History UsefulNotes / BlackHoles

9th Feb '16 7:45:44 PM DKN117
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Lighter stars become a degenerate-matter white dwarf which slowly cools over trillions of years into a black dwarf[[note]]Not to be confused with "brown dwarfs", which are substellar bodies, like large planets, that were never massive enough to sustain fusion to begin with.[[/note]]. According to current estimates, no black dwarfs yet exist, as a star cooling to that level would take longer than the universe has existed. The Sun is expected to become a black dwarf in approximately 1 quadrillion years. Stars with more than 1.4 times the mass of the sun have exceeded the "Chandrasekhar limit" and gravity combines electrons and protons to form neutrons, resulting in a neutron star. Stars whose mass exceeds the Tolman-Oppenheimer-Volkoff limit (about two to three solar masses, and definitely no more than five, but it's still unclear) are so massive that even the neutrons can't resist further collapse;[[note]]Neutron stars are prevented from collapsing further by a pressure called neutron degeneracy pressure. This is caused by the Pauli exclusion principle, and the degeneracy pressure is insufficient to prevent collapse over the Tolman-Oppenheimer-Volkoff. However, it is possible that there are other forms of degenerate matter, which may be capable of preventing further collapse until the object's mass reaches a new limit.[[/note]]it can be assumed that the star collapses down to the event horizon, and past it to a singularity (a single point, or a ring for a rotating black hole).
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Lighter stars become a degenerate-matter white dwarf which slowly cools over trillions of years into a black dwarf[[note]]Not to be confused with "brown dwarfs", which are substellar bodies, like large planets, that were never massive enough to sustain fusion to begin with.[[/note]]. According to current estimates, no black dwarfs yet exist, as a star cooling to that level would take longer than the universe has existed. The Sun is expected to become a black dwarf in approximately 1 quadrillion years. Stars with cores weighing in at more than 1.4 times the mass of the sun have exceeded the "Chandrasekhar limit" and gravity combines electrons and protons to form neutrons, resulting in a neutron star. Stars whose core mass exceeds the Tolman-Oppenheimer-Volkoff limit (about two to three solar masses, and definitely no more than five, but it's still unclear) are so massive that even the neutrons can't resist further collapse;[[note]]Neutron stars are prevented from collapsing further by a pressure called neutron degeneracy pressure. This is caused by the Pauli exclusion principle, and the degeneracy pressure is insufficient to prevent collapse over the Tolman-Oppenheimer-Volkoff. However, it is possible that there are other forms of degenerate matter, which may be capable of preventing further collapse until the object's mass reaches a new limit.[[/note]]it can be assumed that the star collapses down to the event horizon, and past it to a singularity (a single point, or a ring for a rotating black hole).
26th Jan '16 1:37:49 PM FordPrefect
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Unless you're watching ''extremely'' hard SciFi ([[MohsScaleOfScienceFictionHardness like 5.5 or 6]]), a black hole is probably nothing like you've generally seen in fiction. Black holes rank up there with FTL and TimeTravel as one frequently exploited bits of science.
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Unless you're watching ''extremely'' hard SciFi ([[MohsScaleOfScienceFictionHardness like 5.5 or 6]]), a black hole is probably nothing like you've generally seen in fiction. Black holes rank up there with FTL and TimeTravel as one of the most frequently exploited bits of science.
