Conservation Of Information?

[koganbot]

Posting again on a subject I don't understand and never will: what physicists mean by "information." My brain balks at mathematical symbols, but I'm good at concepts; so my guess is that if some articulate physicist were to wander by, he or she could explain "conservation of information" in a way that doesn't totally leave me at sea. Wikipedia hasn't succeeded*, but this passage from the entry on "Black hole information paradox" is useful:

There are two main principles in play:

--Quantum determinism means that given a present wave function, its future changes are uniquely determined by the evolution operator.
--Reversibility refers to the fact that the evolution operator has an inverse, meaning that the past wave functions are similarly unique.

The combination of the two means that information must always be preserved.

What I gather from this is that: (i) any present "state" must have a unique past; you can't have two pasts leading to the same present; and (ii) the present can't lead to multiple futures. Am I interpreting this right? So a quantum waveform (?) version of a Laplace Demon** could reconstitute the past or forecast the future (or maybe, this being quanta, could reconstitute past probability wave something-or-other and forecast future probability wave something-or-other) based on what's known now. Hence information is preserved. So, however you twist it, you'll always have the same information.

When people talk about, say, "conservation of energy," I assume they mean that the amount of energy stays the same, no matter what form it takes. Whereas if someone says "conservation of information," I'd think (or guess, anyway) that what is meant isn't just that the amount of information is constant but that any form ("form"?) the information has taken can be reconstructed and whatever form it will take can be foreseen.

(Are reconstructing and foreseeing identical operations? If they're not, I don't understand how information can be said to be conserved. But then, as I say, I don't know what physicists mean by "information," or if they agree about what they mean by "information.")

This is not intuitive, but what's to come is even less so.

Black holes seemed to pose a problem for the principle in that, whatever you put into a black hole, you'd get the same result, a black hole that eventually irradiates away. (Is that the right way to put it, "irradiates away"?) So different pasts produce the same future; the same future can have more than one past. So that particular future doesn't preserve information about its actual, unique past. Currently, Leonard Susskind and crew believe they've definitively resolved the problem in favor of conservation of information, i.e., the preservation of a unique past, the resolution being by way of the holographic principle, though not everyone is convinced. I won't go into any of that yet.

The question I posed last time is, "When physicists say that information is preserved even after everything's been absorbed into black holes that have subsequently evaporated, do they mean that, e.g., 'The test tomorrow is at 1:00 PM' is preserved?" Certainly in my everyday use of the term "information," "the test tomorrow is at 1:00 PM" is information. So I can simplify my question down to this:

Is "The test tomorrow is at 1:00 PM" preserved (by the principle of conservation of information)? If not, what is preserved?

For some reason, I felt ("felt") last time that the answer to the first question was "No, 'the test tomorrow is at 1:00 PM' is not preserved." I had a sense that what the physicists meant was some broader numerical something-or-other about the "state," not specifics such as "The test tomorrow is at 1:00 PM" or "The Sun has eight planets and scads of minor planetoids." Now I'm tending to think ("think"?) the opposite. If physical information is preserved/conserved, this includes, "The test tomorrow is at 1:00 PM."

I continue to have little idea what I'm talking about. But right now I'd reformulate the question as:

If all physical information is preserved, how can "The test tomorrow is at 1:00 PM" not be preserved?

And a corollary to that one would be:

If all physical information is preserved, and this — somehow — does not include "The test tomorrow is at 1:00 PM" being preserved, then how is it possible that "The test tomorrow is at 1:00 PM" exists even now?

So, to convince myself that all information can be preserved while "The test tomorrow is at 1:00 PM" is not preserved, I'd have to have an explanation for why "The test tomorrow is at 1:00 PM" isn't preserved. And to do that, I'd have to have an explanation for how it can exist now without being physical information. We as physical beings sure seem to have the information that the test tomorrow is at 1:00 PM. So far I can't counter this, can't come up with an explanation of how physical beings can have nonphysical information, or what "nonphysical information" would even mean. I don't think physicists, to the extent that they've thought about it, disbelieve that "mental" and "cultural" information can be conveyed by physical information, or that the latter two sorts of information are different in kind from the former. Actually, I don't know what they think. But how would they even potentially explain the existence of "cultural information" at all if such information is not conveyable physically?

That's what I would need to explain, if I wanted to preserve the principle of "conservation of information" while denying the conservation of "The test tomorrow is at 1:00 PM." Not that I necessarily want to deny that "The test tomorrow is at 1:00 PM" can be preserved. What I'm saying is that I don't know how not to preserve it without destroying the principle of conservation of (physical) information — which for all I know is a wrong principle, but to half understand what physicists mean by it, I'm acting as if it's right. Quantum physics guys seem to believe it needs to be right. So, for the moment at least, I'm counting "The test tomorrow is at 1:00 PM" as physical information, hence preservable by "conservation of information."

So, to reiterate, I think the crucial question here, this time in bold, is: How can "The test tomorrow is at 1:00 PM" exist now without being physical information?

I'm deciding for the time being that it can't, and that therefore it is physical information.

