Wednesday, April 23, 2008

Max Planck at 150

Max Planck, April 23 1858 - October 4, 1947.
(Credits: Max Planck Society)
Today is the 150th birthday of Max Planck. He was born on April 23, 1858, the son of a professor of law at Kiel on the Baltic coast in northern Germany, and grew up in Kiel and Munich.

In December 1924, in a lecture at Munich on the occasion of the 50th anniversary of the begin of his studies at the university there, he remembered how he came to study physics. Actually, he had been given quite a discouraging advice by physicist Philipp von Jolly back then in 1874, when young Max Planck was unsure whether to chose physics or music. Jolly was convinced that physics had become a mature field and an elaborate science, crowned by the recent, firm establishment of the principle of the conservation of energy, and that only minor "grains of dust and bubbles" were left to explore. Nevertheless, Planck was fascinated by the then brand-new theories of thermodynamics and electrodynamics, and wanted to understand them in depth. And he succeeded in that.

Applying the concept of entropy to electromagnetic radiation, he found in the late 1890s a new constant of nature - today known as the Planck constant. This constant, when combined with the speed of light and Newton's constant of gravitation, allowed to formulate units of mass, length and time "completely independent of special material bodies and substances, and valid for all times and even extraterrestrial and non-human civilisations" - natural units now known as the Planck units. And of course, most of all, this constant allowed Planck to write down the correct theoretical description for the spectrum of electromagnetic radiation emitted by a hot body. Curiously, this formula implied that the energy of this radiation comes in small packets of energy - it is quantised. The rest is history, as they say.

Happy birthday, Max Planck!

  • For more about Max Planck, check out the biographies at Wikipedia, Encyclopedia Britannica, or MacTutor. His role in establishing quantum theory is discussed by Helge Kragh in a short essay for PhysicsWorld, Max Planck: the reluctant revolutionary.

  • Besides opening the door to the quantum, Max Planck was a very gifted organiser of science and long-term editor of the prestigious Annalen der Physik. He "discovered" and strongly supported Albert Einstein. The Max Planck Society, which arose from the Kaiser Wilhelm Gesellschaft presided by Planck over a long time, has organised an interesting online exhibit on the occasion of the 50th anniversary of his death in 1997.

  • Today's Planck Units see the light of day in an addendum to the paper Über irreversible Strahlungsvorgänge, ("On irreversible radiative processes"), published as Sitzungsbericht Deutsche Akad. Wiss. Berlin, Math-Phys Tech. Kl 5 440-480 (1899), and Annalen der Physik 306 [1] (1900) 69-122. The Planck Spectrum was published in Über das Gesetz der Energieverteilung im Normalspectrum ("On the law of energy distribution in the normnal spectrum"), Annalen der Physik 309 [4] (1901) 553-563.

  • Planck relates the story about Jolly in a guest lecture on Vom Relativen zum Absoluten (From the relative to the absolute) at the University of Munich on December 1,1924. The German text of the lecture can be found in the collection Max Planck: Vorträge, Reden, Erinnerungen.

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  1. Dear Stefan,

    Thanks for this birthday post! Forgot my post on The Planck Scale?. Btw, the quotation from Planck's paper with the extraterrestrial civilizations came up recently also in Polchinski's colloq (right in the beginning). Best,


  2. Spiegel reports here (in German) that there is some evidence that Max Planck was born Marx Planck, Marx being short for Marcus. Probably changed his name for the obvious reasons in later years.

  3. For a rough English translation see here.

  4. Dear Stefan and Bee,

    I'm a God-in-training, and I want to create a universe where quantum effects on the scale of Avogadro's number of particles are much more apparent to its sentient beings than in your universe. How would I do that?

    (Hey, I can create universes, but that doesn't mean I have a mastery over physics. You're physics experts; can you create universes?)

  5. PS: the most apparent quantum effect of course is the extensive nature of matter that arises from fermions. I mean something beyond that, where cats indeed are in superpositions of dead and alive.

