Chapter 30 Chapter 27 Relativity and Quantum Theory (2)

The Creation of Quantum Theory: Planck and Einstein Quantum theory differs from relativity in many important ways.Almost everyone has heard of the theory of relativity and its founder A.Einstein, but only scientists and a few non-scientists (who either studied science or are interested in science.) know quantum theory.However, almost everyone involved in some aspect of physics (not only physicists, but also chemists, astronomers, biochemists, molecular biologists, metallurgists, etc.) Frequent application of quantum theory and its results.In this regard, general relativity is far behind.Quantum theory not only permeates many disciplines widely, but also, like the theory of relativity, has brought about fundamental changes in our scientific thinking and philosophy of science.The revolutionary nature of relativity and quantum theory has long been recognized by people, but both have been in the stage of theoretical revolution for a long time.

The development of quantum theory has gone through three main stages: classical quantum theory (Planck, Einstein, Bohr, Sophie, Compton), quantum mechanics (De Broglie, Schrödinger, Heisenberg, John Erdan, Born) and, more recently, relativistic quantum mechanics or quantum field theory, both of which are considered revolutions.Indeed, physicists have struggled to find words strong enough to describe the depth and breadth of the quantum revolution. W．According to Weiskopf (1973, 441), "the feat of M. Planck's discovery of the quantum ... created one of the most fruitful disciplines and the most revolutionary developments in natural science".He added that in the three decades since Planck's discovery, "our knowledge of the properties and behavior of matter has undergone a broad and profound transformation" that few periods in history can match. P．Davis (1980, 9) writes: "At the beginning of this century, the advent of the quantum theory of matter led to a revolution in science and philosophy"."It is intriguing that some of the greatest scientific revolutions in history have gone largely unnoticed," he says, because "revolutions were almost as devastating as people imagined— — even beyond the scientific revolution itself." (p. 11)

Quantum theory is generally considered to have been founded in 1900, the year Planck published his concept of the "quantum of action".Planck, unlike Einstein did five years later, did not involve the process by which light or radiation interacts.He discussed only the energy exchange and black body radiation of vibrating particles on the container wall.Through his research, he found that energy exchange is carried out in the form of jumps, and the size is related to the energy value hv, where h is a universal constant in nature introduced by Planck for the first time.As T. S．As Kuhn pointed out, Planck in 1900 simply assumed that the total energy of oscillating bodies (physical bodies, not vibrating ethers) capable of vibrating at frequency v could be composed of a set of The set of unit energy quanta of .Compared with the later concept of light quantum, this assumption is very restrained.The concept of light quantum points out that light is composed of discrete entities with definite properties, and each entity (that is, light quantum) has energy hv.

It's easy to see why Planck didn't even contemplate going a step further with a more substantive assumption: that light is "made up" of discrete particles or globules of energy.First of all, such an assumption is not necessary for his black body radiation formula; secondly, and more importantly, it has irreconcilable contradictions and conflicts with optics, one of the most perfect branches of physics established in the 19th century.The optical theory established by Maxwell, Hertz and others shows that light (and all kinds of electromagnetic radiation) is a wave phenomenon, always oscillating in the process of propagating in space, which is obviously absolutely incompatible with the concept of so-called discrete particles Tolerant.In fact, when Einstein published his photon hypothesis five years later, it contained conceptual difficulties of its own.Because according to this hypothesis, the energy of light quanta depends on the frequency of light, and the frequency of light is converted by measuring the wavelength, and the measurement of wavelength must use "interference" technology, which is precisely the wave optics theory established decades ago Experimental basis.