In our last episode, arbitrary_greay was playing with contrary ideas, drawing a distinction that I probably don't understand:

Best I can guess is to think in programming terms: at the high-level language stage, variables are given names, and when searching for a piece of data stored in a variable, you call its name, which therefore is dependent on its descriptor. Searching the wrong descriptor will give you the wrong variable, and thus the wrong data.

However, at lower levels, compiler and binary languages, the descriptor is only used as a reference to a location. The data in that location does not change regardless of what descriptor is used to simply "remember" where that location is. I'm guess that "information" is referring to the data (the state of being), not the name given to the location.

AG continues in a later comment,

But the reconstruction of neurons and synapses constructs the words and relations between them in "The test tomorrow is at 1:00 PM," not the location of the earth. The reconstruction of "The test tomorrow is at 1:00 PM" is not necessary to the reconstruction of the location of the earth, which would happen independent of any particular evolution of neurons and synapses. That's what I personally mean when I differentiate being "objects in and of themselves" and being a reference to something else, and why a phrase as a linguistic construct is preserved, but not the phrase as a description of something.

Like in programming: the name given to a variable is itself stored as a series of 1s and 0s (or at the physical level, two different phases of silicon) somewhere on a chip. That is conserved. But when we consider it as a pointer to where some other data is, that data is conserved, and not the pointer.

And that's where we left it.

While I agree that one can know the location of the Earth without knowing that the test tomorrow is at 1:00 PM, I don't agree that, if reconstructing the location of the Earth is the result of conserving all physical information, that reconstructing "The test tomorrow is at 1:00 PM" isn't also the result of conserving all physical information. The mechanism that would give us one piece of information would have to give us the other as well. Or if it doesn't, there has to be an explanation of why not, and I can't think of one.

Even if it's true that the Earth would have had a location without the evolution of neurons,*** this is no more significant than that my grandma would have been born even if later on I hadn't been. That doesn't make me any less reconstructible than her, despite my dependence on her and her independence of me. If conservation of information preserves the location of the Earth, it preserves neurons and synapses, and Russian, and me, and English, and how to use it.

And my second way of putting this is: if all "physical information" can be preserved without preserving English and how to use it, then there can be no good way to explain how physical beings right now have and use English. If a future that preserves all physical information can't figure out what a pointer points at, then neither can we. (This is just a more general way of saying what I said above about "The test tomorrow is at 1:00 PM" being preserved if all physical information is preserved.)

AG seems to be distinguishing between, on the one hand, location and the words that designate it (both the location and the words can have a physical existence) and, on the other, the connection between the words and what they designate, which supposedly doesn't have a physical existence, but rather is set by convention. Whereas I'm arguing that if we, now, physical beings, can connect words and what they designate, then, if all physical information about us is preserved, the connections we make between words and what they designate are also preserved, are also contained within the physical information. Otherwise, how is information informative?

The principle seems either/or to me: either some physical beings can use English, in which case their use of English is preserved along with all other physical information that's preserved by the principle of conservation of information, or not all physical information is preserved/conserved.

[EDIT: When I say "the connections we make between words and what they designate are also preserved, are also contained within the physical information," I don't mean the connections are contained as separate pieces of information, the words and what they designate here, and the connections there. See the comment thread for elaboration (here and here).]

I realize that our experience with fossils and archaeology tends to leave us with bones and markings from which we can at most infer behavior and language, meanings, etc. But then, we don't pretend that paleontology and archaeology give us all the information there is.

But anyway, I'm not yet claiming to understand "conservation of information," what it means. It seems unclear to me as a coherent principle. As Mark says, in brackets (the final statement in the second bracket seeming to contradict all that came before):

[posts above have raised the issue that information in physics terms is not necessarily "communicable" -- as it must be for eg Claude Shannon -- bcz it doesn't require the presence of beings that can "read" the information <--- which is an interesting aspect of the problem, but not one that mathematicians and cosmologists spend much time on; they tend to operate as "under god's eye" communications theorists, even when militant atheists; the information that is an object's waveform structure is deemed "objectively readable" even if no one is EVER going to be around who can actually read it] [for maths and physics this is a side-issue however: information in the social sense is very much NOT conserved, vast amounts is lost everytime someone dies -- the mathematical ideal is that, if the full picture of all waveforms could be retrieved, then ALL information, including the fleeting never-spoken thoughts of the long-dead, could be reconstituted, indeed the retrieval and the reconstitution would kind of be the same activity]

My guess now (as opposed to a couple of months ago) is that the Susskind types would believe that information in the social sense is indeed preserved. They damn well ought to, anyway, because otherwise they ought to contend that information in the social sense doesn't exist now, either.

To think otherwise would put language in a spirit realm beyond the reach of physics, biology, and understanding. Or, anyway would put it somewhere beyond physics and biology. (Are there neo-this-ists and neo-that-ists who believe that reason itself has an existence beyond physics and biology and evolution? And are there people who still believe in Cartesian "mind stuff" (if that's what Descartes believed [I don't remember if I reached that part in my reading of Descartes]? I can't say I'm well read in either old or current philosophy.)

