Applications of Classical Physics

(pmaweb.caltech.edu)

80 points | by nill0 3 days ago

7 comments

  • srean 3 days ago
    I will probably date myself with this comment, but in my highschool days there used to be this TV series called the Mechanical Universe produced by Caltech. It was so fantastically good, perhaps peak pedagogy for its time.

    https://youtube.com/playlist?list=PL8_xPU5epJddRABXqJ5h5G0dk...

    • hyperjeff 2 days ago
      I watched that series multiple times when i was in high school and early college. Really inspiring and the visualizations still live in my head. Unusually good production for an educational show. Set a new standard.
  • octed 3 days ago
    For those who would like a print version, this manuscript eventually got published as Modern Classical Physics https://press.princeton.edu/books/hardcover/9780691159027/mo...
    • mhh__ 3 days ago
      I was weighing up (...) buying a copy of this the other day, in a physical bookshop. The thing was so big I couldn't actually buy it.
      • kurthr 3 days ago
        There has always been commentary that the size (over 1300 pages) of the General Rel book Gravitation by Meisner Thorne and Wheeler was done for demonstration purposes. Apparently, modern versions are only 2.5" thick which leads me to believe they must be on incredibly thin paper. I remember it being about 4-5".

        https://www.amazon.com/Gravitation-Charles-W-Misner/dp/06911...

        Maybe tome size a Kip thing?

        • mhh__ 3 days ago
          The thing with MTW is that it's so big that it's quite hard to really mull over it (for me at least).

          it's a book that I can imagine reading a lot in a very quiet world (i.e. basically a dorm or library before phones or computers) but it's very hard to actually get my teeth into it without that.

          • kurthr 3 days ago
            Yeah, unless you're taking a class like ph236 covering the material it's just absurd.

            I hadn't realized it, but it looks like this new book is for ph136 the junior level (1st year grad) general rel prep class.

            https://www.its.caltech.edu/~esp/ph136b/text.html

            • mhh__ 2 days ago
              "General relativity for the gifted amateur" just came out by the way. I suspect an instant classic. I am very rusty so shall be going through it.
    • cshimmin 3 days ago
      Interesting that they changed the author order to put Kip Thorne first... marketing?
  • momoschili 3 days ago
    I just looked through the diffraction chapter and some chapters I'm much less familiar with. This is an incredible ~graduate level text for these subjects. I've been looking for something like this for a while! Thanks!
  • xqcgrek2 3 days ago
    For an idea of how far the average US physics education has been dumbed-down in the past three decades, I doubt a 3rd year US-educated physics graduate student could pass a test on any of the chapters.
    • TimorousBestie 3 days ago
      I don’t think this is very accurate. Classical fluid dynamics is a dying art, yes, but classical mechanics and electromagnetics are still a huge part of the curriculum.
    • momoschili 3 days ago
      The vast majority of US grad students already pass tests on chapters 1-9 (the ones that are taught) before they even begin their "true" graduate career (aka their "masters"). Most graduate E&M (Jackson) and Thermo/Stat (Landau) mech classes cover their individual topics to an even greater level of detail than these materials.

      As for the uncovered subjects, it turns out quantum mechanics occupies a large space of the "new physics" that graduate students are trained to do.

      There are definitely an incredible amount of utility and knowledge to be gained from the classical field theories, and obviously many outstanding and new problems that I think need more attention as well. At the same time let's not understate the utility of quantum mechanics that most grad students are specializing in.

      You are speaking out of turn.

      • xqcgrek2 3 days ago
        sounds like you haven't visited a top-ranked physics department in a while
    • kurthr 3 days ago
      With or without a LLM "partner"?
    • dawnofdusk 3 days ago
      Not really dumbed down, just that it prioritizes quantum physics instead of classical. One can debate whether this is a good set of priorities but it's flippant to say a curriculum focused on quantum mechanics is dumber than one focused on fluids and elasticity/continuum mechanics.
      • AIPedant 3 days ago
        A lot of modern research in classical mechanics is typically covered by applied math and/or mechanical engineering departments, sometimes also applied physics or engineering science. Magnetohydrodynamics is relevant for a lot of proper academic physicists, but by no means all of them. Just a consequence of how academia specialized, for better or worse.
    • slyfox125 3 days ago
      We are victims of our success.
  • reader9274 3 days ago
    Skimmed through chapter 1. That sounds like the way I was taught this subject in high school, nothing revolutionary. Not sure why they're talking so much about its brilliance
    • dawnofdusk 3 days ago
      You learned about stress tensors and PDEs in high school?
  • zokier 3 days ago
    Interesting that relativity is included here; to me it's one of the main things separating modern physics from classical.
    • dawnofdusk 3 days ago
      Typically non-relativistic and non-quantum is called "Newtonian". Classical is just for anything which is not quantized, and so far no one knows how to quantize general relativity.
    • dreamcompiler 2 days ago
      Classical means "not quantum." It doesn't mean "not relativity." Relativity is a classical discipline.
    • matheist 3 days ago
      I think in modern physics "classical" often means "not quantum", rather than "pre-modern".
  • dave333 3 days ago
    [flagged]
    • macintux 3 days ago
      Well, that sounds legit.

