this post was submitted on 03 May 2024
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Science Memes

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[–] [email protected] 25 points 11 months ago (5 children)

Or that the observable universe could be inside of a black hole. Don't watch too many black hole videos before bed.

Planet 9 is not a primordial black hole and it can't hurt you. πŸ™€

[–] [email protected] 14 points 11 months ago (1 children)

From my understanding of primordial black holes, if one were so close as to be in our solar system, it is very small.

Since it's so small, it would have fizzled out through hawking radiation output a long time ago.

So yes, planet 9 is NOT a black hole that can hurt you.

Now, a pocket of warped spacetime that will one day spawn a Chaos Demon? Maybe.

[–] [email protected] 9 points 11 months ago (2 children)

I thought I heard once that our universe could be a holographic projection on a 2D plane surrounding around a black hole.

Don't ask me for any details further than that, because I do not remember.

[–] [email protected] 14 points 11 months ago

There was an episode of PBS Space Time on the holographic principle in general recently, and I believe they've also discussed the black hole thing as well.

[–] [email protected] 6 points 11 months ago

If it's a block hole, it doesn't really matter. A black hole is not more dangerous than a planet with the same mass, it has the same gravity. The only difference is that it's much tinier. If planet 9 is a black hole, it's so small that Sun has stronger gravity (and bigger mass), meaning it's bound to rotate around the Sun the same way every other large body in the Solar system is.

Planet 9 maybe is or isn't a primordial black hole and it won't hurt you.

[–] [email protected] 3 points 11 months ago (1 children)

IIRC, isn't it closer to a white hole, what with expansion? If you were far enough away, you cannot reach 'there' vs being guaranteed to reach 'there' like a black hole. Though really, it's neither. Just curved spacetime.

The fact we think of white holes and black holes as separate entities just goes to show our great lack of understanding of spacetime.

[–] [email protected] 1 points 11 months ago

My understanding is its similar in difference to a protostar and a nova

[–] [email protected] 2 points 11 months ago* (last edited 11 months ago)

I mean, Schwarzschild radius shows that for a medium of constant density (and on a large scale, Universe is fairly uniform) there is an upper limit of a radius of a ball comprised of said medium above which it will form an event horizon.

https://en.wikipedia.org/wiki/Schwarzschild_radius#Calculating_the_maximum_volume_and_radius_possible_given_a_density_before_a_black_hole_forms

Which means that an infinite universe of non-zero density is either a bloody paradox (spend a minute deciding where exactly event horizons should form and whether there will be gaps), or our understanding of gravity and spacetime breaks on ginormous scales just as it does on micro ones.

PS: I have seen no physicists talk about this, so there’s a good chance that there’s a simple resolution to the problem and I’m just stupid.