Planck later said of his bold conception of the energy quantum that it was "a desperate move" (Pace 1982, 370).According to Pace, his reasoning "is crazy", but this "madness is sacred", "only the greatest epoch-making figures can introduce this sacred madness into science".This spirit led him to make "the first great conceptual breakthrough" that distinguished the physics of our time from all of classical physics; it transformed a very conservative thinker "into a somewhat hesitant The determined revolutionaries".Although Planck is often portrayed as a physicist who was forced against his will to take a crucial step towards quantum theory, on many occasions he showed a love for Einstein and his own work. Heartfelt praise for the revolution.He was full of praise for Einstein's theory of relativity (see Holden 1981, 14), saying in a talk: "This new way of thinking ... is far above theoretical scientific research, and even the Institute of Theory of Knowledge any achievements".For Planck, "The theory of relativity brought about a revolution in the concept of physics, which can only be compared in depth and breadth with the revolution in astronomy brought about by the Copernican system."In his speech at the Nobel Prize award ceremony, Planck said, "Either the quantum of action is a fictitious quantity, and the whole derivation of the radiation law is also fictitious, just an empty and meaningless arithmetic game; The derivation is based on correct physical concepts".If it's the latter, he explains, then action quanta will "play a fundamental role in physics."The reason is that it "is something new and unheard of, which requires a fundamental modification of all of our physics since Newton and Leibniz founded calculus on the basis of the continuity of all causal relations." learning concept".In this speech, a cautious Planck did not explicitly use the term "revolution" when referring to his own work.Einstein was fully aware of Planck's position and contribution in creating a new physics. In 1918, Einstein recommended Planck as a candidate for the Nobel Prize in recognition of his "laying the foundations of the quantum theory and enriching the whole of physics, especially in recent years" (Pace 1982, 371).

M．In his eulogy for Planck at the Royal Academy, Born described the turmoil of the entire intellectual world from 1900 to 1905.Born "had no doubt" that Planck's "discovery of the quantum of action" was a major event "comparable to the scientific revolution initiated by Galileo and Newton, Faraday and Maxwell".He had written earlier that "quantum theory goes back to 1900) when Planck announced his revolutionary concept of the quantum or quantum of energy" (196, l).This event, he declared, was "determinative for the development of science" and as such, "it is often regarded as a watershed moment between classical physics and modern or quantum physics".But Born (1948, 169; 171) reminds us not to accept the so-called "universally recognized" point of view lightly, that is, "1900, when Planck made the great discovery, marked the real arrival of a new era in physics", because " In the first few years of the new century, almost nothing happened".Born added, "When I was a student, I remember that Planck's views were rarely mentioned in class. Even if they were mentioned occasionally, it was as a short-lived hypothesis that should be discarded as a matter of course." Born Special emphasis is placed on the importance of Einstein's two papers (written in 1905 and 1907, respectively).However, although Born claimed that after 1900 "Planck had moved on to other fields of research", he "by no means forgot his quantum". This is shown in a 1906 paper by Planck on thermal radiation, which "shows a very impressive step leading to the quantum hypothesis" (Born 1948, 171) .

Einstein also made fundamental contributions to quantum theory in the era when he created the revolution of relativity theory, which fully illustrates the greatness of Einstein.Einstein first mentioned quantum theory in a 1904 paper on statistical physics. In 1906, he again worked on the subject of statistical mechanics, establishing what is today known as the "quantum theory of solid states".More importantly, it was the paper he wrote in March 1905 that marked the transition from Planck's potentially revolutionary ideas to a real, albeit theoretical, revolution. The 1905 paper contained two fundamental assumptions: one was that light or "pure" radiation was conceived to consist of discrete and individual particles or globules (quanta) as it propagated through space; the other was that When matter radiates or absorbs light (or any form of electromagnetic radiation), it does so in the same quantum form.These hypotheses not only constituted a radical shift away from Planck's 1900 hypothesis, but also fundamentally conflicted with the generally accepted physical theories of the time.According to Pace (ibid.), this work has become "Einstein's most revolutionary contribution to physics"; it "overturned all existing ideas about the interaction of light and matter".We have seen that Einstein himself specifically described this discovery as "revolutionary".

Einstein's March 1905 paper was entitled "A Heuristic Viewpoint Concerning the Generation and Transformation of Light". The word "heuristic" is rarely used in physics, it is mainly used in philosophy and pedagogy, which means that some kind of assumption (or statement) is helpful for discovery and explanation, but it does not have to be taken seriously.It stands to reason that Einstein should have used the term again in his 1907 paper on relativity and in A Brief Introduction to Special and General Relativity (1917, English translation 1920), but he did not.He introduced the term in his treatise on optics because he proposed a particle-based concept that probably didn't exist to explain most of the known phenomena of light.The wave theory of light is one of the greatest achievements in physics in the 19th century, and it has been confirmed by light interference experiments.Klein cites others to say that Einstein (Klein 1975, 118) was apparently proposing that "physicists abandon the electromagnetic wave theory of light" when "Maxwell's electromagnetic field theory and the whole of nineteenth-century physics achieved The greatest triumph of the world", except that Einstein's hypothesis has no practical significance.Therefore, what Einstein proposed was only a provisional hypothesis.

