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Up to this point we have
been making the assumption that the Earth spins instead of the Celestial Sphere. Why
are we justified in making such an assumption. We know that the Earth is big! This
fact makes a powerful arguement first put forth by Aristotle that the Earth is just to big
to move. However, others such as Heraclides Ponticus and Pythagoreas believed that
if the rotated much of the motions of the heavens would be easier to explain. Besides the ancient greeks the first people to suspect that the Earth was rotating was gunners. They observed that their projectiles were not hitting their targets when they were shooting over long distances. This effect is called the Corrolis effect, after the Frech engineer who explained it. To understand the corrolis effect lets consider launching a missle at New York from the equator. Lets also say that we are due south of New York. The missle will miss New York by a number of miles because while the missle was in the air the Earth rotated westward underneath the missle so the missle misses New York! Do you know if the missle hits to the West or the East of New York? Well, at the equator the Earth is rotating much faster than it is anywhere else. So when the missle is launched it will have a greater Eastward velocity than it does when it reach the latitude of New York, so the missle will hit to the East of the New York. What do you think is the rotational speed of someone standing at the north Pole? The Corrolis effect is also responsible for the rotation of hurricanes as well as low and high pressure systems. For example, in the northern hemisphere a hurricane rotates clockwise and in the southern hemisphere a hurricane rotates counter-clockwise. Why are they different? Lastly, it is important to note that the Corrolis effect does not prove that the Earth rotates. However, the simplist and most logical exlanation for the effect is that the Earth rotates from East to West. |