Pages

Friday, August 11, 2023

Bose Discovered Photon Spin in 1924

Bose–Einstein statistics are crucial in quantum mechanics for describing systems of multiple identical bosons, like photons. Wonder what Einstein had to do with it?

A new paper tells the story:

As we approach the centenary of the discovery of quantum statistics in 1924, it is important to revisit Bose’s original derivation of Planck’s law usually ignored in most standard presentations of Bose-Einstein statistics. It introduced not only the novel concept of the indistinguishability of photons but also of their intrinsic spin, a fact unknown to most physicists. ...

On June 4, 1924 he sent a short paper ‘Planck’s Law and the Light-Quantum Hypothesis’ to Albert Einstein with the humble request, ‘You will see that I have tried to deduce the co- efficient 8πν2/c3 in Planck’s law independent of the classical electrodynamics, only assuming that the ultimate elementary regions in the Phase space have the content h3. I do not know sufficient German to translate the paper. If you think the paper worth publication, I shall be grateful if you arrange its publication in Zeitschrift f¨ur Physik’.

In a post card dated 2nd July, 1924 Einstein wrote to Bose, ‘Dear Colleaugue, I have translated your work ... It signifies an important step forward and I liked it very much ...... You are the first to derive the factor quantum theoretically, even though because of the polarization factor 2 not wholly rigorously. It is a beautiful step forward’

Bose not only derived the Planck law using the statistics, he descovered spin to account for that factor of 2. He later explained:
‘You know’, he said, ‘my deduction of the Planck law had a factor of 2 missing. So I proposed that it came from the fact that the photon had a spin, and that it can spin either parallel or antiparallel to its direction of motion. That would give the additional factor of 2. But the old man (meaning Einstein) crossed it out (‘budho k´et´e dil´e’ in Bengali, his mother tongue) and said it was not necessary to talk about spin, the factor of 2 comes from the two states of polarization of light.’
Today we call this Bose-Einstein because Einstein translated the paper from English to German, recommended it for publication, and deleted one of the brilliant ideas.

Now we know spin and polarization are the same thing, but we say spin for particles, and polarization for waves.

Quantum spin has a long history of physicists denying that it was real. According to Wikipedia, W. Pauli introduced it in 1924 as an electron having "two-valuedness not describable classically". He first denied that it was spin, and then published a quantum spin theory in 1927.

4 comments:

  1. Yes, photons spin....and so do electrons. You should ask your self what does that also imply?

    What exactly is the difference between a photon and an x-ray, radio, gamma-ray, etc.? They are in an electromagnetic spectrum aren't they? They are just the same thing at different energy levels...but how exactly is that energy expressed?

    What you are calling 'waves' aren't some bullshit ethereal phenomenon or magical floating unassigned math or probabilities. They are oscillations or what happens when you combine two motions, a direction and a spin. Visualize the travel path of a football. What does it do when spinning while travelling? It spirals. Think of what happens if the spinning is faster or slower..now compress this into a two dimensional measurement, Voila, there's your god damn wave and particle flipping duality. It isn't a ridiculous paradox at all, just a oversimplification that has been misinterpreted.

    ReplyDelete
  2. Dear CFT:

    > ``Visualize the travel path of a football.''

    Any one mentions a football in the context of either the QM or the Shrimadbhagwadgita, and I become a bit suspicious. Intentions might not be in doubt; the found necessity to make a reference to those previous/pre-existing/ancient theoretical pronunciations is.

    > ``Visualize the travel path of a football. What does it do when spinning while travelling? It spirals. Think of what happens if the spinning is faster or slower..now compress this into a two dimensional measurement, Voila, there's your god damn wave and particle flipping duality. ''

    No, CFT, I didn't get the ``Voila'' part and the subsequent.

    BTW, comparing the QMcal particle with the football has been the source of too many troubles regarding the QMcal ontology. Einstein committed that mistake (in the context of photons, of all things!), Feynman did (not just for photons but also for electrons), and too many others did too. (I guess at Harvard they have portraits of them all, one above other, all the way up, all done up in durable oil paint and all.)

    > ``It isn't a ridiculous paradox at all, just a oversimplification that has been misinterpreted.''

    Hmm... We, perhaps, are being a wee bit too confident here, aren't we, CFT?

