Thread: Why can't information be destroyed?

I forget whether it was in a thread about black holes on this forum, or in another book I was reading, there was a statement made that information about material falling into a black hole can never be destroyed.

Is this just an assumption about how the Universe works, or an actual law?

Could it be possible to explain (in "layman" terms) why this is the case if it's true?

It's likely I'm just misunderstanding what's meant by information, but doesn't entropy destroy information and a black hole is like a region of infinite entropy?

Hmmm. I don't think there is a layman's explanation. In the many-worlds interpretation of quantum physics, the multiverse is deterministic in the sense that alternative universes are neither created nor destroyed, so there is a one-to-one correspondence between the past and future within the multiverse as a whole. The second law of thermodynamics then relates to our view of only part of the multiverse in which it appears as if entropy is increasing due to pasts being excluded from what we regard as reality due to observation. Thus, if a person places an object in a blackhole, and another version of that same person in an alternative universe places a different object in his version of the same blackhole, then when the blackholes in each of the alternative universes evaporate, the resulting two universes still have to be distinguishable in terms of the differences between the two objects that were placed in the blackholes.

Originally Posted by Daecon

I forget whether it was in a thread about black holes on this forum, or in another book I was reading, there was a statement made that information about material falling into a black hole can never be destroyed.

Is this just an assumption about how the Universe works, or an actual law?

Could it be possible to explain (in "layman" terms) why this is the case if it's true?

It's likely I'm just misunderstanding what's meant by information, but doesn't entropy destroy information and a black hole is like a region of infinite entropy?

There is a philosophical position that information must be preserved. However, as far as I know, there has not been a formal proof that such a conservation law must be obeyed. although most of my friends feel that it must be true and often accept it as an axiom. Here's a scenario that outlines the problem: I toss a book into a black hole. Thanks to Hawking radiation, that black hole will eventually evaporate away. What happened to the information in the book? I have not seen a rigorous demonstration that the information survives, although there's no paucity of attempts (generally of the form "the information is still there, 'somehow' encoded in the radiation that is the legacy of the black hole"). If, as the argument goes, the information is embedded in the radiation, how could one -- even in principle -- recover this information? To my knowledge, that question does not yet have a solid answer. It's a hard problem.

You don't understand what is blackhole.

Once human beings understand blackhole and substance’s movement around it, the science and technology will advance a big step. Then Continuable Generator, Galaxy Travel and much more applications will come out.

Please don't post nonsense.

Originally Posted by Dywyddyr

Please don't post nonsense.

The adorable kitten and cute parakeet make it worth reading.

But you've seen one adorable kitten and cute parakeet, you've seen them all.

Originally Posted by loongjohn

Once human beings understand blackhole and substance’s movement around it, the science and technology will advance a big step. Then Continuable Generator, Galaxy Travel and much more applications will come out.

...especially from the China cranks.

I had not heard that any philosophical position required that information not be destroyed, but I can accept that there is one. Of course in a four dimensional sence nothing that has ever been is ever destroyed since every event andits players are all written into the fabric of the universe. In that sence information is everlasting. However in that sense there is no need to involve black holes. Everything that ever was, IS, somewhere/when in the four dimentional universe.

Originally Posted by Sealeaf

I had not heard that any philosophical position required that information not be destroyed, but I can accept that there is one. Of course in a four dimensional sence nothing that has ever been is ever destroyed since every event andits players are all written into the fabric of the universe. In that sence information is everlasting. However in that sense there is no need to involve black holes. Everything that ever was, IS, somewhere/when in the four dimentional universe.

Really?
Where's the conversation I had last week?
Where's the information I typed out and then scrambled using the super-anti-decryption method ¹?
Of course, if you're invoking "when" and relying on time travel to access that information it might as well be lost/ destroyed.

1 It's the "joke" one. Assign a numerical value to each letter A=1, Z=26, ignore spaces. Then just add all the numbers together repeatedly until you get a single-digit number. A document of any length can be converted to a single digit (the joke being, of course, that there's no way for anyone - intended recipient or enemy - to decrypt it) - where's the information from that?

Originally Posted by Dywyddyr

Originally Posted by Sealeaf

I had not heard that any philosophical position required that information not be destroyed, but I can accept that there is one. Of course in a four dimensional sence nothing that has ever been is ever destroyed since every event andits players are all written into the fabric of the universe. In that sence information is everlasting. However in that sense there is no need to involve black holes. Everything that ever was, IS, somewhere/when in the four dimentional universe.

