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Total Eclipses of the Sun (Expanded edition)

Total Eclipses of the Sun (Expanded edition)

Copyright Date: 1995
Edition: REV - Revised
Pages: 242
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  • Book Info
    Total Eclipses of the Sun (Expanded edition)
    Book Description:

    Eclipses have captured attention and sparked curiosity about the cosmos since the first appearance of humankind. Having been blamed for everything from natural disasters to the fall of kings, they are now invaluable tools for understanding many celestial as well as terrestrial phenomena. This clear, easy-to-understand guide explains what causes total eclipses and how they can be used in experiments to examine everything from the dust between the planets to general relativity. A new chapter has been added on the eclipse of July 11, 1991 (the great Hawaiian eclipse).

    Originally published in 1995.

    ThePrinceton Legacy Libraryuses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

    eISBN: 978-1-4008-6399-0
    Subjects: Astronomy

Table of Contents

  1. Preface to the Paperback Edition
    (pp. vii-viii)
  2. 1 Thirty Centuries of Eclipse Watching
    (pp. 1-27)

    A total eclipse of the Sun is a spectacular, awe-inspiring event. Throughout the past, human beings must have stopped in their daily struggle to survive in order to stare in disbelief at the gradual disappearance and reappearance of the Sun. We have no written records for most of this period. We can only guess at the reaction of neolithic peoples by extrapolating from the reaction of “primitive” peoples now. With few exceptions, they view a total eclipse of the Sun with fear, guilt, a desire to propitiate their gods, and afterwards, an enormous sense of relief.

    Through most of recorded...

  3. 2 Eclipses Explained
    (pp. 28-40)

    Nearly everyone has a rough idea of why solar eclipses occur. If asked, the average man in the street might reply, “Because the Moon moves between the Sun and the Earth.” And he would be right, except that his answer glosses over the incredible accident that the Moon and the Sun appear to have the same size, even though the Sun is actually 400 times larger than the Moon. It is the nearly exact equality of the angular diameters of the Sun and Moon, as seen from the Earth, that makes total eclipses possible at all.

    As Figure 2.1 shows,...

  4. 3 Time, Tide, and Gravity
    (pp. 41-55)

    In 1693, Edmund Halley, fresh from the discovery of his now famous comet, turned to a study of the Moon’s motion. He analyzed a group of lunar eclipses recorded in Ptolemy’s second centuryAlmagest,(a compendium of ancient Greek astronomical observations), a group of ninth century Arabian solar eclipses, and a group of seventeenth century solar eclipses. He concluded that the Moon’s mean speed in its orbit wasnotconstant, but had been accelerating throughout historical time. Now, Kepler’s second law (see Note 3, Chapter 2) leads us to expect that theinstantaneousspeed of the Moon will vary according...

  5. 4 The Chromosphere
    (pp. 56-75)

    Just beyond the sharp edge of the visible Sun, the chromosphere begins. Invisible in full daylight, the chromosphere blazes out in red glory for a few seconds (at second and third contacts) during a total eclipse. The chromosphere is a strange region that lies between the cool photosphere and very hot corona. It is the lowest region of the Sun’s atmosphere in which dynamic and magnetic processes, as well as radiation, heat the gas. Shock waves form here from sound waves that have traveled upward from the noisy photosphere. Heat flows downward from the corona, is converted to light in...

  6. 5 The Solar Corona
    (pp. 76-105)

    The past fifteen years have been an incredibly productive period in developing our understanding of the physical nature of the solar corona. Total eclipses of the Sun have continued to offer astronomers outstanding opportunities for investigation. Non-eclipse observations from satellites, rockets, and ground-based coronagraphs have, however, played an increasingly important role, and together with eclipses have revealed the complicated behavior of the corona. The new observations have, as usual, raised as many questions as they have answered. Astronomers who study the corona are, in effect, unpacking a set of nested Chinese boxes, each one smaller and more intricate than the...

  7. 6 Interplanetary Dust
    (pp. 106-128)

    If you face the western sky during twilight on a clear autumn evening, you will see a long triangular streak of light along the Sun’s apparent path in the sky (the ecliptic). The Italian astronomer Cassini first noticed this phenomenon in 1683 and correctly attributed the light to sunlight that has been scattered from small solid particles that cluster in the plane of the ecliptic. It is now called the zodiacal light (see Figure 6.1).

    Meteor showers are another phenomenon that indicate the presence of solid material in the solar system. The sudden streak of light we call a meteor...

  8. 7 The Earth’s Atmosphere
    (pp. 129-147)

    Atmospheric physicists have been studying the effect of the Sun’s radiation on the upper atmosphere for many years. Although they have a good general understanding of what goes on there, they are totally in the dark on some of the most important details. They study the upper atmosphere in every possible way, using balloons, rockets, aircraft, and satellites, as well as more conventional ground-based instruments. Although experiments during total solar eclipses are not the most important means of studying the atmosphere, they certainly have contributed their fair share to our present knowledge, and you can readily see why. A total...

  9. 8 Waves in the Earth’s Atmosphere
    (pp. 148-165)

    During the last decade, meteorologists and ionospheric physicists have been trying to detect waves in the upper atmosphere that are generated during a total solar eclipse. Such waves were predicted in 1970 by two Canadian physicists, G. Chimonas and C. O. Hines. They reasoned that an eclipse causes a sudden cooling of the troposphere and ozonosphere. The rapid chilling of the air in the umbral shadow might create a pressure imbalance that would spread out, in the form of waves, to great distances. Chimonas and Hines suggested that the properties of such waves would test our present understanding of cooling...

  10. 9 A Test of General Relativity
    (pp. 166-182)

    What subject is more esoteric or abstract to the average man than relativity? Its concepts seem far removed from everyday experience, and are defended from the approach of ordinary mortals by thickets of complex mathematics. People generally respect it but do not understand it. Only the famous equationE=mc², with its practical consequences in the construction of the first atomic bomb, has become part of our popular culture. This situation is unfortunate because relativity stands as one of the major achievements of the human mind and, along with quantum mechanics, one of the two revolutions that swept fundamental...

  11. 10 “I Got Rhythm, You Got Rhythm”
    (pp. 183-189)

    A businessman from Denver arrives in Bangkok after an 18-hour flight. Although it is broad daylight outside his hotel window, his body announces it is ready for its usual 8-hour sleep. Hunger pangs come and go in odd relationship to the clock on the wall. He is experiencing “jet-lag”—the shift of his natural internal rhythms relative to local time.

    Each of us (and indeed all plants and animals) is born with an internal biological clock. It governs our daily cycles of sleep and wakefulness, hunger, irritability, and mental alertness. It regulates the daily rhythm of oxygen consumption, body temperature,...

  12. 11 Future Experiments: Is the Sun Shrinking?
    (pp. 190-196)

    In earlier chapters, I emphasized that experiments at total eclipses are no longer the only way or even the best way of investigating problems in solar astronomy or in any of the other disciplines we’ve mentioned. Observations outside of eclipse, especially from space vehicles, have superceded many kinds of experiments, particularly in astronomy, that formerly required an eclipse. Will this trend continue? Will total solar eclipses gradually lose their appeal to professional scientists and only attract enthusiastic amateurs?

    Nobody can predict the future, let alone the future course of science, with any confidence. However, I would say the answers to...

  13. 12 The Great Hawaiian Eclipse
    (pp. 197-212)

    Most total eclipses are best seen from remote, uncomfortable places such as the middle of the Sahara or the mosquito coast of Surabaya, but not the eclipse of July 11, 1991. Its path of totality passed right over the island of Hawaii, which is famous for its hospitality, its white beaches, and its balmy weather. Thousands of ordinary tourits who had never seen an eclipse decided this was the one to see. All through the autumn of 1990, the airlines and hotels planned for a minor invasion. They were not disappointed; the turnout was one of the largest ever seen....

  14. Postscript
    (pp. 213-214)

    As this book goes to press, scientists are analyzing the observations they obtained at the total eclipse of November 3, 1994. The path of totality passed over northern Chile, Bolivia, Brazil, and Argentina and then out over the Atlantic. Most astronomers chose to observe the eclipse in Putre, Chile, one of the driest cloud-free regions in the world. As luck would have it, the sky was covered with light cirrus that day; nevertheless, we fielded some interesting experiments and obtained useful data during three minutes of totality.

    Among the more novel experiments was a search for infra-red coronal emission lines...