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Astronomy and Cosmology
Astronomy and Astrophysics
Matter-Antimatter black hole collision
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[QUOTE="ohwilleke, post: 6247838, member: 19562"] The nature of the matter-energy within a black hole is not just unknown in practice, but unknowable in theory. Matter particles, antimatter particles, and particles like photons that are neither matter nor antimatter, all have mass-energy and mass-energy is conserved in a merger of black holes. Interactions of black hole with the world beyond the event-horizon and its properties are purely a function of the total amount of mass-energy within the event horizon and its angular momentum (and also its electromagnetic charge in the purely hypothetical possibility of a black hole with electric charge). It is worth restating [URL='https://en.wikipedia.org/wiki/Black_hole']the basics[/URL]: Thus, [URL='https://en.wikipedia.org/wiki/Schwarzschild_black_hole']Schwarzschild[/URL] and [URL='https://en.wikipedia.org/wiki/Kerr_black_hole']Kerr[/URL] black holes have purely gravitational interactions and properties characterized solely by total mass-energy and in the case of Kerr black holes, angular momentum, while [URL='https://en.wikipedia.org/wiki/Reissner%E2%80%93Nordstr%C3%B6m_metric']Reissner–Nordström[/URL] and [URL='https://en.wikipedia.org/wiki/Kerr%E2%80%93Newman_metric']Kerr–Newman[/URL] black holes may not even exist. There is really no reason to imagine that significantly charged black holes should exist, but figuring out if they do or not presents multiple conflicting issues. On one hand, we know of no process where net electromagnetic charge is not conserved. On the other hand, it shouldn't be possible for electromagnetic forces to escape from a black hole formulated in a classical manner. Experimentally, it would also be hard to distinguish charged matter in close orbit around a black hole from charged matter within the event horizon of the black hole itself, something that would have to be done with telescopes from many light years away for the foreseeable future. In theory, the gravitational effects of matter and the gravitational effects of anti-matter are [URL='https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter']indistinguishable[/URL] and they can have angular momentum in the same way. None of the direct experimental tests of this attempted to date have revealed anything to the contrary, and suggest that this is true, but experimental test are so far [URL='https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter']inconclusive[/URL]. This is because direct experimental tests are tricky to extract experimental results from because (1) most anti-matter lives for only fractions of a second in our matter dominated world (except in the case of anti-neutrinos), (2) the anti-matter we have to study involve particles no bigger than individual atoms which makes for a small target to observe and also means that the strength of gravitational forces relative to other forces at play is tiny, and (3) the propagation of individual particles needs to be understood using quantum mechanics and classical mechanics are only statistical averages of probabilistic quantum mechanical motion which is much more complex to analyze. [B]Purely Matter or Antimatter Sourced Black Holes Would Be Unphysical.[/B] Because of the huge flux of neutrinos and antineutrinos through open space over a sufficiently long time, and the flux of photons, we can be confident that there is no such thing as a black hole formed purely from matter or purely from antimatter that can exist long enough to collide into another black hole. Also, since there is no reason to believe that there have ever been antimatter dominated areas of the universe at any time more than a few moments after the Big Bang, the hypothetical proposed is not a physical possibility. This is because there can not physically be any black hole in our universe formed predominantly from antimatter. [B]The Internal Composition Of A Black Hole Doesn't Matter[/B] But, honestly, the matter or antimatter or neither matter or antimatter status of the mass-energy that went into making a black hole is irrelevant anyway. A black hole doesn't have to have any matter inside it to gravitate in the same way. A black hole could be made up of pure photons within the event horizon, and the gravitational effect would be the same, and we would never know it because photons can't escape the event horizon any more than matter can, by definition. The inability of photons to escape is what makes a black hole a black hole. It is possible as a result of Hawking radiation, which is strongly believed to exist in theory but has never been observed (because it is a tiny magnitude effect), but that doesn't change the fact that we don't know and can't really know what is inside a black hole. (There is a huge theoretical discussion regarding the "black hole information paradox" but for purposes of knowing the matter-antimatter-neither composition of what is within a black hole in any meaningful macroscopic way, it doesn't really matter.) None of those assumption are safe outside the domain of applicability of the laws of physics upon which they are based, which is in regions outside black holes. but, even if it did, as noted above, it wouldn't matter. Black holes made entirely of matter, entirely of antimatter, or entirely of photons, for example, would be indistinguishable from each other and behave identically. [/QUOTE]
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Matter-Antimatter black hole collision
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