Really?
Where's the conversation I had last week?
Where's the information I typed out and then scrambled using the super-anti-decryption method ¹?
Of course, if you're invoking "when" and relying on time travel to access that information it might as well be lost/ destroyed.

I'm pretty sure the rule is just that the quantity of information in a system must remain constant. That is where Black Holes cause trouble, since there are only a few traits of a black hole that can be observed from outside the event horizon.


It's not about being able to reconstruct the past from the present. That is clearly impossible. Since we can't perfectly measure the present velocity and location of an object, trying to determine with precision where it came from and when is all the more impossible.

That makes sense, but it doesn't seem to be what Sealeaf's post was implying.

Originally Posted by tk421

Originally Posted by Daecon

I forget whether it was in a thread about black holes on this forum, or in another book I was reading, there was a statement made that information about material falling into a black hole can never be destroyed.

Is this just an assumption about how the Universe works, or an actual law?

Could it be possible to explain (in "layman" terms) why this is the case if it's true?

It's likely I'm just misunderstanding what's meant by information, but doesn't entropy destroy information and a black hole is like a region of infinite entropy?

There is a philosophical position that information must be preserved. However, as far as I know, there has not been a formal proof that such a conservation law must be obeyed. although most of my friends feel that it must be true and often accept it as an axiom. Here's a scenario that outlines the problem: I toss a book into a black hole. Thanks to Hawking radiation, that black hole will eventually evaporate away. What happened to the information in the book? I have not seen a rigorous demonstration that the information survives, although there's no paucity of attempts (generally of the form "the information is still there, 'somehow' encoded in the radiation that is the legacy of the black hole"). If, as the argument goes, the information is embedded in the radiation, how could one -- even in principle -- recover this information? To my knowledge, that question does not yet have a solid answer. It's a hard problem.

Thank you!

I even understood what you were saying!

Such a great explanation!

THANK YOU SO MUCH!

Originally Posted by Dywyddyr

That makes sense, but it doesn't seem to be what Sealeaf's post was implying.

Yeah. That's true. I should have addressed Sealeaf with the correction.

I think "information" is just another one of those words that gets used when another would be less confusing. I think it would be better to call it "complexity".

Black holes cause problems because they are very simple in many respects. I mean, without invoking stuff like the holographic principle, a black hole otherwise appears to have taken lots of very complex matter and reduced it to a single blob that can be described with only a few variables.


Holographic principle - Wikipedia, the free encyclopedia

What about sink holes that swallow buildiings ??

I don't think there is a layman's explanation.

If you can't explain it simply, you don't understand it well enough. -Albert Einstein

Actually that's not always true, but that quote really astounds me.

Yeah. I was going to mention that General Relativity isn't very simple..... but then I thought about it again, and maybe that's because most people don't fully understand it (especially me so far.)

I was under the impression that 'absolutely everything' can be boiled down to information, at the most fundamental level. Thus, as 'absolutely everything' is essentially some form of mass or energy, and the conservation of these properties are set out in well-known laws already, the idea that information cannot be destroyed is merely an extension of these principles to include information.

Originally Posted by Dywyddyr

Please don't post nonsense.

Indeed.

The original question contained the nonsense
"That information cannot be destroyed".

I can't understand how anyone could say information cannot be destroyed, its just too obviously easily to destroy information.

Why can't a black-hole destroy information ?No one went in to verify if it does or doesn't !

Originally Posted by Isilder

Indeed.
The original question contained the nonsense
"That information cannot be destroyed".

Except that, for this discussion, information means physical information: as was pointed out to me in posts #12 & #15.

I can't understand how anyone could say information cannot be destroyed, its just too obviously easily to destroy information.

See here for what's being talked about.

Why can't a black-hole destroy information ?No one went in to verify if it does or doesn't !

And here.

The nonsense I referred to was specifically that given in loongjohn's post - i.e. the entirety of his claim.

Originally Posted by Dywyddyr

Originally Posted by Sealeaf

I had not heard that any philosophical position required that information not be destroyed, but I can accept that there is one. Of course in a four dimensional sence nothing that has ever been is ever destroyed since every event andits players are all written into the fabric of the universe. In that sence information is everlasting. However in that sense there is no need to involve black holes. Everything that ever was, IS, somewhere/when in the four dimentional universe.

Really?
Where's the conversation I had last week?
Where's the information I typed out and then scrambled using the super-anti-decryption method ¹?
Of course, if you're invoking "when" and relying on time travel to access that information it might as well be lost/ destroyed.

