More on this book
Community
Kindle Notes & Highlights
by
Dava Sobel
A boat ride down the Thames from Westminster to Greenwich is a tour through time. Two millennia of history reside along the river's banks from the Roman port of Londinium through the Saxon years.
The zero-degree parallel of latitude is fixed by the laws of nature, while the zero-degree meridian of longitude shifts like the sands of time.
Palatial observatories were founded at Paris, London, and Berlin for the express purpose of determining longitude by the heavens.
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.
English clockmaker John Harrison, a mechanical genius who pioneered the science of portable precision timekeeping, devoted his life to this quest. He accomplished what Newton had feared was impossible: He invented a clock that would carry the true time from the home port, like an eternal flame, to any remote corner of the world.
They that go down to the Sea in Ships, that do business in great waters, these see the works of the Lord, and His wonders in the deep. —Psalm 107
Forced to navigate by latitude alone, whaling ships, merchant ships, warships, and pirate ships all clustered along well-trafficked routes, where they fell prey to one another.
The moon travels a distance roughly equal to its own width every hour.
Galileo himself conceded that, even on land, the pounding of one’s heart could cause the whole of Jupiter to jump out of the telescope’s field of view.
Galileo’s method for finding longitude at last became generally accepted after 1650—but only on land. Surveyors and cartographers used Galileo’s technique to redraw the world. And it was in the arena of mapmaking that the ability to determine longitude won its first great victory.
Indeed, King Louis XIV of France, confronted with a revised map of his domain based on accurate longitude measurements, reportedly complained that he was losing more territory to his astronomers than to his enemies.
Roemer used the departures from predicted eclipse times to measure the speed of light for the first time in 1676. (He slightly underestimated the accepted modern value of 300,000 kilometers per second.)
King Charles II, head of the largest merchant fleet in the world, felt the urgency of the longitude problem acutely,
Christopher Wren, architect of St. Paul’s Cathedral.
Thus the founding philosophy of the Royal Observatory, like that of the Paris Observatory before it, viewed astronomy as a means to an end. All the far-flung stars must be cataloged, so as to chart a course for sailors over the oceans of the Earth.
Even when the bulbs of the hourglass shatter, when darkness withholds the shadow from the sundial, when the mainspring winds down so far that the clock hands hold still as death, time itself keeps on.
In the wake of the Longitude Act, the concept of “discovering the longitude” became a synonym for attempting the impossible.
We take no note of solar time today, relying solely on Greenwich mean time as our standard,
The tower clock that Harrison completed about 1722 still tells time in Brocklesby Park. It has been running continuously for more than 270 years— except for a brief period in 1884 when workers stopped it for refurbishing.
(Under microscopic examination, growth rings resemble a honeycomb with hollows, while the new wood between the rings seems solid.)
The decorated face clashes with the skeletal works—the way a well-dressed woman might look if she stood behind an imaging screen that bared her beating heart.
In this fashion, astronomers built one of the three pillars supporting the lunar distance method: They established the positions of the stars and studied the motion of the moon.
As it was, Harrison stood alone against the vested navigational interests of the scientific establishment.
Rome wasn’t built in a day, they say. Even a small part of Rome, the Sistine Chapel, took eight years to construct, plus another eleven years to decorate, with Michelangelo sprawled atop his scaffolding from 1508 to 1512, frescoing scenes from the Old Testament on the ceiling. Fourteen years passed from the conception to the completion of the Statue of Liberty. The carving of the Mount Rushmore Monument likewise spanned a period of fourteen years. The Suez and Panama Canals each took about ten years to excavate, and it was arguably ten years from the decision to put a man on the moon to the
...more
some modern horologists claim that Harrison’s work facilitated England’s mastery over the oceans, and thereby led to the creation of the British Empire—for it was by dint of the chronometer that Britannia ruled the waves.
“The machine used for measuring time at sea is here named chronometer,” Dalrymple explained, “[as] so valuable a machine deserves to be known by a name instead of a definition.”
Thomas Earnshaw, who ushered in the age of the truly modern chronometer. Earnshaw reduced Harrison’s complexity and Arnold’s prolificacy to an almost platonic essence of chronometer.
Mudge won lasting acclaim for his lever escapement, which appeared in nearly all mechanical wrist- and pocket watches manufactured through the middle of the twentieth century, including the famous Ingersoll dollar watch, the original Mickey Mouse watch, and the early Timex watches.
In comparison tests, chronometers proved themselves an order of magnitude more precise than lunars, primarily because they were simpler to use.
Thus the total world census of marine timekeepers grew from just one in 1737 to approximately five thousand instruments by 1815.
Big surveying ships might carry as many as forty chronometers.
In 1860, when the Royal Navy counted fewer than two hundred ships on all seven seas, it owned close to eight hundred chronometers. Clearly, this was an idea whose time had come.
It’s paved right into the courtyard of the Old a Royal Observatory at Greenwich.
Nevil Maskelyne, fifth astronomer royal, brought the prime meridian to this location, seven miles from the heart of London.
Since time is longitude and longitude time, the Old Royal Observatory is also the keeper of the stroke of midnight.
Astronomers use GMT to time predictions and observations, except that they call it Universal Time, or UT, in their celestial calendars.
Half a century before the entire world population began taking its time cues from Greenwich, the observatory officials provided a visual signal from the top of Flamsteed House to ships in the Thames. When naval captains were anchored on the river, they could set their chronometers by the dropping of a ball every day at thirteen hundred hours—1 P.M.
At one o’clock, the ball drops, like a fireman descending a very short pole. Nothing about the motion even suggests high technology or precision timekeeping. Yet it was this ball and other time balls and time guns at ports around the world that finally gave mariners a way to reckon their chronometers— without resorting to lunars more than once every few weeks at sea.
He wrested the world’s whereabouts from the stars, and locked the secret in a pocket watch.
