Physicists Theorize Out How To Retrieve Information From a Black Hole (sciencemag.org) 82
sciencehabit writes: Black holes earn their name because their gravity is so strong not even light can escape from them. Oddly, though, physicists have come up with a bit of theoretical sleight of hand to retrieve a speck of information that's been dropped into a black hole. The calculation touches on one of the biggest mysteries in physics: how all of the information trapped in a black hole leaks out as the black hole 'evaporates.' Many theorists think that must happen, but they don't know how.
Easy (Score:5, Funny)
Ask a politician or CEO or salesman. They routinely pull information out of a "black hole".
Re:Easy (Score:4, Insightful)
It's more of a brown hole. Many people refer to it, as well as the politician/ceo/salesman, as an "ass" or "asshole".
Fox news (Score:2, Offtopic)
fox news emits no information.
Re: (Score:1)
Why do they expect information to be conserved in the first place? Information loss is common and you don't even need black holes. A simple example is matter-antimatter collision which turns into two photons, so you lose information about the identify of the original particles.
No information is lost in that scenario.
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Really? Explain how you'd retrieve the velocity, direction and spin state of the original particles from the light created by the collision then.
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how you'd retrieve the velocity, direction and spin state of the original particles
This is irrelevant to the physical information content of the system. Physical information is not about how many numbers you can or can't know for every given time. It is basically just the log of the number of possible states the system is in. If you measured everything possible of a given system, it would have no physical information because it would be in a single, specific state.
Try looking up one of many articles that actually explains what physical information is before making assumptions about the
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"This is irrelevant to the physical information content of the system."
So you can't. Well we got there in the end.
" It is basically just the log of the number of possible states the system is in."
Thats not even information since it'll be exactly the same for every similar particle or group of particles in a given enviroment. Its like saying "The colour of a black box is black".
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It doesn't seem to match the definition of information that programmers use routinely in their work. I'm fairly certain that they is a mathematical identity between the two uses of the word, as they both tie back to Shannon, but the use seems to have developed extremely differently.
To a programmer every feature that is used to describe an object represents a certain number of bits of information. Clearly it is being asserted that physicists use a very different meaning. It sounds is if it's something lik
Re: junk physics (Score:2, Insightful)
The connection between statistical mechanics and information theory was made by von Neumann right when talking with Shannon about his now famous work. If you want to complain the defition is bad, you can start by complaining about their work. Or you can be like Viol8 and equivocate in response to every article about physical theory (it has happened at least several times before) and pretend that refusing to learn about a topic is some form of insight.
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I'm not saying the definition is bas, as it clearly isn't. In either field. I'm saying the two fields apparently use the term quite differently. This doesn't make either wrong. And I think that both would agree on the basics, e.g. that a bit is a unit of information.
P.S.: I tend to think of this as an oversimplification, but it's one we've built all our digital hardware around. The problem is it seems to make any relatively prime chunk of information require an infinite number of bits to express accur
Re: junk physics (Score:1)
Your password can have a lot of bits of data but very little information. You notice where they say your password is weak? The complaint is about entrophy. And if you are cool you can measure that and then say something like "my password has 256 bits of data and 3 bits of entrophy."
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While correct, a password usually only has a very little information it is because of the larger embedded context. I.e., if your language is English you find it more common for certain letters to follow other letters, and for letters to follow letters, etc. So the intrinsic information is the number of bits used to express it, but the information in context is the number of bits required to represent it using an optimal compression algorithm using all the contextual information that you know. Both are va
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Ironic comment coming from someone who can't spell a-r-s-ehole.
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Did you pull all that out your backside? Newsflash - you can't go back in time, whether you can mathematically or not is irrelevant. Even mathematically you can just add a modulo function and then its forwards only.
too theoretical for now (Score:1)
But black holes are great (Score:1)
for data compression.
Reservations re Hawking radiation (Score:3, Interesting)
Ignorant amateur here. ISTM that if a virtual pair appears straddling the event horizion, the one that gets away never was inside the black hole to begin with, and thus would not carry away any matter or energy. Isn't the black hole just working as an engine to extract matter/energy from the vacuum near the event horizon? Half of which goes in, making the BH bigger, and half of which escapes to the external universe.
In the unlikely event that that conception is correct, it would be interesting to think about what happens to the vacuum near the event horizion. Does it get depleted of its vacuum energy, or is it an infinite source? If depleted, does vacuum energy flow in from other nearby vacuum to replenish it?
Is the vacuum inside a black hole anything like the external vacuum?
Re: Reservations re Hawking radiation (Score:1)
Re:Reservations re Hawking radiation (Score:5, Informative)
Also, to an external observer this process looks exactly the same as if the black hole itself was slowly emitting particles and shrinking away. And if the black hole is emitting particles, we can use that to determine something about its internal state.
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Not quite. The virtual pair has a net energy of 0, and therefore isn't really "extracting" anything from the vacuum. If the pair weren't straddling a black hole, they'd recombine and disappear and nothing would happen. However, when one member of the pair is sucked into a black hole while the other particle escapes, the escaping particle must have a greater-than-zero amount of energy. Because of that, and the requirement that the two particles balance each other out, the black hole has necessarily absorbed a negative-energy (not negatively-charged, mind you, actually negative energy) particle, causing the black hole to shrink ever so slightly. Basically, while the particles originally came from vacuum, the energy was taken from the black hole. Also, to an external observer this process looks exactly the same as if the black hole itself was slowly emitting particles and shrinking away. And if the black hole is emitting particles, we can use that to determine something about its internal state.
This is correct. The article is specifically addressing a mechanism by which quantum teleportation could release this information across the horizon. Granted to tell exactly what this is you would need to know the instaneous spin to a ludicrous precision, understand how quantum gravity works, understand the exact structure within the black hole, and several other far off concepts. However it is an interesting approach to solving this problem and could further research efforts.
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It's not negative energy.
The farther away the particle is from the event horizon, the more energy it has---the closer it is to the event horizon, the less energy it has. As the particle falls into the blackhole, the combined system (particle + black hole) actually lose energy, resulting in a drop in mass---which is conveniently carried away by the particle leaving the event horizon area.
That sure sounds equivelant to a negative energy or mass to me.
Re: (Score:1)
As I understand it, that's kind of like asking in a rocket launch, why the exhaust (which stays on Earth) ends up with all the particles that add had decreased gravitational potential energy, while the rocket ends up with all the particles with increased gravitational potential energy. The particle potential energies changed because of how their positions changed with respect to the Earth; the Earth didn't selectively grab all the ones that were going to go negative anyway and let the rest go.
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I was wondering about something related to this.
Would the escaping particles be equal measures of matter and anti-matter?
And if so, if the black hole was originally made up predominantly of matter, would the radiation process change the ratio of matter and antimatter in the universe (or at least locally)?
Or is there some force or field that would only let same-charge particles to escape, allowing you to determine what it was originally made of?
Re: (Score:1)
Half of which goes in, making the BH bigger, and half of which escapes to the external universe.
It actually makes the BH smaller. The virtual particle at the event horizon has more energy than the same virtual particle inside the blackhole... so the blackhole loses mass when that virtual particle falls in (and the other `virtual' particle appears to be coming out of the horizon). It's weird, but you take a 5 solar mass star, collapse it into a black hole, and it will be much less than 5 solar masses...
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It's weird, but you take a 5 solar mass star, collapse it into a black hole, and it will be much less than 5 solar masses...
First, a 5 solar mass star will likely shed more than enough of it to survive as a neutron star, or possibly even a white dwarf like our Sun will end up. If it were to somehow collapse without blowing off any of its mass, it would just meet the mass of the smallest known stellar mass black hole, and in reality they typically shed the vast majority.
Second, it's not strange at all that the object that remains has much less mass than the progenitor. Add the mass flung away in the explosion, and the kinetic ene
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Easy, (Score:1)
just go to blackhole.com
Maybe (Score:2)
It's not like there is a lot of experimental evidence here, one way or the other.
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Your point being?
That you are a Poindexter.
Send it to Guantanamo? (Score:1)
Does that get information, or just data?
"Theorize out"? (Score:2)
Physicists Theorize Out
Did they theorize the shit out of this thing?
Well (Score:2)
Why don't they use water-boarding? It works so well, as we all know.
Theory schmeory (Score:1)
/dev/null earns its name because the device is so small nothing can be read from it. Oddly, though, physicists have come up with a bit of theoretical sleight of hand to retrieve a speck of information that's been sent to /dev/null. The calculation touches on one of the biggest mysteries in physics: how all of the information written to /dev/null hole leaks out as heat from the CPU and gets 'dispersed' by the heat sink. Many theorists think that happens, but they don't know how to put humpty dumpty together
Have you tried: (Score:1)
Sounds like Mathematical Masturbation (Score:2)
Call me when there is an experiment to back it up. Otherwise it is just speculation.
Susskinds "Black Hole Wars" gives background (Score:3)
Out there in all of vast existence... (Score:1)
It's "hypothesize" (Score:1)