Nature’s Clocks

Nature’s Clocks: How Scientists Measure the Age of Almost Everything

Doug Macdougall
Copyright Date: 2008
Edition: 1
Pages: 288
Stable URL: http://www.jstor.org/stable/10.1525/j.ctt1pnx0t
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  • Book Info
    Nature’s Clocks
    Book Description:

    "Radioactivity is like a clock that never needs adjusting," writes Doug Macdougall. "It would be hard to design a more reliable timekeeper." InNature's Clocks,Macdougall tells how scientists who were seeking to understand the past arrived at the ingenious techniques they now use to determine the age of objects and organisms. By examining radiocarbon (C-14) dating-the best known of these methods-and several other techniques that geologists use to decode the distant past, Macdougall unwraps the last century's advances, explaining how they reveal the age of our fossil ancestors such as "Lucy," the timing of the dinosaurs' extinction, and the precise ages of tiny mineral grains that date from the beginning of the earth's history. In lively and accessible prose, he describes how the science of geochronology has developed and flourished. Relating these advances through the stories of the scientists themselves-James Hutton, William Smith, Arthur Holmes, Ernest Rutherford, Willard Libby, and Clair Patterson-Macdougall shows how they used ingenuity and inspiration to construct one of modern science's most significant accomplishments: a timescale for the earth's evolution and human prehistory.

    eISBN: 978-0-520-93344-6
    Subjects: Geology
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Table of Contents

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  1. Front Matter (pp. i-vi)
  2. Table of Contents (pp. vii-viii)
  3. LIST OF ILLUSTRATIONS (pp. ix-x)
  4. ACKNOWLEDGMENTS (pp. xi-xii)
  5. CHAPTER ONE No Vestige of a Beginning . . . (pp. 1-20)

    While hiking in the Alps one day in 1991, Helmut Simon and his wife had a disturbing experience: they discovered a body. It was partly encased in the ice of a glacier, and their first thought was that it was an unfortunate climber who had met with an accident, or had been trapped in a storm and frozen to death. Word of the corpse spread quickly, and a few days later several other mountaineers viewed it (see figure 1). It was still half frozen in the ice, but they noticed it was emaciated and leathery, and lacking any climbing equipment....

  6. CHAPTER TWO Mysterious Rays (pp. 21-44)

    In the cold Warsaw November of 1891, a young Polish woman, just turned twenty-four, packed up her belongings and boarded a train to Paris. She wanted to study science at the Sorbonne, and, although she did not have much money, she was ambitious and very determined. She knew she could stay with her sister, who had moved to Paris earlier, and (this must seem remarkable to any present-day student struggling to finance his or her education) she could attend the great French university for free. Paris transformed her life; four years after arriving there, she married a well-known French scientist,...

  7. CHAPTER THREE Wild Bill’s Quest (pp. 45-71)

    When the Twenty-ninth International Congress of Americanists was held at the American Museum of Natural History in New York in September 1949, there were three hundred attendees from thirty-five different countries. At the opening session they listened attentively to a talk given by a forty-year-old nuclear chemist from the University of Chicago named Willard F. Libby. It was an unusual venue for a chemist, but Libby’s topic was dear to the hearts of the archaeologists in the audience: he spoke about a new method for dating archaeological artifacts that had been developed in his laboratory. “We have reason to believe,”...

  8. CHAPTER FOUR Changing Perceptions (pp. 72-100)

    In its early years—in the 1950s and 1960s—radiocarbon dating changed people’s perceptions of both human and glacial chronology. It didn’t actually change the ages of things, of course, but it did change people’s understanding of the ages of things, sometimes quite radically. When Libby developed the method, a few other techniques that used radioactivity to probe the chronology of the Earth’s past already existed, as will be told later in this book. They, too, were in the early stages of development, and were not yet very sophisticated. But, more important, they were all based on radioactive isotopes with...

  9. CHAPTER FIVE Getting the Lead Out (pp. 101-130)

    By a curious coincidence, in the late 1940s and early 1950s, just as Libby, Arnold, and Anderson were developing radiocarbon dating as a way to measure samples that are just thousands of years old, there was a parallel project underway to develop methods capable of dating samples from the other end of the time spectrum: near the time of the Earth’s formation, billions of years before the present. Not only was this work taking place almost simultaneously, it was going on literally right next door at the University of Chicago.

    During the Second World War, many of America’s best chemists...

  10. CHAPTER SIX Dating the Boundaries (pp. 131-158)

    William Smith is a very common name, and it is likely that there were many William Smiths born in eighteenth-century England. Most of them probably led fruitful lives, worthy of more than passing interest. But, as far as geologists are concerned, there is only one who matters: the William Smith who virtually single-handedly put together the first true geological map of Britain ever produced. The author Simon Winchester wrote a book about Smith and his work, calling itThe Map That Changed the World.Smith’s map was the culmination of years of observation and investigation, and it was—and still...

  11. CHAPTER SEVEN Clocking Evolution (pp. 159-189)

    The end of the Cretaceous period came, in a twist on T.S. Eliot’s famous line, not with a whimper, but with a bang. A very big bang that was felt around the globe, equivalent, it has been estimated, to the explosion of at least 100,000 billion tons of TNT, or about 8 billion times the energy released by the atomic bomb that devastated Hiroshima at the end of the Second World War. You would not want to have been around at the end of the Cretaceous.

    The environmental crisis that ended the Cretaceous period and closed the Mesozoic era was...

  12. CHAPTER EIGHT Ghostly Forests and Mediterranean Volcanoes (pp. 190-218)

    Most geologists are historians—not historians as we usually think of them, but historians of the Earth. They talk about the Cretaceous or the Precambrian as easily as conventional historians discuss the sixteenth century. And, like conventional historians, geologists tend to have specialties. Some are experts in what was going on during the Jurassic period; others spend their careers examining trilobites from the Cambrian or metamorphic rocks from the Archean. But all historians, regardless of what slice of time they study, need a time line to order events and fit them into the wider historical picture. For geologists, the particular...

  13. CHAPTER NINE More and More from Less and Less (pp. 219-238)

    This chapter is about modern dating practices, which does not mean meeting someone over the Internet. Rather, I’d like to take a brief look at a few of the advances of recent years that make the field of geochronology so pervasive in the earth sciences today, and so exciting. The inventiveness and power of some of the methods used to measure the past, I believe, are not given enough credit. Reports of radiometric age determinations are close to being commonplace; the more “exciting” ones are almost as likely to pop up in the newspaper or on TV as in a...

  14. APPENDIX A THE GEOLOGICAL TIME SCALE (pp. 239-240)
  15. APPENDIX B PERIODIC TABLE OF THE CHEMICAL ELEMENTS (pp. 241-244)
  16. APPENDIX C ADDITIONAL NOTES (pp. 245-250)
  17. GLOSSARY (pp. 251-256)
  18. RESOURCES AND FURTHER READING (pp. 257-264)
  19. INDEX (pp. 265-271)
  20. Back Matter (pp. 272-272)

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