A cross section of the Kerr black hole spacetime. A light blue ellipse describes the ergosphere; its boundary is labeled the “Stationary Limit Surface.” A rotation axis divides this ellipse in half along its minor axis, so the bulge is equatorial. Inside the ellipse there are spherical inner and outer horizons which share the same axis. In the center is the ringlike singularity.

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1. Robert McNees (mcnees@mastodon.social)'s status on Wednesday, 26-Jul-2023 15:42:33 UTC Robert McNees

   in reply to

   Here is a “cross section” of a Kerr black hole.

   The ergosphere is the light blue region outside the horizon. One can move in and out of the ergosphere, but it is not possible to remain at rest once inside. One *must* move in the direction of the black hole’s rotation.

   (Note: When thinking about black holes, it is often a good idea to view relativity as describing rules for how and where things are allowed to move, rather than sticking with Newtonian ideas like forces and accelerations.)