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Unformatted text preview: planets appear as points of light in the sky, and we have no direct way of knowing how far away they are. We can specify their position by giving angles that define a direction -- the direction for pointing to them. Motion means moving from one angular position to another, and the amount that the object moves is given as an angle. The "speed" of the motion is how fast its angular position changes. It would be given in degrees per second (or per year). [If somebody was in front of you and then moved to the right side of you, his angular position would have changed by 90 degrees. If this took place in 5 seconds, the angular speed would be 90/5 = 18 degrees per second.]...
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- Fall '10