I'm going to guess (without knowing) that Sean Carroll and Leonard Susskind and those types would actually not accept that "an object's waveform structure is... [merely] 'objectively readable' even if no one is EVER going to be around who can actually read it." And I'm kind of hoping, therefore, that they won't accept that social information is lost when someone dies. The dead person's "social" information should be as preserved and reconstructible as any other information. What I'm guessing they would not accept are (1) that it's okay to make your system work by positing a hypothetical but nonexistent entity that "could" read the information, a Laplace Demon of the waveforms or a god or some such (rather, your system needs to function on its own, without adding something imaginary to it; or what you've added must have physical attributes, which you then have to take into account and explain as part of the system, the explanation including how it physically got there); and (2) that the ability to read information is not itself information. In case my double-negative sentence structure is confusing I'll state these in the positive: these quantum physicists should believe that (1) You don't need to assume (and aren't allowed to assume) a god's-eye view or a special Laplace Demon of the waveform because (2) the ability to read the information is information itself and is therefore preserved along with the (rest of) the information. Conversely, if at the end you have to introduce something else, from outside your system, then the information hasn't been conserved. I'll append a (3) which is a variation on (1): "objective" and "subjective" are not terms within quantum physics (you don't talk about "objective quarks" and "subjective quarks," or conduct calculations with the terms "objective" and "subjective"), even if "objective" is a term that some people use to compliment results of quantum physics that they agree with and think are established. So the phrase "objectively readable" has no explanatory power, and can't be called in to make a physical theory work.****

(I do have a question that belongs here, but I won't say it right off.)

So what I'm wanting those quantum physicists to assume (what would seem consistent) is that skills — including the ability to use information, to read it, to understand "The test tomorrow is at 1:00 PM" — are themselves information and are preserved along with all other information. So the information that is preserved includes the aforementioned ability of the information to read and understand itself.*****

Of course, this seems totally absurd, that after every piece of matter is absorbed into black holes that subsequently evaporate, nonetheless we have information left that can read and interpret itself. It's as if we've been made immortal.

But of course, maybe it's equally absurd that we can read and interpret information now, though we most assuredly can. And the fact that we can read and interpret information now is the linchpin of my argument (to the extent I've got an argument).

But I'm not sure (not understanding physics) that the holographic principle doesn't appear equally absurd, in the exact same way as information's ability to read itself appears absurd. And though the holographic principle may turn out to be wrong, it's not being dismissed out of hand by physicists. Of course I don't come within a million and one miles of pretending to understand the holographic principle. What I gather about the holographic principle, though, is that (saith Wikipedia, speculatively) "the entire universe can be seen as a two-dimensional information structure 'painted' on the cosmological horizon, such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies." So the holographic principle isn't saying we are represented by a two-dimensional information structure on a two-dimensional cosmological horizon, or can be transformed into a two-dimensional information structure on a cosmological horizon, but that, under an alternate description, we literally are information within a two-dimensional information structure on the cosmological horizon — information that can read and interpret itself, therefore, since we can and do read and interpret information. Pixels reading and interpreting pixels!

I think I used the statement "this is not intuitive" earlier in this post.

A few paragraphs ago I said I had a question. Since we, individually and collectively, aren't a Laplace Demon of the waveform and don't have a god's-eye view, should we not question whether we do indeed know how to read and interpret information, since we certainly don't know how to read and interpret all of it? Not that I know if this is a relevant question. This post is not wallowing in relevance anyway. But if we can't read and interpret all information now, how can this global ability exist in a post-black-hole future that conserves our abilities? If a demon doesn't currently exist — if the information doesn't itself create and contain a demon — what right do we have to say that all information has been conserved?

By the principle of conservation of information as I've decided to interpret it, all of my grandmother's information has been preserved and is capable of interpreting itself right now. If indeed this is true, it's not come to my notice.

An answer might be that all information is being conserved, but that it isn't all being interpreted by one centralized overall intelligence, and doesn't need to be. It can affect things piecemeal, this particular thing here affected by that particular bit of information, etc., in the aggregate this resulting in all information being preserved. Presumably all information was being conserved prior to the existence of any intelligence in the universe. An out might be to say that "prior" and "subsequent" have nothing to do with the subject, given reversibility. But then you run into Carroll's questions about whether we do indeed have reversibility. Another out is to say that information need not affect only conscious, intelligent beings: all a piece of information needs is that there be things ("things") that respond to the presence of the piece of information and don't respond (or respond differently) to the absence of the piece of information.

-----
*Nonetheless, here are some relevant Wikipedia links:

http://en.wikipedia.org/wiki/Quantum_state
http://en.wikipedia.org/wiki/Quantum_information
http://en.wikipedia.org/wiki/Physical_information
http://en.wikipedia.org/wiki/Black_hole_information_paradox
http://en.wikipedia.org/wiki/Holographic_principle

Honestly, I've not read through all of these. I need to get this posted, so I can take a nap.

