TransWikia.com

No apparent horizon in a Schwarzschild black hole?

Physics Asked on May 11, 2021

Wikipedia claims (Apparent horizon):

it is possible to slice the Schwarzschild geometry in such a way that there is no apparent horizon, ever, despite the fact that there is certainly an event horizon.

Can anyone please clarify what exactly this slicing is? How should one slice the Schwarzschild spacetime in such a way that there is no apparent horizon ever?

One Answer

An apparent horizon is the boundary between radially outwards directed photons that fall in before they reach you and those which do reach you. If you are in the frame of an external stationary observer rays on the horizon never reach you, as you can see in Droste coordinates. But if you transform to the frame of an infalling observer, the rays at the horizon do reach you when you fall through it, which can be seen in Raindrop coordinates, where the grr component of the metric tensor is not 0 anymore. For the transformation from Droste to Raindrop click here, but there is still a horizon - just not an apparent one. So you can still see your feet when you fall into a black hole, but the light they emitted after they crossed the horizon will only reach your eyes after your head crossed the horizon too.

Answered by Gendergaga on May 11, 2021

Add your own answers!

Ask a Question

Get help from others!

© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP