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So a black hole is this large, sphere-blob shaped fluid thing that distorts space and time, making a weird hole in space(even after 5 years, I still don't exactly get what a black hole is exactly and where the mass goes when it eats xD).

So, let's say, we make a huge antimatter(opposite charge, same mass as matter) star and send it into the black hole. What would happen? The antimatter would annihilate with the matter made black hole, or is it wrong to assume a black hole is made of matter?(I assume not much would happen if the antimatter can't react with the matter, because the black hole would probably get its original charge messed up.)

What about if we created a huge exotic matter(same charge, opposite mass) star and sent it into a black hole? Would the repulsive force successfully destroy a black hole? According to Kurzgesagt and several articles cited by them, exotic matter is able to keep a wormhole stable, so wouldn't it be able to annihilate the black hole or something? Or have I made a misunderstanding?

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  • $\begingroup$ Wikipedia's discussion of exotic-matter includes several classes, only one of them is "negative mass". I'm curious why you've proposed a tag wiki that only includes negative mass. Why not adapt a more general definition instead of one matched only to your own question? $\endgroup$ – uhoh Mar 6 '19 at 6:27
  • $\begingroup$ @uhoh I didnt know that exotic matter has other meanings. I just knew this from Kurzgesagt. $\endgroup$ – Max0815 Mar 6 '19 at 18:38
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    $\begingroup$ There is strong evidence that black holes do exist. But exotic matter and its alleged properties are just a hypothesis. It's not okay to mix real things with the stuff of imagination. I mean, you can, but don't expect any coherent result out of that. $\endgroup$ – Florin Andrei Mar 6 '19 at 19:54
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    $\begingroup$ @Max0815 tag wikis and excerpts should be written carefully and thoughtfully. The reason many are blank is that nobody has felt confident enough to do it correctly. I think at least checking Wikipedia first would be an absolute minimum before proposing a change. Other readers will rely on your definitions in the future, and if the tag definitions have a problem, it could cause trouble for other people in the future. It's really great that you are looking into this, but please write them carefully and check a few sources first. Thanks! $\endgroup$ – uhoh Mar 6 '19 at 22:25
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    $\begingroup$ @uhoh I will do this in the future :) Sorry bout that. $\endgroup$ – Max0815 Mar 6 '19 at 23:42
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Black holes are not "made of matter". They are better described as structures of gravity/warped spacetime. However, they do grow when absorbing things with positive mass-energy.

Antimatter still has positive mass-energy, so the black hole cheerfully gobbles it up.

Now, exotic matter with negative energy density might indeed decrease the size of the black hole, akin to some form of enforced evporation process. (paper1, paper2) This is highly speculative since there are various theoretical reasons why exotic matter does not exist, and many kinds of hypothetical exotic matter that might work differently.

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  • $\begingroup$ Ah, nice answer. I'll wait a few more days and see if there is any other into I can gather :). +1 $\endgroup$ – Max0815 Mar 6 '19 at 2:44
  • $\begingroup$ "Black Holes are not made of matter", says Anders. And yet, Black Holes are allegedly the objects that contain more mass than any other item in the cosmos. $\endgroup$ – White Prime Mar 6 '19 at 7:52
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    $\begingroup$ @WhitePrime - Having mass is not the same as being made of matter. Remember that binding energy changes the total mass of bound systems. arxiv.org/abs/astro-ph/0406095 estimate black holes to contain just 0.00007 of the total mass-energy of the universe, less than stars and way less than intracluster gas or dark matter. $\endgroup$ – Anders Sandberg Mar 6 '19 at 9:42
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    $\begingroup$ @WhitePrime No. Black holes can be any size and mass, from microscopic to galactic level. The distinction between mass, energy, and their effects on the geometry of spacetime is very much blurred by general relativity. What is characteristic of black holes is the extreme density of mass/energy, which induces an extreme curvature of spacetime. The ultimate fate of matter collapsing into a black hole is difficult to describe, what is important here is the strongly distorted chunk of spacetime which becomes the true identity of the black hole. $\endgroup$ – Florin Andrei Mar 6 '19 at 19:40
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    $\begingroup$ @WhitePrime A supermassive BH with the mass of a billion Suns has an average density less than water. The mass is concentrated in a point at the centre, while the rest of the giant sphere defined by the event horizon is (apart from a bit of infalling matter & photons) empty space. $\endgroup$ – Chappo Hasn't Forgotten Monica Mar 6 '19 at 21:24

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