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How do black holes destroy information and why is that a problem?

backreaction.blogspot.com

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Re: How do black holes destroy information and why is that a problem?

#21

Post by jinushaun »

JDEW wrote: post #15
maxheadroom wrote: post #4

To save you the read, the summation is in the second-to-last paragraph: > As you have probably noticed, I didn’t say anything about information. That’s because really the reference to information in “black hole information loss” is entirely unnecessary and just causes confusion. The problem of black hole “information loss” really has nothing to do with just exactly what you mean by information. It’s just a term that…

I think the article is already quite concise. Moreover it is nicely written and explains a current open problem in physics from first principles. A summary like this is useful if the underlying article is bloated and clickbait-y but in this case potentially detracts a reader from a good article. As featured on the front page a few days ago [1]: knowledge without understanding is meaningless. [1] https://www.theguardi…

It’s the opposite of well written and concise! The writing style is very much like someone talking, full of sentences that are too long or too short.

Re: How do black holes destroy information and why is that a problem?

#22

Post by swebs »

TeMPOraL wrote: post #18
sohkamyung wrote: post #12

Earlier quoted context omitted.

I believe the 'No-hair theorem' is closest to a 'law' that says Black holes destroy information [1]. If it is true, then when you throw anything into a black hole, information about what you threw in (whether it is a chair, a star, a planet, etc.) is 'lost' as to the outside world they all yield the same observable parameters of the black hole. [1] https://en.wikipedia.org/wiki/No-hair_theorem

IANAPhysicist, but couldn't information be radiated away? When you have a particle and antiparticle annihilating, the information about what collided and when is carried away by the radiation from that annihilation event; nothing remains at ground zero to be inspected. As matter traverses the accretion disk and falls towards the event horizon, couldn't information about it be radiated away? As an observer, you could…

Outside the event horizon, sure. But imagine the (extremely) far future when the universe is dominated by black holes and even those photons have been absorbed. You would not be able to extract any information about the past universe aside from its mass.

Re: How do black holes destroy information and why is that a problem?

#24

Post by platz »

TeMPOraL wrote: post #18
sohkamyung wrote: post #12

Earlier quoted context omitted.

I believe the 'No-hair theorem' is closest to a 'law' that says Black holes destroy information [1]. If it is true, then when you throw anything into a black hole, information about what you threw in (whether it is a chair, a star, a planet, etc.) is 'lost' as to the outside world they all yield the same observable parameters of the black hole. [1] https://en.wikipedia.org/wiki/No-hair_theorem

IANAPhysicist, but couldn't information be radiated away? When you have a particle and antiparticle annihilating, the information about what collided and when is carried away by the radiation from that annihilation event; nothing remains at ground zero to be inspected. As matter traverses the accretion disk and falls towards the event horizon, couldn't information about it be radiated away? As an observer, you could…

As it stands, as far as we know, Hawking radiation is completely thermal and random, so as the article states, you can't tell the initial state from the final state even if you collect all the radiation.

> observing the accretion disk

Well that is not part of the black hole now, is it.

Re: How do black holes destroy information and why is that a problem?

#25

Post by effie »

TeMPOraL wrote: post #18
sohkamyung wrote: post #12

Earlier quoted context omitted.

I believe the 'No-hair theorem' is closest to a 'law' that says Black holes destroy information [1]. If it is true, then when you throw anything into a black hole, information about what you threw in (whether it is a chair, a star, a planet, etc.) is 'lost' as to the outside world they all yield the same observable parameters of the black hole. [1] https://en.wikipedia.org/wiki/No-hair_theorem

IANAPhysicist, but couldn't information be radiated away? When you have a particle and antiparticle annihilating, the information about what collided and when is carried away by the radiation from that annihilation event; nothing remains at ground zero to be inspected. As matter traverses the accretion disk and falls towards the event horizon, couldn't information about it be radiated away? As an observer, you could…

Yes the radiation from the infalling body gives the remote observer some information about what is going on with the body. From their viewpoint, the process of fall into the hole takes infinite time, or in other words, it never completes. The longer the time of observation, the longer the wavelengths of the radiation from the body, so the less and less information is obtained, until the radiation is so red shifted that it is not measurable. That is when the acquisition of information stops. The body still falls down after that, it is a never-ending process but for practical purposes the body is gone.