    Best,
    --Ajit

    ReplyDelete
  3. @Ajit,
    Modern Physics glorifies paradox, they consider it a design feature as they can maintain any absurdity under it, publish any paper, get sited, get grants, and never be proven wrong, especially if they chose to focus on something no one can actually question.

    You said:
    "Hmm...We, perhaps, are being a wee bit too confident here..."

    No, and there is no 'WE'. I'm an individual looking for workable answers. I'm not woke, I don't have multiple personality disorder, and I'm not the Queen of England talking in the third person. It is also not 'too confident' to seek answers when everyone else just wants to repeat absurdity and call it a solution. I will also plainly state, I lay no claim to originating what I am conveying. I merely looked for an answer that didn't depend on needless bullshit and abstraction to work.

    IF you are going to say there is an electromagnetic spectrum,
    There are certain unavoidable conclusions you are going to have to entertain and stop trying to avoid.

    On one end of the spectrum you have the lower energy particles, what we call infra-red(heat) and radio. In the middle you have visible light (photons) and at the high end you have x-rays and gamma-rays etc. Since they are on the same spectrum, this automatically implies similarity of structure and behavior. One end of the spectrum is the same in nature as the other end, just at a different energy level, I believe this is commonly referenced all the time. So nothing too original here to mention yet.

    Now, consider photons spinning. They sort of have to, since it is known they can be charged. Charge is not a '+' or a ' -' except diagrammatically, so what is it? Spin in a particular direction from a frame of reference. If photons spin, and these photons are structurally the same thing as infra-red and gamma-rays just at different energy levels, how is this energy expressed? Exactly? What is carrying the energy? We are talking photons here, so there is no complex differing variation of structure to hide behind. We are talking about particles that all have a wavelength, longer at the bottom of the scale, shorter at the top of the scale. What is the wavelength? Exactly what is the cause of the measurement? besides just a number and position we look up on chart?

    To these questions, we can apply an answer that takes what is known, and uses it to fill in the implications which have been left vacant. The spin is the easiest to consider, as it is common to all particles in the entire spectrum, and yet must have some differentiation since the whole spectrum is already traveling at c yet each level has a different wavelength...so where's the length of the wave coming from? It isn't magic.

    The only aspect of the photon left (that we know of) to be considered is the rate of the spin. What would a differing rate of spin look like? This fits with the wavelength of each particle, as a slower rate of spin would result in a slower oscillation during movement, and which would also appear as a longer wave when measured in two dimensions and put on a graph. The faster the spin of the particle, the shorter the oscillation will be. This explanation does away with the stupidity of employing a silly paradox, the 'particle-wave' duality nonsense which just dodges the question. This explanation could also be used to explain where all the supposedly missing mass of the universe is, and dovetails nicely with entropy. The 'missing' mass of the universe isn't any kind of matter per se, it's carried in the form of the lower end of the spectrum as heat, the infra-red energy which is just a photon at a lower energy level. Individually, a photon's effective mass is quite small, but considering the amount of them, and how all processes produce heat and eventually become pretty much nothing but heat, collectively, that's far more mass than what you could consider baryonic matter.

    ReplyDelete
    Replies
    1. There is a lot of good in your reply, but I shall only pick out one erroneous statement:

      > ``Charge is not a '+' or a ' -' except diagrammatically, so what is it? Spin in a particular direction from a frame of reference.''

      No, that's not what charge is --- whether in a non-relativistic theory or relativistic one, and whether in classical theory or QMcal. Charge and spin are completely different types of attributes (``properties'') of particles.

      Neutron, for example, has no charge, but it still carries a spin.

      As to the charge: It is the property that determines the strength of the ``charge-ful'' (say electrostatic) interaction, and its nature (attractive or repulsive). In classical theory, e.g. in electrostatics, charge determines the Coulomb force. In classical relativistic theory, the standard way to express interactions is using the scalar and vector potentials. In QMcal theory, the interaction is captured in a different manner (i.e. with different governing equations, but still, with the potentials entering the equations --- Schrodinger's or Dirac's). Spin, on the other hand, is supposed to refer to a part of the angular momentum, and in any case, also refers to that part of the magnetic dipole moment which cannot be attributed to the orbital part.

      > ``This explanation does away with the stupidity of employing a silly paradox, the 'particle-wave' duality nonsense which just dodges the question. ''

      No comments, except for noting that it indeed was a paradox.

      Best,
      --Ajit

      Delete