Gravity increases with distance! Possiblities? [closed]

Question

So I was thinking of a world inside a black hole. In this inside black hole world, as you move from the event horizon to the center of the black hole gravity decreases. So you can enter the event horizon and survive but you can never escape it. Also there would be no singularity. The center would be a spherical body along with orbiting moons and mini suns. Is this possible if I introduce a repulsive force that is much stronger than gravity but decays much faster? If so how big can I make this world and have it still be possible? And would moons and mini suns be possible?

Answer 1

It is not a real black hole.

The entity which seems like a black hole because of its external appearance is actually a piece of technology; a built thing. The beings who made it used the thing to connect our universe to the pocket dimension where they reside, and then they went in. This thing, which looks like a black hole from the outside, has the qualities you want for your story on the inside. The pocket dimension is what you describe on the inside.

The reasons that these beings sequestered themselves in this pocket dimension can be dealt with in the story.

As regards other things that look like black holes, they are just black holes. Probably.

Answer 2

It's your story

As you can see in the comment section, there are a lot of theories about black holes. The difficult thing is that we cannot observe anything directly inside a black hole. We can infer a lot from observing indirect effects and 'normal' astrophysics physics, but the real answer is that we simply don't know.

A sort of solar system inside the black hole is highly unlikely. The amount of mass to create the black hole would need to be practically condensed to an area smaller than there is room for. If you go down the planets inside route, an extra repulsive force is just something minor to add to the whole of the story. Any theory as to why would be nearly equally plausible. Gluon quarks might be racting differently. The black hole might be so dense the weak force might start repelling. Spontaneous creation of a positive and negative particle that then cancel each other out happens so often inside a black hole that it starts repelling matter, but less and less towards the event horizon. Take your pick or grab any other semi plausible fringe science.

It might not be an answer you're hoping for, but it's the best I can give.

Answer 3

What you probably want is a Kerr-Newman black hole. When a black hole is spinning, the central singularity expands out into a ring, and if the black hole has a strong electric charge, the combined gravitational and electric force on a charged planet due to the black hole's charge counters that due to the mass in a region inside the ring singularity, creating an inner event horizon containing a pocket of 'normal' spacetime inside the black hole.

This paper discusses periodic orbits inside the inner region of a Kerr-Newman black hole (which are often not circular/elliptical, but precess wildly) and speculates in the abstract on entire civilisations hiding inside supermassive black holes.

I should mention, it's considered very unlikely that highly-charged Kerr-Newman black holes would form naturally, because the charge repels like charges and attracts unlike ones, causing the black hole to self-neutralise. And the interior geometry is mathematically idealised, and thought to be highly unstable to realistic distributions of infalling matter. You may need to hand-wave such difficulties away.

The Kerr-Newman black hole is interesting for other reasons, too. One is that like the non-rotating version (the Reissner–Nordström black hole) the 'maximal analytic extension' (translation: we extend the solution off the edges of the map where we're not sure the physics really applies) consists of an infinite ladder of universes. You can go into the black hole in one universe and pop out into the distant past of another universe. Another is that there may be 'closed time-like lines' (translation: a naturally existing time machine) that allows you to loop back in time, perform Turing-impossible infinite calculations, etc. If they exist, I'm sure they would be of great interest to advanced alien civilisations.

Answer 4

Yes... with some caveats.

To make a black hole you need a sufficiently large mass in a small enough radius, such that the Schwarzschild Radius of the body is larger than its radius. When you look at the math and start modelling things it turns out that you need extremely dense matter to pull this off. Even neutron stars aren't massive enough at their insane density to push their Schwarzschild Radius outside of the radius of the star itself.

So the first thing you're going to need is a material that is significantly more dense than pure neutronium. Perhaps you can find a way to control WIMPs and use them to pack a lot more mass into your contstruct. Or find some sort of field trickery to pack some other massive particles together. Maybe you just have some way of directly manipulating the Higgs Field to increase mass. How you do it is up to you, just as long as you can put enough mass in one place to get the job done.

Once you have that hyper-density material all you need now is to form enough of it into a large spherical shell. On the outside of the shell the gravity will be the same as for a solid sphere of the same mass and radius. The Schwarzschild Radius just needs to be larger than the shell's radius and you're a black hole. The fun part is that spherical shells have no gravity on the inside. Every point of the enclosed volume is affected by the entire mass of the shell, but it all cancels out. From the inner wall all the way to the center of the shell the net effect of all that mass cancels out, giving you a large volume with virtually no gravity at all.

Of course you now have a solid shell of the densest material ever created, so getting in and out is going to be a slight problem. You can't just make holes in the sphere since that will mess up the symmetry of the mass distribution and wreck your nice, peaceful interior. Any imbalance in the mass would cause tides and gravity, pushing anything on the inside towards the far wall, where it will probably fall prey to the immense mass and become a thin smear of degenerate matter.

One other issue is that nobody really knows what would happen to space inside a structure like this. Even though the forces are all balanced out, that's not the same as saying that they don't exist at all. If gravity is a result of the slope of curved space (the change in the curvature of space?) it seems plausable to think that mass produces some sort of stress on space itself. Balancing the mass distribution flattens out the curvature, but maybe the stress results in huge time dilation or some other side effect. If you're using wormholes to get in and out then you'll need to be careful about temporal tides... you don't want parts of your body running at different speeds.

There's a group of physicists right now working on using massive shells to manipulate time dilation, which they plan to use to send things (like people) on million-year journeys while slowing time for the contents so much that it seems faster. Maybe they can answer the question about what would happen inside this kind of construct.

Answer 5

It's your world, you make the rules

Do what you like. You are the god of your creation, you could make it happen. If you want a world inside a black hole, make it happen. May it be through space magic or through a technobabble device. If it makes that world possible it's pretty much explanation enough. Your device could be a counterforce to the destructive gravitational forces inside the event horizon. Even Star Trek does that trick: their transporters have a component that "compensates" for the Heisenberg Uncertainty Principle... which is completely bollocks, of course, but it works.

But a word about realism...

A world inside a black hole is not just highly unlikely, but at least close to impossible. Yes, we can't know what's going on inside a black hole, but that doesn't mean, that everything is possible. Despite its name a black hole is not really a hole. It's just a super heavy object of such a mass that it's messing with the curvature of space time. In fact, every large object (large = planet sized) has a perceivable influence on the curvature. Every object has this gravitational lens effect. Picture it as a hyper dense sphere rather than an actual hole.

So your depiction (intended as "sci-fi fantasy"), is pretty close to what black holes are seen like IRL (at least with the most recent theories). But moons? Or a solar system? Nah... The center is just too dense that more than just one single core could be possible.

How could this work?

Well, assumed you have that device running for millenia... built by that one ancient... blablabla... you know that trope... If a black hole prepared in such a way sucks other solar systems into its event horizon, those spatial bodies cannot escape... BUT because of that device those aren't sucked into the core rather just orbiting it.

Answer 6

No need for space magic..

There are already theories about all sorts of things. Coiled-up dimensions, and maybe some forces that act on different scales/dimensions. There may be Einstein-Rosen-Bridges, and connections to parallel universes, and then there are theories of many worlds..

Other than these more exotic theories, there's a already a fudge factor ("correction term") in General Relativity gravity models that is called dark matter / dark energy. IIRC it's basically repulsive. If that black hole had stabilized the hollow world by having sucked in some dark energy? That could be the way to traverse the event horizon without destructive tidal forces .. it's a rough ride across the event horizon on a lump of dark matter, surfing down the wave of dark energy....

And what could be neater than to make the hole even blacker by adding more dark energy.. and the rest of the universe gets a bit brighter :)