At its introduction in 1915, the general theory of relativity did not have a solid empirical foundation. It was known that it correctly accounted for the "anomalous" precession of the perihelion of Mercury and on philosophical grounds it was considered satisfying that it was able to unify Newton's law of universal gravitation with special relativity. That light appeared to bend in gravitational fields in line with the predictions of general relativity was found in 1919 but it was not until a program of precision tests was started in 1959 that the various predictions of general relativity were tested to any further degree of accuracy in the weak gravitational field limit, severely limiting possible deviations from the theory. Beginning in 1974, Hulse, Taylor and others have studied the behaviour of binary pulsars experiencing much stronger gravitational fields than found in our solar system. Both in the weak field limit (as in our solar system) and with the stronger fields present in systems of binary pulsars the predictions of general relativity have been extremely well tested locally.
On the largest spatial scales, such as galactic and cosmological scales, general relativity has not yet been subject to precision tests. Some have interpreted observations supporting the presence of dark matter and dark energy as a failure of general relativity at large distances, small accelerations, or small curvatures. The very strong gravitational fields that must be present close to black holes, especially those supermassive black holes which are thought to power active galactic nuclei and the more active quasars, belong to a field of intense active research. Observations of these quasars and active galactic nuclei are difficult, and the interpretation of the observations are heavily dependent upon astrophysical models other than general relativity or competing fundamental theories of gravitation, but they are qualitatively consistent with the black hole concept as modeled in general relativity.
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Q. I'm planning to take the physics gre, and i would like to know what's the best way to prepare. I've been told by friends who have taken the exam that a sound and thorough understanding of General Physics (from a general physics textbook which covers all areas of physics in general) is more than enough to get a high score in the physics subject tests (700+) and that studying entire texts which focus exclusively on one specialized topic (either quantum.. atomic..or.. relativity, etc..) may actually hurt my preparation. Of course, a much broader consensus would be preferred...so please help...opinions are welcome!
Asked by kwame - Sun Apr 20 17:54:52 2008 - - 1 Answers - 0 Comments
A. The first thing you want to do is get your hands on the 4 old physics GRE tests that are available. The answers and solutions are also available. (Whatever you do, don't buy the purple REA physics GRE test book, the questions there are far harder than the real questions). I suggest taking one of the tests under test conditions. Grade yourself and see which sections you do well in. Work through every single problem on the test. Repeat with the others at various points in your study. Your friends are right, it's better to have a broad understanding then spend a lot of time on a specific topic. The questions individually aren't that hard, it's simply that they cover such a broad range of topics. Memorize the solutions to the basic… [cont.]
Answered by PhysicsGirl - Sun Apr 20 20:53:36 2008