**Laplace, living in the days when Newtonian physics still held sway, believed that if somehow you could know the position and momentum of all particles, you could perfectly reconstruct the past and completely know the future. The imaginary entity that has this vast knowledge, "the future just like the past [being] present before its eyes," has subsequently come to be called Laplace's Demon.

***I don't know if this is right, actually, that "location of the Earth" can make sense as something theory-independent and language-independent. I don't think I need to have an opinion on whether it can, though the concept "location" sure seems comparative, like any form of measurement. AG's distinction seems to be that location is physical (hence will be preserved if physical information is conserved), whereas "1 PM" is conventional (a way of talking about time and location), and while we can choose and change our conventions, we can't change what physical locations are. But my reasoning here is that the location of the Earth is entirely dependent on its relation to something else. Take away Sun and Milky Way etc. and "the location of the Earth" becomes a nonsense phrase. But to make such comparisons, between location of Earth and Sun, and where the Earth is in its rotation, requires brains, even if those brains can apply the comparisons to stars and planets etc. that existed before there were humans. We certainly need theory and language to assign a location to the Earth. And I don't see how we can have any information on the location of the Earth (relative to the Sun or to anything else) without using conventions for talking about location (miles, hours, etc.). Maybe I'm not thinking this through, but the idea of "information" and the idea of "conventions for distinguishing between things and measuring them" seem connected to one another like Siamese twins.

I'll reiterate, a "theory-independent location of the Earth" or "language-independent location of the Earth" is something I don't need to have an opinion on, one way or another, and I don't think anything rides on how anyone "decides" the issue, ever. We'll still need the theories, and language, no matter what. Language-independent locations are something we don't have access to. Language is what creates the access and is what we use to designate a location. So if I had to choose I'd say that "location" is something that doesn't make sense outside of the use of language and of the needs and purposes of language users, the ones who determine location in discourse with one another. "Location" doesn't exist at some "deeper" level. But, as I've also been saying, this question takes us off-topic, and if you disagree with my last two sentences that shouldn't affect our discussion of what is preserved when we say that "information" is preserved. Even if "1:00 PM" is different in kind from "the Earth's location," I don't see how the former can escape being preserved along with all other physical information.

But while I'm here in this footnote gabbing, I'll note that, if we're talking about the location of the Earth, and saying that this is information that is conserved, we mean "location of the Earth" as we currently use the phrase but not as anyone would have used a phrase like it one thousand years ago, when the earth was believed to be fixed and in the center rather than in motion. The heavens were defined as what was above, and the meaning of the term "earth" precluded its being in the heavens. Also note that — as far as I can tell — the holographic principle that supposedly confirms the principle of conservation of information also does a whammy on the idea of "the location of the Earth," which differs depending on whether we're thinking of the 3-D Earth we experience or the Earth as 2-D information on a distant "surface." (Does the holographic principle assume the two "locations" can be translated one to the other as exact equivalents? I'd expect it would, but what I expect isn't based on understanding.)

****As far as I know, the term "mental" plays no role in physics either; our everyday distinction between the "physical" and the "mental" isn't of two states of being, one material and the other immaterial. Presumably, what we call "mental" can be explained physically, though that doesn't mean it has been, yet.

Regarding "information," I suppose someone could talk about "potential information" analogous to how one talks about "potential energy." But for energy to be energy you don't have to call on something from outside of physics, a god's eye or an intelligence or "objectivity." Energy's effects, when it goes from potential to kinetic, are on bodies (or whatever) that are actually part of physics theory. I know quantum physics has something called "virtual particles," a concept I wouldn't dream of pretending to understand. (Wikip: "Virtual particles [just like 'real' particles] are also excitations of the underlying fields, but [unlike 'real' particles] are 'temporary' in the sense that they appear in calculations of interactions, but never as asymptotic states or indices to the scattering matrix. As such the accuracy and use of virtual particles in calculations is firmly established, but their 'reality' or existence is a question of philosophy rather than science." That first sentence contains terms that I don't understand, of course.) But for there to be a "virtual intelligence" to be affected by our preserved information, it would have to play an actual role in calculations made by physicists, I'd think. If information has no conceivable effect on anything, how can it be information, or be anything? That's not a rhetorical question, since maybe there's a good answer. I would guess a good answer would be that it does have an effect on something, not that it doesn't need to. But I don't know.

****Sean Carroll may well have said this, or said the exact opposite, in From Eternity To Here, which is a terrific book that I highly recommend but that I understood too poorly to retain much of, especially now that it's back in the library.

Comments

Getting rid of Laplace's Demon

[koganbot]

A way to get rid of the need for a Laplace Demon or for the vacuous idea of "objective information":

Is there something equivalent to a holographic principle that literally gets me and my pen and my understandings into a post-black-hole future? Something that's an alternative but equivalent way of describing the universe? This would make the Laplace Demon unnecessary, since no one would need an interpreter to reconstruct me, my pen, and my understandings: we're already there, albeit as pixels.

The world of ordinary experience is a hologram

[koganbot]

A month ago I made it back to the library and copied these down from Susskind and from Carroll. Unfortunately there are gaps in my notes.

