In Search of Time: The History, Physics, and Philosophy of Time
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In Search of Time: The History, Physics, and Philosophy of Time
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Overview
Time surrounds us. It defines our experience of the world; it echoes through our every waking hour. Time is the very foundation of conscious experience. Yet as familiar as it is, time is also deeply mysterious. We cannot see, hear, smell, taste, or touch it. Yet we do feel it—or at least we think we feel it. No wonder poets, writers, philosophers, and scientists have grappled with time for centuries.
In his latest book, award-winning science writer Dan Falk chronicles the story of how humans have come to understand time over the millennia, and by drawing from the latest research in physics, psychology, and other fields, Falk shows how that understanding continues to evolve. In Search of Time begins with our earliest ancestors' perception of time and the discoveries that led—with much effort—to the Gregorian calendar, atomic clocks, and "leap seconds." Falk examines the workings of memory, the brain's remarkable "bridge across time," and asks whether humans are unique in their ability to recall the past and imagine the future. He explores the possibility of time travel, and the paradoxes it seems to entail. Falk looks at the quest to comprehend the beginning of time and how time—and the universe—may end. Finally, he examines the puzzle of time's "flow," and the remarkable possibility that the passage of time may be an illusion.
Entertaining, illuminating, and ultimately thought provoking, In Search of Time reveals what some of our most insightful thinkers have had to say about time, from Aristotle to Kant, from Newton to Einstein, and continuing with the brightest minds of today.
Product Details
| ISBN-13: | 9781429987868 |
|---|---|
| Publisher: | St. Martin's Publishing Group |
| Publication date: | 06/04/2024 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 356 |
| File size: | 2 MB |
About the Author
Dan Falk has written about science for The Boston Globe,The Globe and Mail,TheWalrus,Astronomy,Nature, and New Scientist, and has been a regular contributor to the CBC Radio programs Ideas and Quirks and Quarks. His awards include a Gold Medal for Radio Programming from the New York Festivals and the Science Writing Award in Physics and Astronomy from the American Institute of Physics. His first book, Universe on a T-Shirt, won the 2002 Science in Society Journalism Award from the Canadian Science Writers' Association. He lives in Toronto, Canada.
Read an Excerpt
In Search of Time
Journeys Along a Curious Dimension
By Dan Falk
McClelland & Stewart Ltd
Copyright © 2008 Dan FalkAll rights reserved.
ISBN: 978-1-4299-8786-8
CHAPTER 1
HEAVENLY CLOCKWORK
Time's natural cycles
The first grand discovery was time, the landscape of experience.
— Daniel Boorstin, The Discoverers
The city of Drogheda, just half an hour north of Dublin by Irish Rail's InterCity service, isn't at the top of most tourists' Ireland itineraries. Even Lonely Planet, which praises the surrounding counties for their historical and cultural wealth, describes this small coastal city as "charmless." As my taxi heads west, however, the view steadily improves, with Drogheda's industrial clutter giving way to the rolling hills and green valleys of County Meath. And just a few kilometers farther inland lies one of the most important prehistoric monuments in all of Europe — the "passage tomb" of Newgrange.
Most visitors to Newgrange approach from the south side of the Boyne, through the main visitor center, but for my early morning appointment I have to come from the north side of the famous river, past Newgrange Farm, where the sound of birds and cowbells fills the morning air. As the taxi rounds the last bend in the road, the monument itself — a shallow, circular, grass-covered mound some eighty meters across and a dozen meters high — comes into view. The outer walls are lined with blocks of white quartz that glitter in the sunlight. I'm met by Claire Tuffy of the Office of Public Works, which manages the site, and together we climb the gentle hill leading to the tomb's main entrance.
The structure, Tuffy explains, dates from around 3100 B.C. — making it five centuries older than the Great Pyramid at Giza in Egypt, and a full thousand years older than the "trilithons" at the center of Stonehenge. The Neolithic people who lived in Ireland at that time would have been farmers, tending grain crops and herding livestock. The Boyne — Tuffy nods toward the river, half-hidden by trees and low hills — was their highway. They had likely been farming the land for a thousand years before construction at Newgrange began. "Their tools were stone and wood — no metal," Tuffy points out. The quartz was transported from what is now County Wicklow, some eighty kilometers away. One can only imagine the Herculean effort required to move, shape, and lift the nearly two thousand stones used to construct the monument.
