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1、A. Einstein, Ann. Phys. 17, 1321905 Concerning an Heuristic Point of View Toward the Emission and Transformation of Light A. Einstein Bern, 17 March 1905 (Received March 18, 1905) Translation into English American Journal of Physics, v. 33, n. 5, May 1965 A profound formal distinction exists between
2、 the theoretical concepts which physicists have formed regarding gases and other ponderable bodies and the Maxwellian theory of electromagnetic processes in socalled empty space. While we consider the state of a body to be completely determined by the positions and velocities of a very large, yet fi
3、 nite, number of atoms and electrons, we make use of continuous spatial functions to describe the electromagnetic state of a given volume, and a fi nite number of parameters cannot be regarded as suffi cient for the complete determination of such a state. According to the Maxwellian theory, energy i
4、s to be considered a con- tinuous spatial function in the case of all purely electromagnetic phenomena including light, while the energy of a ponderable object should, according to the present conceptions of physicists, be represented as a sum carried over the atoms and electrons. The energy of a po
5、nderable body cannot be subdivided into arbitrarily many or arbitrarily small parts, while the energy of a beam of light from a point source (according to the Maxwellian theory of light or, more generally, according to any wave theory) is continuously spread an ever increasing volume. The wave theor
6、y of light, which operates with continuous spatial func- tions, has worked well in the representation of purely optical phenomena 1 区别 有重量的 电磁的 速度 空间的 参量 代表，表示为 连续的 再分 随意的，反复无常的 起作用 and will probably never be replaced by another theory. It should be kept in mind, however, that the optical observatio
7、ns refer to time averages rather than instantaneous values. In spite of the complete experimental confi rma- tion of the theory as applied to diff raction, refl ection, refraction, dispersion, etc., it is still conceivable that the theory of light which operates with con- tinuous spatial functions m
8、ay lead to contradictions with experience when it is applied to the phenomena of emission and transformation of light. It seems to me that the observations associated with blackbody radia- tion, fl uorescence, the production of cathode rays by ultraviolet light, and other related phenomena connected
9、 with the emission or transformation of light are more readily understood if one assumes that the energy of light is discontinuously distributed in space. In accordance with the assumption to be considered here, the energy of a light ray spreading out from a point source is not continuously distribu
10、ted over an increasing space but consists of a fi nite number of energy quanta which are localized at points in space, which move without dividing, and which can only be produced and absorbed as complete units. In the following I wish to present the line of thought and the facts which have led me to
11、 this point of view, hoping that this approach may be useful to some investigators in their research. 1. Concerning a Diffi culty with Regard to the The- ory of Blackbody Radiation We start fi rst with the point of view taken in the Maxwellian and the electron theories and consider the following cas
12、e. In a space enclosed by completely refl ecting walls, let there be a number of gas molecules and electrons which are free to move and which exert conservative forces on each other on close approach: i.e. they can collide with each other like molecules in the kinetic theory of gases.1Furthermore, l
13、et there be a number of electrons which are bound to widely separated points by forces proportional to their distances from these points. The bound electrons are also to participate in conserva- tive interactions with the free molecules and electrons when the latter come 1This assumption is equivale
14、nt to the supposition that the average kinetic energies of gas molecules and electrons are equal to each other at thermal equilibrium. It is well known that, with the help of this assumption, Herr Drude derived a theoretical expression for the ratio of thermal and electrical conductivities of metals
15、. 2 平均 瞬时 实验的，试验性的确认 衍射 折射 散射 令人信服的，可想象的 矛盾，反对 发射 转换 黑体 辐射 荧光 阴极 紫外的 容易地 分配与. . . 一致 分布 量子 在下文 介绍 研究者 关于 分子，微粒 施以影响 运动的 必然 成比例的 结合 保守的 very close. We call the bound electrons “oscillators”: they emit and absorb electromagnetic waves of defi nite periods. According to the present view regarding the o
16、rigin of light, the radiation in the space we are considering (radiation which is found for the case of dynamic equilibrium in accordance with the Maxwellian theory) must be identical with the blackbody radiation at least if oscillators of all the relevant frequencies are considered to be present. For the time being, we disregard the radiation emitted and absorbed by the oscillators and inquire into the condition of dynamical equilibrium associated with the interaction (or collisi