26th Jan '16 1:37:25 PM FordPrefect
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* Magic: Black holes don't gain any super-magic powers of suction when they become black holes. Their mass exerts the same gravitational force as a star, planet, or any other object of the same mass. If our sun were suddenly turned into a black hole, nothing would happen to us. [[note]] other than the fact that all that energy normally radiated from the sun is suddenly gone[[/note]] Well, nothing would happen to the planet, though we'd most likely die off from cold and starvation. If we wanted to study a black hole, we could put a probe in orbit around it the same way we put probes around other astronomical bodies. It's not going to instantly spiral to its doom (at least not any faster than it would around anything else)[[note]]However, since a black hole is ''far'' smaller than a star and does not emit radiation except very faint Hawking radiation, the probe could orbit it much closer. Tidal forces aside, that if it's too close to the hole could destroy the probe, this means if orbits very close, it could be unable to leave its orbit unless it had a very powerful engine.[[/note]]
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* Magic: Black holes don't gain any super-magic powers of suction when they become black holes. Their mass exerts the same gravitational force as a star, planet, or any other object of the same mass. If our sun were suddenly turned into a black hole, nothing would happen to us. [[note]] other than the fact that all that energy normally radiated from the sun is suddenly gone[[/note]] Well, nothing would happen to the planet, though we'd most likely die off from cold and starvation. If we wanted to study a black hole, we could put a probe in orbit around it the same way we put probes around other astronomical bodies. It's not going to instantly spiral to its doom (at least not any faster than it would around anything else)[[note]]However, since a black hole is ''far'' smaller than a star and does not emit radiation except very faint Hawking radiation, the probe could orbit it much closer. Tidal forces aside, that if it's too close to the hole could then itcould destroy the probe, this means so if it orbits very close, it could be unable to leave its orbit unless it had a very powerful engine.[[/note]]
26th Jan '16 1:36:26 PM FordPrefect
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* Black: Oh sure, it's black beyond what looks like the horizon, but it may well glow brightly from heat generated by whatever it is that they're sucking in, and from accretion. [[http://www.wired.com/wp-content/uploads/2014/10/ut_interstellarOpener_f.png A real black hole might look more like this]] if enough matter has gone in. And even then, the black isn't anywhere you can fall into; you won't even know when you've fallen in the real event horizon, assuming you haven't already been torn apart by tidal forces. * Flat: Staying away from the more [[TimeyWimeyBall wibbly-wobbly]] stuff, it's convenient to think of a black hole as a tiny sphere and the event horizon is a shell around it. Once you hit the shell, you're stuck. It's also going to look pretty much exactly the same as you circle it, regardless of the direction you chose. The objects orbiting it do so due to spin.
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* Black: Oh sure, it's black beyond what looks like the horizon, but it may well glow brightly from heat generated by whatever it is that they're sucking in, and from accretion. [[http://www.wired.com/wp-content/uploads/2014/10/ut_interstellarOpener_f.png A real black hole might look more like this]] if enough matter has gone in. And even then, the black isn't anywhere you can fall into; you won't even know when you've fallen in through the real event horizon, assuming you haven't already been torn apart by tidal forces. * Flat: Staying away from the more [[TimeyWimeyBall wibbly-wobbly]] stuff, it's convenient to think of a black hole as a tiny sphere and the event horizon is as a shell around it. Once you hit the shell, you're stuck. It's also going to look pretty much exactly the same as you circle it, regardless of the direction you chose. The objects orbiting it do so due to spin.
26th Jan '16 1:29:59 PM FordPrefect
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However, you'd probably be long dead before that anyway, as black holes come with some dangers attached due to the infinite gravity they exert: First, you'll be spaghettified (this ''is'' the scientific term for it); the tidal forces of the black hole are so strong that, if you were going in feet first, your feet would feel a stronger attraction than your head and thus your body would stretch out (incidentally, this occurs in more applicable situations, such as returning space shuttles, as well - the difference is that the attraction difference is so minor that the astronauts do not stretch a measurable amount). The gravity exerted by black holes is so strong that it can even deform atoms. On the upside, the bigger a black hole is, the less drastic this effect becomes on its edge; in fact, for a supermassive black hole, an individual should survive at least past the event horizon[[note]]For less massive ones, you'll be dead before you even cross the event horizon[[/note]]. The second big danger is good old radiation, due to gravitational blueshifting. Any radiation hitting you from the outside would be blueshifted (given higher frequencies, and therefore energy, as opposed to redshifting, which decreases the frequency of electromagnetic radiation and therefore their energy) and thus a lot more dangerous, to the point that, [[http://jila.colorado.edu/~ajsh/insidebh/realistic.html according to some simulations]], it would be the thing that would kill you before you could reach the singularity, assuming a black hole big enough to neglect tidal effects. The thing is known as ''[[http://discovermagazine.com/2011/jun/26-strange-physics-singular-views-inside-black-holes/article_view?b_start:int=2&-C= inflationary instability]]'' and, according to scientists, [[ThereIsNoKillLikeOverkill its effects would go very far beyond of just vaporizing your body.]]