We pass the richly decorated sandstone blocks that mark the entrance, and approach the iron gate that now protects the interior. Tuffy unlocks it and we step inside, ducking our heads because of the low ceiling. Though circular on the outside, the interior of the tomb is long and narrow, cutting deep into the center of the mound. We make our way cautiously toward the rear of the chamber. Soon the entrance is little more than a tiny square of light in the distance behind us. Without the electric lights installed overhead every few meters, it would be pitch black. It is also eerily quiet. For the pair of bats that have built their nest here, it is no doubt the perfect home.
The tomb stretches twenty-five meters in length but rarely spans more than a meter across. At the far end are three small alcoves that branch off from the main passage, giving the tomb an elongated cruciform design. Though known to the modern Irish since the seventeenth century, the site wasn't properly excavated until the 1960s, when archeologist Michael O'Kelly and his team discovered the cremated bones of at least five individuals, on basin-like stones in the alcoves at the rear of the tomb. Workers also uncovered intriguing Neolithic artwork. Several of the stones are decorated with geometrical patterns; the most complex is a trio of overlapping spirals at the very back of the tomb.
As we stand in the rear chamber, Tuffy shines her flashlight at the layers of cobbled stones that arch overhead. "That roof has not been restored, and it is still perfectly watertight after five thousand years of Irish weather," she says. Why would Neolithic farmers have gone to that much trouble to protect the bones of the dead from a little water? Perhaps the spirits of the ancestors were thought to live on, she speculates. And while today is sunny, Tuffy reminds me with a smile that her country has been known to have the occasional spot of rain. "Maybe it's every Irish person's idea of heaven, to be dry for ever and ever," she muses.
But the most intriguing feature of Newgrange is neither its walls, nor its roof, nor its artwork. It is not what one sees at any one place, but rather what one sees at a particular time. Every winter, on the morning of the shortest day of the year — the winter solstice — sunlight streams through a small opening above the main entrance, known as the "roof box," illuminating the back of the tomb. This seemingly innocuous event — a sliver of sunlight briefly creeping into a dusky burial chamber in the dead of winter — is what makes Newgrange unique. These weathered stones allow us to glimpse, however dimly, into the minds of those who first considered the matter of time.
The Sun in the Cave
Were the roof box and passage constructed along a slightly different angle, the solstice event would not happen. Could it be a coincidence, a chance alignment? Almost certainly not, says astronomer Tom Ray of the Dublin Institute for Advanced Studies, who investigated the geometry of Newgrange in the 1980s. "As an astronomer, as a mathematician, I'm looking at the statistics and saying, the chances of this being an accident are very, very small," Ray told me when I visited him in his Dublin office. The solar alignment "was their intention." Andrew Powell, writing in a prominent archeological journal a few years ago, reached the same conclusion: "There can be no doubt that this was an integral feature of the tomb's design."
The modern name Newgrange comes from the Gaelic Uaimh na Gréine, "The Cave of the Sun." In fact, even before those first excavations in the Sixties, there were local legends about sunlight entering the cave at a particular time of year. O'Kelly wondered if it might involve the winter solstice, as such alignments are well known in later Neolithic monuments. So he camped out in the cave overnight, waking up early on the morning of December 21, 1969, to see for himself (and, just to be sure, he repeated the experiment the following year). Ray, telling me the story, is mildly amused. "From the point of view of an astronomer, you don't need to actually do that," he says. "You could have just done a bit of surveying, and that would have told you the answer. So we have this sort of romantic image of Michael O'Kelly stuck in the back of the chamber, on the shortest day of the year, waiting for the sun to rise. And lo and behold, when it did, he realized that the light came into the main chamber of Newgrange." As O'Kelly noted in his journal that morning:
At exactly 8:54 hours GMT the top edge of the ball of the sun appeared above the local horizon and at 8:58 hours, the first pencil of direct sunlight shone through the roof-box and along the passage to reach the tomb chamber floor as far as the front edge of the basin stone in the end recess.
