I know that currently, black hole civilizations are only theoretical. But here are my thoughts on why black hole civilizations are impossible.

Black Hole Civilization Issues

1. Gravity

This is an obvious issue. There is just so much gravity around a black hole. The closest you could get to a black hole without having a weirdly shaped orbit would be 3 times the radius of the black hole or in other words 3 times the size of the event horizon. This changes if the black hole is rotating as pretty much all black holes are but still, that is pretty far. Also, it is very unlikely that a planet would form around a black hole because the gravity is so strong.

But even if you could get closer than 3 times the size of the event horizon, there is another gravitational effect that would get you long before you reach $r_{isco}$. That is tides. The average tidal range on earth is 2 feet or .6 meters. Around a black hole, this would increase by an unimaginable amount. The radius at which tidal forces wouldn't significantly effect you is way bigger than $r_{isco}$. So big in fact, that the planet would most likely have to be a rogue planet just passing by in order to survive near a black hole. That or be made out of something very dense like metal which wouldn't be effected by tidal forces as much as rock would. But a planet made entirely out of metal poses more issues including magnetism which is already an issue with the black hole itself.

2. Magnetic Field

The main problem with the black hole's magnetic field is simply the strength of it. A neutron star can erase your credit card before the neutron star is even visible to your eyes. The magnetic field of a black hole is even stronger, just like the gravity being stronger. Anything magnetic or that relies on magnets would stop working before the planet is even in orbit. If you assume the planet is made entirely out of metal, this black hole magnetic field would cause there to be a strong electric field around the planet which in turn would cause there to be a strong magnetic field. This planetary magnetic field would align with the black hole magnetic field and be yet another reason the planet wouldn't survive. The magnetic force would be so great that it together with the tidal force would spaghettify the planet and anything on it. And even if the force didn't tear the planet to shreds, you would still have the planet move towards the black hole like 1 magnet attracting another magnet.

3. Radiation

Now, I'm not talking about Hawking radiation here. I am talking about the radiation that occurs near a black hole because of fast moving particles. There are jets of radiation at the poles of the black hole. But that isn't the only radiation there is. There is also an almost constant amount of radiation due to particles orbiting the black hole. Any civilization that could survive the gravity and magnetism surely wouldn't survive the radiation. I mean, just think about it. The radiation around a black hole is like a constant amount of gamma rays. And yes, it is gamma rays because the black hole acts like a particle accelerator releasing a lot of very high energy photons. Sure, the gravitational redshift might shift it to X rays but still, a lot of radiation at very high energies. There is no way a civilization could survive black hole level radiation or even neutron star level radiation because even with the planetary magnetic field, it just isn't enough for radiation protection. Total extinction would result, even microbes wouldn't survive, and civilization would be impossible.

But is my reasoning true? Or is it possible for a black hole civilization to survive?

posted over 5 years ago

Caters‭

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