Dava Sobel

Longitude

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    Abby Lefeminehas quoted2 years ago
    The British Parliament, in its famed Longitude Act of 1714, set the highest bounty of all, naming a prize equal to a king’s ransom (several million dollars in today’s currency) for a Practicable and Useful means of determining longitude.
    Abby Lefeminehas quoted2 years ago
    In the course of their struggle to find longitude, scientists struck upon other discoveries that changed their view of the universe. These include the first accurate determinations of the weight of the Earth, the distance to the stars, and the speed of light.
    Abby Lefeminehas quoted2 years ago
    express purpose of determining longitude by the heavens.
    Abby Lefeminehas quoted2 years ago
    Renowned astronomers approached the longitude challenge by appealing to the clockwork universe: Galileo Galilei, Jean Dominique Cassini, Christiaan Huygens, Sir Isaac Newton, and Edmond Halley, of comet fame, all entreated the moon and stars for help.
    Abby Lefeminehas quoted2 years ago
    The active quest for a solution to the problem of longitude persisted over four centuries and across the whole continent of Europe.
    Abby Lefeminehas quoted2 years ago
    on October 22, 1707, at the Scilly Isles four homebound British warships ran aground and nearly two thousand men lost their lives.
    Abby Lefeminehas quoted2 years ago
    such clocks would slow down, or speed up, or stop running altogether.
    Abby Lefeminehas quoted2 years ago
    Precise knowledge of the hour in two different places at once—a longitude prerequisite so easily accessible today from any pair of cheap wristwatches—was utterly unattainable up to and including the era of pendulum clocks.
    Abby Lefeminehas quoted2 years ago
    At the Equator, where the girth of the Earth is greatest, fifteen degrees stretch fully one thousand miles. North or south of that line, however, the mileage value of each degree decreases. One degree of longitude equals four minutes of time the world over, but in terms of distance, one degree shrinks from sixty-eight miles at the Equator to virtually nothing at the poles.
    Abby Lefeminehas quoted2 years ago
    port clock, every hour’s discrepancy between them translates into another fifteen degrees of longitude.
    Abby Lefeminehas quoted2 years ago
    Every day at sea, when the navigator resets his ship’s clock to local noon when the sun reaches its highest point in the sky, and then consults the home-
    Abby Lefeminehas quoted2 years ago
    . Since the Earth takes twenty-four hours to complete one full revolution of three hundred sixty degrees, one hour marks one twenty-fourth of a spin, or fifteen degrees. And so each hour’s time difference between the ship and the starting point marks a progress of fifteen degrees of longitude to the east or west.
    Abby Lefeminehas quoted2 years ago
    To learn one’s longitude at sea, one needs to know what time it is aboard ship and also the time at the home port or another place of known longitude—at that very same moment.
    Abby Lefeminehas quoted2 years ago
    This difference makes finding latitude child’s play, and turns the determination of longitude, especially at sea, into an adult dilemma—one that stumped the wisest minds of the world for the better part of human history.
    Abby Lefeminehas quoted2 years ago
    ture, while the zero-degree meridian of longitude shifts like the sands of time.
    Abby Lefeminehas quoted2 years ago
    Here lies the real, hard-core difference between latitude and longitude—beyond the superficial difference in line direction that any child can see: The zero-degree parallel of latitude is fixed by the laws of na
    Abby Lefeminehas quoted2 years ago
    Likewise the Tropic of Cancer and the Tropic of Capricorn, two other famous parallels, assume their positions at the sun’s command. They mark the northern and southern boundaries of the sun’s apparent motion over the course of the year.
    Abby Lefeminehas quoted2 years ago
    while observing the motions of the heavenly bodies. The sun, moon, and planets pass almost directly overhead at the Equator.
    Abby Lefeminehas quoted2 years ago
    They loop from the North Pole to the South and back again in great circles of the same size, so they all converge at the ends of the Earth.
    Abby Lefeminehas quoted2 years ago
    The latitude lines, the parallels, really do stay parallel to each other as they girdle the globe from the Equator to the poles in a series of shrinking concentric rings.
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