find your way to a friend’s house, listen to the radio, or microwave a frozen pizza. Invisible light shows us things we would never otherwise see, including our own skeletons and brains and the history of our universe.

  I was reminded of just how much we rely on invisible light, and how mysterious it remains to us, during a visit from my sister and her family. It was a lazy summer afternoon, and we were sprawled across a few couches sharing a bowl of popcorn. My niece, her shoulders crimson after a day outdoors, was chatting on her cell phone, holding up a promising finger to her mother, who was scolding her for not using sunscreen. My brother-in-law, meanwhile, was asking my opinion on an article he’d read proposing that Wi-Fi be banned in schools because of its dangers. We were all depending on invisible light (for the microwave popcorn, the cell-phone service) while being concerned that it might harm us (sunburn, mysterious Wi-Fi health threats) and confused about what to do to protect ourselves.

  We need it, and it surrounds us, yet we remain uneasy about living with invisible light, partly because we fear what is unknown. After all, most of us don’t know much about “all the light we cannot see.” This book aims to change that.

  My hope is to expose the hidden side of the spectrum, to make the invisible (at least temporarily) visible and vivid to you. As you’ll see, each of the different varieties of invisible light—from gamma rays to infrared to ultraviolet—has its own characteristics and peculiarities, as distinct as red is from blue. We’ll meet rays that pass through solid matter instead of being reflected by it and others that cause water to boil. Some come from deep space and zoom through astronauts’ brains; others are left over from the birth of the universe. You may be surprised to find how much of our world and our history is touched by invisible rays. They rescued lives when the Titanic went down. They help determine the daily weather. Some can produce sudden, lethally destructive damage in human bodies.

  We’ll split our exploration into two equally important parts. In some chapters we’ll go back in time to meet the pioneering scientists who first “saw” the invisible. Until the eighteenth century, no one had the faintest idea that there might be such a thing as light that cannot be detected by human vision, and until the nineteenth century no one had any proof of its existence. But once the discoveries of invisible light began, they avalanched, until most of today’s indispensable aspects of life, the ones we take for granted, depend on them.

  In other chapters we’ll explore how these phantoms affect our lives and our bodies as they provide their near-magical conveniences, from the cell phone in your pocket to the radio in your car. What role does invisible light play in our medicine, our technology, and our culture in the twenty-first century? What new opportunities for its use are on the horizon?

  Like my family lazing around the living room that summer afternoon, you probably have questions about how invisible light is affecting your health. What are the microwaves from your cell phone doing to your brain? What is radiation, and how much of it are you exposed to? Which invisible ray causes the most annual deaths? Which foods are most radioactive? This book will answer all those questions, clarifying once and for all the controversial claims about radiation’s health consequences. Some of the things you’ll learn will soothe you (ultraviolet light can decrease your risk of cancer), and some will shock you (a sing
le whole-body CT scan delivers more radiation than was received by Hiroshima survivors a mile from ground zero), but in every case context is key. Myths will be busted, and wild facts will abound.

  CHAPTER 1

  Light Fantastic

  If God really did say, “Let there be light,” it was no small housewarming present. There is a lot of light in the universe—one billion photons of light for every subatomic particle. In terms of individual items in the cosmos, including the components of atoms, photons constitute 99.9999999 percent of everything. The universe is literally made of light. And that includes not only ordinary everyday visible light but also the vast majority of light—the kind we cannot see.

  Light is an astonishing entity, and the quest to understand it has obsessed the greatest thinkers in disparate cultures through the centuries. The ancient Greeks, probably by sheer dumb luck, were the first to hit upon a key aspect of visible light—that it does not exist independent of us as observers. Physics now tells us that light is made up of intertwined magnetic and electrical fields. Since neither magnetism nor electricity is visible to our eyes, light is inherently invisible.

  When we look at a bright orange sunset, we’re not directly perceiving actual light. Rather, the energy reaching us from those electromagnetic pulses stimulates billions of neurons in our retinas and brains, which then fire to arouse a complex neurological architecture that produces in us the sensation of orange. An entire biological empire is thus as essential to the existence of brightness and colors as the photons themselves.

  The Greeks didn’t know anything about brain structure, of course, yet they still figured out that light is a sensation, with no existence independent of the observer—which was either amazingly perceptive or just a lucky guess. But the Greeks had light’s direction wrong. Knowing that its speed appeared instantaneous, they didn’t imagine that a pulse of light originating in a candle sped in our direction until it struck our eyes. On the contrary, they regarded light as a ray traveling outward from our pupils. This belief, that our eyes project an illuminating beam, was universally embraced for more than a millennium. Even so, a few early iconoclasts envisioned eyesight as an interplay between this supposed eye ray and something emitted by other sources.

  The classical thinker who came closest to the truth about light was the Roman Lucretius, who in the first century BCE, in his On the Nature of Things, wrote, “The light and heat of the sun are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air.”

  Lucretius’s view of light as particles—later supported by Isaac Newton—included that profound “lose no time” characterization, showing that he believed light moved immeasurably fast. But whether scientists considered its speed merely superquick or instantaneous, light remained popularly regarded as a phenomenon that originates in the eye for centuries to come.

  The first true breakthrough came from the mathematician and astronomer Alhazen—formally known as Abu Ali al-Hasan ibn al-Hasan ibn al-Haytham—who lived in Egypt during the golden age of Arab science. Around the year 1020, when the rest of the world was in the intellectual coma of the Dark Ages, Alhazen said that vision results solely from light entering the eye; nothing emanates from the eye itself. His popular pinhole camera obscura, which drew astonished yelps of wonder when visitors observed the phenomenon, gave weight to his arguments, for here was a full-color “motion picture” of nature splayed out on the walls. But Alhazen went much further. Light, he said, consists of streams of tiny, straight-moving particles that come from the sun and are then reflected by various objects. Sounds simple, perhaps, but Alhazen’s spot-on conclusions were six centuries ahead of anyone else’s.

