# Repulsive black holes [closed]

Assume that somehow negative mass could exist. Each "normal" particle that we know of has a negative mass equivalent but with all other properties the same (including charges). As a result, negative photons exist as well as negative energies and forces. Unless another force cancels it out negative matter attracts negative matter and negative matter repels positive matter. Objects with no mass are their own negative particle. In order to conserve mass and energy, negative matter, when touching its normal equivalent will produce a net of no energy (it may produce a normal energy and equal negative energy).

With this mass star like objects could form star-like objects in which these negative masses are flung together at high enough velocity that the strong (negative baryons and negative mesons) and electromagnetic (negative protons and negative electrons) forces make them bond. These particles, because of their negative mass, attract each other (the signs cancel out).

Normal matter, with enough acceleration, could accumulate in the center of these "stars" pulling more matter in. At some critical point, the mass pulls the negative mass in towards the center which dispels the normal mass. Then, because of strong and gravitational forces, is held together while the center makes a negative matter black hole anagram (because that's so large I'm going to call it a nmbha).

What I know:

1.) nmbhas should behave like a black hole with normal negative matter,

2.) nmbhas repel normal matter, and

3.) from those two there should be a negative event horizon, that although "naked" to us would not be naked to negative matter.

So:

1.) How do objects approaching a nmbha act?

2.) How does light bend around a nmbha?

3.) What critical point of mass to negative mass does the "star" begin? And

4.) What would happen if nmbhas got close to a black hole?

(p.s. this is hard science because I would like to see how these values affect the equations)

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## closed as unclear what you're asking by J_F_B_M, The Anathema, AndreiROM, Brythan, HohmannfanMar 27 '16 at 16:46

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• Hi tox123, sadly I have troubles to understand your question. Your second sentences seems to say that starlike objects can create starlike objects that (via forces) bond negative mass. These bonded particles repel each other. Why wouldn't they repel each other before? Do they repel positive matter? Next part: If kinetic forces get high, things tend to explode and scatter instead of accumulate. You not only have particles pushing everywhere when colliding, but they actually push themselves around just by being I don't see how (with hard-science) you want to get an answer to that? – J_F_B_M Mar 27 '16 at 15:37
• @J_F_B_M I edited it, is it better? – tox123 Mar 27 '16 at 19:47
• I think that rather than asking questions based on the assumption that this works, you should first ask for a reality-check as to whether it would work. That would make it easier to get past the inconsistent parts. – Brythan Mar 27 '16 at 23:52
• @Brythan that's a good idea, but the captain must sink with his ship. – tox123 Mar 27 '16 at 23:53
• Do you mean "analogue" rather than "anagram"? I don't see where your proposed object is a rearrangement of the letters of anything, but I do see where it is a thing that is "similar in design, origin, or use" to something else (Merriam-Webster, "analogue"). – nitsua60 Mar 28 '16 at 13:13

I'll admit to being confused by a couple things:

• The idea of negative photons. I really don't know what you mean by this. Photons are massless, and will still be massless.
• The accumulation of "normal matter". I'm not entirely sure why "normal matter" - which you say would be repelled by matter with negative mass - would collect at the center of such objects. You would have to have head-on collisions for this to be possible, and that seems unlikely. To be frank, your entire third paragraph confuses me. There isn't any reason why "normal matter" should attract matter with negative mass.
• Electromagnetism binding the stars together. Like charges repel, meaning that here, just as in "normal matter", you would need to overcome this. Electrostatic repulsion would try to push the particle apart, not pull them together.
• Negative event horizon. I have no idea what you mean here. However, I'll discuss the significance of this later.

To understand how a black hole with negative mass would affect objects around it, it would be good to model it using the Schwarzschild solution. The Schwarzschild solution is actually a vacuum solution, meaning that it describes how space is curved in a vacuum. The reason that it is useful in general relativity, though, is that it describes how space curves in a vacuum surrounding a point mass.1

Behavior of a particle around a black hole with negative mass

The general relativistic effective potential for a massive particle orbiting a Schwarzschild black hole is2 $$V_{\text{eff}}(r)=\overbrace{-\frac{GM}{r}+\frac{L^2}{2r^2}}^{\text{Newtonian}}-\overbrace{\frac{GML^2}{r^3}}^{\text{relativistic}}$$

From here, we can determine the behavior of a test particle nearby.

Gravitational lensing

In general relativity (for an object with "positive" mass), the formula for the deflection of a light ray by a point mass is $$\theta=\frac{4GM}{c^2r}$$ This is a factor of two greater than the deflection predicted by Newtonian gravity. Note that the point mass approximation works just fine for an object like the Sun, or a stellar black hole.

In the case of negative mass, the same formula is valid. We can see that the derivation given in Introduction to Gravitational Lensing (page 10) is still valid. You simply have a potential $\Phi$ of a reversed sign.

Time dilation

The formula for gravitational time dilation is $$t_0=t_f\sqrt{1-\frac{2GM}{c^2r}}$$ In the normal case where $M>0$, $t_f>t_0$. However, in the case where $M<0$, $t_f<t_0$! In other words, an observer near a negative mass black hole will seem to age faster, not slower.

