Teen Homework Help
In 1821, Mexico finally won its independence from Spain after a long war. It was a lot like the American Revolution against Britain; heroic generals led an army of poor, brave farmers against the Spanish army and by sheer guts wore the Spanish down. The constitution written in 1824 even called the new nation the United States of Mexico. It was larger than the United States, covering all of modern Mexico plus the western third of the modern United States.
Manassas. Fredericksburg. Chancellorsville. Richmond. Appomattox.
In these places and dozens of others, some too far away from civilization to be remembered, the sound of rifles and the drumming of hoofbeats echoed through the valleys and tore apart towns as the armies of North and South engaged in the terrible conflict that was the Civil War.
What do the Earth, electric motors, and your computer all have in common?
These things are all influenced by magnets.
The Earth has a liquid metal core that acts like a bar magnet. It gets its magnetism from being near electrical currents beneath the surface. Because the Earth is not perfectly shaped, every so often the direction of the field will change. Scientists have found evidence that this has occurred at least 171 times over the past 71 million years. How do they know that? Magnets!
In the summer of 1942, the Japanese were winning their war with the United States. They had sunk or crippled America's battleship fleet at Pearl Harbor, and snapped up a chain of islands across the Pacific which could, if fortified, form an impenetrable barrier to the U.S. Navy. Now the Imperial Japanese Navy was looking for a knockout blow, to destroy the American aircraft carriers before American industry replaced its losses.