Chapter 1: Roads to Reality SPACE, TIME, AND WHY THINGS ARE AS THEY ARE None of the books in my father's dusty old bookcase were forbidden. Yet while I was growing up, I never saw anyone take one down. Most were massive tomesa comprehensive history of civilization, matching volumes of the great works of western literature, numerous others I can no longer recallthat seemed almost fused to shelves that bowed slightly from decades of steadfast support. But way up on the highest shelf was a thin little text that, every now and then, would catch my eye because it seemed so out of place, like Gulliver among the Brobdingnagians. In hindsight, I'm not quite sure why I waited so long before taking a look. Perhaps, as the years went by, the books seemed less like material you read and more like family heirlooms you admire from afar. Ultimately, such reverence gave way to teenage brashness. I reached up for the little text, dusted it off, and opened to page one.

The first few lines were, to say the least, startling. "There is but one truly philosophical problem, and that is suicide," the text began. I winced. "Whether or not the world has three dimensions or the mind nine or twelve categories," it continued, "comes afterward"; such questions, the text explained, were part of the game humanity played, but they deserved attention only after the one true issue had been settled. The book was The Myth of Sisyphus and was written by the Algerian-born philosopher and Nobel laureate Albert Camus. After a moment, the iciness of his words melted under the light of comprehension. Yes, of course, I thought. You can ponder this or analyze that till the cows come home, but the real question is whether all your ponderings and analyses will convince you that life is worth living.

That's what it all comes down to. Everything else is detail. My chance encounter with Camus' book must have occurred during an especially impressionable phase because, more than anything else I'd read, his words stayed with me. Time and again I'd imagine how various people I'd met, or heard about, or had seen on television would answer this primary of all questions. In retrospect, though, it was his second assertion regarding the role of scientific progressthat, for me, proved particularly challenging. Camus acknowledged value in understanding the structure of the universe, but as far as I could tell, he rejected the possibility that such understanding could make any difference to our assessment of life's worth. Now, certainly, my teenage reading of existential philosophy was about as sophisticated as Bart Simpson's reading of Romantic poetry, but even so, Camus' conclusion struck me as off the mark. To this aspiring physicist, it seemed that an informed appraisal of life absolutely required a full understanding of life's arenathe universe.

I remember thinking that if our species dwelled in cavernous outcroppings buried deep underground and so had yet to discover the earth's surface, brilliant sunlight, an ocean breeze, and the stars that lie beyond, or if evolution had proceeded along a different pathway and we had yet to acquire any but the sense of touch, so everything we knew came only from our tactile impressions of our immediate environment, or if human mental faculties stopped developing during early childhood so our emotional and analytical skills never progressed beyond those of a five-year-oldin short, if our experiences painted but a paltry portrait of realityour appraisal of life would be thoroughly compromised. When we finally found our way to earth's surface, or when we finally gained the ability to see, hear, smell, and taste, or when our minds were finally freed to develop as they ordinarily do, our collective view of life and the cosmos would, of necessity, change radically. Our previously compromised grasp of reality would have shed a very different light on that most fundamental of all philosophical questions. But, you might ask, what of it? Surely, any sober assessment would conclude that although we might not understand everything about the universeevery aspect of how matter behaves or life functionswe are privy to the defining, broad-brush strokes gracing nature's canvas. Surely, as Camus intimated, progress in physics, such as understanding the number of space dimensions; or progress in neuropsychology, such as understanding all the organizational structures in the brain; or, for that matter, progress in any number of other scientific undertakings may fill in important details, but their impact on our evaluation of life and reality would be minimal. Surely, reality is what we think it is; reality is revealed to us by our experiences. To one extent or another, this view of reality is one many of us hold, if only implicitly. I certainly find myself thinking this way in day-to-day life; it's easy to be seduced by the face nature reveals directly to our senses.

Yet, in the decades since first encountering Camus' text, I've learned that modern science tells a very different story. The overarching lesson that has emerged from scientific inquiry over the last century is that human experience is often a misleading guide to the true nature of reality. Lying just beneath the surface of the everyday is a world we'd hardly recognize. Followers of the occult, devotees of astrology, and those who hold to religious principles that speak to a reality beyond experience have, from widely varying perspectives, long since arrived at a similar conclusion. But that's not what I have in mind. I'm referring to the work of ingenious innovators and tireless researchersthe men and women of sciencewho have peeled back layer after layer of the cosmic onion, enigma by enigma, and revealed a universe that is at once surprising, unfamiliar, exciting, elegant, and thoroughly unlike what anyone ever expected. These developments are anything but details. Breakthroughs in physics have forced, and continue to force, dramatic revisions to our conception of the cosmos.

I remain as convinced now as I did decades ago that Camus rightly chose life's value as the ultimate question, but the insights of modern physics have persuaded me that assessing life through the lens of everyday experience is like gazing at a van Gogh through an empty Coke bottle. Modern science has spearheaded one assault after another on evidence gathered from our rudimentary perceptions, showing that they often yield a clouded conception of the world we inhabit. And so whereas Camus separated out physical questions and labeled them secondary, I've become convinced that they're primary. For me, physical reality both sets the arena and provides the illumination for grappling with Camus' question. Assessing existence while failing to embrace the insights of modern physics would be like wrestling in the dark with an unknown opponent. By deepening our understanding of the true nature of physical reality, we profoundly reconfigure our sense of ourselves and our experience of the universe. The central concern of this book is to explain some of the most prominent and pivotal of these revisions to our picture of reality, with an intense focus on those that affect our species' long-term project to understand space and time. From Aristotle to Einstein, from the astrolabe to the Hubble Space Telescope, from the pyramids to mountaintop observatories, space and time have framed thinking since thinking began.

With the advent of the modern scientific age, their importance has been tremendously heightened. Over the last three centuries, developments in physics have revealed space and time as the most baffling and most compelling concepts, and as those most instrumental in our scientific analysis of the universe. Such developments have also shown that space and time top the list of age-old scientific constructs that are being fantastically revised by cutting-edge research. To Isaac Newton, space and time simply werethey formed an inert, universal cosmic stage on which the events of the universe played themselves out. To his contemporary and frequent rival Gottfried Wilhelm von Leibniz, "space" and "time" were merely the vocabulary of relations between where objects were and when events took place. Nothing more. But to Albert Einstein, space and time were the raw material underlying reality. Through his theories of relativity, Einstein jolted our thinking about space and time and revealed the principal part they play in the evolution of the universe.

Ever since, space and time have been the sparkling jewels of physics. They are at once familiar and mystifying; fully understanding space and time has become physics' most daunting challenge and sought-after prize. The developments we'll cover in this book interweave the fabric of space and time in various ways. Some ideas will challenge features of space and time so basic that for centuries, if not millennia, they've seemed beyond questioning. Others will seek the link between our theoretical understanding of space and time and the traits we commonly experience. Yet others will raise questions unfathomable within the limited confines of ordinary perceptions. We will speak only minimally of philosophy (and not at all about suicide and the meaning of life). But in our scientific quest to solve the mysteries of space and time, we will be resolutely unrestrained.

From the universe's smallest speck and earliest moments to its farthest reaches and most distant future, we will examine space and.