<blockquote>
  <p>How exactly can Hawking's Radiation carry the information?</p>
</blockquote>

<p>It does not, if you mean information about the interior of the black hole.</p>

<p>The relevant theorem is the <a href="https://en.wikipedia.org/wiki/No-hair_theorem" rel="nofollow noreferrer">No Hair Theorem</a>.  Basically you can only get gross statistical properties of black holes, nothing else and no information about the interior structure (meaning any info inside stored in any way, stays there or is lost as randomized radiation).</p>

<p>If you accept the No Hair Theorem then Hawking radiation would be essentially random in character, giving you no more information about the black hole than the No Hair Theorem allows you to know.  This would mean "information" being lost as a black hole evaporates.</p>

<blockquote>
  <p>How is it possible for information to exist at the event horizon?</p>
</blockquote>

<p>I don't think it's possible for anything to exist <em>at</em> the event horizon for any time.  It's a surface of zero thickness (as I understand it) and no actual substance.  Nothing can stop there and no real thing could be said to be "on" the horizon, just passing through it.</p>

<p>One of the complication of discussing black holes in relation to things like quantum-scale elementary particles is that while we can't say exactly where a particle is (the uncertainty principle) "classical" general relativity (i.e. without quantum theory) doesn't incorporate this at all and so the idea of a particle having a precise position is perfectly reasonable in classical general relativity.  But that's unlikely to be the case in whatever theory we end up with that links general relativity and quantum field theories.</p>

<p>I suspect you are hearing things related to the <a href="https://en.wikipedia.org/wiki/Holographic_principle" rel="nofollow noreferrer">Holographic principle</a>.  This is pretty much beyond my real understanding in any depth, but note that it is intimately linked with trying to connect String Theory, gravity (and hence a kind of quantum gravity), Thermodynamics and a notion of "information" within those multiple contexts.  I personally don't intend to try and read too much into this as it's beyond cutting edge theory for me (beyond my "event horizon" I suppose :-) ).  However I'd suggest being wary of reading too much into this idea given the present state of the theories involved.</p>

CC BY-SA 3.0
2018-04-13T02:20:25.823Z
How can we analyze the ripple ?  It's not clear if a ripple's effects can reach an external viewer.  The event horizon is a surface separating events an external viewer can detect from ones they can't.  The implication is that ripples *on* that surface are not detectable until an infinite time has passed for the observer.  I'm not an expert in this, but that's my understanding of it.  This also relates to the question can anything ever been seen to reach an event horizon from outside ?
StephenG - Help Ukraine
CC BY-SA 3.0
2018-04-13T02:24:56.223Z
As mentioned by @ userLTK, similar to that of a stone falling into the river and creating ripples. When some object falls into the black hole we can analyse what type of object was it. So nothing have to be on the surface we can understand by the activities of black holes. It seems, black hole is a terminator not recycle bin.
Arshdeep Singh
CC BY-SA 3.0
2018-04-13T02:30:51.777Z
maybe that’s what’s taken from by hawking’s radiation(neither do I hold much of a knowledge about this topic:) outsiders would be able to see the information only if the holographic principle is correct, it seems!
Arshdeep Singh
CC BY-SA 3.0
2018-04-12T21:46:50.250Z
2018-04-12T21:46:50.250Z
StephenG - Help Ukraine
<p>I hate to answer questions like this because they're very complex ideas that are often attempts at explaining in simpler ways to laymen and the "How/why" questions can be long and not always easy to understand.   See <a href="https://physics.stackexchange.com/questions/29175/why-is-information-indestructible">this related question with some very nice long and complex answers</a>. </p>

<blockquote>
  <p>If the mass was swallowed by the blackholes then every single particle
  should be inside the event horizon as they brought towards the black
  hole at very high velocity and it's becoming difficult to imagine that
  some particles were left at the horizon itself</p>
</blockquote>

<p>Particles don't have to be retained at the event horizon for information to be retained just outside.   This gets tricky, but an image of the particle, not the particle itself is retained.  While it's an imperfect analogy, dropping a stone in water creates ripples, which spread out and shrink over time.  By carefully analyzing those ripples, you can determine the mass and size of the stone and when it was thrown in.   </p>

<blockquote>
  <p>How is it possible for information to exist at the event horizon?</p>
</blockquote>

<p>Information doesn't exist "at" the event horizon.  Nothing can exist at the event horizon in a practical sense, stuff passes through the event horizon, but from the perspective of a person some distance away, they see the object falling into the black hole take forever to get there (in reality the visibility red-shifts beyond recognition very quickly), but if you could see it with some kind of super-long-wave imaging device, and a supercomputer to put the information together, you could in theory see everything that ever fell into the black hole by carefully observing the light that escapes from it.</p>

<p>So, nothing is actually encoded on the event horizon (the video got that point wrong).  It's all images that take a very long time to reach the viewer from just outside the event horizon due to extreme time dilation.</p>

<blockquote>
  <p>How exactly can Hawking's Radiation carry the information?</p>
</blockquote>

