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Old 12-June-2008, 09:36 PM
Chris Hillman Chris Hillman is offline
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Default Multilayered structure of available theories

Quote:
Originally Posted by rcglinsk View Post
How do we know how the orbital mechanics of the situation work? Why would keppler's law necessarily apply in contexts it was not created in?
I often use "quasi-Keplerian" to refer to the textbook analysis of test-particle motion in a strong field situation, e.g. in a model such as the Schwazschild vacuum solution. This is justified because it turns out that, as was first shown by Einstein himeslf, we can analyze such scenarios using standard perturbation theory. That is, we approximate the motion as a perturbation of Keplerian motion.

More generally, there is a very well-established formalism, Post-Newtonian formalism, for studying quite general scenarios by using the fundamental laws of gtr to obtain a kind of power series representing the scenario as a perturbation from a correspoding Newtonian scenario.

Quote:
Originally Posted by rcglinsk View Post
How do we know that the pulse from a pulsar means an object is spinning?
This is one of those situations where sending someone to Wikipedia might be appropriate. Ask again if WP doesn't help.
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Read these PF posts. Avoid Wikipedia--- except for these versions. Read this and this suggested sticky. When asked for advice, I always say: never take advice!
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