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However, you'd probably be long dead before that anyway, as black holes come with some dangers attached due to the infinite gravity they exert: First, you'll be spaghettified (this ''is'' the scientific term for it); the tidal forces of the black hole are so strong that, if you were going in feet first, your feet would feel a stronger attraction than your head and thus your body would stretch out (incidentally, this occurs in more applicable situations, such as returning space shuttles, as well - the difference is that the attraction difference is so minor that the astronauts do not stretch a measurable amount). The gravity exerted by black holes is so strong that it can even deform atoms. On the upside, the bigger a black hole is, the less drastic this effect becomes on its edge; in fact, for a supermassive black hole, an individual should survive at least past the event horizon[[note]]For less massive ones, you'll be dead before you even cross the event horizon[[/note]]. The second big danger is good old radiation, due to gravitational blueshifting. Any radiation hitting you from the outside would be blueshifted (given higher frequencies, and therefore energy, as opposed to redshifting, which decreases the frequency of electromagnetic radiation and therefore their energy) and thus a lot more dangerous, to the point that, [[http://jila.colorado.edu/~ajsh/insidebh/realistic.html according to some simulations]], it would be the thing that would kill you before you could reach the singularity, assuming a black hole big enough to neglect tidal effects. The thing is known as ''[[http://discovermagazine.com/2011/jun/26-strange-physics-singular-views-inside-black-holes/article_view?b_start:int=2&-C= inflationary instability]]'' and, according to scientists, [[ThereIsNoKillLikeOverkill its effects would go very far beyond of just vaporizing your body.]]
26th Jan '16 1:28:43 PM FordPrefect
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Of course, nobody knows what'll happen after that, but there still are some theoretical predictions: You'll actually never even notice crossing it. You won't even fall into the apparent black void below you at all -- it is in fact ad , ''not'' the event horizon itself. [[http://jila.colorado.edu/~ajsh/insidebh/schw.html You would just continue accelerating as the view before you warps into a straight line]], until you hit the singularity and are compacted into an infinitely small point. Or you could find your molecules randomly rearranged as a small, green space-cat with tentacles for legs. However, you'd probably be long dead before that anyway as black holes come with some dangers attached due to the infinite gravity they exert: First, you'll be spaghettified (this ''is'' the scientific term for it); the tidal forces of the black hole are so strong that, if you were going in feet first, your feet would feel a stronger attraction than your head and thus your body would stretch out (incidentally, this occurs in more applicable situations, such as returning space shuttles, as well - the difference is that the attraction difference is so minor that the astronauts do not stretch a measurable amount). The gravity exerted by black holes is so strong that it can even deform atoms. On the upside, the bigger a black hole is, the less drastic this effect becomes on its edge; in fact, for a supermassive black hole, an individual should survive at least past the event horizon[[note]]For less massive ones, you'll be dead before you even cross the event horizon[[/note]]. The second big danger is good old radiation, due to gravitational blueshifting. Any radiation hitting you from the outside would be blueshifted (given higher frequencies, and therefore energy, as opposed to redshifting, which decreases the frequency of electromagnetic radiation and therefore their energy) and thus a lot more dangerous, to the point that, [[http://jila.colorado.edu/~ajsh/insidebh/realistic.html according to some simulations]], it would be the thing that would kill you before you could reach the singularity, assuming a black hole big enough to neglect tidal effects. The thing is known as ''[[http://discovermagazine.com/2011/jun/26-strange-physics-singular-views-inside-black-holes/article_view?b_start:int=2&-C= inflationary instability]]'' and, according to scientists, [[ThereIsNoKillLikeOverkill its effects would go very far beyond of just vaporizing your body.]]