The basic parameters used to describe a wave are velocity, wavelength and frequency.In the energy quantum hv concept of the Einstein particle hypothesis, the frequency v is often derived through the wave equation, and the wavelength parameter is determined using the "interference" technique.But in the concept of light quantum, the parameter wavelength, which is extremely important for wave theory, has no obvious physical meaning for particles or light quanta.The opposition between continuous or fluctuating properties and discrete or particle properties was so stark that Einstein was compelled to write his thesis: "Suppose our insights are true".Planck always believed that light and other forms of electromagnetic radiation are composed of waves and are therefore infinitely divisible: discrete energy elements or quanta are just an effect of the interaction of continuous waves and materialization, such as in the absorption of light What is shown in the process of deduction radiation, but it is not the basic characteristics of light waves.Other physicists have long held this view as well.According to Einstein's 1905 hypothesis, light itself is composed of discrete elements, or quanta, that is, light (and any form of electromagnetic radiation) must have a "cell"-like structure.In Einstein's concept, quantum is the basic feature of light itself, rather than manifested in the process of interaction between light and matter.Although scientists and historians of science generally refer to it today as "Einstein's quantum theory of light".But the concept of the photon was established very late, and it additionally has the property of momentum.Moreover, Einstein insisted until his deathbed (as in an interview a week before his death) that it was "not a theory" because it did not provide a satisfactory explanation of optical phenomena.

Although Einstein's papers are hypothetical, suggestive, incomplete, and theoretical, there is one section in it that is extremely important, definitive, and verifiable by direct experimentation.This part is Einstein's discussion on the photoelectric effect. The phenomenon of the photoelectric effect was discovered by Hertz in 1887.Many of its properties are P.Observed by Leonard in 1902.In the phenomenon of the photoelectric effect, incident light shining on a metal surface induces the emission of electrons.Experiments have shown that the incident light must exceed a certain frequency before electrons can be ejected; experiments have also shown that the "critical" frequencies of different metals are different.Einstein pointed out that, assuming that light is composed of discrete quanta, it is "simplest to conceive" that a "quantum of light imparts all its energy to a single electron".If the light (or radiation) is monochromatic and the frequency is v, then the energy of each photon is hv. This energy will do two things: overcome the binding force of the metal to electrons and do "work" (P); give A certain function (E) of radiating electrons; the energy possessed by electrons when they leave the metal surface is expressed by the formula:

E+P=hv or E=hv-P. Einstein's formula explains some of the laws of the photoelectric effect.One rule is that the kinetic energy E of a radiating electron has nothing to do with the brightness or intensity of the light, but only with its frequency. (Einstein's interpretation is that light intensity is a measure of the number of photons, indicating the number of radiating electrons, not the energy).The formula also reveals the quantitative relationship between the energy E of the radiated electrons and the frequency v of the incident light.Another rule is that each metal has a certain minimum frequency in the process of photoelectric radiation.The explanation of Einstein's formula is: the photoelectric effect can only occur when the frequency is large enough to make hv greater than P. Einstein's formula also predicts: E changes directly according to the change of v; if the relationship diagram between kinetic energy and frequency is given according to the experiment, then the slope of the straight line is Planck's constant h.Soon after, J, J.Thomson's student A. L．