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When You Fall Into a Black Hole, How Long Have You Got?
- PaulHoule 14y agoIt's not any more possible to get into a black hole interior than it is to get out because black holes don't have an interior.
- teilo 14y agoThey have an event horizon. Everything past that is inside the black hole. Things absolutely can and do pass the event horizon. That is how the mass of the black hole increases. That is also the problem the article is addressing. This creates a paradox in that it allows a single quantum particle to be poly-entangled - something that is not allowed by our current understanding of quantum mechanics. Therefore, what really happens? No one knows for sure. If the no-drama principle correct (which is implied by Einstein's theory of gravity), in that you cannot feel gravity when you are in free-fall, you pass through the event horizon just fine, and then die when you are torn apart by tidal forces. (Of course, the tidal forces kick in outside the event horizon in smaller black holes - but that's beside the point). If the no-drama principle is correct, then there is a fundamental and insoluble contradiction in our understanding of physics. That's the point of the article.
- Xcelerate 14y agoParticles can't be poly-entangled? Why not? A wavefunction is by definition a function of all particles. Breaking it into a separate function for each particle is merely an approximation to facilitate calculations.
- teilo 14y agoPardon my lack of precision. I should have said "thoroughly entangled". What you say is true of partial entanglement. But partial entanglement is not what we are dealing with in event-horizons and virtual pairs. As the article states, in order to maintain consistency between observers, all particles must be thoroughly entangled.
- Xcelerate 14y agoInteresting. I'm not an expert on the subject; could you explain what thorough entanglement vs partial is?
- PaulHoule 14y agoNo, stuff that falls inside the black hole stacks up around the event horizon, which really grinds stuff up to the planck scale and transforms it to maximum entropy hawking radiation. falling into it, it has enough degrees of freedom to put you into any kind of virtual reality, so you might experience falling into a singularity or somehow travelling into an "asymptotically flat spacetime" but I'm certain that the classical picture of a black hole is completely wrong.
- teilo 14y agoAnd you are welcome to be as certain as you wish. But I would point out that without black holes having an interior, there can be no Hawking radiation in the first place. Your statement is therefore internally inconsistent.
- PaulHoule 14y agothere might be something "on the other side" but there's no reason to believe that it has a 3+1 signature or is anything like the space we know at all.
- pdonis 14y agothere might be something "on the other side" but there's no reason to believe that it has a 3+1 signature or is anything like the space we know at all. There is plenty of reason to believe that, if a horizon does form, the region of spacetime on the other side will be spacetime, not something completely different. There are some (speculative) reasons to believe that quantum effects might possibly prevent horizons from ever forming, but that would mean there is no "other side".
- pdonis 14y agostuff that falls inside the black hole stacks up around the event horizon, which really grinds stuff up to the planck scale and transforms it to maximum entropy hawking radiation This looks like a mixture of misunderstanding the classical picture of a black hole, and misunderstanding how the classical picture is altered by quantum effects. Classically, stuff that falls inside the black hole does not "stack up" around the horizon; it just falls in, past the horizon and on to the singularity, where it is destroyed. There is no established theory of how quantum effects alter the classical picture, but there is at least one "semi-classical" picture of how Hawking radiation is produced (the one that Hawking originally came up with) that doesn't require any "grinding up" of infalling matter at the horizon.
- teilo 14y agoI love how Physics is like the biggest, grandest game of Sudoku ever played. You can get so far, certain that everything is about to fall into place, and then you reach a contradiction. And what better place to find the contradiction than at the event horizon of a black hole. Good stuff.
- javert 14y agoIf you reach a contradiction, it means you've done something wrong. To me, this article is a partial confirmation of earlier suspicions that the physics community has lost touch with reality.
- shmageggy 14y agoThe history of science shows your conception is a bit too stringent. It sounds a bit like Popper's extreme views on falsification in philosophy of science, whereby a theory must either pass every empirical test that is thrown at it, or be flatly rejected. The history of science (Kuhn, etc) shows that this is just not how it works. In general, when a theory fails a test it is tweaked and revised to accord better with the data, and sometimes (usually after the theory gets much more complex) a new, usually simpler, revolutionary theory replaces it. Now, since we can't go toss stuff into black holes, theoretical physics at this level is more like pure math, where the "observations" are the calculations of the theorists. When the calculations don't add up and a contradiction is found it doesn't mean that they've lost touch with reality. On the contrary, they are bringing their theories into closer congruence with reality.
