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How To Destroy a Black Hole
KentuckyFC writes "The critical concept that makes a black hole black is the event horizon: a theoretical boundary in space through which light and other objects can pass in one direction but not the other. Since light cannot escape the event horizon, it must be black. The event horizon is a nuisance to astrophysicists because it hides the interesting new physics that must go on inside a black hole. What they would like is a way to get rid of the event horizon so that they can see what goes on behind it. It turns out that just such a thing may be possible, say physicists. According to the mathematics of general relativity, the event horizon should disappear if a black hole were fed enough charge and angular momentum relative to its mass. However the calculations are so fiendish (PDF) that nobody knows whether the black hole would shed this extra angular momentum and charge before it could settle into a stable 'naked' state. However, the possibility that the event horizon could be destroyed raises the question of what astrophysicists would see behind this veil. According to some, black holes are regions of spacetime with infinite curvature called singularities. Many believe that 'naked' singularities cannot exist in nature. And yet there are enough question marks to suggest that this mystery is far from settled."
On a less serious note, does Rule 34 apply to naked singularities?
Remember to maintain your supply of
People thought communicators were way to far out too when TOS came out. Now we take
them for granted.
Now I don't think there are going to be any practical experiments around this theory /. but I'll go ahead and repeat it; a lot of scientists are heavily inspired by
anytime soon but "this shit" has to start somewhere. It's been said many times before
on
science fiction and, especially when they are young, love to see if their favorite
tech from their favorite shows are feasible.
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All of my lost left sox.
Two bolts from my motorcycle.
The lost chord.
George Bush's dignity.
Several B-19s last seen headed towards Bermuda.
An iPhone 4G prototype.
Darl McBride's balls.
And I'm sure there's more.
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Thing 2: How is this a good thing to do? Aren't they basically stating that they don't understand how or why this is occurring, but they want to destroy something to figure out what goes on behind it? When are they planning to do this? December 21st, 2012?
They're scientists and engineers. "Break something to see how it works" is how scientists and engineers of all walks of life think. They're just thinking bigger than most. I gotta salute them for that.
Demanding constant attention will only lead to attention.
Since light cannot escape the event horizon, it must be black.
Right, because anyone imprisoned anywhere must be black, because only blacks break the law and get locked up.
Information theory is life. The rest is just the KL divergence.
I once read a bit about black holes, and one of the things I read was: a black hole doesn't necessarily have to be very dense. It can also be sparse (and the larger, the sparser it can be). For example, if you'd take a lot of stars and planets, and put them together (but not too close together), then at one point if you make this large enough, it'll also be a black hole: there appears an event horizon around all this matter. But inside of it are still stars with gaps between them, maybe some planets orbiting around them, ... So now I wonder, if the above is true: can someone live inside that? Would there be any noticeable difference between being inside of that, and the other side (the outside) of this event horizon?
I sure am dumb
We always hear about singularities necessitating event horizons, but the converse is most certainly not true. An event horizon may exist without a singularity inside of it.
It depends on scale more than anything. Small black holes almost certainly require a singularity, but a black hole the mass of a galactic cluster actually has a very low average density. So while at the event horizon space-time is very much distorted, on the inside it may not be distorted enough to overcome common everyday forces (the trick of treating a collection of mass as a point source of force doesnt work from inside that collection of mass)
"His name was James Damore."
There are a number of factors to overcome when making singularity porn:
1. once you put it in, it's a real bitch to take it back out
2. nobody has ever successfully pulled out in time
3. they start at sucking and never manage to make it to the sex part
4. Ebony has a trademark on the term "black hole"
5. it's kind of a tease to watch because as much as they constantly approach the "event horizon", they never quite reach it
If you can't say something nice, make sure you have something heavy to throw.
The singularity is a lie. By which I mean, it's not as if this mass is all really in one infinitesimal dot...it's just that you do any characterization of that mass when even light can't escape. So no, you wouldn't be destroying the singularity since we don't really know that's what it is, but, if they do happen to change the black hole by adding charge and angular momentum, and it allows radiation to escape it will cease to be a black hole.
I would like to find a black hole that's just barely massive enough and then try this.
Finally, I think they're just trying to do a thought experiment whereby they change the shape or topology of the event horizon. Imagine a toroidal event horizon for example.
One of the problems with approaching a black hole (aside from massive amounts of radiation around ones actively eating matter) is the fact that the force of gravity increases as you approach the mass responsible for the gravity.