  6. Dear God-in-training,

    If you fiddle with the laws of nature, chances are you'll remove the 'sentient beings'. I've 'created' dozens of universes, unfortunately I had to notice they don't describe the one I seem to live in. You don't have to do anything except assuming that the state of cats is in the Hilbert space and has the eigenvalues 'dead' and 'alive'. Don't expect your cat to be impressed by that. Best,


  7. ”I'm a God-in-training, and I want to create a universe where quantum effects on the scale of Avogadro's number of particles are much more apparent to its sentient beings than in your universe. How would I do that?”

    Sit down inside LHC during it operation.

  8. It's amazing that Max Planck was 42 when he came up with the quantum theory of blackbody radiation. Schroedinger was 39 when he came up with the wave equation of quantum mechanics, and Born was 44 when he published the fact that the probability of finding the electron in a given small volume was proportional to square of the wavefunction at that point.

    But many of the innovators of quantum theory were still in their twenties when writing their most famous papers. Heisenberg was just 25, Einstein 26, Dirac and Pauli were both 27, and Bohr was 28.

    There must have been many older professors around at the time, so why did so few of them jump on the quantum mechanics bandwaggon? Were they just unable bother to play with the mathematics and try to work things out due to old age and lack of time, or was it more a case that they didn't want to get involved because quantum ideas were initially unfashionable with those trained in classical mechanics?

  9. Hi nige,

    I don’t think that the age is a meaningful criterion. There is video on that topic:” On Getting Creative Ideas” delivered at March 14, 2007 by someone who apparently have an idea what he is talking about.

    Regards, Dany.

    P.S. If I remember correctly, M.Born originally missed that point.

  10. Dear Bee,

    no, I've not forgotten the Planck scale post - that's where I knew the story from in the first place :-) Yeah, but sorry, I had forgotten to add a link to the post...

    Hi Andreas,

    thanks for pointing out this Marx Planck story! It sounds like kind of joke - but there is even an official statement by the Max Planck Society about this news. The Bottomline is that they want to stick with Max, because Planck used this name when signing letters as a kid, and on the occasion of this "Rigorosum" for the PhD - that's the most offical event in the life of a German scientist ;-)

    Best, Stefan

  11. Hi Dany,

    Thanks for referring to which I hadn't seen before.

    It's interesting that in the questions and answers session (at 40-47 minutes) Gell-Mann is asked about the problem that string theory is excessively "creative" (unobserved dimensions, particle, no falsifiable predictions) rather than dealing with down to earth facts. Gell-Mann replies (45-46 minutes) that superpartners are a stringy prediction but not only is it not a falsifiable prediction, it wouldn't even prove string theory if superpartners were found:

    "But you could of course technically have broken supersymmetry without having superstrings! So enemies of superstrings, who seem to have turned up in various places, can always say that. But I think that finding superpartners will be very encouraging ... but attacking a theory that hasn't yet been constructed is a little strange. I think mostly it's about money. Some people would like to some of the money that goes to the smart people who work on superstring theory to go to them. Maybe they're right."

    Gell-Mann came up with the eightfold way / SU(3) particle symmetry patterns at age 32 and proposed quarks at 35. George Zweig independently proposed quarks at the same time, when he was aged 27.

    "I believe that problem formulation is actually more difficult than problem solution in many cases." - Gell-Mann

    He talks about the fact that school is the one place in life where problems are formulated for you, and that elsewhere in life the hardest part is formulating the problem in a soluble way. This usually requires what Gell-Mann calls "thinking outside the box". (I don't know what thinking inside a box is, so this popular expression seems to be meaningless.)

  12. Hi nige,

    nige:”I don't know what thinking inside a box is, so this popular expression seems to be meaningless.”

    Each one of us uses his own metaphors and images. It doesn’t a matter if that help to solve a problem.

    I would say that M.Planck was thinking “inside a box”. The problem was with box and the experimental curve didn’t allow any unconstraint imagination: just find a math that described it, what does it mean we will discuss later. It bothers me that I still don’t understand his solution much more than whether superpartners exist or not.

    Using M.Gell-Mann example, I see there different problem: given 9 points, connect them by four straight lines without going outside the box. Usually only intuition tells you whether you are going to find something more sophisticated or simply broke your neck.

    In contrast to M. Gell-Mann this is up -> down axiomatic approach. Obviously we need both.

    Regards, Dany.

    P.S. I consider M. Gell-Mann “interpretation” of SR completely wrong. Space-time in SR is rigid but geometry is different (Minkowski world +,-,-,-). The rotations of the observer don’t touch the geometry even in GR.

    In addition, two other Saba interpretations are not convincing (in soft words). And association raised by his last slide I prefer not to describe. I agree with you that he now much more creative than at age 32-35. Notice that he was the only one survived smoothly discovery/prediction of quarks.

  13. Hi Stefan,

    I find it sort of ironic that a scientist of such a conventional nature and conservative views, while attempting to only clean up a few loose ends instead opened a Pandora’s box that still plaques us today. In reading the literature on Plank there was a time he had wished he’d never started in the first place. Schrodinger, who would himself be later daunted in part by Plank’s discovery and the logical consequences of its extension I feel mirrored Plank’s own thoughts and frustrations when he said:

    "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved."



  14. Phil Warnell:” I find it sort of ironic that a scientist of such a conventional nature and conservative views, while attempting to only clean up a few loose ends instead opened a Pandora’s box.”

    That is physics all about; all one should do is to find perfect fit to the empirical facts. Wait to the next Pandora’s Box soon.

    "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved."

    Here it is completely different story. N.Bohr et al were “excessively creative”.

    Regards, Dany.

  15. Hi Dany,

    “That is physics all about; all one should do is to find perfect fit to the empirical facts.”

    Yes that is how it happens sometimes as it did with Plank. However, I wouldn’t say that the likes of Maxwell/Faraday or Einstein did what they did not to simply clean up a few loose ends; more they realized the ends were ragged and so things required a whole new approach. A bit of a difference I would say!

    “Here it is completely different story. N.Bohr et al were “excessively creative”.”

    In light of the following Bohr statement I would contend it be the opposite:

    “There is no quantum world. There is only an abstract physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.”



  16. Hi Dany,

    Cathode rays had been identified as electrons by J.J. Thomson in 1897, and since you can get cathode rays (electrons) emitted from metals at sufficient temperature, it was clear that electrons were a component of the atom when Planck was theorising.

    As you say, he had the empirical black body radiation spectrum.

    But he also had Maxwell's equations and the very early work on the Rayleigh-Jeans law available in 1900 (whose complete theoretical derivation wasn't published until 1905), which is identical to Planck's law in the asymptotic limit of low frequencies. The Rayleigh-Jeans law is perfectly correct for low frequencies, but breaks down at high frequencies in what was known as the "ultraviolet catastrophe".

    According to the Rayleigh-Jeans law, the radiating power should tend towards infinity as the frequency tends towards infinity!

    This was obviously wrong theoretically for logical reasons, e.g., if it was true then all abjects at any temperature would emit high-energy radiation at an immense radiating power. Since we don't detect X-ray emission from all objects, the Rayleigh-Jeans law is wrong at high frequencies.

    If you compare the two formulae, Planck's reduces exactly to the Rayleigh-Jeans law for low frequencies. Planck's law contains an exponential suppression on radiating power which only becomes significant at high frequencies, and it contains Planck's constant h which determines the scale at which the exponential suppression kicks in.

    Rayleigh-Jeans law:

    spectral radiance = 2ckT/{lambda^4}

    Planck law:

    spectral radiance = 2(c^2)h/[{lambda^5}{exp(hc/{lambda * kT}) - 1}].

    It's extremely clever mathematically and physically. Exponential suppression factors are common in natural science. E.g., many things have a maximum limit. So if x = y for small values of x but x has the maximum limit of z, it is often the case that complete relationship is:

    x = z[1 - exp(-y/z)].