<p>The precise words in the video are</p>

<blockquote>
  <p>"If information is stored on the surface of a black hole, hawking
  radiation has a chance of learning about the information encoded there
  and carrying it away"</p>
</blockquote>

<p>So, you're asking a question about an "if" and a "chance of", very far from a certainty.   I'm not educated enough in the various theories to say how hawking radiation might pick up information from the black hole's formation and history.  My limited understanding is that it can't.   That Hawking radiation is "new" information so to speak, not carried off bits of old information, but that offends information theory . . . which is a problem for quantum theorists.  Please don't take my word for any of this stuff.</p>

<p>Professor Matt Strassler writes a series of articles that try to explain modern physics to people like me and his stuff gets a top review from me.   <a href="https://profmattstrassler.com/articles-and-posts/relativity-space-astronomy-and-cosmology/black-holes/black-hole-information-paradox-an-introduction/" rel="nofollow noreferrer">His article on this subject is probably worth a look</a> and he touches on some of the "We don't knows" in better detail.  I remember watching one of professor Susskind's lecture on holograms, black holes and information theory on youtube and enjoyed that as well (there's more than one, easily googled, so I won't link).   </p>

CC BY-SA 3.0
2018-04-12T21:00:36.913Z
2018-04-12T21:00:36.913Z
userLTK
<p><b>A theory about Blackholes storing the information from the universe.</b></p>

<p>Being said that Blackholes are condensed mass sufficient enough to break every particle into different elementary particles, broken particles will eventually reach the center(or they break down the time they reach there).</p>

<p>Some say that the information is stored on the surface instead, which can be carried by the Hawking's Radiation.</p>

<p>Questions:</p>

<ol>
<li><p>How exactly can Hawking's Radiation carry the information?</p></li>
<li><p>How is it possible for information to exist at the event horizon? </p></li>
</ol>

<p>(If the mass was swallowed by the blackholes then every single particle should be inside the event horizon as they brought towards the black hole at very high velocity and it's becoming difficult to imagine that some particles were left at the horizon itself).</p>

<p><i>Maybe</i>: If the information is on the event Horizon then it might not have broken to elementary particles!</p>

CC BY-SA 3.0
2018-04-12T17:42:03.460Z
Do you have a source that says the information on the surface can be carried by Hawking radiation?   I'm not an expert in this field by any means, but I don't think that's accurate.
userLTK
CC BY-SA 3.0
2018-04-12T17:49:34.977Z
[YouTube](https://www.youtube.com/watch?v=yWO-cvGETRQ) This channel(Kurzgesagt) is quite reliable. You can skip this video to the 8th minute.
Arshdeep Singh
CC BY-SA 3.0
2018-04-12T20:49:37.783Z
I don’t have a source yet, but I believe it has been proven you can get no useful info from this
JSCoder says Reinstate Monica
CC BY-SA 3.0
2018-04-13T07:36:52.253Z
A black hole may preserve the information, but that doesn't necessarily imply that the information can be retrieved in any coherent fashion. A crude analogy: if you get a sorted deck of cards and start shuffling it, the deck preserves your shuffles, but you generally can't reconstruct the shuffles by examining the order of the cards.
PM 2Ring
<black-hole><hawking-radiation><event-horizon>
Information Paradox with Hawking's Radiation
Arshdeep Singh
# Information Paradox with Hawking's Radiation

(Asked by: username_0 on 2018-04-12)

**A theory about Blackholes storing the information from the universe.**

Being said that Blackholes are condensed mass sufficient enough to break every particle into different elementary particles, broken particles will eventually reach the center(or they break down the time they reach there).

Some say that the information is stored on the surface instead, which can be carried by the Hawking's Radiation.

Questions:

1. How exactly can Hawking's Radiation carry the information?
2. How is it possible for information to exist at the event horizon?

(If the mass was swallowed by the blackholes then every single particle should be inside the event horizon as they brought towards the black hole at very high velocity and it's becoming difficult to imagine that some particles were left at the horizon itself).

*Maybe*: If the information is on the event Horizon then it might not have broken to elementary particles!

**Tags:** black-hole, hawking-radiation, event-horizon

> **Comments:**
> **username_1**: Do you have a source that says the information on the surface can be carried by Hawking radiation?   I'm not an expert in this field by any means, but I don't think that's accurate.  
> **username_0**: [YouTube](https://www.youtube.com/watch?v=yWO-cvGETRQ) This channel(Kurzgesagt) is quite reliable. You can skip this video to the 8th minute.  
> **username_2**: I don’t have a source yet, but I believe it has been proven you can get no useful info from this  
> **username_3**: A black hole may preserve the information, but that doesn't necessarily imply that the information can be retrieved in any coherent fashion. A crude analogy: if you get a sorted deck of cards and start shuffling it, the deck preserves your shuffles, but you generally can't reconstruct the shuffles by examining the order of the cards.  

---

## 2 answers

### Answer by username_4 on 2018-04-12. Score: 1 | Accepted answer

> How exactly can Hawking's Radiation carry the information?

It does not, if you mean information about the interior of the black hole.

