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StudyGuide3

# StudyGuide3 - Astronomy 309R Spring 2009 Study Guide to...

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1 Astronomy 309R – Spring 2009 Study Guide to Help Prepare for Exam 3 Please read chapters 6, 7, and 8 in Hawley & Holcomb, and the articles by Gray and by Luminet et al. that are assigned for homework. General relativity will be on the 3 rd exam, but black holes will only be on the 4 th exam. What is the Speed-of-Light Postulate? When we say that the speed of light is constant, what are we implying that the speed of light is independent of? (It is independent of the motion of the source of light and is also independent of the velocity of the observer.) What are caveats to the applicability of the Speed-of-Light Postulate? (When light propagates inside water, glass, or another transparent medium, its speed is reduced. This is a consequence of the interaction of light with the medium, and does not contradict special relativity.) Why can way also say that the constancy of the speed of light is a “fact”? (The constancy has been tested in numerous experiments.) What is the speed of light in vacuum, in meters per second, or other units, such as kilometers per second? [While the Wikipedia is unreliable in general , it has a nice article on the speed of light, please read it: http://en.wikipedia.org/wiki/Speed_of_light . You can also take a look in: http://en.wikipedia.org/wiki/History_of_special_relativity .] What is the statement of the Special principle of relativity (this is the other postulate of special relativity, in addition to the Speed-of-Light Postulate)? (The special principle of relativity is similar to the statement of Galilean invariance: All physical laws are the same to observers moving with respect to each other, and with respect to the universe as a whole, with constant velocities.) The special principle of relativity can be distinguished from the general principle of relativity, or the equivalence principle, which generalizes the statement about all physical laws being equal to freely falling observers. What is a reference frame ? (It is a system of coordinates, or a perspective, in relation to which the measurements of size, position, and motion can be made.) What are inertial frames ? (An inertial frame is a reference frame moving with constant velocity with respect to the universe; Newton’s laws of motion are applicable inside any inertial frame. Any inertial frame moves with constant velocity with respect to any other inertial frame. Constant velocity can include the zero velocity, that is, the absence of motion, as a special case.) What are the implications of the Speed-of-Light Postulate for simultaneity? (Two events that appear simultaneous to one observer may not appear simultaneous to another. Two events that are simultaneous to one observer will not appear simultaneous to any observer moving with finite velocity with respect to the first observer along the direction connecting the two events.)

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2 State and explain the Paradox of Spheres. (What is the formulation of the paradox? How does our abandoning of the intuitive notion of simultaneity, which states that events
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