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Compasses
compass
"A person standing in prayer should direct his or her heart toward Jerusalem."
Berakhot 30a
POLAR OPPOSITES
  • The magnetic North Pole indicated by a compass is actually 1,400 miles away from the geographic North Pole.
  • The first known compass was made in China over a thousand years ago.
  • Scientists believe that the Earth's magnetic field flips its north and south poles every few tens of thousands of years.
OPPOSITES ATTRACT
Long before GPS satellites were invented, humans relied on compasses to navigate on land. A compass's needle always points north, so a traveler can easily figure out which way to go.
 
A compass works because of magnetism. As it turns out, the Earth's inside is like an enormous magnet. According to one theory, this is because its core is filled with super-hot molten (melted) iron under extreme pressure, which forces it to form into crystals. As a result of the heat radiating from the Earth's core and the Earth's rotation, this iron turns in a rotating pattern, creating magnetic forces. If you think of the Earth as having a giant magnet buried inside of it, then one end of the magnet would be near the North Pole.
 

Since a compass's needle is actually a small magnet itself, it is drawn to the Earth's inner magnet. The principle of "opposites attract" tells us that the south end of the needle is attracted to the North Pole (or close to it) and turns itself in that direction.

The magnetic field has to travel nearly 4,000 miles from the Earth's core to its surface, making it pretty weak by the time it reaches a compass. Therefore, the needle on a compass must be a very light magnet that balances and rotates on a frictionless point (free of anything that would hold it back from moving easily); the magnetic field just isn't strong enough to move the needle otherwise.

THE RIGHT DIRECTION
Even though the Earth’s magnetic field pulls a compass needle to point north, there’s one compass that seems to defy the laws of nature. A recent invention, the “Jerusalem Compass” was designed to point toward the holy city from anywhere in the world. It’s a useful product because, since Biblical times, Jews have always prayed facing the direction of Jerusalem and the beit hamikdash. In a synagogue, the aron kodesh (holy ark), which houses the Torah scrolls, faces Jerusalem. And in private homes (in cities west of Jerusalem, such as in North America), a beautiful mizrah (“east”) sign adorns the eastern wall to indicate which way to direct our prayers—to Jerusalem in the east, the city that God chose.

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How Compasses Work