Hughes and others conducted their own confirmatory experiments, which proved the correctness of Einstein's formula.But the really decisive experiment was RA.Millikan made; these experiments not only confirmed Einstein's formula, but also obtained a new, very accurate Planck's constant h (see Wheaton 1983). Millikan's paper (1916) on these experiments is rather peculiar.Although he admits that "in every case" Einstein's "photoelectric effect formula" can "predict the experimental observations with precision", he also adds that the "half-particle theory" from which Einstein derived the formula , which currently appears to be completely untenable".He repeated his position that year, noting that Einstein's "electromagnetic light cell hypothesis" was "bold" and actually "crude".In On the Electron (1917), Millikan wrote that Einstein's formula was "a prediction as bold as the hypothesis that supported him," but that Einstein's radical prediction had absolutely no "logical basis."Millikan said how amazing it was to find that "this formula of Einstein" could accurately predict "the facts that Millikan and others" obtained experimentally"! In his book, Yan Ran is a Millikan, the enemy of the revolution, did not tell his readers truthfully that his own purpose in conducting these experiments was to overthrow Einstein's formulas, including the light quantum hypothesis on which the formulas were based. In 1949, Millikan admitted that in his lifetime spent ten years "testing Einstein's 1905 formula". He wrote, "Contrary to all my expectations, in 1915 I was compelled to announce that it was unquestionably confirmed experimentally, although it seemed inconsistent Common sense. " Millikan (1948, 344) articulated his reasons for rejecting Einstein's concept of light quanta: they "seem to completely contradict our entire knowledge of the interference phenomena of light", as well as the experimental basis of wave theory. 1911; Einstein himself felt that he had to publicly "declare the expedient character of the concept of the quantum of light" because it "seems to be incompatible with the wave theory which has been fully verified".Pace found that Einstein's caution was "almost misunderstood as his indecision," a fact that could explain many puzzling phenomena.For example, Einstein's supporter von Laue wrote to Einstein in 1907 that he was delighted to hear that Einstein had "abandoned his light quantum hypothesis".Von Laue was not alone in his misunderstanding. In 1912, Sommerfeld said that Einstein no longer insisted on "the audacious views he put forward (1905)".And Millikan declared in 1913, "I believe that 'Einstein' had, about two years ago, . . . given up" his concept of the quantum of light. In 1916, Millikan again declared that although Einstein's formula was confirmed experimentally, the "physical theory" on which it was based proved to be "totally untenable, so I believe that Einstein himself no longer Stick to it."But Pace, who has delved into Einstein's papers and letters, notes that "there is no evidence that he at any point abandoned any of the proclamations he made in 1905". R．Stowell (1975, 75-77) declared with convincing evidence in 1975 that Einstein never wavered from his light quantum hypothesis and that, in fact, he himself was "increasingly convinced that suspect". Until 1918, Rutherford (see Pace 1982, 386) also said, "This apparent connection between energy and frequency has not yet been explained by physics." When studying this episode, Pace pointed out, "Even After the photoelectric effect prediction was confirmed and accepted, hardly anyone except Einstein himself did any work on the photon of light".As evidence, Pace cites Einstein's 1922 Nobel Prize congratulations.Einstein was not awarded for his theory of relativity, nor his quantum theory of light, but "for his contributions to theoretical physics, especially for the discovery of the law of the photoelectric effect." Therefore, we can only conclude that In conclusion, Einstein's revolutionary contribution was only at the stage of theoretical revolution at that time, and did not receive actual support. The fact that Millikan attempted to deny Einstein's new ideas cannot simply be taken to mean that there was a general trend against Einstein's pioneering ideas in the physics community at that time.The general attitude toward Einstein's theoretical ideas is one of dismissal rather than active polemic.As a truly great scientist, Millikan was indeed an exception. In 1913, an