1 6 6 D O C . 1 5 6 O N B A S I C C O N C E P T S O F P H Y S I C S another particular state B through the emission of light. There is a definite proba- bility for such a transition to occur in a particular atom during a particular second. The theories assert that even when I know the state of an atom as precisely as pos- sible, it would then still be impossible in principle to calculate just when that atom would in fact make its transition to the state B, based on the natural laws. This means that we abandon causality “in principle.” All the fundamental laws of nature are supposed in principle to be of this statistical type, & only our incomplete ability to observe the processes in practice has led us to believe in strict causality up to now. It is already interesting enough to find that a reasonable science is at all possible after having abandoned strict causality. It can furthermore not be denied that this abandonment has led to considerable successes in theoretical physics and yet, I must openly admit that my scientific instinct bristles against the requirement that strict causality be abandoned. In any case, however, it must be admitted that we are currently far from being able to implement that requirement which appeared so self-evident to our scientific predecessors.[13] One achievement of the development in recent times sketched above must be mentioned, since it is of decisive and lasting importance. The properties of the ra- diation as given above have led to comparing radiation to a gas whose molecules are moving in the direction of propagation of the radiation & carry an energy that depends solely on the color or frequency of the radiation. This is thus a combina- tion of the wave theory with a corpuscular theory of light.[14] A wave theory of mat- ter arose in analogy to this combination it attributes, conversely, an oscillating field to a beam of moving material particles.[15] This analogy leads us to assign properties to a current of particles that corresponds to the interference properties of light or of roentgen rays. This assertion has been confirmed by experiments. It was found that a beam of cathode rays, i.e., a beam of moving electrons, will be diffracted by the molecular lattice of a crystal in an analogous manner to the diffraction of a beam of roentgen rays or of light by an optical diffraction grating. We are dealing here with a new property of matter, which could not be described by previous strictly causal theories of motion.[16] There is still a certain hope that the field theory, with its universal causal structure, can be adapted to the newly rec- ognized experimental facts. But we should not fail to mention that the most suc- cessful theoreticians of the younger generation do not believe in such a possibility. In any case, our generation cannot be accused of having wasted its mental forces on unimportant problems of detail. Refinement of empirical knowledge, refine- ment of theoretical deductions, and struggling with the most deep-seated problems of principle in close association with the empirical facts characterize the current tempestuous phase of development in physics. (A. Einstein) [p. 8] [p. 9]
Previous Page Next Page