    This formula reduces to simply x = y in the asymptotic limit z >> y, but when y increases to bigger values relative to z, the exponential limit effect begins to kick in and the straight line begins to curve gradually until (where y/z is large), the asymptotic solution becomes x = z.

    E.g., if you do more and more exercise initially your fitness may increase in direct proportion to the amount of daily exercise. But eventually, the returns for increasing exercise begin to diminish and you approach an optimal fitness level which cannot be significantly improved.

    Planck's law utilises exponential suppression on frequency in a brilliant mathematical way, but it also has a theoretical basis. Planck published several theoretical derivations of the law, each based on slightly different assumptions.

    However, the theory of an infinite number of electric charge oscillators in equilibrium (e.g., outer electrons in atoms on the inner surface of a hot cavity) producing blackbody radiation is well established.

    Usually textbooks mix up the history and claim falsely that the ultraviolet catastrophe is the failure in the Bohr atomic model of 1913, in that an electron orbiting a proton has centripetal acceleration a = (v^2)/r and therefore should be radiating electromagnetic waves according to Maxwell's equations, whereby any charge that accelerates should radiate.

    The "ultraviolet catastrophe" here is that the electron spirals into the nucleus because it must radiate energy as it orbits, so it falls in.

    This is not what Planck is addressing in his multi-oscillator theory, although it does give a picture for what the Rayleigh-Jeans law is saying about the (false) classical prediction radiation from a single electron orbiting a nucleus, even though the Rayleigh-Jeans law was developed 8-13 years before the Bohr atom was proposed.

    As the electron spirals into the nucleus in the classical mechanics of the atom, it orbits faster and faster, so the frequency of the radiation emitted increases towards infinity.

    Pierre Prévost (1751–1839) in 1791 showed that all bodies radiate heat. This was initially unpopular, since it unseated the popular caloric theory.

    The thing is, people will always say that if something is not losing energy, it can't be radiating!

    They don't realise that when all things are radiating, nothing loses energy. This is simply an equilibrium, because the radiation from one body is received by others which then re-radiate it, so everything is in equilibrium.

    Most things that appear static and constant in nature are actually in an equilibrium, radiating and receiving energy at a similar rate. In quantum field theory, charges are exchanging field quanta which produce forces.

    A spinning charge like an electron should have centripetal acceleration if of non-zero size and really spinning, so it should be emitting radiation just from the spin. This could be the exchange radiation, the field quanta.

    However, this is currently regarded as heresy and ignored by everybody just we can't actually see the electron spinning and because of the wavefunction collapse philosophy (as Einstein mocked this Mach-Bohr-Heisenberg philosophy: the Moon isn't there when you are not looking at it).

    The hypocrisy is that some of the same people who use philosophy to ignore investigating simple models for empirical facts like electron spin (proved by the Stern-Gerlach experiment), nevertheless are quite happy to theorise about completely undetectable, uncheckable 11 dimensional M-theory, unobserved superpartners, etc.

    "You are crazy because everyone agrees that the electron only spins for real when we are measuring it; it doesn't spin at other times because we can't check that it is spinning when we aren't looking at it. We are sensible and rational because we are working on 11 dimensional M-theory which has no evidence!"

    Why do so many people buy this hypocrisy? Why do they believe in supernatural complexity, i.e. speculative belief systems lacking any mechanism or evidence?

    So many people seem sure that gravity is mediated by spin-2 gravitons, just because of one way of approaching the problem first taken by Pauli and Fritz in the 1930s, which may not be the simplest approach. Then they start with the circular argument:

    "Nobody has a better theory!"

    "So you are claiming that you have asked everyone and checked everyone's theory on the planet?"

    "No, but I'm sure that all alternative theories are crackpot, so I don't need to read any of them!"

    It's not the best of times to be interested in investigating simple approaches to big problems.


