Is “information is physical” contentful?which has ignited a long in addition to irksome discussion. I scream upwardly that precisely about xxx years ago, I was somewhat excited nearly the "idealism" that hides inward statements such as "physics is all nearly the information". When you lot practise physics – or whatsoever proper science, for that affair – you lot don't approach the the world "practically". You don't demand to "feel" the meat, scents, materials. Instead, you lot stand upwardly for them yesteryear precisely about abstract concepts, yesteryear information, in addition to yesteryear existent or complex numbers – that's the most typical mental attitude of the physicists who supercede "intuitive objects" amongst coordinates, observables, positions, momenta, moving ridge functions.
It doesn't genuinely affair that "pork is existent matter" in addition to you lot scream upwardly its gustation in addition to consider it primary. Instead, inward physics, pork is composed of precisely about concepts in addition to quantities that may live written on the newspaper in addition to communicated as information. There's precisely about sense inward which "the ideas are primary" is preferred inward physics over "the affair is primary" – sense inward which idealism beats materialism inward physics. And this betoken becomes peculiarly strong inward quantum mechanics because quantum mechanics entirely calculates the probabilities that propositions nearly observations are right – it doesn't allow you lot to assume that precisely about "matter amongst objective properties" exists independently at every moment. So idealism wins.
Great. I think that already the 2 paragraphs higher upwardly are also talkative in addition to repetitive. These are genuinely trivial matters in addition to those xxx years ago, I decided that they're trivial indeed. So the excitement entirely lasted for hours or days. If you lot don't empathise that physics ultimately deals amongst "ideas" or "information" or "numbers", non amongst "matter" (in the manual sense inward which toolers in addition to lathe operators bargain amongst "matter"), you lot can't practise physics. On the other hand, everyone who does physics inward whatsoever meaningful manner must understand, at to the lowest degree to precisely about practical, intuitive extent, everything that is right in addition to that may live hiding behind the judgement "information is physical".
OK, then let's evaluate the proposition
Information is physical.Is it correct? Is it deep? Is it important? Before nosotros response these 3 questions, nosotros should know what the judgement genuinely means. There are at to the lowest degree 3 uncertainties that complicate the interpretation of the judgement "information is physical": What is "information"? What is "is"? In particular, Bill Clinton has asked: What is "is"? Can "is" live oral? And what is "physical"? Did Max Born's granddaughter genuinely desire to move physical or did she misinterpret the adjective? :-)
Again, you lot should improve give a clear plenty response to these 3 questions earlier you lot endeavor to determine whether "information is physical" is a correct, deep, or of import sentence. And permit me tell that all these 3 "partial" questions are genuinely deeper, to a greater extent than meaningful, in addition to to a greater extent than of import than the query you lot started with, whether "information is physical".
Information is such an uncomplicated concept that it cannot genuinely live reduced to whatsoever simpler concepts. Various questions or sentences or events may accept several or many or infinitely many options a priori. One doesn't know which i is true, which i genuinely happened, a priori. So he doesn't know precisely about information. Once a detail choice, option, or response is chosen, the data becomes known. My "definition" of data is round out in addition to this circularity is unavoidable, at to the lowest degree to precisely about extent. You precisely can't construct definitions of uncomplicated concepts from nothing.
Instead, as inward mathematical axiomatic systems, you lot demand to postulate the beingness of precisely about basic objects or relations in addition to you lot demand to postulate precisely about axioms that these objects obey. You may tell lots of deep in addition to of import things nearly the data but "information is physical" isn't genuinely i of them.
Information may live expressed inward nats, natural digits. When \(N\) options are every bit likely, \(p_i=1/N\), the data nearly which choice is right corresponds to \(\ln N\) nats (dimensionless units) of information. Some people similar to limited data inward bits. One chip is \(\ln 2\) nats. So to distinguish \(N\) options, you lot demand \(\ln northward / \ln 2 = \log_2 northward \) bits of information. Other bases are possible as well. The base of operations \(e\approx 2.718\) is the natural one. The previous judgement itself is arguably to a greater extent than of import a lesson for a physicist than the vague philosophical "information is physical".
When the \(N\) options aren't every bit probable but they accept the probabilities \(p_i\) obeying \(\sum_i p_i = 1\), the data is carried yesteryear the Shannon entropy\[
south = -\sum p_i \ln p_i.
\] This quantity measures how much fourth dimension you lot demand to reserve when you lot desire to transmit the data through a channel. We precisely saw that the data is related to the entropy. And entropy is a concept that nosotros know from thermodynamics – the scientific discipline nearly "heat" that may live measured, felt, in addition to studied fifty-fifty if you lot can't come across the atoms or other uncomplicated edifice blocks. Because of the park relationships betwixt energy, temperature, in addition to entropy, the modify of the data or entropy may live manifested as heat. If a organization is capable of carrying i extra nat of information, its oestrus capacity increases yesteryear \(k\) or so, the Boltzmann constant, precisely about \(1.38 \times 10^{-23}\) joules per kelvin. Whenever you lot stair out how difficult is to oestrus an object yesteryear work, you lot stair out how much data the object may behaviour inward its "atomic storage of information".
Those insights are of import in addition to every physicist should acquire at to the lowest degree basics of thermodynamics in addition to statistical physics. In precisely about sense, these to a greater extent than specific statements tin live interpreted as "refinements" of the suggestion that "information is physical". But I think it's right to tell that the sentence
Information is physical.is precisely also vague, also humanities-oriented, in addition to a somebody who likes to tell such propositions shouldn't live assumed to empathise thermodynamics or statistical physics. The vague judgement may "encode" precisely about wisdom nearly thermodynamics in addition to statistical physics but unless a somebody rediscovers or learns thermodynamics in addition to statistical physics, he doesn't know the "code" then from his perspective, the judgement doesn't genuinely instruct him anything nearly thermodynamics in addition to statistical physics.
The vague judgement higher upwardly is real analogous to sentences such as
A virtual particle is physical.and millions of others. The betoken is that many people similar to pick a concept – examples are higher upwardly – in addition to attach the words "is real" or "is physical" or "exists" or similar, real full general verbs in addition to adjectives. And they pretend that the resultant is precisely about deep wisdom or at to the lowest degree a deep question.
Influenza A virus subtype H5N1 virtual particle is real.
The path integral is real.
Climate modify is real.
The electromagnetic potential is physical.
Gluons exist.
I don't think that such questions are deep. They behaviour a real footling data because they're precisely combinations of precisely about basic words. And they're rather random combinations. Random combinations don't necessarily Pb to real meaningful sentences – "the publish v is green" is a pop example. And to brand things much worse, the verbs in addition to adjectives that are used to construct these sentences are real low-information words. In particular, "is" carries almost null information. That's why e.g. the Russian linguistic communication frequently omits it altogether. "Moi brat – vrag" is their "My blood brother is an enemy." As you lot tin see, Slavs handgrip that the articles "the" in addition to "an" behaviour null information, too. They're fired. Words "exist", "real", in addition to "physical" don't behaviour also much information, either.
Some of these sentences may bring something rather meaningful. I deliberately mentioned the example
The electromagnetic potential is physical.Particle physicists would commonly tell that this judgement is faux because the electromagnetic potential \(A_\mu\) isn't gauge-invariant. Therefore, nosotros can't uniquely associate the values of the fields \(A_\mu(x,y,z,t)\) amongst a real-world situation. We can't practise that because the gauge-transformed values of the potential\[
A'_\mu(x,y,z,t) = A_\mu (x,y,z,t) + \partial_\mu \lambda (x,y,z,t)
\] are every bit expert to depict the same physical situation. You may come across that I clarified the describing word "physical". What I genuinely meant yesteryear "is physical" was "is gauge-invariant" in addition to the potential wasn't approximate invariant.
The approximate invariance – in addition to similarly, independence on the inertial frame, coordinate system, selection of observer, whether observations are made etc. – are "subtleties" that move far harder to determine nearly sentences such as "something is physical". Before you lot acquire physics upwardly to a sufficient depth, you're non fifty-fifty aware that such subtleties could exist. The to a greater extent than you lot learn, the to a greater extent than subtleties you lot know, in addition to the to a greater extent than you lot know that it was naive to worship sentences such as "information is physical".
It matters whether you lot genuinely desire your sentences to live well-defined in addition to utter nearly precisely about specific thing; or whether you lot desire them to live vague, pretending to live deep, in addition to live useless. If you lot desire the former, you lot are to a greater extent than probable to pick a to a greater extent than well-defined linguistic communication in addition to adjectives such as "gauge-invariant" instead of "physical". Well, "physical" may supercede the to a greater extent than well-defined adjectives in addition to it tin live clear from the context but the occupation is that precisely about people deliberately desire the pregnant of the news "physical" to stay ambiguous, in addition to it's a problem, non a virtue.
I also mentioned that the sentences of the flat "something is physical" are analogous to the sentences "something is real". To a large extent, these 2 sentences are genuinely completely equivalent. And later on all, the judgement "something exists" may live considered nevertheless precisely about other synonym. The words "real" in addition to "exist" are as ill-defined inward full general as the news "physical". Philosophers may earn their salary for postulating novel dogmas nearly the validity of sentences such as "something is real" but I think that physicists handgrip that these sentences in addition to the enquiry of such sentences has basically no value.
"A virtual particle is real" or "a virtual particle is physical" are true to the extent that the concept of a virtual particle (and thousands of others that could live used as examples) are exploited inward correct, legitimate physics enquiry in addition to physical analyses of precisely about phenomena. These concepts play precisely about role in addition to they touching on the predictions – in addition to the outcomes of the actual experiments. Because the physical analyses using "virtual particles", "path integrals", "gluons", in addition to lots of other concepts aren't wrong, nosotros may tell that "virtual particles are physical" inward this basic sense. And then is the information.
On the other hand, this is a real general, tolerant interpretation of the phrase "something is physical". If nosotros remove to interpret "something is physical" inward a narrower, to a greater extent than well-defined way, nosotros may determine that the judgement "a virtual particle is physical" is false. After all, the describing word "virtual" may live said to live the antonym of "real". We split upwardly particles inward Feynman diagrams to existent in addition to virtual – in addition to amongst this interpretation of the words "real" in addition to "virtual", the judgement "a virtual particle is not real" is tautologically true!
The instance of the "information" is fully analogous at precisely about level. The data may live said to live unphysical because it depends on the cognition of the observer, sometimes on the reference frame, on the selection of ensembles inward statistical physics, in addition to other things. In general, the phrase "something is physical" is also vague in addition to unrefined.
I also think that an extra give-and-take nearly a couplet of propositions, "information is physical" in addition to "physics is informational", entirely adds precisely about other layer of worthless babbling. Both sentences clearly endeavor to tell something nearly the role of the data inward the existent world. The precise content of that contention isn't genuinely clear in addition to well-defined, as discussed above. But the divergence betwixt these 2 ill-defined statements is fifty-fifty smaller than the well-definedness of each of them separately! "Information is physics" is mostly foggy in addition to the expansion of the give-and-take yesteryear precisely about other suggestion "physics is informational" makes the fog fifty-fifty thicker. The same is true nearly many other "clever ideas" that people were adding inward Aaronson's irksome thread.
To summarize, I think that it's precisely incorrect to acquire carried away amongst vague metaphysical sentences such as "information is physical" in addition to construct a whole faith on the worshiping of the alleged depth of such statements. I believe that a somebody who is learning to think as a physicist must empathise rather early that the actual deep physics is composed of much to a greater extent than well-defined in addition to specific statements than "information is physical" in addition to that this vague contention leads to lots of subtleties in addition to nuances – inward precisely about sense, all of our of import cognition of physics is made of such subtleties in addition to nuances. So the people who endeavor to print the laymen amongst "information is physical" are ultimately contributing to the laymen's misunderstanding of the divergence betwixt scientific discipline in addition to philosophy, scientific discipline in addition to religion, physics in addition to an empty humanities utter where the truthfulness is derived from constant repetition in addition to authorities.
The laymen should live honestly told that legitimate physicists to a greater extent than frequently than non consider the utter nearly propositions such as "information is physical" to live a waste matter of fourth dimension in addition to everyone who genuinely starts to think as a physicist – including you lot – should consider it a waste matter of time, too. I genuinely think that this lesson is rather slow for the laymen to learn.