Bohr, who was far away in Copenhagen, Denmark, naturally could not have noticed without warning that a paper that might give him a fatal blow was about to be published in the Cavendish Laboratory run by his teacher Rutherford.
At this time, Bohr was in his own office in the Institute of Theoretical Physics building at the University of Copenhagen, delivering his high-pitched speech with great interest.
The only difference from before was that the audience sitting on the sofa was no longer just his assistant Kramers, but also John Slater, who had just graduated from Harvard University with a Ph.D. and traveled across the ocean to Copenhagen for gold plating.
Slater was the first American to come to the Institute of Theoretical Physics. This American who was willing to accept new things also brought a new idea to the institute, that is, Einstein's photons exist, but at the same time they also There will be a certain kind of wave that guides the behavior of photons, making their motion consistent with Maxwell's wave theory.
This time, before Bohr could take action, Kramers was the first to jump out and teach the newcomers a lesson.
He righteously refuted Slater's idea, copied Bohr's words when he reprimanded him, and tried to persuade the American to accept his boss's view that the photon could not exist.
However, Bohr did listen to part of Slater's ideas, and he thought of the corresponding principle he had proposed before: phenomena in the atomic category and phenomena in the macroscopic scope can each follow the laws of their respective scopes, but when considering the microscopic When the laws within the range extend to the classical range, the numerical results it obtains should be consistent with those obtained by the classical laws.
He felt that the newcomer Slater's ideas were not without merit. It was worth spending some effort to use the correspondence principle to correct the fallacies in it, and maybe he could write a good paper.
As a result, the three people began to stay in the same office day after day to "co-write" a new paper, just like the previous communication Bohr wrote to "Transactions of the Natural Sciences". The specific division of labor is as follows:
Bohr was responsible for pacing back and forth in the room with his pipe in his mouth, occasionally mumbling his views to the two of them.
Kramers was still responsible for faithfully recording, never missing a single word from his teacher's mouth, never missing a spark of thought in his notebook.
However, as the point-maker, Stray seemed to have nothing to do with what was happening in front of him. He could only sit on the sofa on the other side and stare at the ceiling.
In less than a week, Bohr satisfactorily concluded his new theory, which was surprisingly fast in the history of Bohr's paper writing.
But the content of the paper has changed beyond recognition, and there is basically no trace of Slater's original ideas.
Accordingly, the order of authors of this paper is Bohr, Kramers and Slater, so the theory proposed by the three of them is called "BKS theory". This paper is also called the "BKS paper".
Of course, Bohr is well-deserved as the first author: this paper, which is dozens of pages long, is densely packed with words, but there is not even a single mathematical equation.
In his first paper on gamma ray scattering, Chen Muwu only used the law of conservation of momentum and the law of energy conservation, which are known to high school students and even junior high school students.
Based on these two conservation laws, Chen Muwu derived the conclusion of the existence of photons.
In order to insist on the bottom line that photons do not exist, Bohr came up with an extremely bold idea: starting from the corresponding principle he proposed before, he denied the two basic laws of physics, momentum conservation and energy conservation!
Bohr proposed in the BKS theory that the laws of momentum conservation and energy conservation in these classical physics only hold true in the statistical average of a large number of collision events, and under microscopic conditions, the momentum and energy of a single electron when affected by electromagnetic waves do not. Conservation.
His risky move completely negated the theory proposed in Chen Muwu's first paper.
Because whether it was Chen Muwu's first paper or the physicists who conducted a lot of experiments after reading the paper, all they did was to measure the wavelengths of incident and scattered gamma rays respectively. This is indeed a kind of statistics. Average results.
But even so, Bohr needed to spend a lot of space in his paper to construct an extremely tortuous and complex new theory in order to provide an alternative analysis for the scattering of gamma rays.
Nowadays, there is only one way to refute Bohr's BKS theory, and that is to find evidence to prove that wavelength changes are not just statistical averages, but can be intuitively reflected in single photons and single electrons. In other words, classical physics The two conservation laws in , also apply in particle collisions.
What a coincidence, isn't it?
The photos Chen Muwu asked Kapitsa and Blackett to take were just to prove this point!
…
When Einstein first proposed the light quantum theory, in order to confirm its correctness, he proposed a not-so-famous thought experiment, "Einstein's Soap Bubble" at the Salzburg Conference in 1909:
He first asked everyone to imagine that the heat of a cathode ray tube could be adjusted so low that only a single electron could escape from the cathode filament every time.
The electron will run straight toward the anode and hit a point on the screen there (see Figure a).
This was just an ordinary particle movement, no one bothered to think about it, and the scientists present accepted this view.
Einstein also asked everyone to imagine that the energy of a light source is adjusted very low, so that the light source can only emit a single energy quanta at a time.
If light is indeed the electromagnetic wave that Planck believed, then the light emitted from this point source should be a spherical wave, like an expanding soap bubble, "spreading" evenly in all directions at the same time (Figure b).
However, when this spherical wave is absorbed somewhere, all the energy in the soap bubble will suddenly be concentrated at that point, because it can only be absorbed as a whole energy quanta (Figure c).
It obviously doesn't make sense that the energy of light disperses like expanding soap bubbles when it propagates, but magically concentrates on one point when it is absorbed.
In the end, Einstein concluded that it would be reasonable if light was a particle like an electron during the entire process of emission, propagation, and absorption.
His soap bubble paradox did not attract the attention of the scientists present.
In 1917, when using Bohr's atomic model to deduce the quantum radiation law, Einstein discovered that atoms can only emit one photon in one direction at a time, and it is absolutely impossible to produce a spherical wave like a soap bubble. Then atoms and electromagnetic fields between them, thermal equilibrium will never be reached.
An atom emits a photon in a certain direction, and the photon moves in a straight line until it reaches its destination and is absorbed by another atom.
Here, photons behave like particles like electrons, but have no wave properties, completely contrary to all experimental phenomena related to light interference and diffraction for more than a hundred years.
In order to perfectly resolve the irreconcilable contradiction between the two, Einstein once hypothesized that there might be a "ghost field" that conforms to Maxwell's equations, allowing photons to also conform to the form of waves.
But the soap bubble paradox he proposed a few years ago once again trapped him in a cocoon.
The "ghost field" of a point light source will inevitably spread outward in the form of a spherical wave, but photons can only appear in a certain place.
Einstein was unable to give a strict mathematical expression to this "ghost field", so he did not formally publish a paper. Instead, he only proposed this idea in a small circle of scientists such as Lorenz and Sommerfeld.
Bohr also knew about the "ghost field" proposed by Einstein. He believed that the concept of ghost fields was similar to the statistical average he proposed in the BKS theory.
So even though he knew that Einstein was a firm supporter of the quantum theory of light, Bohr carefully sent a copy of his BKS paper to Einstein, who had returned to Germany, wanting to hear his opinion. .
As for the original copy of the paper, of course he sent it to the Royal Society's "Transactions of the Natural Sciences".
…
While Bohr's paper was still floating on the ship, running along the sea route from Copenhagen to London, Kapitsa and Blackett were busy preparing for the end of the semester.
Mahjong tiles, small, boxy pieces of bamboo, were so harmful that Kapitsa determined that he would play no more than two rounds a day until the spring semester exams and thesis defense were over.
And Chen Muwu, who had nothing to do and was at ease, had already begun to enjoy his leisure time in summer.
(End of chapter)
