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Descriptions of black holes often include stories of a person falling through the event horizon. Since the physics inside the event horizon is dramatically different than outside the EH, are biological processes even possible inside? Can a human being remain conscious/alive after passing the event horizon?

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Since the physics inside the event horizon is dramatically different than outside the EH, are biological processes even possible inside?

The physics inside is not dramatically different. The equivalence principle says that the laws of physics operate in exactly the same way.

If you want a person to be able to stay alive for any given time $t$ inside the event horizon, then this can happen, provided that the black hole is big enough and doesn't have a violent accretion disk. They will have some maximum time they can live before they hit the singularity, and this time is proportional to the mass of the black hole.

For realistic astrophysical black holes, the person might be killed by radiation or tidal forces before or after reaching the event horizon.

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  • $\begingroup$ Thanks. I only have a superficial understanding. But for a person to remain conscious biological processes like blood flowing, neurochemicals passing around the brain, and such must continue. Are all the particles free to move about in such fashion after passing the event horizon? I was under the impression that the paths of each particle (much less the entire person) would no longer be so freely flowing. $\endgroup$
    – Chris
    Apr 8, 2019 at 23:40
  • $\begingroup$ It's worth mentioning that for a supermassive black hole like those found in the center of many galaxies, the tidal forces are weak enough at the horizon that a human could survive falling in. $\endgroup$
    – tparker
    Apr 8, 2019 at 23:55
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Locally, the laws of physics are exactly the same inside of a black hole (at least in classical general relativity; we don't really know how quantum mechanics modifies this picture). In fact, it is logically possible that the entire observable universe is inside of a really, really, really, really, really, really, really big black hole. If it were big enough, then we would have no way of noticing.

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