From Leonard Susskind's The Black Hole War, p. 298:

The three-dimensional world of ordinary experience — the universe filled with galaxies, stars, planets, houses, boulders, and people — is a hologram, an image of reality coded on a two-dimensional surface. This new law of physics, known as the Holographic Principle, asserts that everything inside a region of space can be described by bits of information restricted to the boundary.

On page 411, Susskind says that this boundary is "only an imaginary mathematical surface with no real substance." So anything can enter or leave. But we can think of something called "anti de Sitter space" in which the angles in triangles add up to less than 180 degrees. He describes it as like the reverse of a Mercator projection: anything close to the boundary gets smaller, infinitely small, without crossing the boundary. So in effect the boundary is impenetrable. "Everything inside a box with impenetrable walls can be described by bits of information stored in pixels on the walls."

Then (pp 416-417) he goes into the work of Juan Maldacena. This is where my notes are incomplete. But Maldacena showed that a world with four dimensions (three dimensions of space and one dimension of time) without gravity can alternately be described (is "dual" to) (is mathematically equivalent to, I assume) a world with five dimensions (four of space and one of time) with gravity, if the space in this [4 + 1]-dimensional world is an anti de Sitter space. Paraphrasing Susskind:

growing and shrinking [in size] in the [3 + 1] half of the duality is exactly the same as moving back and forth along the [fourth] direction in the other half of the duality.

If Life Is A Can Of Soup, What Am I Doing On The Label?

[koganbot]

Susskind (pp 418-419) continues, describing an idea of Edward Witten's:

Anti de Sitter space... is like a can of soup. Horizontal slices through the can represent space; the vertical axis of the can is time. The label on the outside of the can is the boundary, and the interior is the space-time continuum itself.

...Witten explained that by injecting enough mass and energy into the can, a black hole could be created. That raised a question. According to Maldacena, there must be a second description — a dual description — that makes no reference to the inside of the can. The alternate description would be in terms of a two-dimensional Quantum Field Theory of particles similar to gluons that move on the label. The existence of a black hole in the soup must be equivalent to something in the boundary hologram, but what was that something? In the Boundary Theory, Witten argued that the black hole in the soup was equivalent to an ordinary hot fluid of elementary particles — basically just gluons.

If I'm understanding this, we're taking a description of something that includes gravity (and hence black holes) and creating an exactly equivalent description that subtracts a dimension and gets rid of gravity, therefore gets rid of black holes, while retaining the information that was poured into the black hole in the previous description. If I've got that right.

The explicit mechanism remains unclear

[koganbot]

This is from Sean Carroll, From Eternity To Here, p. 283; what he's calling "four-dimensional" is what I was calling "3 + 1 dimensions" (three of space, one of time, no gravity) in the previous two comments:

So we make a black hole in anti-de Sitter space and then let it evaporate. Is information lost? Well, we can translate the question into an analogous situation in the four-dimensional theory. But that theory doesn't have gravity, and therefore obeys the rules of ordinary quantum mechanics. There is no way for information to be lost in the four-dimensional nongravitational theory, which is supposed to be completely equivalent to the five-dimensional theory with gravity. So, if we haven't missed some crucial subtlety, the information must somehow be preserved in the process of black hole evaporation.

...But you can see that the argument, while seemingly solid, is nevertheless somewhat indirect. In particular, it doesn't provide us with any concrete physical understanding of how information actually gets into Hawking radiation. Apparently it happens, but the explicit mechanism remains unclear.

(And I'll reiterate on my own behalf that I don't have a concrete physical understanding of what "information" is, or what one means by saying that it's preserved. Also, how do we manage to inhabit five-dimensional anti de Sitter space to begin with?)

Do pointers have a point?

[koganbot]

By the way, what I wrote in my post may incidentally give the false impression that I think that language is fundamentally about pointing, which isn't right. Some words can point, but not all words must point. You can have the words "Frank's apartment," and some equivalent in some other language (except I don't know any other language, but maybe "l'appartement de François" or "François appartement" might work in French); and we can point to my apartment as what the words are referring to, no matter which of the two expressions we use.

And we can have a command like "Come here," and an equivalent command in another language (Google Translate gives me "Viens ici"), but now, with these phrases, there's no third thing, "Come hereness" or "the fact that you want someone [or some being] to come here," that we can point to. Or perhaps you could point at a particular spot, and the other person or being [a robot, say, or a dog] could know that that's a command or a request to come to the spot you pointed at; but still, that gesture doesn't point at some "come hereness" or "the fact that you want darling Fido to come to a particular spot." (Try pointing at the fact that you want darling Fido to come to a particular spot. Just try it. Also, you might not want Fido to come to a particular spot. In fact, you personally don't want Fido to come to that spot, but you were instructed to indicate to Fido that he come to that spot — or you thought you were, but in fact you misunderstood the instructions; so no one wants Fido to come to that particular spot. And the person who wrote the instructions is dead anyway. Nonetheless you've just commanded Fido to come to that spot.)