But our view today is not precisely the same as it would have been five thousand years ago. For one thing, Ray explains, the earth's axis wobbles periodically over thousands of years. The phenomenon is related to the precession of the earth's rotation axis: as the earth spins, the axis itself gradually revolves with respect to the solar system, in a cycle that lasts about 26,000 years. The related wobble — astronomers call it "nutation" — causes a periodic change in the tilt of the axis. Today, the axis is tilted 23.5 degrees; at the time Newgrange was built, the tilt was slightly greater — about 24 degrees. The upshot of that small shift, Ray explains, is that the shortest day of the year was a little bit shorter back then, and the longest day was a little bit longer. That, in turn, affects the time of sunrise and sunset. Today, on the solstice — as O'Kelly noticed — several minutes pass between sunrise and the first penetration of sunlight into the rear of the tomb. Five thousand years ago, however, it would have been bang on. "You would have captured the sun just as it rose," says Ray.
The solstice sunrise at Newgrange is still a remarkable event. Every year, thousands of people take part in a lottery for the privilege of a morning visit to the tomb in the week of December 21. Because the main passageway is angled upward, those first rays of sunlight don't hit the back wall; instead, as O'Kelly observed, they hit the ground a few meters short of the rear of the tomb. It is that first strike of sunlight inside the tomb that those lucky visitors watch for. "Nobody takes their eye off the ground," says Tuffy, who has probably witnessed the event more often than anyone else in recent years. "You lose your sense of how much time has passed. And despite the fact that everybody is watching the floor, people inevitably miss the first beam of light." Soon the beam is about the length and width of a pencil, Tuffy says. "And then very quickly it gets longer and wider, and it moves down the floor." By the time it reaches the middle of the chamber — just a few minutes later — it's nearly twenty centimeters wide, and surprisingly intense. "It's a lovely, warm color," she says. "And then the whole room is so bright you can see right up as far as the capstone. You can see the faces of all the people gathered in the room."
What does the solar alignment tell us about the Neolithic people who moved so many massive stones into place, in such a precise way, to build such a structure? We can imagine that the builders of Newgrange — as one could say of people in any farming community today — took an intense interest in the passing of the seasons and the motions of the heavenly bodies, particularly the sun and moon. In those days, before the glare of streetlights and shopping malls, the skies would have been pristine. True, Irish weather is often rather gray — but on every clear, cloudless night, the sky would have presented a dynamic celestial display for all to see. The regularity of the heavens — the daily rising and setting of the sun, the monthly waxing and waning of the moon, the annual parade of the seasons — would have been impossible to ignore.
"Certainly they had an interest in astronomy," says Ray. He cautions, though, against projecting modern Western terms onto a culture so different from ours; we have to be careful about labeling those Neolithic farmers "astronomers" or calling Newgrange an "observatory" — although, as we'll see, scholars of all stripes can hardly refrain from using that particular term (one is tempted to call it "the 'o' word") when discussing elaborate Neolithic sites. Still, there is no question that those early farmers had a keen awareness of the heavens. "There clearly was an interest in the two main heavenly bodies," says Ray. "Whether there were sort of religious connotations as well, I don't know, and I don't think anybody else knows either."
The First Hominids
Our earliest ancestors had no clocks and calendars, but they had something that functioned in a similar way: nature itself. Early humans must have been captivated by time's endless cycles, as reflected in the rhythmic motions of the heavenly bodies, for many thousands of years. Today we look down at our watches (and the LCD clocks on our cell phones); our ancestors would have looked up at the sun, moon, and stars. And very likely a more basic awareness originated much earlier, from the time our ancestors first walked upright and chipped away at the first crude stone tools. But extrapolating from bones and tools to thoughts and beliefs is an enormous and endlessly frustrating challenge, and even the most plausible ideas are rarely proven beyond all doubt. Such efforts have been bolstered in recent years by remarkable advances in genetics, cognitive science, primate studies, and, of course, archeological discoveries. Even so, the farther back we look, the more scattered and ambiguous the clues become.
Anthropologists suspect that even the earliest hominids — the first members of the human family — had some sort of temporal awareness, long before our own species, Homo sapiens, emerged as the dominant creature on our planet. Those early hominids, living several million years ago, "probably had a rudimentary conception of time similar to our own," argues John Shea of the State University of New York at Stony Brook. They had "an understanding of the past, an understanding of the future — and the ability to perceive the future in terms of contingencies, in terms of 'if this, then that will happen.'" Shea didn't use the word "consciousness" — the word still carries a lot of baggage in many scientific disciplines — but it seems reasonable to assume that a creature that is conscious of itself and its environment would also have at least a rudimentary awareness of time. Early hominids had enough of an awareness of past and future to live in cooperative social groups and to hunt large animals across a harsh and varied landscape, Shea says. They could learn from the past and try to predict future events; they could mentally sort through different courses of action and imagine what kinds of results they would produce. (Psychologists call this "mental time travel," and we will look at it more closely in Chapter 5.)
Evidence that those early human ancestors could plan for the future can be found around the edges of ancient lake beds in Africa and the Middle East, where archeologists have found numerous large deposits of stone tools crafted by early humans, seemingly stockpiled in strategic locations around the landscape. Perhaps, Shea suggests, they planned such caches so that the tribe would always be within a short distance of material that could be turned into weapons if the need arose. Even the sophistication of the tools suggests some degree of planning: carefully chipped hand axes were almost certainly intended not for a single carving session but for repeated use. It seems that these hominids understood, in some way, past and future; they sensed that survival meant knowing not only what was over the next hill, but also what was to come the following day or the following season. As rudimentary as it may have been, they clearly had some conception of time.
One of the most intriguing — and controversial — early human behaviors is the ritual burial of the dead, a practice that emerges only in the most recent chapter of the hominid story. Such practices at least hint at our ancestors' conception of life and death, and, perhaps, of "eternity." The first signs of systematic burial can be seen about 100,000 years ago with the Neanderthals, an offshoot of the human family tree that lived in Europe and western Asia. Modern Homo sapiens, however, had far more elaborate burials. Before we examine such practices in detail, it's worth looking at the complex relationship between these two branches of the human family.
A Meeting of Minds
The Neanderthals make their first appearance around 130,000 years ago, and thrived until about 25,000 years ago. They lived in the same geographical area as Homo sapiens at the same time — they certainly overlapped in southwestern Europe during the Upper Paleolithic period, beginning around 40,000 years ago — and shared many of the same traits. Yet there would be no confusing the two species. Neanderthals were stocky and muscular, with sloping foreheads and pronounced browridges. Even if given a shave and dressed in modern clothing, a Neanderthal would draw gasps on the streets of any twenty-first-century city. They actually had bigger brains than modern humans — though size, as we shall see, is not everything.
Some Neanderthal traits seem remarkably human: they crafted stone tools, learned to control fire, enjoyed a meat-heavy diet, and cared for their elderly and sick (as revealed by the bones of individuals who lived on for many years in spite of severe disability). "There could be no more compelling indication of a shared humanity," anthropologist Richard Klein has put it. (Recently there has been a debate as to whether the Neanderthals and Homo sapiens occasionally interbred; the emerging consensus, based on DNA studies as well as the fossil record, seems to be that such matings happened rarely, if ever.) What is clear, however, is that their lifestyles — and their mental capabilities — were worlds apart.
(Continues...)
Excerpted from In Search of Time by Dan Falk. Copyright © 2008 Dan Falk. Excerpted by permission of McClelland & Stewart Ltd.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
Contents
Preface,Introduction,
01 HEAVENLY CLOCKWORK Time's natural cycles,
02 YEARS, MONTHS, DAYS The quest for the perfect calendar,
03 HOURS, MINUTES, SECONDS Dissecting the day,
04 IN TIME'S GRASP Time and culture,
05 THE PERSISTENCE OF MEMORY A bridge across time,
06 ISAAC'S TIME Newton, Leibniz, and the arrow of time,
07 ALBERT'S TIME Spacetime, relativity, and quantum theory,
08 BACK TO THE FUTURE The science of time travel,
09 IN THE BEGINNING The search for the dawn of time,
10 BEYOND THE BIG BANG The frontiers of physics and the origin of time's arrow,
11 ALL THINGS MUST PASS The ultimate fate of life, the universe, and everything,
12 ILLUSION AND REALITY Physics, philosophy, and the landscape of time,
Notes,
Bibliography,
Index,