to:
Of course, nobody knows what'll happen after that, but there still are some theoretical predictions: You'll actually never even notice crossing it. You won't even fall into the apparent black void below you at all -- it is in fact ad , ''not'' the event horizon itself. [[http://jila.colorado.edu/~ajsh/insidebh/schw.html You would just continue accelerating as the view before you warps into a straight line]], until you hit the singularity and are compacted into an infinitely small point. Or you could find your molecules randomly rearranged as a small, green space-cat with tentacles for legs. However, you'd probably be long dead before that anyway anyway, as black holes come with some dangers attached due to the infinite gravity they exert: First, you'll be spaghettified (this ''is'' the scientific term for it); the tidal forces of the black hole are so strong that, if you were going in feet first, your feet would feel a stronger attraction than your head and thus your body would stretch out (incidentally, this occurs in more applicable situations, such as returning space shuttles, as well - the difference is that the attraction difference is so minor that the astronauts do not stretch a measurable amount). The gravity exerted by black holes is so strong that it can even deform atoms. On the upside, the bigger a black hole is, the less drastic this effect becomes on its edge; in fact, for a supermassive black hole, an individual should survive at least past the event horizon[[note]]For less massive ones, you'll be dead before you even cross the event horizon[[/note]]. The second big danger is good old radiation, due to gravitational blueshifting. Any radiation hitting you from the outside would be blueshifted (given higher frequencies, and therefore energy, as opposed to redshifting, which decreases the frequency of electromagnetic radiation and therefore their energy) and thus a lot more dangerous, to the point that, [[http://jila.colorado.edu/~ajsh/insidebh/realistic.html according to some simulations]], it would be the thing that would kill you before you could reach the singularity, assuming a black hole big enough to neglect tidal effects. The thing is known as ''[[http://discovermagazine.com/2011/jun/26-strange-physics-singular-views-inside-black-holes/article_view?b_start:int=2&-C= inflationary instability]]'' and, according to scientists, [[ThereIsNoKillLikeOverkill its effects would go very far beyond of just vaporizing your body.]]
26th Jan '16 1:24:42 PM FordPrefect
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In fact, space-time will become quite freaky around the event horizon: the closer you get to the event horizon, the [[YearInsideHourOutside slower time becomes]] (due to relativity, however, you won't notice it). In fact, if an observer outside the event horizon could see you, they would see as you get closer and closer (and get redder, due to gravitation red shift, while everything you see would be bluer), you would go slower and slower until you hit the edge of the event horizon at which point you would appear to ''stop''. You won't ''actually'' stop, that's just what they'll see. This is because spacetime around the black hole's event horizon is so warped that light would take a progressively longer time to reach a distant observer as you approach the event horizon -- ad infinitum. They'd never see you actually touch the horizon, and the light you emitted would slowly be red-shifted to the point of invisibility. This prediction, however, assumes zero mass of incoming object and neglects quantum effects, so reality may be more tricky.
to:
In fact, space-time will become quite freaky around the event horizon: the closer you get to the event horizon, the [[YearInsideHourOutside slower time becomes]] (due to relativity, however, you won't notice it). In fact, if an observer outside the event horizon could see you, they would see as you get closer and closer (and get redder, due to gravitation red shift, while everything you see would be bluer), you would go slower and slower until you hit the edge of the event horizon at which point you would appear to ''stop''. You won't ''actually'' stop, that's just what they'll see. This is because spacetime around the black hole's event horizon is so warped that light would take a progressively longer time to reach a distant observer as you approach the event horizon -- ad infinitum. They'd never see you actually touch the horizon, and the light you emitted would slowly be red-shifted to the point of invisibility. This prediction, however, assumes zero mass of a zero-mass incoming object and neglects quantum effects, so reality may be more tricky.
26th Jan '16 1:23:58 PM FordPrefect
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Black holes are strange things. Besides the singularity at the center[[note]]Assuming it exists, since it's believed it's an artifact caused by breakdown of relativity under those conditions, that would disappear with a -still not existent- theory of quantum gravity[[/note]], there is the event horizon, the point of no return, that once you cross it...[[DepartmentOfRedundancyDepartment you can't return]]. Once inside the event horizon, you literally cannot go back: spacetime is curved in such a way by the black hole's mass that any path you take leads to the same place: the singularity. In three-dimensional space the Black Hole is not a disc. The singularity is an infinitely small point in space that sucks things in from all around, so the event horizon is more like a ball - with the singularity at the center. Rotating black holes also have ergosphere: a region near event horizon, where space-time spins around the black hole at speeds so great that you'd need to move faster than light just to stay still, let alone move in a direction counter to the black hole's rotation.