- javert 14y agoA theory must either pass every empirical test that is thrown at it, or be flatly rejected. Well, that's how reality actually works. Statements about reality are either true or false. How many physicists would even agree with that? Therein lies my distrust of modern physics, or at least part of it. I'm no fan of Popper, though. The history of science (Kuhn, etc) shows that this is just not how it works. I'm no fan of Kuhn either, though. He also probably wouldn't agree with my litmus test of "Statements about reality are either true or false."
- ableal 14y ago"[...] observers who are freely falling—whether into a black hole or toward the ground—don’t feel the force of gravity, [...]" They will if there's enough of a gradient and the observers are not ideal points. Many years ago, Larry Niven wrote a story (http://en.wikipedia.org/wiki/Neutron_Star_%28short_story%29 http://en.wikipedia.org/wiki/Neutron_Star_%28short_story%29 ) where tidal forces killed observers trying to orbit a neutron star.
- teilo 14y agoYes, but in a sufficiently massive black hole, it is still possible to pass the event horizon unscathed. Thus, the paradox still exists.
- alecst 14y agoMy friend told me: "Looking out from [falling into] a black hole you see the life of the universe pass before you. That means if you've managed to fall into a black hole, no one in the history of the universe cared enough to rescue you."
- bithive123 14y agoIsn't that equally true of any kind of hole?
- alecst 14y agoBlack holes fudge with time and other holes don't.
- pdonis 14y agoLooking out from [falling into] a black hole you see the life of the universe pass before you This is not correct. You will only see the portion of the universe's history that is in your past light cone; there will be a lot of the life of the universe that you will never see if you fall into a black hole, because you will be destroyed in the singularity at the center before light from most of the universe has a chance to reach you.
- iwwr 14y agoWell, given that you can't travel backward once you've crossed the event horizon, can neural signals travel in a direction opposite the center of the singularity? Meaning, once neural and sensory activity stops then you are dead, even if your body has not yet experienced the crushing gravitational effects. You are dead as soon as you cross the event horizon. Though it may be possible to design some machines that can do computation in this unidirectional fashion. Consider something like: http://en.wikipedia.org/wiki/Rule_110 http://en.wikipedia.org/wiki/Rule_110 Another possibility is finding a really enormous black hole, large enough that stuff can live inside it: http://www.technologyreview.com/view/423608/planets-could-orbit-singularities-inside-black-holes/ http://www.technologyreview.com/view/423608/planets-could-or... Of course, humans are not wired topologically to survive in such an environment, but if there is an energy source and computing restrictions are followed, it may be possible to grow a civilization inside an event horizon. A 1 trillion solar mass black hole would have an event horizon at about half a light year, enough room for a few solar systems, depending on our good luck.
- SilasX 14y agoInteresting: to have a working brain or computer inside the event horizon, you would have to set it up so that all the information flows must move along surfaces whose points are all equidistant from the center (except for write-only operations, which could move centerward).
- gizmo686 14y agoI don't think that is an issue, as you are not supposed to be able to detect if you are under a gravitational influence. I suspect what happens is that becuase all of your brain is being accelerated towards the center at the same rate as the neural signals, it would continue operating normally.
- monochromatic 14y agoTidal forces would be a problem though (if not at the event horizon, then at least increasingly so as you approach the singularity). Basically, whatever part of you is closest to the singularity experiences more gravity than the parts that are farther away.
- stephengillie 14y agoI get this feeling we'll see idiot daredevils doing "black hole falls" in 300 years. They'll be posted on YouHoloTube or whatever video display system we're using then.
- archivator 14y agoHere's a not-so-scientific but rather fun YouTube video on the topic: http://www.youtube.com/watch?v=3pAnRKD4raY http://www.youtube.com/watch?v=3pAnRKD4raY
- omegant 14y agoComplete ignorant question: there is always the discussion of "falling" in to a black hole, but could it be possible to "hang" something from outside the event horizont?(given an infinitely strong and quite long wire). If so, could it be possible to send any signal outside? Is it possible for a particle to vibrate in a radial axis away from the blackhole once inside the event horizont?. Does a particle follow in an orbit around the black hole once inside the event horizont? Or the acceleration towards the center is so big that is a vertical fall? I think that this last question is somehow replied on the article but I can't understand it. Amazing topic indeed!. Edit: some corrections.
- neolefty 14y agoInstead of a string, how about a continuous stream of rocket fuel? You'd need a large enough black hole that: * the gravitational acceleration at the event horizon can be overcome by your rocket engines * the tidal forces at the event horizon don't kill you Your reaction mass (rocket fuel) would be sacrificed to the black hole, but with outside help, could you escape the event horizon?