  The Renaissance turned up the juice on the “What is light?” debate, which eventually took on the quality of a food fight. In the late seventeenth century, Newton joined astronomer Johannes Kepler in arguing that light is a stream of particles, while men such as Robert Hooke, Christiaan Huygens, and, soon, Leonhard Euler insisted that light is a wave. But what is it a wave of? They thought there had to be a substance doing the waving, so these Renaissance scientists decided that space was filled with a plenum (later called an ether), an invisible substance that facilitated the movement of magnetic and electrical energy.

  One obvious fact managed to sway many in favor of Newton’s particle idea. When light from the sun passes a sharp edge, such as the wall of a house, it casts a sharp-edged shadow on nearby objects. That’s what particles moving in a straight line should do. If instead light were made of waves, it ought to spread out—diffract—as ocean waves do when passing a jetty. To the particle proponents, the existence of sharp-edged shadows, combined with Newton’s reputation as a genius, made the wave proponents seem like nut jobs.

  The particles-versus-waves controversy eventually took a curious turn. As if some wise King Solomon ruled nature, everyone was soon declared right. The biggest breakthrough came from Scottish physicist and mathematician James Clerk Maxwell, who in 1865 showed that all light is a self-sustaining wave of magnetism with an electric pulse wiggling at right angles to it. One type of pulse stimulates the other, so that both the electrical and the magnetic waves continue indefinitely. From then on, science called light an electromagnetic phenomenon.

  All light consists of a dual wave. A magnetic pulse is accompanied by an electric pulse positioned at a ninety-degree angle to it. (Molecular Expressions at Florida State University)

  But where did this phenomenon come from? In 1896, the Dutch physicist Hendrik Lorentz figured out that the existence of a strange phenomenon—light splitting itself in two within a strong magnetic field—must mean that the rapid motion of some tiny, unknown, negatively charged particle has to be the source of all light everywhere in the universe. A year after he drew this astoundingly prescient conclusion, the first subatomic particle was discovered. This was the electron, whose movements are indeed the sole creator of all light. For predicting the existence of the electron before its actual discovery, Lorentz won the Nobel Prize in 1902.

  How exactly is light—any light, all light—created? When an atom gets struck by energy—from a quick zap of electricity or a collision with a stray electron or the introduction of heat—its wiggling motion is jolted into a greater speed. This extra energy excites the atom’s electrons, which give a figurative yelp and jump to an orbit farther from the nucleus. They don’t like to be there, so in a fraction of a second they fall back into a closer, smaller orbit. As they do so, the atom surrenders a bit of energy. Since energy is never lost under any circumstances, this energy must manifest itself in some other way. And it does. A bit of light, a photon, materializes out of the emptiness as if by magic—then instantly rushes away at its famous breakneck speed. That’s the only way light is ever born. Out of seeming nothingness, whenever an electron moves closer to its atom’s center. Simple, really.

  So light can be thought of as a set of two waves, one of electricity and one of magnetism, or as a weightless particle called a photon. Taking our cue from Albert Einstein, we might visualize a photon as a tiny bullet, an energetic speck with no mass, weighing nothing and with the curious property of being unable to ever stop moving. Nowadays, most people who think about such things (we science nerds) find it easiest to visualize light as a wave when it’s en route from point A to point B and as a photon when it finishes its journey by crashing into something. But one may call light a photon or a wave and be equally correct.

  The twentieth century brought us quantum theory, which—in addition to showing that solid objects such as electrons can behave as energy waves, too—revealed something extremely weird: when an observer uses an experimental apparatus to determine the location of photons or subatomic particles such as electrons, these entities always behave as particles and do things only particles can do, such as pass through one little hole or another but not both at once. But when no one’s measuring where exactly each photon is situated, they behave as waves that blurrily pass through
both holes in a barrier simultaneously to create an interference pattern on a detector located beyond the openings—which only waves can do.

  Thus the observer and, weirdly, the information in his or her mind plays a critical role in whether light exists as a wave or as a tiny discrete object. The same is true for particles of matter. What you see depends on how you observe and what you know. Most physicists now think that a human consciousness is required to make a photon or an electron’s “wave function” collapse so that it occupies a particular place as a particle. Otherwise it’s just a theoretical object with neither location nor motion.

  Just a century ago, the local realism mind-set of science, and even common sense, held that all objects, including atoms and photons, have an existence independent of our observation of them. But that’s been replaced by a more modern view—that our observation itself is necessary for the very existence of photons and electrons, a spooky prospect.

  But does an electron’s wave function collapse and turn into an actual particle if a cat is watching? Would light always be waves and never discrete photons if no humans were around? Our best answers are “Who knows?” and “Yes” respectively, but obviously this whole business is Wonderland-strange.*

  Let’s make this strangeness clearer. A century ago, if we detected a bit of light (or even a physical particle) arriving at an instrument with which we could measure its incoming direction, we’d have confidently plotted out its previous path. No longer. Now we say that it had no path before we started to observe it. It possessed no real existence as an actual photon or electron or whatever it was. Rather, its observed existence is its only existence. Observation establishes reality. Nothing else is certain. As the late physicist John Wheeler put it, “No phenomenon is a real phenomenon until it’s an observed phenomenon.”

  Which brings us to our next question: why can we observe some kinds of light with the naked eye and not others?