Monday, August 11, 2014

Rothman on oversimplified textbooks

A reader quotes a essay:
Physicist Tony Rothman said terrible things about all of Physics in the 2011 May-June issue of American Scientist in the article "The Man Behind the Curtain: Physics is not always the seamless subject it pretends to be"

"Nevertheless, as a physicist travels along his (in this case) career, the hairline cracks in the edifice become more apparent, as does the dirt swept under the rug, the fudges and the wholesale swindles, with the disconcerting result that the totality occasionally appears more like Bruegels Tower of Babel as dreamt by a modern slumlord, a ramshackle structure of compartmentalized models soldered together into a skewed heap of explanations as the whole jury-rigged monstrosity tumbles skyward" ...

"One doesn't have to go so far in quantum theory to be confused. The concept of electron "spin" is basic to any quantum mechanics course, but what exactly is spinning is never made clear. Wolfgang Pauli, one of the concept's originators, initially rejected the idea because if the electron was to have a finite radius, as indicated by certain experiments, then the surface would be spinning faster than the speed of light. On the other hand, if one regards the electron as a point particle, as we often do, then it is truly challenging to conceive of a spinning top whose radius is zero, not to mention the aggravation of infinite forces"

Then he attacks the 2-slit experiment:

"....Rather than describing how the light interacts with the slits, thus explaining why it behaves as it does, we merely demand that the light wave meet certain conditions at the slit edge and forget about the actual forces involved. The results agree well with observation, but the most widely used of such methods not only avoids the guts of the problem but is mathematically inconsistent"

He goes on and on...attacking Lagrangian mechanics, ....etc

"The great swindle of of introductory physics is that every problem has an exact solution. Not only that, students are expected to find it.
Of course the books say what is spinning -- the electron spins. What they do not do, and cannot do, is to give a classical model of a mechanical spinning electron to visualize. Quantum mechanics shows that the electron behaves differently from those classical objects, but there really is an electron and it really does spin.

He also complains that some systems can be solved numerically, but not in closed-form exact formulas. Some are also chaotic, making long-term prediction an impossibility. And real-life problems are more complicated that the over-simplified textbook examples.

That essay concludes:
“Explanation” in physics generally means to find a causal mechanism for something to happen, a mechanism involving forces, but textbook optics affords no such explanation of slit experiments. ...

Such examples abound throughout physics. Rather than pretending that they don’t exist, physics educators would do well to acknowledge when they invoke the Wizard working the levers from behind the curtain. Even towards the end of the twentieth century, physics was regarded as received Truth, a revelation of the face of God. Some physicists may still believe that, but I prefer to think of physics as a collection of models, models that map the territory, but are never the territory itself. That may smack of defeatism to many, but ultimate answers are not to be grasped by mortals. Physicists have indeed gone further than other scientists in describing the natural world; they should not confuse description with understanding.
Some people argue that Newtonian gravity theory is not really an "explanation" of the solar system, because it fails to give a causal mechanism for how the mass of the Sun exerts its force on the planets. I thought that was where Rothman was going in the penultimate paragraph, but then he seems to say that physics does not require any such explanation.

It seems entirely appropriate to me for physics textbooks to explain what they can, and not speculate much about what they cannot explain. Maybe after discussing the hydrogen atom, the book should say that a carbon atom is a whole lot more complicated. But isn't that obvious?

So of course physics textbooks are going to give particle and wave descriptions of light, and give the quantum mechanics description. If you find that intellectually dissatisfying, that's too bad, because that is the best we can do.

Like other physics expositors, he cannot resist talking about Einstein, and mentions:
Einstein did not consider his theory of gravitation — general relativity — complete until he could derive his field equations from an action, a feat that the mathematician David Hilbert accomplished five days before Einstein himself.
I am a little surprised he phrases it that way, because there is no evidence that Einstein derived the field equations from an action. Hilbert and Einstein had many meetings in 1915 before they each published those general relativity papers. Hilbert's paper describes the action, and Einstein's 5-days-later paper does not.

