Compass: Which Way is North?
c2634 BC
-2634 -2634
120.00E39.00N
SCI

CHINA
	If you need to go east through the woods, but there are no signs telling you the way, a compass can sure come in handy.
	A compass is a magnetized needle pivoted in the middle so it can swing freely in a case. Since the earth has a magnetic field, the small compass magnet swings around to point toward the earth's magnetic north.
	So, if you want to go east, move the compass so North on the case aligns with the north end of the needle, then look at the case and see which way is east.
	Actually, it's not quite that simple, since magnetic north isn't always true north. But for compass navigation buffs, there are maps that tell how to correct for the error.
	The first people to use magnetic compasses were probably Chinese sailors, who may have floated magnetized needles on pads of straw or cork.
	Magnetic compasses were once used on wooden ships, but the metal of modern ships interferes with the earth's magnetism, so they use gyroscopic compasses.
	Gyroscopic compasses are based on the tendency of a spinning wheel to resist changes of direction. A wheel, or "gyroscope," is mounted so it can swivel in all directions, so no matter which way the ship turns, the gyroscope continues to point the same way.