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1. Robert McNees (mcnees@mastodon.social)'s status on Tuesday, 14-Nov-2023 19:58:55 UTC Robert McNees

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   Outside the black hole (r > 2M) there are two sorts of radial null geodesics: light rays can follow a path that moves outward (towards larger r) or one that moves inward (towards smaller r).

   Inside (r < 2M) the two sorts of null geodesics both head inwards, towards smaller r.

   Notice that at each point along the infalling observer's worldline, they find themself inside a "light cone" defined by the two sort of radial null geodesics emitted at their previous location, the instant before.