It is interesting to note that any black hole with negative mass would necessarily have a naked singularity, and so events inside the black hole could be observed3. The cosmic censorship hypothesis states that naked singularities are impossible, so if these objects existed, that would be violated (as would several energy conditions). Additionally, Gleiser & Dotti show that in the Schwarzschild case (angular momentum $J=0$), the singularity is perturbatively unstable. The black hole likely would not last long.

1 We can see from the derivation of the Schwarzschild metric that it works just fine for negative masses. The effects will simply be different.
2 See here and here (pdf here).
3 Instead of your "negative event horizon", there would simply be no event horizon.

• a negative event horizon is an event horizon that effects negative matter in the same way a normal event horizon effects normal matter. – tox123 Mar 27 '16 at 23:26
• @tox123 I'm not sure I follow. Neither normal matter nor negative matter can break the speed of light, so there really wouldn't be a difference. – HDE 226868 Mar 27 '16 at 23:37
• no the key difference here is that as normal matter approaches the event horizon it gets pushed back, no normal matter exiting the negative event horizon can return, but no negative matter entering can leave. – tox123 Mar 27 '16 at 23:42
• @tox123 That's still the same concept, though. The event horizon would have the same properties as an event horizon formed by a normal black hole; the difference here is that negative mass is attracted instead of normal mass, and normal mass is repelled instead of negative mass. Anyway, a negative event horizon can't exist here; a negative mass black hole implies a naked singularity. – HDE 226868 Mar 27 '16 at 23:50
• why? does negative distance appear too? – tox123 Mar 27 '16 at 23:52

Assume that somehow negative mass could exist.

This is unassumable. Mass is a scalar quantity and thus cannot (so far as poor mathematics goes) be negative.

If it did exist, it would have some outrageous properties. It would also require negative light to exist. When normal electrons come down from a higher orbit to a lower one, they emit electromagnetic radiation. A negative electron (not positron as we know it, but "negative electron") would emit negative light (whatever that would be).

So no. With the science we know so far, this stuff cannot be assumed. Maybe the assumption is far too smart to fit in our minds with our current knowledge and maybe it is just too obviously against all physical models as we know them. Conclusion is, at this point of scientific development, we cannot assume negative mass.

With this mass star like objects could form star-like objects in which these negative masses are flung together at high enough velocity that the strong and electromagnetic forces make them bond. These particles, because of their negative mass, gravitationally repel one another.

Why does the negative matter (not antimatter but negative-matter) get flung together at high velocities when it is already repelling itself? Atoms and molecules on the whole tend to be neutrally charged, thus making electromagnetic forces void. Gravity is the undisputed king when you discuss huge distances and large objects in the universe.

And surprisingly, it happens that even if there did exist negative matter, gravity within its particles would still be POSITIVE. That is, negative matter particles would attract each other, not repel. This is why:

$F_{gravity} = \frac{G*m_1*m_2}{r^2}$

As you can see in the equation, it does not matter if both the masses were positive or negative. If both masses are negative, still when multiplied, the negative part would be cancelled out and you would be left with a net positive gravitational force.

However if one particle has positive mass and the other had negative mass ... hmm, now that would be fun to watch.

Eventually, the negative gravity contributes enough kinetic energy that the forces get extraordinarily high.

For the love of everything sane and simple, you can replace "negative gravity" phrase with "repulsion".

p.s. I fail to understand what this sentence means at all. You lost me here, buddy/girlie.

Normal matter may accumulate in the center of these "stars" pulling more matter in.

Ah, finally we get to get normal matter involved. Lord! How I was waiting for this moment!

No, as I showed you with Newton's simple equation of gravity, in fact normal and negative matter would repel each other while each type of matter would attract other particles of the same matter. So no, you either get stars made of completely positive matter or stars made of completely negative matter, but not both.

At some critical point, the mass pulls the negative mass in towards the center which dispels the normal mass.

??? :S :S :S ???

Why would negative matter dispel the normal matter at all? This doesn't smell right :(

Then, because of strong and electromagnetic forces, is held together while the center makes a negative matter black hole anagram (because that's so large I'm going to call it a nmbha).

I posted a question on physics SE whether an antimatter blackhole would cancel out a normal matter blackhole. Turns out that in a blackhole, the information about charge is lost. A blackhole made of matter and one made of antimatter would both fuse together to form a large blackhole.

Which means that your nmbha would behave simply like a normal blackhole for all intents and purposes.

How would objects approaching a nmbha act? How does light bend around a nmbha? What critical point of mass to negative mass does the "star" begin? What would happen if nmbhas got close to a black hole?

• A couple concerns. 1) I don't understand your first point. Scalar quantities can be negative. 2) Can you flesh out your point about "negative light" more? When I last checked, atomic electron transitions were mass-independent. 3) Wormholes $\neq$ opposites of black holes. In fact, the Schwarzschild solution for a non-rotating, electrically neutral black hole can describe a wormhole, albeit a non-traversable one. 4) I don't think using Newtonian gravity in a general relativistic situation is a good idea. – HDE 226868 Mar 27 '16 at 21:35