      > Many so-called mainstream physicists who believe in quantum theory dismiss your theory as pseudoscience. What is Mills Grand Unified Theory of Classical Physics (GUTCP) underlying the SunCell® that harnesses the new, pollution-free primary power source based on forming Hydrinos®?

      • martinpw 3 days ago
        Classic scam to separate gullible wealthy investors from their money - delivering a revolutionary product real soon now - for the past 35 years:

        https://en.wikipedia.org/wiki/Brilliant_Light_Power

      • omneity 3 days ago
        For me it’s the double question marks that showed me how serious they are:

        > Q: What is the founding principle of Mills GUT-CP??

      • dave333 2 days ago
        On page 15 of the Introduction in

        https://brilliantlightpower.com/GUT/GUT_Volume_1/

        there's a list of 19 (counted em) shortcomings of Quantum Theory based on Schrodinger math.

        • macintux 2 days ago
          That doesn’t change the fact that using “so-called” is a red flag. The physicists are mainstream.

          That doesn’t make them right, but using derogatory language like that is not helping make the case against them.

          • dave333 2 days ago
            Not sure who wrote that, but it was not me.
    • nathan_compton 3 days ago
      This purely classical model doesn't make any fucking sense.
      • dave333 3 days ago
        [flagged]
        • nathan_compton 3 days ago
          Oh I don't know, the one that predicts the numbers correctly in a simple, transparent way everyone can apply, especially when compared to the ramblings of a weirdo trying to sell something?

          If you can find the place on this website where he demonstrates the calculation that gives the energy levels of the hydrogen atom or the band gap of a metal, please show me.

          • gus_massa 3 days ago
            Getting the energy levels of Hydrogen with a semiclasical method is not difficult. It's the Bohr atom with some disguise. Helium is hard.
            • dave333 2 days ago
              Chapter 7 of https://brilliantlightpower.com/GUT/GUT_Volume_1/ covers two electron atoms.
              • gus_massa 2 days ago
                From https://en.wikipedia.org/wiki/Helium_atom

                > Helium's first ionization energy is −24.587387936(25) eV. This value was measured experimentally. The theoretic value of Helium atom's second ionization energy is −54.41776311(2) eV. The total ground state energy of the helium atom is −79.005154539(25) eV, or −2.90338583(13) Atomic units a.u., which equals −5.80677166(26) Ry.

                Where are those calculations in chapter 7? I can't find them. I only find a few nice closed formulas. Hydrogen has closed formulas (almost), but Helium not.

                If you compare it with the Wikipedia page, the energy of Helium has no closed formulas. There are four approximated method, and the list exclude the brute force method of using Gaussian[1] or Psi[2] that can solve any molecule with a high approximation using a decomposition into a big number of orbitals.

                If they can give a nice closed formula for Helium (without magical ad hoc constants), it would be huge. Nobody has one, nobody believe there is one. It doesn't matter if the derivation of the formula makes no sense, the Bohr atom made no sense in 1913, but he had a nice formula that made sense like 20 years later.

                [1] https://en.wikipedia.org/wiki/Gaussian_(software)

                [2] https://en.wikipedia.org/wiki/PSI_(computational_chemistry)

                • dave333 2 days ago
                  First ionization energy of two electron atoms calculation is shown on p266 (p292 in the reader app) with a table showing agreement with experiment for many 2-electron atoms on p269 (p296 in reader app).
                  • gus_massa 12 hours ago
                    It's very interesting, but I'm still not convinced. It's not 100% agreement, only 99.99% agreement and in many of this experiments the errors are so low that a .01% difference is ruled out.

                    I think it's an interesting method to use a classical model to aproximate atoms, and I surprised that it gives very close results, but I think at the end it's like the Bohr atom, that works in simple cases but fails in the complicated ones. I'll try to think an example where the quantum mechanics effects are big enough to cause a problem.

          • dave333 3 days ago
            [flagged]
        • mhh__ 3 days ago
          There is no spooky action at a distance as per se
    • bomba_tom 3 days ago
      This (brilliant light power) is generally believed to be fraud and/or pseudo science. And the founder (Randall Mills) has been around for over 30 years, collecting money, never producing anything meaningful. So be cautious.
      • dave333 2 days ago
        It's amazing how most people use Wikipedia as the ultimate authority. Try reading the book there's a lot of excellent content that doesn't require following the math in detail, although the math is there in detail to support the theory.

        https://brilliantlightpower.com/GUT/GUT_Volume_1/