That "come here" and "viens ici" are the same thing and can be translated from one to the other still doesn't mean that there's some common third thing in no language that they point to. (Don't say, "they each point to the same meaning," as if the meaning were some third thing that magically linked the two phrases.) And actually, "Frank's apartment" only makes sense embedded in a whole bunch of behaviors, and doesn't have any meaning outside those behaviors. I can imagine a language that consists entirely of the phrase "Come here" (someone says "Come here" and the other person goes to where she thinks she's been instructed), but I can't imagine a language that consists entirely of the phrase "Frank's apartment" unless in that language (unlike English) that phrase always works behaviorally, as something like a request or a command or a warning. E.g., I say "Frank's apartment" and you pick up a package and bring it to Frank's apartment. (One hopes the package contains something of value.) So the phrase "Frank's apartment," in that language, means something like the English phrase "bring this to Frank's apartment."

[None of what I just wrote is original with me. I'm aping Wittgenstein, hoping I'm doing a good job of it.]

So, here's a question: in a future where all information was dumped into black holes that have evaporated, but the information still exists by virtue of there being an alternate description that needs neither gravity nor one of the spatial dimensions,* and so "Venez à l'appartement de François" is preserved, what language is the information in? One answer might be "all," but what "all" means is that "The pieces of information are in whatever language they were originally in" (should I add the phrase "or some equivalent"?). Somewhere amidst all this info floating about we've got the information that allows the information to be understood (as well as the understanding, which is also information — and yes I still don't have an intuitive understanding of "as well as the understanding, which is also information"). [EDIT: The way I wrote this last sentence is misleading; go down several comments for my clarification.] Presumably, any language can be learned by anything with the capacity to learn a language.

[koganbot]

(cont'd)

I'd assume that there's also some information for which there never was any language — say, some information that we could get from the rocks of Earth if we'd adequately developed theories and a vocabulary, but we never got there. This not-yet-linguistic info is also preserved. As pixels? (See previous parenthesis regarding my not having an intuitive understanding of what I'm saying. I also have no idea if blokes like Susskind would concur with the three sentences preceding the current parenthesis.)

*Not that I know which spatial dimension Maldacena is talking about, since he's leaving us with three in his gravity-free universe and I don't understand quantum physics anyway.

A moment of consciousness retained for perpetuity isn't multiple moments of consciousness

[koganbot]

Somewhere amidst all this info floating about we've got the information that allows the information to be understood (as well as the understanding, which is also information — and yes I still don't have an intuitive understanding of "as well as the understanding, which is also information").

Well, the word "also" might be misleading. What allows the information to be understood isn't a piece of information ("this is the piece of information that instructs us how to understand this other information") but rather the behavioral context in which the information exists — "behavioral context" meaning the pieces of information as surrounded by other information. That is, if we insisted we needed an instruction on how to connect "come here" and "viens ici," we'd also need an instruction on how to use the instruction, and on into an infinite regress. Whereas actually, the procedure in which "come here" is embedded is what makes "come here" comprehensible, and being embedded in a similar procedure is what makes "viens ici" equivalent to "come here." So I'd say that — in an alternate description in which everything is information on a boundary — as we build up information, the understanding and use of the information builds up with it, as does consciousness, at some point. (Assuming the holographic principle is correct.) So not only am I, under an alternate description, some information on a boundary, but along with other information we get my consciousness too — without my "consciousness" being separate information from the information that encodes my biology and the stuff around it.

(The fact that I'm typing these words doesn't mean I'm feeling them.)

And it's not two separate consciousnesses, me on the boundary and me where I experience myself. It's just two different descriptions.

But given conservation of information (well, let's say it's given, even though I don't even know what this means), isn't my consciousness at this very moment projected into every moment in the future, so it's happening perpetually, just as my consciousness ten years ago is happening now and my consciousness now was already embedded in information ten years ago?

Well, imagining this stuff is true, I'd say that my consciousness of whatever I'm doing right this moment isn't repeating in the next moment, and the moment after that, and on into infinity. It's just that the information that contains whatever I'm conscious of doing now exists as information back into the past and forward into the future. So the information in the far future has me conscious now, and my being conscious now somehow exists — as information — in the far future (just as it exists now as information), but it's still my being conscious now, experienced once, even if that single experience seems to exist perpetually.

Again, that these fingers are typing these words doesn't mean I'm feeling them. Just, I'm drawing an analogy between me and my present consciousness and my typing being information on a boundary, on the one hand, and, on the other hand, me and my present consciousness and typing being information that's conserved for all moments in the future. If there's only one me and my current moment of consciousness and my current typing in the first instance (info on a boundary), then, by analogy, there's only one me and my current moment of consciousness and my current typing even while all this continues, perpetually, to be info on boundaries in the future.*

But maybe not.

*Er, aren't there waveforms and probabilities involved here too (asks he who does not understand quantum physics)?

[dubdobdee.livejournal.com]

returning to this via the shock-tactic means of not really reading any of the relevant material - including your subsquent posts -- it suddenly strikes me that the "two dimensionality" refers to something like a programming language (which can exist in the form of a ribbon of zeros and ones: one dimension is the ribbon itself, the other being the valuescale that can be 0 or 1). Is it being claimed that the cosmos can be modelled as a vast self-generating (and in some important sense self-reading) combination program-&-supercomputer?

