MadSci Network: Physics |
If I understand Dan Mayer's response correctly, I think that he was making an analogy comparing the greater complexity of the sphere of the earth to a simple circle (a slice through the equator). That being said, the "excess radius" would be caused by the fact that the earth is not a perfect sphere. Using the volume or surface area equations that he gave, and solving for 'R'(using the actual surface area (or volume) of the earth)would give the AVERAGE RADIUS of the earth. The actual radius of the earth, say, in the town where you live, would of course be a length from the surface to the exact center of the earth. This radius would change from locations north or south of this spot. This is because the 'sphere' of the earth bulges at the equator. If you took the AVERAGE radius of the earth, measured from all spots on the surface, and used this value for 'R' in the equation he gave for surface area: Area = 4 pi R ^2 , the numbers should equal out with no "excess radius" I hope that this makes it a little clearer. Jay Shapiro
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