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Forum List  Follow Ups  Post Message  Back to Thread Topics  In Response To Posted by Bruce on February 10, 2002 22:26:52 UTC 
There are several perspectives which are very different. I will mention three. The remote observer, the local shell observer, and the remote observer observing from a proper frame. The remote observer is the 'GR bookkeeper who is at rest in flat spacetime far away from M' who will use the ticks on her (you) clock and, coordinate time dt, to observe the astronaut falling radially towards the black hole. The local shell observer at rest on a spherical shell (which encircles the black hole at constant r but outside the event horizon) uses his (your husband) clock, local shell time dtshell, to observe the astronaut as the astronaut crosses over a local spherical shell of constant r. And finally the remote observer (me)observing from a proper frame who uses the proper wristwatch time (dt) of the falling astronaut to observe the falling astronaut motion inside and outside the black hole. This is really a unique perspective because it allows us to observe the falling astronaut even after he is no longer causally connected to our universe (he crossed over the event horizon. Of course this is speculative but the calculations are fundamentally based on Einstein's theory of gravity, general relativity). The following equations are simple to use and they are derived from the Schwarzchild metric which was the first solution to Einstein's field equations and are based on an idealized nonspinning spherically symmetric black hole. M in the equations is mass converted to units of length (meters) where one solar mass = 1477 meters. This means for a solar mass black hole the singularity is at r = 0 and the event horizon is r = 2M (2954 meters) and the photon sphere is r = 3M (4431 meters), etc.. The curvature term in these equations is (12M/r).


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