official document recommending Einstein to be elected as a member of the Prussian Academy of Sciences reflected the general attitude of the physics community at that time.Signed on this document are four great scientists and supporters of Einstein, they are M.Planck, W.Nernst, H.Rubens, and E.Warbur.This document, published in 1962 (see Pace 1982, 382), spoke highly of Einstein's outstanding contributions, and it even declared: "In every major field of research that has greatly enriched modern physics, Einstein has contributed to almost every Contributions to great problems." Then they felt that Einstein should be forgiven "for sometimes . , they add: "It is impossible, even in the most delicate sciences, to introduce radically new ideas without a little adventure." Even Homer got it wrong. Quantum theory and spectroscopy: Bohr's model of the atom What has been said above is not the only clue to the development of quantum theory. In 1912, a young Dane working in Rutherford's laboratory in Manchester proposed a new and revolutionary model of the atom. N．Bohr first came into contact with Rutherford's atomic model, which was like a highly shrunk solar system, with electrons like "orbiting planets" around the central nucleus.The revolution of Bohr's model is that the new "atomic model" can explain the radiation and absorption of light of a certain frequency.He adopted Planck's radiation theory, which states that there are "apparently divisible radiations" of energy.He then noted that "the general applicability of Planck's theory of the behavior of atomic systems was first noted by Einstein," and developed by other physicists.It is a well-known fact that Bohr postulated that an electron in a stable orbit neither radiates nor absorbs energy, but when it "jumps" from a stable orbit to another orbit with lower energy, the atom will radiate A light quantum; on the contrary, when an electron absorbs a light quantity of , it will "jump to a higher energy orbit. Bohr pointed out that based on this, he was able to derive several known laws of spectroscopy. This is the famous The origin of the revolutionary "classical" quantum theory. It is difficult to judge how Beer saw the revolutionary nature of his theory in the first place.From 1913 to 1924, he certainly tried to include as many classical concepts as possible in his theory, so that it appeared in a form "in keeping with the great tradition".However, Bohr referred to his original theory simply as an atomic "model", which brings to mind the specific term "heuristic" that Einstein used in his 1905 paper on the quantum of light.By the early 1920s, almost no one doubted the revolutionary nature of Bohr's theory, and most philosophers were aware of it.Later developments of Bohr's theory included extending from one-electron atoms (hydrogen) to two-electron atoms (helium); introducing the concept of elliptical orbits.Many physicists have contributed to the development of this great theory, besides Bohr, another important figure is A.Sophie.Like all revolutionary scientific ideas, Bohr's quantum theory was not immediately universally accepted by the scientific community, although he was numerically more consistent with the laws found in experiments.Perhaps the reason for this delay was not due to the revolutionary nature of Bohr's model of the atom and quantum theory of spectroscopy, but rather the impact of the First World War.After the war, almost every famous scientist became interested in important results of the development of quantum theory. Bohr's theory is intrinsically linked to Einstein's because both assume that electrons interact with photons in a one-to-one fashion.When expressing the photoelectric effect, Einstein considered the situation that the photon has enough energy to cause the energy-absorbing electron to radiate and detach from the surface of the material, which is an extreme condition in Bohr’s theory (inter-ionization); when the photon energy When smaller, the electrons do not leave the atom, but simply "jump" to a higher orbital.The incredible difficulty in Bohr's theory is the concept of the so-called discrete state and stationary state, that is, the concept of orbit.And, like Einstein, Bohr made a hypothesis that directly contradicted the basic principles of Maxwell's physics.Maxwell believed that a charged body (electron) moving in an electric field (a positive electric field around the nucleus) must radiate.According to all the accepted physical principles, an orbiting electron must continuously reduce its energy due to radiation, so its orbit will also continuously decrease until it finally falls into the nucleus.But Bohr assumed that an electron could revolve around the nucleus in a stable orbit without releasing energy and causing radiation, which was the main obstacle to the acceptance of this theory. M． V．Laue was one of the opponents. His main reason for doubting Bohr's theory was that it directly violated Maxwell's physics. Those who started studying physics in the 1930s, like myself, will certainly recall what it was like back then.At that time, one of the features of quantum theory courses (and many textbooks) was to have a historical review before getting down to business.In the historical review, students can follow step-by-step the failure of classical radiation theory (including the principle of equipartition) and the stages in the development of quantum theory (pioneered by Planck and Einstein).Then, the principles of spectroscopy and the interpretation of these principles by Bohr's theory are discussed, followed by Sommerfeld's development of circular orbits in Bohr's theory into elliptical orbits.This stage tends to place particular emphasis on the historical significance of the experiments of Millikan, Frank, and Hertz.Finally, students will gradually learn about the spin of electrons, the concept of quantum numbers, and the great Pauli Exclusion Principle.It now appears that the reason for the historical examination of the reasons for the acceptance of quantum theory is that the professors who taught the courses and the authors of the textbooks felt the need to let students understand the experiences of previous scientists, how they were transformed, and how they were accepted. Forced to accept a completely new concept with an incomplete physical basis.This is a hallmark of the revolutionary nature of quantum theory. An in-depth study of Bohr's writings from 1913 to 1923 reveals that although he used Planck's constant and involved Einstein's theory of the photoelectric effect, he did not explicitly declare his endorsement of the quantum theory of light.That is to say, his work is mainly to study the absorption and radiation of light when the electron orbit (that is, the energy level) changes, but does not involve the nature of light and the propagation of light.In his original paper (1913), Bohr admitted that he had introduced a quantity "incompatible with the principles of classical electrodynamics, namely Planck's constant" (see Holden and Kuhn 1969; Miller 1984).In retrospect, Bohr's theory appears to be a bizarre combination of the notion of quantization and the assumption of discontinuity that classical mechanics uses to determine steady states.Bohr (1963, 8) evidently understood that his "atomic model" was not yet perfect, an incomplete elementary form, because its "basic ideas were in contrast to those tried and admired principles of classical electrodynamic theory. conflict".As M.What Klein discovered, between 1910 and 1913, like M.Planck and H. A．Scientists like Lorentz put forward the sharpest criticisms of Einstein's light quantum theory only limited to "the theory of light quantum cannot explain the interference and diffraction of light at all" (1970).Bohr himself said in a 1913 lecture that atoms emit pure radiation rather than light quanta.From 1913 until about 1920, Bohr tried to reconcile the classical wave theory of light with the theory of atomic radiation, eventually establishing what he called the "correspondence principle."But A．