The relevant theorem is the [No Hair Theorem](https://en.wikipedia.org/wiki/No-hair_theorem). Basically you can only get gross statistical properties of black holes, nothing else and no information about the interior structure (meaning any info inside stored in any way, stays there or is lost as randomized radiation).

If you accept the No Hair Theorem then Hawking radiation would be essentially random in character, giving you no more information about the black hole than the No Hair Theorem allows you to know. This would mean "information" being lost as a black hole evaporates.

> How is it possible for information to exist at the event horizon?

I don't think it's possible for anything to exist *at* the event horizon for any time. It's a surface of zero thickness (as I understand it) and no actual substance. Nothing can stop there and no real thing could be said to be "on" the horizon, just passing through it.

One of the complication of discussing black holes in relation to things like quantum-scale elementary particles is that while we can't say exactly where a particle is (the uncertainty principle) "classical" general relativity (i.e. without quantum theory) doesn't incorporate this at all and so the idea of a particle having a precise position is perfectly reasonable in classical general relativity. But that's unlikely to be the case in whatever theory we end up with that links general relativity and quantum field theories.

I suspect you are hearing things related to the [Holographic principle](https://en.wikipedia.org/wiki/Holographic_principle). This is pretty much beyond my real understanding in any depth, but note that it is intimately linked with trying to connect String Theory, gravity (and hence a kind of quantum gravity), Thermodynamics and a notion of "information" within those multiple contexts. I personally don't intend to try and read too much into this as it's beyond cutting edge theory for me (beyond my "event horizon" I suppose :-) ). However I'd suggest being wary of reading too much into this idea given the present state of the theories involved.

> **Comments:**
> **username_4**: How can we analyze the ripple ?  It's not clear if a ripple's effects can reach an external viewer.  The event horizon is a surface separating events an external viewer can detect from ones they can't.  The implication is that ripples *on* that surface are not detectable until an infinite time has passed for the observer.  I'm not an expert in this, but that's my understanding of it.  This also relates to the question can anything ever been seen to reach an event horizon from outside ?  
> **username_0**: As mentioned by @ username_1, similar to that of a stone falling into the river and creating ripples. When some object falls into the black hole we can analyse what type of object was it. So nothing have to be on the surface we can understand by the activities of black holes. It seems, black hole is a terminator not recycle bin.  
> **username_0**: maybe that’s what’s taken from by hawking’s radiation(neither do I hold much of a knowledge about this topic:) outsiders would be able to see the information only if the holographic principle is correct, it seems!  

---

### Answer by username_1 on 2018-04-12. Score: 0

I hate to answer questions like this because they're very complex ideas that are often attempts at explaining in simpler ways to laymen and the "How/why" questions can be long and not always easy to understand. See [this related question with some very nice long and complex answers](https://physics.stackexchange.com/questions/29175/why-is-information-indestructible).

> If the mass was swallowed by the blackholes then every single particle
> should be inside the event horizon as they brought towards the black
> hole at very high velocity and it's becoming difficult to imagine that
> some particles were left at the horizon itself

Particles don't have to be retained at the event horizon for information to be retained just outside. This gets tricky, but an image of the particle, not the particle itself is retained. While it's an imperfect analogy, dropping a stone in water creates ripples, which spread out and shrink over time. By carefully analyzing those ripples, you can determine the mass and size of the stone and when it was thrown in.

> How is it possible for information to exist at the event horizon?

Information doesn't exist "at" the event horizon. Nothing can exist at the event horizon in a practical sense, stuff passes through the event horizon, but from the perspective of a person some distance away, they see the object falling into the black hole take forever to get there (in reality the visibility red-shifts beyond recognition very quickly), but if you could see it with some kind of super-long-wave imaging device, and a supercomputer to put the information together, you could in theory see everything that ever fell into the black hole by carefully observing the light that escapes from it.

So, nothing is actually encoded on the event horizon (the video got that point wrong). It's all images that take a very long time to reach the viewer from just outside the event horizon due to extreme time dilation.

> How exactly can Hawking's Radiation carry the information?

The precise words in the video are

> "If information is stored on the surface of a black hole, hawking
> radiation has a chance of learning about the information encoded there
> and carrying it away"

So, you're asking a question about an "if" and a "chance of", very far from a certainty. I'm not educated enough in the various theories to say how hawking radiation might pick up information from the black hole's formation and history. My limited understanding is that it can't. That Hawking radiation is "new" information so to speak, not carried off bits of old information, but that offends information theory . . . which is a problem for quantum theorists. Please don't take my word for any of this stuff.

Professor Matt Strassler writes a series of articles that try to explain modern physics to people like me and his stuff gets a top review from me. [His article on this subject is probably worth a look](https://profmattstrassler.com/articles-and-posts/relativity-space-astronomy-and-cosmology/black-holes/black-hole-information-paradox-an-introduction/) and he touches on some of the "We don't knows" in better detail. I remember watching one of professor Susskind's lecture on holograms, black holes and information theory on youtube and enjoyed that as well (there's more than one, easily googled, so I won't link).


---

