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A History of Compasses
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The
first compass was invented in China two thousand years ago.
It was discovered by the Chinese magician Luan Te. He had a
board game similar to chess in which one of the game pieces
was a spoon. When he emptied the metal playing pieces onto the
board, the spoon would spin around until the handle was pointing
north. It didn't matter if it was night or day or where the
board was placed; the spoon handle always pointed north. What
did matter was what kind of metal the spoon was made out of.
His spoon was made from "tzu shih," or "loving stone," which
we know as lodestone. Lodestone is a magnetic iron ore found
in nature. Although all of Luan Te's game pieces were made of
lodestone, the spoon was able to spin because of its rounded
bottom and long handle.
Next, Chinese magicians made the turtle compass. This compass
consisted of a wooden turtle with a piece of lodestone in its
belly and an iron needle pushed through the tail end until it
hit the lodestone. When the turtle was balanced on a sharp piece
of bamboo, the needle would point north. It was soon discovered
that when a piece of iron was rubbed on the lodestone it would
become magnetized.
The first liquid compass was also invented by the Chinese. A
magnetized piece of iron shaped like a fish was floated in a
bowl of water. Compass makers then replaced the fish with a
floating needle, which showed the direction more clearly. Because
iron loses its magnetism, the Chinese began experimenting with
other metals and combinations of metals. They heated iron and
carbon together and made steel. Steel is stronger than iron
and less likely to rust. It also holds its magnetism for a very
long time.
The compass had come a long way from a lodestone spoon, but
there was still one problem: Lodestone was needed to magnetize
the steel needles. It was discovered in 1000 A.D., when steel
was being poured into a mold, that if the mold was aligned in
a north-south direction and the steel was cooled off immediately,
it would become permanently magnetized. It would become
a magnet. This happens because the steel is poured in line with
the earth's magnetic field and is cooled quickly. Lodestone
was no longer needed.
In over a thousand years, the liquid compass has changed very
little and is still used today. You can find liquid compasses
on boats, in cars, and carried by hikers. But there is still
one problem with the magnetic compass: It is not always accurate,
especially when near metal. At the North and South Poles such
compasses do not work at all. In the early 1900s, Elmer Sperry
invented the gyrocompass. The gyrocompass is not a magnetic
compass and is not affected by any of the factors that create
problems for a magnetic compass. A gyrocompass always points
north. It doesn't matter if you're in outer space, at the bottom
of the ocean under the North Pole in a submarine, or upside
down in an airplane; it always points north.
A gyrocompass has a wheel that is spun by an electric motor.
When a gyrocompass is set to point north, it holds that direction
as long as the motor is turned on. See if you can find out more
information on the gyrocompass in our links to online libraries.
And please e-mail the
professor to let him know what you find.
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