Re: How do black holes destroy information and why is that a problem?

#26

Post by raphaelj »

jinushaun wrote: post #21
JDEW wrote: post #15

Earlier quoted context omitted.

I think the article is already quite concise. Moreover it is nicely written and explains a current open problem in physics from first principles. A summary like this is useful if the underlying article is bloated and clickbait-y but in this case potentially detracts a reader from a good article. As featured on the front page a few days ago [1]: knowledge without understanding is meaningless. [1] https://www.theguardi…

It’s the opposite of well written and concise! The writing style is very much like someone talking, full of sentences that are too long or too short.

That's because it's a direct transcript of the Youtube video above.

Re: How do black holes destroy information and why is that a problem?

#28

Post by TheOtherHobbes »

TeMPOraL wrote: post #18
sohkamyung wrote: post #12

Earlier quoted context omitted.

I believe the 'No-hair theorem' is closest to a 'law' that says Black holes destroy information [1]. If it is true, then when you throw anything into a black hole, information about what you threw in (whether it is a chair, a star, a planet, etc.) is 'lost' as to the outside world they all yield the same observable parameters of the black hole. [1] https://en.wikipedia.org/wiki/No-hair_theorem

IANAPhysicist, but couldn't information be radiated away? When you have a particle and antiparticle annihilating, the information about what collided and when is carried away by the radiation from that annihilation event; nothing remains at ground zero to be inspected. As matter traverses the accretion disk and falls towards the event horizon, couldn't information about it be radiated away? As an observer, you could…

When it comes to black holes, no one is a physicist.

The problems appear when you try to apply GR and the rest of classical physics - which all assume spacetime is continuous and analytically smooth - to a situation it can't handle.

It's a good tool for normal spacetime, it's fine for making predictions all the way up to an event horizon, but it's absolutely unable to say anything useful about what happens at an event horizon - never mind beyond one.

Because the question isn't "What happens to an astronaut or a chair at the event horizon?" It's "What happens to wave equations and quantum fields at the event horizon?"

If all information is lost at the the event horizon, quantum theory stops working in a catastrophic way. There are no fields, no particles, no interactions, possibly not even raw spacetime.

If it isn't lost, then something else happens, but no one is sure what it is yet.

Hawking's theory works on the basis that some relationships persists across the horizon - actually they stretch back to the formation of the black hole - but he seems to have assumed that it's possible to ignore the limits set by the Planck length/time. There are good reasons for thinking this is unlikely to be true.

Without a theory of quantum gravity - or rather of quantum spacetime - this is all guesswork. It isn't even possible to prove the No Hair Conjecture.

So although it's currently assumed that mass, angular momentum, and charge are conserved (and therefore not all information is lost), there's no proof for this, and no explanation why these features would be conserved while others aren't.

Re: How do black holes destroy information and why is that a problem?

#30

Post by ivansavz »

TeMPOraL wrote: post #18
sohkamyung wrote: post #12

Earlier quoted context omitted.

I believe the 'No-hair theorem' is closest to a 'law' that says Black holes destroy information [1]. If it is true, then when you throw anything into a black hole, information about what you threw in (whether it is a chair, a star, a planet, etc.) is 'lost' as to the outside world they all yield the same observable parameters of the black hole. [1] https://en.wikipedia.org/wiki/No-hair_theorem

IANAPhysicist, but couldn't information be radiated away? When you have a particle and antiparticle annihilating, the information about what collided and when is carried away by the radiation from that annihilation event; nothing remains at ground zero to be inspected. As matter traverses the accretion disk and falls towards the event horizon, couldn't information about it be radiated away? As an observer, you could…

> the information about what collided and when is carried away by the radiation

This is where the thermal nature of the radiation emitted by the black hole comes in. Physicist use the term "thermal radiation" to mean it is in a mixed state that cannot encode information (crude analogy: as if someone has pressed all the keys of a keyboard at once, you see that some keys are being pressed but this "signal" cannot be decoded).

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