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CHAPTER ONE
Imaginary Lines
When I'm playful Is use the meridians of longitude
and parallels of latitude for a seine, and drag the
Atlantic Ocean for whales.
--MARK TWAIN, Life on the Mississippi
Once on a Wednesday excursion when I
was a little girl, my father bought me a
beaded wire ball that I loved. At a
touch, I could collapse the toy into a flat
coil between my palms, or pop it open to make a hollow
sphere. Rounded out, it resembled a tiny Earth,
because its hinged wires traced the same pattern of
intersecting circles that I had seen on the globe in my
schoolroom--the thin black lines of latitude and longitude.
The few colored beads slid along the wire
paths haphazardly, like ships on the high seas.
My father strode up Fifth Avenue to Rockefeller
Center with me on his shoulders, and we stopped to
stare at the statue of Atlas, carrying Heaven and Earth
on his.
The bronze orb that Atlas held aloft, like the wire
toy in my hands, was a see-through world, defined by
imaginary lines. The Equator. The Ecliptic. The Tropic
of Cancer. The Tropic of Capricorn. The Arctic Circle.
The prime meridian. Even then I could recognize,
in the graph-paper grid imposed on the globe, a powerful
symbol of all the real lands and waters on the
planet.
Today, the latitude and longitude lines govern
with more authority than I could have imagined forty-odd
years ago, for they stay fixed as the world changes
its configuration underneath them--with continents
adrift across a widening sea, and national boundaries
repeatedly redrawn by war or peace.
As a child, I learned the trick for remembering the
difference between latitude and longitude. 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. The meridians
of longitude go the other way: 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.
Lines of latitude and longitude began crisscrossing
our worldview in ancient times, at least three centuries
before the birth of Christ. By A.D. 150, the cartographer
and astronomer Ptolemy had plotted them on
the twenty-seven maps of his first world atlas. Also
for this landmark volume, Ptolemy listed all the place
names in an index, in alphabetical order, with the latitude
and longitude of each--as well as he could gauge
them from travelers' reports. Ptolemy himself had
only an armchair appreciation of the wider world. A
common misconception of his day held that anyone
living below the Equator would melt into deformity
from the horrible heat.
The Equator marked the zero-degree parallel of
latitude for Ptolemy. He did not choose it arbitrarily
but took it on higher authority from his predecessors,
who had derived it from nature while observing the
motions of the heavenly bodies. The sun, moon, and
planets pass almost directly overhead at the Equator.
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.
Ptolemy was free, however, to lay his prime meridian,
the zero-degree longitude line, wherever he
liked. He chose to run it through the Fortunate Islands
(now called the Canary & Madeira Islands) off the
northwest coast of Africa. Later mapmakers moved
the prime meridian to the Azores and to the Cape
Verde Islands, as well as to Rome, Copenhagen, Jerusalem,
St. Petersburg, Pisa, Paris, and Philadelphia,
among other places, before it settled down at last in
London. As the world turns, any line drawn from pole
to pole may serve as well as any other for a starting
line of reference. The placement of the prime meridian
is a purely political decision.
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 nature,
while the zero-degree meridian of longitude
shifts like the sands of time. 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.
Any sailor worth his salt can gauge his latitude well
enough by the length of the day, or by the height of
the sun or known guide stars above the horizon. Christopher
Columbus followed a straight path across the
Atlantic when he "sailed the parallel" on his 1492
journey, and the technique would doubtless have carried
him to the Indies had not the Americas intervened.
The measurement of longitude meridians, in comparison,
is tempered by time. 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. The
two clock times enable the navigator to convert the
hour difference into a geographical separation. 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. 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-port clock, every hour's
discrepancy between them translates into another fifteen
degrees of longitude.
Those same fifteen degrees of longitude also correspond
to a distance traveled. 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.