Obviously the "program" element doesn't exist as a ribbon with zeros and ones, it exists somehow within the (sub-atomic? waveform?) building materials of the universe-across-time: the argument is (perhaps?) that there's a sense in which it must be mappable onto such a ribbon, and hence into a 2D form.

^^^I have no idea if any of the above is correct or ever clear -- it's just that the argument that "readability" would have to be part of the information-to-be-conserved reminded me (very dimly) of Hofstadter's "Godel, Escher, Bach: the Eternal Gold Braid" (or whatever it's called). I haven't looked at this for half-as-long-again as A Brief History, mind you -- and I'm not sure I even finished it the first time round.

[koganbot]

I don't know enough (obv.) to answer your first question, but let's say the answer is "yes," anyway. Susskind uses the word "pixels," after all.

But I don't see why the program element can't exist as a ribbon with zeros and ones. Not that I have an argument as to why it can. I don't know enough about zeros and ones and physics. But if gravity in one description can be gluons in another, why can't programming be pixels? (Not that I know if that's a good analogy.)

But I'd then argue that you don't have one set of pixels that's the programming and a different set that's ordered by the programming, but that rather when pixels start relating to one another, the programming comes along with this interaction. (Don't ask me what I mean, but I'm drawing an analogy to Wittgenstein's argument that being embedded in a language-game is what makes a command like "Bring me a brick" meaningful, rather than a specific instruction separate from "Bring me a brick" that tells you how to respond to the command, "Bring me a brick.")

[dubdobdee.livejournal.com]

I'd then argue that you don't have one set of pixels that's the programming and a different set that's ordered by the programming, but that rather when pixels start relating to one another, the programming comes along with this interaction

Yes, this is what I was getting at (very handwavily) with "combination program-&-supercomputer": the two elements are both parts of a self-producing whole.

Since the whole at some point will include actual human-built computers, some of the programming will precisely be ribbons with zeros and ones: but I'm imagining that at an early stage of the evolution of this er thing, the element which effects the programming functioning won't yet be this, and certainly couldn't start with this (because how would a ribbon with zeros and ones be self-generating to the point that it became self-reading?)

[koganbot]

Do we need the word "ribbon" here?

Isn't the question "How can zeros and ones be generating to the point that it became self-reading" exactly equivalent to "how can chemical combinations become self-replicating"? I'm not sure. But if all of the universe (incl. all of life) is "an image of reality coded on a two-dimensional surface," i.e., " bits of information stored in pixels on the walls" (Susskind), then it's zeros and ones that are becoming self-reading, I'd think. (I'll emphasize that I don't even know how modern-day zeros and ones constitute the computer I'm using.)

[dubdobdee.livejournal.com]

"Ribbon" is actually only needed to organise the ones and zeros in a 2D format, as "two-dimensionality" was raised as a puzzle? I just wonder if this was where the 2-dmiensionality emerged, viz that the universe could be (by some* process) be read as long "line" of ones and zeros. So what's the argument that's being made? That the Universe is in some abstract sense mappable ONTO a 2D-format structure -- or that it actually IS one (viz arrives as one)? (Perhaps I can answer this question be reading some of your links...)

*intrinsic? non-instrinsic?

Isn't the question "How can zeros and ones be generating to the point that it became self-reading" exactly equivalent to "how can chemical combinations become self-replicating"?

Not really: "chemical combinations" surely implies a pre-existing smorgasbord of possiblities that "zeros and ones" doesn't. The former is far further along a line of immanent dynamic than the latter. Which is why I don't think that the universe IS (in "reality"?) a 2D object.

But I think we're at the impasse of trying to imagine "initial conditions" that would get us to where we currently are -- including "the test tomorrow is at 10pm". I can't actually imagine initial conditions in a 2D form OR as "chemical combinations" -- but my lack of imagination may not be a contentful argument!

[koganbot]

Susskind's argument really does seem to be that the universe is a 2D-format structure. But as he's a string theorist, I also assume he thinks there are a whole other bunch o' dimensions under different descriptions (?). So we're not talking about "mappable onto" but exactly equivalent descriptions or something.

[koganbot]

2-dimensionality emerged, I think, because the entropy of a black hole is proportional to the area of the surface of its event horizon rather than to the volume of the region enclosed in the event horizon (that's how Carroll puts it, anyway). Of course, I don't know how one exactly gets to that particular result. Math is involved, not to mention mass, and gravity.

[dubdobdee.livejournal.com]

In algebraic or projective geometry I'd say that "mappable onto" and "exactly equivalent description" are the same thing. But they're not necessarily the same thing in physical cosmology -- algebraic or projective geometry being an abstract model of physical cosmology. However, while I'd say this, I'm not sure the mathematicians we're discussing would say this: they'd (perhaps) say that the model is the program (handwavily combined with the machinery to realise the program).

