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Name: Sean M.
Status: other
Age: 15
Location: N/A
Country: N/A
Date: 7/14/2004


Question:
My question is involving the Earth's orbit of the Sun, but it is difficult to explain without using a drawing of some sort to describe it. Generally, when people picture the Earth orbiting the Sun, they picture the Sun as a stationary body in the center and the Earth rotating around at a constant speed. But as we know, the Sun is not stationary, as it is also moving throughout the Milky Way. Picture the Sun drawn towards the top of a piece of paper, and the Earth drawn just above it. Now, draw a dotted line in a circular path to the left side of the paper, and draw the sun again. Have this distance represent six months of motion for the Sun. Since it takes the Earth twelve months to make one full orbit around the sun, then six months would be one-half of an orbit. Since the Earth started as being drawn on top of the Sun at the beginning of this picture, it should end up being drawn below the Sun after the six months of motion. However, this would force the Earth to travel a much greater distance. And, for the Earth to make it back above the Sun in our drawing after another six months, the Sun would have the greater distance to travel. Can the Earth accelerate and decelerate throughout space? If so, it would have to give off some kind of energy, according to the Law of Conservation of Energy. It can not do work without expelling energy.


Replies:
Imagine that you are in an airplane in constant level flight. There is no experiment that you can do inside the airplane that would tell you if you were in motion or at rest. You behave as if all is at rest. The flight attendant does not call up to the pilot to ask her how fast she is flying the plane in order to figure out how to pour the coffee.

DO NOT DO THIS:

Take a yo-yo out and twirl it about your head at a constant rate. No problem. But the plane is moving! In your frame of reference, it is uniform circular motion. Someone on the ground would not see uniform circular motion, but rather some sort of cycloid or epicyclical motion.

So is the case with us orbiting the sun as the sun orbits the galactic center.

---Nathan A. Unterman



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