- yaks_hairbrush 14y agoNo. Inside the event horizon, all paths lead to the singularity. If you had gravitational sensors on your spacecraft, they would show the singularity all around you.
- ars 14y agoSo which way do you actually fall is all directions are down? Or from your point of view you are motionless?
- yaks_hairbrush 14y agoPresuming you're just letting gravity do its work and not, say, firing engines to resist... You'd be in free fall, and that's a perfectly nice reference frame. Within that frame, your gravitational sensors would observe certain doom in every direction. This sphere of doom would get smaller until you were ripped apart from the tidal stress.
- psykotic 14y agoGreg Egan's Planck Dive short story is worth a read: http://gregegan.customer.netspace.net.au/PLANCK/Complete/Planck.html http://gregegan.customer.netspace.net.au/PLANCK/Complete/Pla...
- deltasquared 14y agoI wouldn't worry so much about the event horizon so much as what is right outside of it. The tidal forces and the x-rays resulting from said forces are pretty much lethally intense. http://chandra.harvard.edu/chronicle/0104/tidal/index.html http://chandra.harvard.edu/chronicle/0104/tidal/index.html
- pdonis 14y agoThe X-rays don't come from "tidal forces" by themselves, they come from tidal forces acting on matter falling into a black hole.
- astrodust 14y agoDoesn't "tidal force" dictate that it's acting on something? What is a force if there's nothing for it to act against? Just as it takes two to tango, you can't have a force without two participants at opposing ends.
- pdonis 14y agoDoesn't "tidal force" dictate that it's acting on something? Tidal gravity is equivalent to spacetime curvature, so it's there whether or not there is matter falling into the hole; the term "tidal force" is sometimes used to refer just to that fact. But X-rays won't be produced unless enough matter is falling in and being acted on by the tidal force. If there were no large quantities of matter falling in, a very small object like, say, an astronaut in a rocket ship, could fall in and not encounter any X-rays, but the tidal force would still be there (and could potentially pull his ship and him apart). I wasn't sure if that distinction was clear.
- astrodust 14y agoI'd always understood that tidal forces were related to objects large enough to have a measurable differential in orbital period from one side of the object to the other. In the ordinary universe this often plays out on small moons in a low orbit around very large planets such as Jupiter. A definition (http://en.wikipedia.org/wiki/Tidal_force http://en.wikipedia.org/wiki/Tidal_force): "The term tidal force is used to describe the forces due to tidal acceleration." You can't have acceleration without an object being accelerated. Not trying to split hairs here, but to try and establish if it's possible to have a force that's not acting on anything.
- Metapony 14y agoI'm guessing the answer to this riddle is "the rest of your life".
- patrickgzill 14y agoThe rest of your life?
- kyllo 14y agoThe event horizon is the point where the gravitational pull is pulling you at nearly the speed of light so that there is no possible escape velocity for any particle that has mass, correct? I'm no physicist, but if gravity were to act on a human body with that much force, wouldn't the force alone kill you? I imagine the force of the pull would be stronger than the force holding together the atoms that make up the tissue of your body, and you would disintegrate into a stream of particles accelerating toward the singularity. Am I way off here? If a smaller object approached an object of such great mass that not even light can escape its gravitational pull, wouldn't the smaller mass's particles inevitably be funneled into a single-file line until they are absorbed into the singularity?
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- pdonis 14y agoif gravity were to act on a human body with that much force, wouldn't the force alone kill you? No, because you don't feel this "force" of gravity; you are in free fall, just like astronauts on the International Space Station. Your body will be subject to tidal gravity because it has a finite size; the effects you talk about in the rest of your post (your body's atoms being pulled apart, etc.) are due to tidal gravity, not "the force of gravity" per se. But for a large enough black hole, tidal gravity is small enough to be bearable at the horizon.
- jbri 14y agoHow much gravitational force does the Sun exert on you? Do you feel any of it? A constant gravitational field doesn't change anything - everything is accelerating the same amount, in the same direction. What can cause problems is the difference between the gravitational field at two different points (for example, when a planet gets too close to a star, it can be torn apart due to the force exerted on the near side being much greater than the force exerted on the far side). But this isn't the same as the overall strength of the field, and a sufficiently large black hole could have a very survivable field gradient at the event horizon.
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- satori99 14y agoAll this Blackhole talk reminds me of the excellent Frederick Pohl novel, Gateway. And its sequel Beyond the Blue Event Horizon. Both of which deal with humans interacting with these regions of the universe for the first time. http://en.wikipedia.org/wiki/Gateway_%28novel%29 http://en.wikipedia.org/wiki/Gateway_%28novel%29