The date the compass was first invented is unknown.
The ancient Greeks
knew about the attractive properties of magnetism. The oldest known reference to lodestone’s properties appeared in 600 BC, when the Greek philosopher Thales of Miletus noted iron’s attraction to it. Thales attempted to explain the phenomenon through 'animism', presuming that the lodestone possessed a 'soul'.
It is thought that
the Chinese were aware that you could magnetise an iron bar by stroking
it with lodestone (also spelt 'loadstone' ) as long as 2000 years ago. Lodestone appeared in China in divining boards used by fortune tellers to predict the future and in simple compasses for explorers.
Lodestone is a naturally occurring magnetic rock, a magnetic oxide of
iron. All varieties of magnetite display signs of magnetism, but of them, only lodestone possesses distinctly north-south polarity. That makes lodestone rare. Lodestone and other magnetic iron ores often occur in igneous and metamorphic rocks found around the world.
The word 'lode' means 'way', so a lodestone is literally a 'way
stone' as it shows you the way.
By the tenth century, the idea of using
iron magnetised in this way to determine direction had been brought to
Europe, probably from China, by Arab traders.
By the 12th century very
simple compasses were in use in the Mediterranean and despite the fact
that the magnetic compass was in general use in the Middle Ages, little
was known about precisely how it worked.
For more information on loadestone see this page in MagLab's site
What is a compass?
A compass consists of a freely suspended magnet, shaped like an arrow, positioned
in a case that has north, south, east and west marked on the base. The case is held horizontally and rotated until the point of the arrow is pointing to the 'North Pole' marking on the base.
A compass-arrow will point north
unless a strong magnetic field is overpowering the earth's field. Therefore when using a compass you should not be anywhere near a magnet or electromagnet.
If you put a magnet near a compass the compass-arrow
will point towards the magnet's south pole. This is because the arrow in the compass is a tiny magnet itself and....
LIKE poles REPEL
and
OPPOSITE poles ATTRACT
Click here to find out how we use compasses to plot a magnetic field
About this site
The compass
Click here
Lodestone is a naturally occurring magnetic rock, a magnetic oxide of
iron. All varieties of magnetite display signs of magnetism, but of them, only lodestone possesses distinctly north-south polarity. That makes lodestone rare. Lodestone and other magnetic iron ores often occur in igneous and metamorphic rocks found around the world.