to:
Black holes are strange things. Besides the singularity at the center[[note]]Assuming it exists, since it's believed it's an artifact caused by breakdown of relativity under those conditions, that would disappear with a -still not existent- theory of quantum gravity[[/note]], there is the event horizon, the point of no return, that once you cross it...[[DepartmentOfRedundancyDepartment you can't return]]. Once inside the event horizon, you literally cannot go back: spacetime is curved in such a way by the black hole's mass that any path you take leads to the same place: the singularity. In three-dimensional space the Black Hole is not a disc. The singularity is an infinitely small point in space that sucks things in from all around, so the event horizon is more like a ball - with the singularity at the center. Rotating black holes also have an ergosphere: a region near the event horizon, where space-time spins around the black hole at speeds so great that you'd need to move faster than light just to stay still, let alone move in a direction counter to the black hole's rotation.
17th Oct '15 8:49:13 AM samanato
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* Black: Oh sure, it's black beyond what looks like the horizon, but it may well glow brightly from heat generated by whatever it is that they're sucking in, and from accretion. [[http://www.wired.com/wp-content/uploads/2014/10/ut_interstellarOpener_f.png A real black hole would probably look more like this.]] And even then, the black isn't anywhere you can fall into; you won't even know when you've fallen in the real event horizon, assuming you haven't already been torn apart by tidal forces.
to:
* Black: Oh sure, it's black beyond what looks like the horizon, but it may well glow brightly from heat generated by whatever it is that they're sucking in, and from accretion. [[http://www.wired.com/wp-content/uploads/2014/10/ut_interstellarOpener_f.png A real black hole would probably might look more like this.]] this]] if enough matter has gone in. And even then, the black isn't anywhere you can fall into; you won't even know when you've fallen in the real event horizon, assuming you haven't already been torn apart by tidal forces.
16th Oct '15 7:29:38 PM samanato
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# You just fry yourself point-blank with the concentrated beam of blueshifted gamma-rays you made [[https://youtu.be/JQnHTKZBTI4?t=2m35s by screwing with relativistic speeds]]. And this happens ''before'' you even break ''c''. This is the most likely outcome. [[ShootTheShaggyDog Happy dying!]]
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# You just fry yourself point-blank with the concentrated beam of blueshifted gamma-rays you made [[https://youtu.be/JQnHTKZBTI4?t=2m35s by screwing with relativistic speeds]]. And this happens ''before'' you even break ''c''. This is the most likely outcome. [[ShootTheShaggyDog Happy dying!]]

# You manage to kill yourself faster because space beyond the event horizon has warped by the gravitational forces to the point the only way direction you can move is further in. At best you can manage to stay in place long enough for the black hole to dissipate on its own and you might live long enough to do so since time is moving extra slow for you. A lot of time will have passed for everyone not breaking light speed barriers beyond event horizons [[note]]see page quote for an alternate possibility[[/note]]. # The desired scenario - you appear outside the Black Hole with data in hand, you don't go in again, and the universe somehow doesn't switch off. Congratulations, not only have you rewound ''the entire universe except yourself,'' defying all laws of physics, but you have defied all possible logic too. You are now God. Or possibly [[Series/DoctorWho The Doctor]].
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# You only manage to kill yourself faster because space beyond the event horizon has warped by the gravitational forces to the point the only way direction you can move is further in. At best you can manage to stay in place long enough for the black hole to dissipate on its own and you might live long enough to do so since time is moving extra slow for you. A lot of time will have passed for everyone not breaking light speed barriers beyond event horizons [[note]]see page quote for an alternate possibility[[/note]]. possibility[[/note]] # The desired scenario - you appear outside the Black Hole with full memory of your experience and data in hand, you don't go in again, and the universe somehow doesn't switch off. Congratulations, not only have you rewound ''the entire universe except yourself,'' defying all laws of physics, but you have defied all possible logic too. You are now God. Or possibly [[Series/DoctorWho The Doctor]].
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