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. On the deck of a rolling ship,
such clocks would slow down, or speed up, or stop
running altogether. Normal changes in temperature
encountered en route from a cold country of origin to
a tropical trade zone thinned or thickened a clock's
lubricating oil and made its metal parts expand or contract
with equally disastrous results. A rise or fall in
barometric pressure, or the subtle variations in the
Earth's gravity from one latitude to another, could
also cause a clock to gain or lose time.
For lack of a practical method of determining longitude,
every great captain in the Age of Exploration
became lost at sea despite the best available charts
and compasses. From Vasco da Gama to Vasco Nunez
de Balboa, from Ferdinand Magellan to Sir Francis
Drake--they all got where they were going willy-nilly,
by forces attributed to good luck or the grace of God.
As more and more sailing vessels set out to conquer
or explore new territories, to wage war, or to
ferry gold and commodities between foreign lands,
the wealth of nations floated upon the oceans. And
still no ship owned a reliable means for establishing
her whereabouts. In consequence, untold numbers of
sailors died when their destinations suddenly loomed
out of the sea and took them by surprise. In a single
such accident, on October 22, 1707, at the Scilly Isles
near the southwestern tip of England, four homebound
British warships ran aground and nearly two
thousand men lost their lives.
The active quest for a solution to the problem of
longitude persisted over four centuries and across the
whole continent of Europe. Most crowned heads of
state eventually played a part in the longitude story,
notably King George III of England and King Louis
XIV of France. Seafaring men such as Captain William
Bligh of the Bounty and the great circumnavigator
Captain James Cook, who made three long voyages
of exploration and experimentation before his violent
death in Hawaii, took the more promising methods to
sea to test their accuracy and practicability.
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. Palatial observatories were founded at Paris,
London, and Berlin for the express purpose of determining
longitude by the heavens. Meanwhile, lesser
minds devised schemes that depended on the yelps
of wounded dogs, or the cannon blasts of signal
ships strategically anchored--somehow--on the open
ocean.
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.
As time passed and no method proved successful,
the search for a solution to the longitude problem assumed
legendary proportions, on a par with discovering
the Fountain of Youth, the secret of perpetual
motion, or the formula for transforming lead into
gold. The governments of the great maritime nations--including
Spain, the Netherlands, and certain
city-states of Italy--periodically roiled the fervor by
offering jackpot purses for a workable method. 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.
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.
Harrison, a man of simple birth and high intelligence,
crossed swords with the leading lights of his
day. He made a special enemy of the Reverend Nevil
Maskelyne, the fifth astronomer royal, who contested
his claim to the coveted prize money, and whose tactics
at certain junctures can only be described as foul
play.
With no formal education or apprenticeship to any
watchmaker, Harrison nevertheless constructed a series
of virtually friction-free clocks that required no
lubrication and no cleaning, that were made from materials
impervious to rust, and that kept their moving
parts perfectly balanced in relation to one another, regardless
of how the world pitched or tossed about
them. He did away with the pendulum, and he combined
different metals inside his works in such a way
that when one component expanded or contracted
with changes in temperature, the other counteracted
the change and kept the clock's rate constant.
His every success, however, was parried by members
of the scientific elite, who distrusted Harrison's
magic box. The commissioners charged with awarding
the longitude prize--Nevil Maskelyne among them--changed
the contest rules whenever they saw fit, so as
to favor the chances of astronomers over the likes of
Harrison and his fellow "mechanics." But the utility
and accuracy of Harrison's approach triumphed in the
end. His followers shepherded Harrison's intricate,
exquisite invention through the design modifications
that enabled it to be mass produced and enjoy wide
use.
An aged, exhausted Harrison, taken under the
wing of King George III, ultimately claimed his rightful
monetary reward in 1773-after forty struggling
years of political intrigue, international warfare, academic
backbiting, scientific revolution, and economic
upheaval.
All these threads, and more, entwine in the lines
of longitude. To unravel them now--to retrace their
story in an age when a network of geostationary satellites
can nail down a ship's position within a few feet
in just a moment or two--is to see the globe anew.