  17. Hi Phil,

    In my comment I referred to the “quantum jumps” only. If we remain confined within the box of our discussion (not drifting off topics) then the situation is as follows (to avoid any misinterpretation, I consider M.Gell-Mann the father of Elementary Particles Physics):

    1)Inside the box; I would recommend to the Gell-Mann’s girl to study first what are the axiomatic definitions of a point and a line. My youngest son repeatedly use the same approach and I desperately try to explain him what is the difference between to be clever (חכם) and excessively creative (חכמולוג). So far without success. By the way, notice that A.Einstein was almost obsessive using box as metaphor/image in GR;

    2)No doubt we need to go outside the box (GR was the only exception). However, as M. Gell-Mann explains, when you go outside the box, you should be careful not to go too far, since then you may find yourself outside the physics. N.Bohr was a famous example.

    Regards, Dany.

    P.S. Most favorite statement of my son is:” I promised but didn’t promise to fulfill (empirically; הבטחתי,אבל לא הבטחתי לקיים). You easily recognize here J. von Neumann tensor (Kronecker) product state (E.Schrödinger “entanglement”). Indeed, that leads to the solipsistic infinite chain (F.London, E.Bauer, and E.P. Wigner in W&Z).

  18. Hi nigel,

    I apologize but I didn’t understand your comment. Perhaps, we have different background. My statements about content and asymptotic behavior of M.Planck solution are based mainly on:
    A.Einstein, Phys.Zeit. 10,185,(1909).
    L.Mandel and E.Wolf “Optical coherence and quantum optics”.

    Regards, Dany.

  19. Hi Phil and Nigel,

    I would like to add something.

    I have only superficial knowledge in history of science and may be I am wrong. However, our discussion triggered my curiosity and I reread A.Einstein “Uber die spezielle und die allgemeine Relativitatstheorie, gemeinverstandlich.”

    Roughly, I would say we meet three different investigation strategies presented by three great physicists:

    1)M.Planck – down-> up inside the box;
    2)M.Gell-Mann – down -> up outside the box;
    3)A.Einstein – up -> down inside half of the box.

    Let me explain what I mean.

    From ED A.Einstein returned back to the Newtonian mechanics in order to reformulate it for the Minkowski geometry. From there he “jumps” to the GR circumventing ED and its wave nature. Similarly to M.Gell-Mann he was intrinsically elementary particles physicist. Paradoxically, I would say that A. Einstein was not comfortable with fields.

    To support that statement, I quote the following (it is my translation from Russian since I don’t know German; I hope that the outcome is not distorting the origin): Ch.1, par. 2, “Coordinate system”, “One may talk about height of the cloud also when there is no real measurement rod reaching the cloud in reality”.

    That is wrong. The center of mass of the cloud can’t be defined. The cloud can’t be modeled by the rigid body. Mathematically it is described by field. Indeed using modeling we may reduce the number of parameters. For example, in QM (electron, A.Tonomura et al) the brute force measurement should contain at least 100,000 outcomes; the standard QM formalism reduces it to three parameters. Perhaps here lie the roots of A. Einstein rejection of QM.

    In GR A.Einstein used field of the Newtonian coordinate systems (observers; each one defined by its inertial mass). I am not sure that it is identical to the system contained the single observer imbedded in the given gravitational field (in analogy with Maxwell-Lorentz ED). I need reread V. A. Fock, “Theory of Space, Time and Gravitation” to check that. Then in Ch.2, par. 28, “Exact formulation of the general principle of relativity”, he wrote:” But in gravitational fields the rigid bodies with the Euclidean properties do not exist; therefore, the notion of the reference frame based on rigid body is inapplicable in GR”.

    That obviously contradicts the empirical evidence.

    And we continue with Ch.2, par. 29, “Solution of the gravitational problem on base of the general principle of relativity”: “Then we introduce the following hypothesis: the gravitational field affects the measurement rods, clocks and free moving material points in accordance with the same laws also in the case when the existing gravitational field can’t be deduced from simple coordinate Galileo’s transformation”.

    In principle, today we can do that using Yang-Mills- Utiyama procedure. Even if the same eq. of motion will be obtained, that will provide the derivation of the “postulate” for the identity of gravitational and the inertial mass. That is also something.

    Regards, Dany.


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