Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Tim Rentsch Newsgroups: comp.arch Subject: Re: Is Intel exceptionally unsuccessful as an architecture designer? Date: Mon, 23 Sep 2024 05:56:27 -0700 Organization: A noiseless patient Spider Lines: 136 Message-ID: <86zfny7clg.fsf@linuxsc.com> References: <2935676af968e40e7cad204d40cafdcf@www.novabbs.org> <2024Sep18.074007@mips.complang.tuwien.ac.at> <2024Sep18.220953@mips.complang.tuwien.ac.at> <20240922114808.000001f9@yahoo.com> <868qvj96lx.fsf@linuxsc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Date: Mon, 23 Sep 2024 14:56:28 +0200 (CEST) Injection-Info: dont-email.me; posting-host="40d4d7003de17e58b0545a97e9ee45d8"; logging-data="2864232"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18hLwwpejOMuIekP4hQL8kku6ionL8A2o0=" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:f1ZKJFK725e7DLUSSTxvs9GGVCc= sha1:JKLxtphNYF7h9bOhrzhHig2hlHQ= Bytes: 9084 mitchalsup@aol.com (MitchAlsup1) writes: > On Sun, 22 Sep 2024 13:10:34 +0000, Tim Rentsch wrote: > >> Michael S writes: >> >>> On Sat, 21 Sep 2024 20:30:40 +0200 >>> David Brown wrote: >>> >>>> Actual physicists know that quantum mechanics is not complete - it is >>>> not a "theory of everything", and does not explain everything. It >>>> is, like Newtonian gravity and general relativity, a simplification >>>> that gives an accurate model of reality within certain limitations, >>>> and hopefully it will one day be superseded by a new theory that >>>> models reality more accurately and over a wider range of >>>> circumstances. That is how science works. >>>> >>>> As things stand today, no such better theory has been developed. >>> >>> Actually, such theory (QED) was proposed by Paul Dirac back in 1920s and >>> further developed by many others bright minds. >>> The trouble with it (according to my not too educated understanding) is >>> that unlike Schrodinger equation, approximate solutions for QED >>> equations can't be calculated numerically by means of Green's function. >>> Because of that QED is rarely used outside of field of high-energy >>> particles and such. >>> >>> But then, I am almost 40 years out of date. Things could have changed. >> >> Quantum electrodynamics, aka QED, is a quantum field theory for the >> electromagnetic force. QED accounts for almost everything we can >> directly see in the world, not counting gravity. >> >> The original QED of Dirac, as expressed in the Dirac equation, has a >> problem: according to that formulation, the self-energy of the >> electron is infinite. To address this deficiency, for about 20 >> years physicists applied a convenient approximation, namely, they >> treated the theoretically infinite quantity as zero. Surprisingly, >> that approximation gave results that agreed with all the experiments >> that were done up until about the mid 1940s. >> >> In the late 1940s, Richard Feynman, Julian Schwinger, and Shinichiro >> Tomonaga independently developed versions of QED that address the >> infinite self-energy problem. (Tomonaga's work was done somewhat >> earlier, but wasn't publicized until later because of the isolation >> of Japan during World War II.) It wasn't at all obvious that the >> QED of Feynman and the QED of Schwinger were equivalent. That they >> were equivalent was established and publicized by Freeman Dyson >> (while he was a graduate student, no less). >> >> The problem of the seeminginly infinite self-energy of the electron >> was addressed by a technique known as renormalization. We could say >> that renormalization is only an approximation: it is known to be >> mathematically unsound, breaking down after a mere 400 or so decimal >> places. Despite that, QED gives numerical results that are correct >> up to the limits of our ability to measure. A computation done >> using QED matched an experimental result to within the tolerance >> of the measurement, which was 13 decimal places. An analogy given >> by Feynman is that this is like measuring the distance from LA to >> New York to an accuracy of the width of one human hair. >> >> QED has implications that are visible in the "normal" world, by >> which I mean using ordinary equipment rather than things like >> synchrotrons and particle accelerators, and that leaves atoms >> intact. Basically all of chemistry depends on QED and not on >> anything more exotic. >> >> There are three fundamental forces other than the electromagnetic >> force, namely, gravity, the weak force, and the strong force. The >> strong force is what holds together the protons and neutrons in the >> nucleus of an atom; it has to be stronger than the electromagnetic >> force so that protons don't just fly away from each other. The weak >> force is related to radioactive decay; it works only over very >> short distances because the carrier particle of the weak force is >> fairly massive (about 80 times the mass of a proton IIRC). For >> comparison the carrier particle of the electromagnetic force is the >> photon, which is massless; that means the electromagnetic force >> operates over arbitrarily large distances (although of course with a >> strength that diminishes as the distance gets larger). >> >> The strong force (sometimes called the color force) is peculiar in >> that the strong force actually *increases* with distance. That >> happens because the carrier particle of the color force has a color >> charge. For comparison photons are electrically neutral. It's >> because of this property that we never see isolated quarks. >> Basically, trying to pull two quarks apart takes so much energy that >> new quarks come into existence out of nothing. > > It does not come out of nothing, it comes out of the energy being > applied to pull the 2 quarks apart. Once the energy gets that big, > it (the energy) condenses into a pair of quarks which then pair up > to prevent the quarks from being seen in isolation. Yes, when I said that the new quarks come into existence out of nothing I meant nothing other than the energy being put in to pull the old quarks apart. >> Quarks come in three >> "colors" (having nothing to do with ordinary color), times three >> families of quarks, times two quarks in each family. The carrier >> particle of the strong force is called a gluon, and there are eight >> different kinds of gluons. (It seems like there should be nine, to >> allow each of the 3x3 possible combinations of colors, but there are >> only eight.) The corresponding theory to QED for the strong force >> is called QCD, for Quantum chromodynamics. >> >> A joke that I like to tell is because the carrier particle for the >> strong force can change a quark from one color to another, rather >> than calling it a gluon it should have been called a crayon. >> >> The field theories for electromagnetism, the strong force, and the >> weak force have been unified in the sense that there is a >> mathematically consistent framework that accommodates all three. >> That unification is only mathematical, by which I mean that there >> are no testable physical implications, only a kind of tautological >> consistency. We can see all three field theories through a common >> mathematical lens, but that doesn't say anything about how the three >> theories interact physically. >> >> The gravitational force is much weaker, by 42 orders of magnitude, >> than the other three fundamental forces. The General Theory of >> Relativity is not a quantized theory. There are ideas about how to >> unify gravity and the other three fundamental forces, but none of >> these "grand unified" theories have any hypotheses that we are able >> to test experimentally. It's unclear how gravity fits in to the >> overall picture. > > Are you not amazed that everything physicists know about the > universe can be written in 13 equations. Not really, no. Most of those equations are a lot more complicated than 1+1=2. It's worth remembering that when Maxwell originally wrote down the equations for electromagnetism there were sixteen equations, not four. It was only after the development of vector notation that the sixteen equations were expressed as only four equations.