Just because you can't 'tangibly' locate the conversation, it doesn't mean information passed through having it doesn't still exist somewhere.

For instance, to talk, you needed to vibrate your vocal chords, so that those vibrations could be heard, as sound waves - this was the information in your brain being 'coded-up' into a wave for transmission.

Even though those sound waves went into someone's ear, as you intended, and that person may have forgotten the information after their brain decrypted the sound wave into language, the sound wave travelled elsewhere between and beyond, like the waves from a stone hitting a pool of water. These waves moved other atoms and particles, changing their position and momentum, which are both types of information about atoms. Thus, the information lives on in other forms... But your friend still forgot what time to meet you at the train station...

Originally Posted by NoCoolAvatar

Just because you can't 'tangibly' locate the conversation, it doesn't mean information passed through having it doesn't still exist somewhere.

Nonsense.

For instance, to talk, you needed to vibrate your vocal chords, so that those vibrations could be heard, as sound waves - this was the information in your brain being 'coded-up' into a wave for transmission.
Even though those sound waves went into someone's ear, as you intended, and that person may have forgotten the information after their brain decrypted the sound wave into language, the sound wave travelled elsewhere between and beyond, like the waves from a stone hitting a pool of water. These waves moved other atoms and particles, changing their position and momentum, which are both types of information about atoms. Thus, the information lives on in other forms... But your friend still forgot what time to meet you at the train station...

And eventually (i.e. within a very short time) those atmospheric vibrations will be subsumed in the general chaos of ordinary atmospheric movement and be lost irrevocably.
The noise will drown the signal so that it becomes irretrievable.

Originally Posted by Dywyddyr

Originally Posted by NoCoolAvatar

Just because you can't 'tangibly' locate the conversation, it doesn't mean information passed through having it doesn't still exist somewhere.

Nonsense.

And eventually (i.e. within a very short time) those atmospheric vibrations will be subsumed in the general chaos of ordinary atmospheric movement and be lost irrevocably.
The noise will drown the signal so that it becomes irretrievable.

I fear you have misunderstood. Please let me restate:

The signal itself, that you say gets 'drowned out', is not 'the information' that remains after the event (not in that particular 'signal' form, anyway). The original information has transformed, much like energy transforms from one type to another (in fact, energy transformation is a manifestation of information exchange).

You are quite right that the wave eventually dissipates; but to do so, it transfers its energy on the way, changing the momentum of particles etc. Thus, the information taken from your sound wave changes the information (momentum) possessed by the particles - i.e. they have incorporated your information.

So while you are correct to say that the 'decode' of the conversation itself is irretrievable, the total information in the system remains the same - i.e. no information is lost; like energy, it has transformed to another form.

You say yourself that the 'vibrations [are] subsumed in... atmospheric movement'. What I am saying is that this change in atmospheric movement is your original information (albeit transformed), so the total information in the system remains.

Originally Posted by NoCoolAvatar

I fear you have misunderstood. Please let me restate:

The signal itself, that you say gets 'drowned out', is not 'the information' that remains after the event (not in that particular 'signal' form, anyway). The original information has transformed, much like energy transforms from one type to another (in fact, energy transformation is a manifestation of information exchange).

You are quite right that the wave eventually dissipates; but to do so, it transfers its energy on the way, changing the momentum of particles etc. Thus, the information taken from your sound wave changes the information (momentum) possessed by the particles - i.e. they have incorporated your information.

So while you are correct to say that the 'decode' of the conversation itself is irretrievable, the total information in the system remains the same - i.e. no information is lost; like energy, it has transformed to another form.

You say yourself that the 'vibrations [are] subsumed in... atmospheric movement'. What I am saying is that this change in atmospheric movement is your original information (albeit transformed), so the total information in the system remains.

Then you appear to be, somehow, conflating information in the physical sense with information in the sense of the words spoken - "this was the information in your brain being 'coded-up' into a wave for transmission".

Originally Posted by Dywyddyr

Then you appear to be, somehow, conflating information in the physical sense with information in the sense of the words spoken - "this was the information in your brain being 'coded-up' into a wave for transmission".

Is not the information in your brain (your ideas, the things you want to say) transformed into sound-wave energy when you speak? Or changes in the physical constitution of the paper you write them on?

What you are challenging here, (I think), is whether it is possible for physical information to come from the sounds you make when speaking. If you were to shout in my ear loud enough, you could burst my eardrum. A physical manifestation of the spoken word.