With small black holes, as you approach (feet first) the difference in gravitational pull at your feet would be many times larger than the gravitational pull at your head. You would be literally ripped apart, down to the molecular level. This is known as "Spaghettification".
http://en.wikipedia.org/wiki/Spaghettification
However, with a large enough black hole, you should be able to pass the event horizon before these tidal forces grow large enough to rip you apart. Of course, this does you no good, because once you are inside the event horizon you cannot exert a great enough force to prevent yourself from falling deeper until the forces ARE great enough to rip you apart.
But for a large black hole, in theory, you could cross the event horizon without being ripped apart.
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Although no one knows what happens at the end point of black hole evaporation it is unlikely it would leave a naked singularity since the mass of the singularity is what is being 'evaporated'. Besides, even if there was a naked singularity around just before the thing evaporates it would be kicking out so much energy you wouldn't be able to get anywhere near it. A 1kg black hole evaporating would release the equivalent energy to a large thermonuclear weapon in a fraction of a second.
Peel back an Event Horizon? Get blasted with Radiation/Exotic particles,etc... Um just think what happens to the axis area... They are evaporating just not in a observable curvature that we can understand or detect.
Hey Hawkins back me up on this...
<robotic voice> that's what she said. ha. ha. ha.
liberate tutamae ex inferis
I'm not an expert on this by any means, but here's my two cents...
Try not to think of it in terms of light trying to escape in a straight line and just not being strong enough to do it. Instead, think of the straight line as not being straight. Gravity wells curve space-time (a Google Images search for "spacetime" will yield some familiar diagrams of spheres resting on a fabric), and the event horizon of a singulatiry is the point in that curvature where it's so "steep" that it curves back in upon itself. This is difficult to show in the aforementioned diagrams, because it's less about the picture and more about the math behind it.
Basically, from behind the event horizon it's impossible to escape not because you don't have enough force to get away but because all paths lead back to the singularity.
If somebody with more knowledge/expertise on the subject can correct/elaborate, please do.
http://publicvoidlife.blogspot.com
(Disclaimer: I Am A Physicist, but this is not my area of expertise, and only the experts understand those equations.)
It's not feeding it mass that does the trick; it's feeding it charge and angular momentum. The only reason you feed it more mass is because you need mass to carry the charge and momentum into the hole.
What you get if you feed it charge and angular momentum is a spinning monopole. I think they are postulating that a spinning monopole causes rotational frame dragging, and if you do it right you can get the charged frame dragging effects to cancel out the gravitational effects -- namely, the event horizon.
After you do all that, what will be left? Like the article says, nobody knows. That's why it's exciting.
Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
That allows information from inside the event horizon to leak outside (which is all the astrophysicists really need) and allows the evaporation of black holes, but the event horizon would remain intact. However, we have never seen Hawking Radiation (yet) and it depends some on certain assumptions being valid. One of these assumptions is that the singularity is something "physical".
A lot of cosmologists don't like infinities, so don't like singularities, but let us consider what "infinite gravity" would actually mean. It would mean you have a vertical gravitational well, with the universe being the "walls" of this well. As far as the universe is concerned. the actual hole that makes up the interesting part of the well is on the outside, just as the air in a physical well is outside the brick lining that comprise the walls. Since what we call "physical" are the objects inside the universe, it makes no logical or rational sense to talk of something that is on the outside as being "physical". You can detect it using the usual rules of topology and geometry (you can't apply any topological transformation to a torus to produce a sphere), but if you picture yourself as a Flatlander on the surface of said torus, you could NEVER observe the region on the outside that distinguishes the torus from a sphere. You could infer it existed, you could even prove that it has certain properties, but that's it.
Cosmologists and topologists don't get along, which is why space/time existed as fact in geometry long, long before any physicist accepted it was real. Einstein is said to have loathed and despised the concept, and only grudgingly accepted it had to be true after being dragged, kicking and screaming, by his theories into reaching no other answer. (You might gather from this I have a low opinion of certain branches of physics.)
But precisely because the rules of topology FORBID a torus to become a sphere, it would be impossible for a genuinely infinite-gravity singularity to evaporate completely. Instead of their evaporation speeding up as they shrank, it would have to slow down -- if they evaporated at all. Entirely the opposite of what physics expects. There's no reason for them TO evaporate, however. It is only required in cosmology to meet the requirements of the 2nd Law of Thermodynamics, but thermodynamics only applies to what exists. A hole is a region where the walls do NOT exist.
There is a third possibility. Under the standard model for space/time, time is orthogonal to space. If space is bent at 90' to all other spacial dimensions, then it is no longer space. It is time. This means that not only is there a singularity at the heart of every black hole, it would be the SAME singularity. There would have only ever been one singularity, right at T=0, and the throats of all black holes would be directly and permanently hard-linked to this. There would still be no evaporation at this end of time (it has already happened).