In his influential 1922 treatise "Atomic Structure and Spectral Lines", the only thing about the correspondence principle that surprised him was that it "retained so much of wave theory that even in spectral processes that are absolutely quantum in character The same is true" (p. 254).Sophie finally said, "Modern physics is currently facing irreconcilable contradictions." (p.56) Bohr himself even proposed to abandon what he called "the so-called light quantum hypothesis".An examination of this exciting age not only shows how much confusion has arisen in the attempt to establish a satisfactory quantum theory of spectroscopy in relation to the model of the atom, but also shows that the integration of revolutionary new ideas with classical physics How difficult it is to combine.Sommerfeld (1922, 254) pointed out that modern physics must bravely admit the contradiction between the new and the old, and should "frankly admit their incompatibility", W.Pauli strongly agrees with this point of view. Bohr's theory met all the tests of a scientific revolution.For example, Rutherford declared in a letter published in the "Natural Science" magazine in 1929 that "Professor Bohr's bold use of quantum theory to explain the generation of spectra" constituted a revolution. He said that Bohr's theory was "A direct development of the Planck hypothesis, profoundly revolutionary for physics", 1969, J.Sir Cockcroft pointed out that Bohr's "combining classical mechanics and quantum theory to describe the motion of electron orbits" was a great development, which "promoted the revolutionization of atomic theory".Like the Cartesian revolution, the Bohr revolution did not last long.Just as Descartes' work was later discarded and developed, some basic content of Bohr's theory was incorporated into another revolution, the quantum mechanics revolution.In the course of the quantum revolution, the Bohr revolution can be regarded as the first stage. Passing Quantum Mechanics: The Great Quantum Revolution In 1926, Einstein's concept of the quantum of light earned the title "photon".The term photon was coined by the American physical chemist G. N．Lewis, but he used it to describe a slightly different concept than optoelectronics.Although Lewis' original concept had long been abandoned, the photon quickly became a standard word in physics (see Stuwell 1975, 325).However, the photon concept in the mid-1920s was different from Einstein's original light quantum. It also included certain special properties, the most important of which was momentum. This was not considered by Einstein at first, but he did introduce it in 1916. Momentum (P=hv/c) properties; this concept appeared even as early as 1909 in J.In a paper by Stark (see Pace 1982, 409).The idea that photons may have momentum is P.Debye and A. H．It was proposed by Compton in 1923.In fact, Compton also made one of the most sensational discoveries of modern physics, the Compton effect that bears his name today.Compton proved based on irrefutable experimental facts: "Radiation quantum has directional momentum and energy" (Stuwell leqs, 232). L．Reflecting on the history of the work, Stewell points out that Compton's motivation, unlike Millikan's a decade earlier, was not to test Einstein's predictions.Stuwell also found that A.Sophie used the term "Compton Effect" for the first time in his congratulatory letter to Compton on October 9, 2008.Sophie also revealed that Compton's results were "the main subject of discussion" with Einstein that first summer. Although Compton's results initially caused some controversy, it was soon recognized (like Heisenberg) that the Compton effect was a turning point not only for the quantum theory of radiation, but for all of physics.Compton realized early on how revolutionary his work was. In a 1923 lecture to the American Association for the Advancement of Science (published in the Franklin Institute Journal in 1924), Compton affirmed that his discovery "made our conception of the process of propagation of electromagnetic waves, Revolutionary change." However, when he published another article in "Proceedings of the National Academy of Sciences" (9:350-362), he said: "The current quantum concept of diffraction has absolutely no impact" on classical wave theory.Einstein, finally seeing his ideas confirmed, declared that there are now two different theories of the nature of light: the wave nature and the particle nature, "both are indispensable, and, it must be admitted, have no logic whatsoever. connection, despite two decades of tremendous effort by theoretical physicists (to try to find some connection)." Around the same time, L.Inspired and inspired by Compton's achievements, de Broglie proposed the concept of matter waves.In a paper published in 1923, he cited "Compton's latest results", as well as the photoelectric effect and Bohr's theory as reasons for his conviction of wave-particle duality, declaring that Einstein's concept of the quantum