The way it appears to me, Einstein was tentative about general relativity until two things happened in the fall of 1915: (1) he learned that Hilbert could use a covariant action to derive essentially the same field equations that Grossmann published in 1913; and (2) he was able to use those equations to extend Poincare's analysis of the relativistic effect on Mercury's orbit. Einstein then had to hurry up and publish so he could claim full credit, or else Hilbert would get credit.

8 comments:

  1. Speaking of oversimplified, I've never understood how Gell-Mann escaped crackpot status with his promotion of toy computer models (complexity science). t'Hooft seems to be entranced by it, and so too Philip Anderson with his idolizing of Stuart kauffmanns toy biology modeling. It seems the 'complexity science' he spawned is nothing more than physicists becoming envious of computer science.

    This doesn't look like good science to me:

    http://www.santafe.edu/research/working-papers/

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  2. Tony Rothman has a good point. In actual fact, when you do ask a teacher about the murky (bullshit) answers that prop up physics, you almost always get a hostile answer that is designed to deflect any attention to the ridiculous man behind the curtain spackling fudge all over the equations. Physics text books should make a point of drawing attention to the bullshit, not deflecting good questions away from figuring out what is actually going on. Whatever it is that is going on, it isn't more esoteric complex math that hardly anyone can claim to understand without a Phd.

    In response to Anonymous, whoever that is, computer models are useless as science. In reality the results of experiment are determined by what actually happens, not a predetermined assumption modeled in code. Climatic modeling is a prime example of this fiasco of reasoning. If all your climate computer models use the same incorrect assumptions based on what you want to happen, and then your model does what you designed it to do, what does that have to do with the climate? Nothing. If you can cause any variable you like to have any degree of impact or freedom in your model, what does this tell us about reality? Nothing. The only thing it tells us is what you want to be true, much like any other incredibly soft pseudo science.

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  3. CFT,

    I don't think those with advanced math capabilities are necessarily advantaged..

    http://www.physicsoverflow.org/21784/yang-mills-millenium-question-and-dynin-formalism

    The two responses are funny:

    "His approach is on the whole sensible (and interesting)", A. Neumaier

    "...this approach is fundamentally crackpot", Ron Maimon

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  4. "Nevertheless, as a physicist travels along his (in this case) career, the hairline cracks in the edifice become more apparent, as does the dirt swept under the rug, the fudges and the wholesale swindles, with the disconcerting result that the totality occasionally appears more like Bruegels Tower of Babel as dreamt by a modern slumlord, a ramshackle structure of compartmentalized models soldered together into a skewed heap of explanations as the whole jury-rigged monstrosity tumbles skyward"

    So, he dislikes ad-hoccing.

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  5. The Quantum Fiasco continues unabated:

    http://www.math.columbia.edu/~woit/wordpress/?p=7076#comments

    The usual Professional Liars have made an appearance talking up their respective books. The various Idolizers, Mathematical Masturbators, and "Its already solved, the JustUs system of Science triumphs again!" make for an amusing read. Plenty of Pot and Kettle to go around.

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    Replies
    1. I agree with this:

      I’ve browsed and known people who are interested in these foundational issues. I find a lot of them (not all by any means) dogmatically defend Einstein’s views on quantum mechanics, and therefore these discussions always lead to advertising hidden variables, most notoriously Bohmian mechanics. If you’re actually interested in getting into this stuff, I think you will have to work hard to distinguish serious attempts to understand what is going on versus countless papers containing large quantities of pseudoscience about ‘photons telepathically mind-reading backwards in time’ (that’s almost an exact quote from one person I know working on this stuff).

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    2. Woit was the worst offender: nothing matters to him except the aesthetic value of the formalism. He is no better than the strings crowd.

      In fact, the entire comments section displayed an appalling lack of interest in empiricism, classical logic, and craftsmanship. It was either regurgitate or idolize.

      The only comment I liked was from the non-scientist, Peter Morgan.

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    3. If QM has still unclear foundation after decades of attempts to understand it, then there is a good reason to look on the facts, which forced people to create KM, differently. There is a possibility that these facts can be interpreted without creating KM at all.

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