A fourth (and fifth) possibility is that black holes never actually form at all. There's an entire alternative model in cosmology which prohibits them outright, giving you that fourth option. Then, Professor Hawking's work on imaginary time and the curvature of time around singularities would eliminate the need for a singularity outright. If you factor time curving as well as space, then space/time never vanishes to a point. Space/time would become parabolic, giving it a minimal state, but there is no moment in which any variable hits zero or any infinite states are achieved.
There's probably others I've either not heard of, or have heard of and forgotten. But at least five different ways DO exist and are recognized in modern physics as possible in which no black hole singularity of the kind imagined would arise. That means there is simply no theoretical ground (right now) to assume that this new theory has any meaning or would make any sense.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
The title of the paper is "Destroying black holes with test bodies," and the language about "destroying" black holes is echoed in both the arxiv blog summary and the /. summary. This may be somewhat misleading. They're actually talking about processes that would strip away the event horizon, leaving behind a naked singularity. The black hole wouldn't have been "destroyed," but just changed into a different form. The authors themselves put the word "destroying" in quotes in the paper.
The paper doesn't settle this one way or the other. It says shows that if you use a certain set of approximations, the result is that the event horizon can go away. However, there is no particular reason to believe that the approximation is correct.
The real issue here isn't whether a black hole can actually be transformed this way, it's the question of whether cosmic censorship holds. If cosmic censorship fails, then general relativity is fundamentally flawed as a classical field theory, because it fails to make predictions. John Earman's famous way of expressing this is that anything could come out of a naked singularity: lost socks, green slime, even horrible things like Nixon's "Checkers" speech or Japanese monster-movie creatures.
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I did Ph.D. research on this exact subject a decade ago, and at a quick glance I didn't see anything new in this paper. A spinning and/or charged black hole in theory can be spun or charged to the point where a naked singularity would appear. But, the harder you spin/charge the black hole, the harder it tries to neutralize itself by preferentially emitting particles of a given angular momentum or charge. So the equality probably is a physical limit. I thought someone had proven that years ago, but I've been out of the field for a while.
This looks kind of like someone wrote a paper so they could go to a conference or something. There doesn't appear to be anything earth-shattering (or black hole-shattering) here.
Does not apply to a black hole, IMO.
Not until stellar engineering encompasses more than theory.
Oblig., but not XKCD for a change.
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That's what Japan is for.
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
Ding ding ding - we have a winner. This is the point that so many cosmology shows on Discovery Channel or Science Channel (or whatever) completely fail to mention; they keep describing black holes as "so massive, even light can't escape" without explaining why (Michio Kaku, Alex Fillipenko, (sp) I'm looking at you). See Wikipedia for the details, but the important point is that escape velocity is dependent on an object's mass divided by its radius. So if mass goes high enough, or radius low enough, you get an escape velocity greater than the speed of light: AKA an event horizon.
... the place where the escape velocity equals the speed of light.
Say it again, and remember it later:
The event horizon is
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
You're bringing horribly naive Newtonian physics into a realm they do not belong in. Stop before you make yourself sounds like even more of a fool.
As you fall into a black hole the event horizon appears to move away from you from your point of view. An external observer on the other hand would never see you cross the horizon due to other effects, just see you falling ever more slowly into it as the light from you takes ever longer to reach them. You'd see some odd effects from crossing the event horizon but you'd continue to observe things.
http://casa.colorado.edu/~ajsh/singularity.html
http://jila.colorado.edu/~ajsh/insidebh/schw.html
The event horizon is precisely the point at which you will be traveling at the speed of light...
No it's not. Matter cannot go at the speed of light and never does. Nothing can go faster than light. That's the whole bloody point of relativity. Stop watching bad sci-fi movies. There are I believe odd effects for certain observers who might see you but practically speaking you'd just be moving at just something like 0.99c. But that's just due to the acceleration of the black hole and it will continue to increase even after you cross the event horizon.
As soon as the flashlight passes through the event horizon, it'll disappear: not even the light from it will be able to reach you.
Nope, you continue seeing the flashlight. Well in some way at least. The event horizon for you has receded. Another way to think of it is that while the light is no longer moving towards you, sort of hovers at the event horizon, you're now moving towards the light. Relative velocity is all that matters. You'll get some odd relativistic distortions I believe, makes me wonder if a human nervous system even survive them, but you'll continue to observe things that went before you through the even horizon.