of light was "absolutely universal".The work of Einstein, Bohr and Compton inspired him to accept the "objective reality of light quanta". De Broglie did not explain the wave-particle duality of light in a physical sense, but he firmly believed that this duality is a universal characteristic of nature. Even ordinary matter (such as electrons) has particle and wave properties at the same time. The revolutionary concept was first established by de Broglie in his doctoral thesis (submitted on November 25, 1924), and then further developed by Einstein.It is worth pointing out that it was Einstein's work that brought Schrödinger's attention to matter waves (see Wheaton 1983).De Broglie's hypothesis was confirmed by experiments conducted by American scientists Davidson and Germer and British GP Thomson (son of J.J. Thomson).And more importantly, it was the prelude to the new quantum mechanics with which the names of Schrödinger and Heisenberg are associated (see Klein 1964; Yarmore 1966; Raman and Forman 1969; Stewell 1975, and Miller 1984).The great significance of this new scientific revolution (especially after M. Born introduced the concept of probability waves) lies in that quantum mechanics became the core content of physics and natural science in the second half of the 20th century. There is such a well-known fact in the history of science that since the 1920s, Einstein refused to accept quantum mechanics, thinking that it was nothing more than an "expedient" explanation of nature, which caused Einstein to disagree with the entire physics community.The main point Einstein objected to was that the new physics introduced the idea of ​​probability as its basis lacking classical causality and certainty, and the resulting incompleteness of describing nature (this seems to be entirely to him) .Nevertheless, Einstein recognized that quantum mechanics was a great advance in the development of physics, albeit an expedient hypothesis.He recommended Schrödinger and Heisenberg, the co-creators of quantum mechanics, as candidates to the Nobel Committee (see Pace 1982, 515).Intriguingly, Einstein himself made important contributions to the statistical foundations of quantum mechanics. The history of the quantum mechanical revolution, or the second quantum revolution, and its rapid transition from the potentially revolutionary to the theoretical to the scientific revolution phases, is a natural subject of study in a chapter of this book.The revolutionary significance of quantum mechanics to the development of physics has become evident in the past half century.这些发展对科学和思维方式的重要性，近几十年几乎任何一本科学哲学著作都对它作了深入阐述（见玻恩1949；戴维斯1980；费困曼1965；雅莫尔1974和苏帕尔1977）。 古典量子论的最后堡垒 在本章结束之前，我们介绍一个严肃的插曲，它能够说明爱因斯坦光量子概念的真正革命性质。1924年，也就是康普顿宣布康普顿效应的发现一年之后，玻尔（同H．A．克拉摩和J．C．斯拉特一道）发表了一篇论文，旨在反对光子概念。玻尔在他的原子理论中采用了量子概念，而这一原子理论很快得到了普遍接受并使物理学的这一学科发生了革命性的变化。当时，量子论中还存在着许多无法解释的困难问题，直到几年后建立了量子力学，这些问题才得到解决。但玻尔理论同普朗克最初的量子论一样，本身并没有涉及到"自由辐射场"，也就是光或其它电子辐射在空间的量子化问题。爱因斯坦1905年的论文发表后的二十年间，玻尔和许多物理学家一样，他们虽然接受了量子论，但只承认光在辐射和吸收时的量子化，而不是光本身的量子化。他们必须记住，大量实验（包括干涉实验和衍射实验）以似乎无懈可击的证据证明了光的连续波动传播。 玻尔-克拉摩-斯拉特假说是玻尔最后一次坚持他反对用量子论对光作一般性描述的立场。他坚信，他自己的"对应原理"能在辐射和吸收量子论和已经广为认可的电磁波传播理论之间的鸿沟上架起一座桥梁。在1919年及其以后的几年中，他甚至表达过这样的愿望：如果对维护"我们的经典辐射理论"有必要的话，他将不惜迈出最为极端的一步——放弃能量守恒原理（见斯图威尔1975，222）。 1922年12月11日，他在诺贝尔奖颁奖仪式上作演讲时，再次提到了这个问题。当时他解释说："近年来，爱因斯坦理论的预言已经得到了……精确的实验证实。"但他又立刻补充说："尽管具有启发性意义"，但爱因斯坦的"光量子假说"与所谓的干涉现象"完全不能相容"，因此，不可能在辐射本质意义上解释光。"这成了1924年的玻尔-克拉摩-斯拉特论文的主题，论文的主要目的是：探索辐射特性的原因，"但并不涉及任何与光在自由空间传播定律相背离的光的电磁波理论"，而只研究"虚辐射场与发光原子相互作用这一特例"。这篇论文中，作者声明：在单次原子相互作用过程中，他们将"抛弃…能量与动量守恒原理的一个直接运用"，他们认为，守恒原理仅在宏观统计水平上是有效的，对单个原子并不适用。在此前两年，索未菲曾说过：抛弃能量守恒原理可能是医治光的波粒二象性疾病"最好的药方"（佩斯1982，419）。几年后，海森伯（1929）在评述这段历史时指出，"玻尔-克拉摩-斯拉特理论代表了古典量子论危机的顶点"（佩斯1982，419）；按照佩斯的说法，它是"古典量子论的最后一座堡垒"。 斯拉特后来在致B． L． F． D．瓦尔登的信中说，"能量和动量统计守恒的思想"是由"玻尔和克拉磨上升为理论的，这和我更好的见解完全相反"（斯图威尔1975，292）。斯拉特指出，玻尔和克拉摩有充分的理由说明"在当时的条件下，没有任何现象需要假定空间中光微粒（或量子）的存在。"斯拉特"对抛弃量子论获得的益处同放弃能量守恒和因果律造成的损失作了比较，终于被所获得力学机制的简单性所征服"。 否定这一理论的意见"非常之多"（斯图威尔&7）。然而，真正的答案并没有在理论讨论中出现，而是来自于直接的实验。关于实验结果，我们不妨引用赫胥黎曾经说过的话："一个漂亮的假说被一个丑陋的事实扼杀了。"实验毋庸置疑地证明，能量和动量守恒定律即使在单一原子层次上也是有效的。这一判决性实验采用的正是康普顿效应技术。第一批实验结果是柏林的W．玻特和H．盖革获得的，而后，A． H．康普顿和A． W．西蒙得到了更为精确的结果。 1925年4月21日，玻尔一听到这个消息，立即写到："目前最迫切的事情是，给我们革命性的努力以尽可能体面的葬礼"（见斯图威尔1975，301；佩斯1982，421）。同年7月，他在《物理学杂志》上发表文章，两次提到了革命。他写到，"我们必须为这样的事实作好准备：经典电动力学理论所需要的推广，要求对那些迄今为止一直描述自然的概念进行革命性的变革"。这段插曲和玻尔对他的议论，也许正显示了量子论的巨大威力，它是那样伟大以致于使人们不自觉地使用革命的语言。