This is what interested me about the two-dimensionality: and the surface-of-a-black-hole hologram being the same dimensionality as a ribbon of ones and zeros. BUT I could be totally barking up a ridiculous tree of my own speculative device here: we're beyond far enough in that I'm not going to be able to offer anything else useful without actually embarking on some of this reading myself. And even then...

[koganbot]

Don't know when I'm going to have time to read, either, though I've taken From Eternity To Here out of the library again as my non-vocation-related entertainment (crowding out novels and movies and such).

To change the subject slightly, based entirely on my interpretation or misinterpretation of that single sentence I quoted above from the Wikip article about the Holographic principle ("the entire universe can be seen as a two-dimensional information structure 'painted' on the cosmological horizon, such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies," this sentence constituting most of what I've read in that article so far), something is exactly equivalent to something else, but our experience of and the way we think things work here in macroscopic 3-D Land are only a special case and were we to continue on beyond our general experience things would get weird, or something (but presumably we'd still have consistent laws for 3-D Land, just ones that give weird results, or something, and we'll get a clearer bead on what's happening when we go to equivalent descriptions that are about the hologram). ["3-D Land" actually means 3-Spatial D and 1-Time D.]

Meanwhile, Susskind seems to be saying that we (incl. the entire universe) are a hologram and that "hologram" is the right description, period. At least in that sentence he seems to be saying so, unless he's just saying that the theory says so. ("The three-dimensional world of ordinary experience — the universe filled with galaxies, stars, planets, houses, boulders, and people — is a hologram, an image of reality coded on a two-dimensional surface.") But he, 't Hooft, and Thorn were the basic generators of the principle, according to Wikip. (I think he'd say that the principle thoroughly gets rid of the notion that when black holes evaporate information is destroyed, but I think he also says that a lot of these ideas including much of Hawkings' hasn't been confirmed or tested; but presumably a whole hunk of other stuff that physicists do currently believe would have to be rethought if information isn't conserved and black holes turn out not to behave the way Hawkings says they do.) I'm not sure what generated the holographic principle, actually, owing to the poorness of both my reading comprehension and my memory when it comes to The Black Hole War. Is it primarily there to preserve the principle of conservation of information, or are there a whole lot of other problems it seems to solve as well?

[koganbot]

Of course, computers require electricity. I'd assume (without knowing) that in the hologram, electricity is made of zeros and ones too.

Escher and anti de Sitter space

[koganbot]

I read the first half of GEB many years ago; then it came due at the library. But iirc, Susskind illustrates the idea of anti de Sitter space with a picture by Escher (though I don't know if it's the one I just linked). Pasting in a paragraph from one of my comments upthread:

On page 411, Susskind says that this boundary is "only an imaginary mathematical surface with no real substance." So anything can enter or leave. But we can think of something called "anti de Sitter space" in which the angles in triangles add up to less than 180 degrees. He describes it as like the reverse of a Mercator projection: anything close to the boundary gets smaller, infinitely small, without crossing the boundary. So in effect the boundary is impenetrable. "Everything inside a box with impenetrable walls can be described by bits of information stored in pixels on the walls."

Some useless information, supposed to drive my imagination

[koganbot]

Several possibly relevant articles I found tonight while Web surfing:

"Astrophysics: Fire in the hole!" (from two-and-a-half years ago)

"Reluctant to abandon the one required to encode information in the Hawking radiation, they decided to snip the link binding an escaping Hawking particle to its infalling twin. But there was a cost. 'It's a violent process, like breaking the bonds of a molecule, and it releases energy,' says Polchinski. The energy generated by severing lots of twins would be enormous. 'The event horizon would literally be a ring of fire that burns anyone falling through,' he says. And that, in turn, violates the equivalence principle [of general relativity] and its assertion that free-fall should feel the same as floating in empty space — impossible when the former ends in incineration."

"No Black Holes Exist, Says Stephen Hawking — At Least Not Like We Think" (from almost 2 years ago)

"Stephen Hawking now thinks 'there are no black holes'" (from almost 2 years ago)

"Black holes should be treated more like massive galactic washing machines... [T]he quantum effects around a black hole, like weather on Earth, churn so violently and unpredictably that it's just impossible to either predict the position of an event horizon or expect uniform effects for stuff crossing it. While the theoretical basis, that information is preserved, remains, in practice it's so difficult as to be impractical."

"Stephen Hawking may have finally solved the black hole 'information' problem" (last summer)

"The information stored in these holograms is then emitted in the form of quantum fluctuations, though the data is so scrambled as to be useless for all intents and purposes."

"Hawking’s other proposed option is that black holes might serve as gateways into other universes. 'The existence of alternative histories with black holes suggests this might be possible,' Hawking said. 'The hole would need to be large and if it was rotating it might have a passage to another universe. But you couldn’t come back to our universe.'"

For all I know, these are all out of date. I was just bumming around, looking unsuccessfully for something that would explain this quotation, presented in the NY Times without elaboration:

"The big question is, how can something so tiny like a black hole influence the entire galaxy itself? The belief now is that they know how to talk to one another."