## Foundations of the Theory of Gravitation

In 1911, Albert Einstein restarted his work on the general theory of relativity by considering the influence of gravitation on the propagation of light. After a new calculation, he discovered already in his first paper that the bending of light in the gravitational field of the sun should be measurable.138 In another paper, entitled 'On the Theory of the Static Gravitational Field,' he derived the consequences from a static gravitational field on the electromagnetic and thermal processes.139 In...

## Towards the Unified Field Theory

In his communication, entitled 'Do Gravitational Fields Play an Essential Role in the Structure of Elementary Material Particles ', Einstein said 'Neither Newton's law of gravitation nor the relativistic gravitational theory has brought along progress in the theory of the constitution of matter up to now. In contrast to that it will be demonstrated in the following that indications exist that the elementary entities forming the bricks of atoms are held together by gravitational forces 154 With...

## The Completeness Problem

As Niels Bohr noted 'While, so far, relatively few persons had taken part in the discussions reported in this article, Einstein's critical attitude towards the views on quantum theory adhered to by many physicists was soon after brought to public attention through a paper with the title Can Quantum-Mechanical Description of Physical Reality Be Considered Complete , published in 1935 by Einstein, Podolsky and Rosen.'240 This joint paper started with the following remark 'Any serious...

## The Discussions on Epistemological Problems

In a brief exchange of notes during A. H. Compton's lecture at the fifth Solvay Conference, Ehrenfest passed on the following note to Einstein 'Please don't laugh There is a special section in the purgatory for professors of quantum theory, where they would be obliged to listen to ten hours of lectures on classical physics every day ' Einstein responded 'I simply laugh at the naivety. Who knows who would laugh in a few years '217 Niels Bohr had met Albert Einstein for the first time in April...

## The Bohr Sommerfeld Atom

In early 1913 Niels Bohr developed the theory of atomic spectra.5 He started with the simplest atom, that of hydrogen, which consists of a positively charged nucleus and an electron circulating in different but stable orbits in accordance with the quantum number. Otherwise the classical laws of mechanics and electrostatics (for electrical attraction) apply, but the rotation (or, in fact, the angular momentum) becomes 'quantized.' The laws of electrodynamics concerning, for instance the...

## Are There Quantum Jumps

In an article entitled 'Are There Quantum Jumps ', Erwin Schrodinger wrote 'But in every case, however complicated the actual motion is, it can be mathematically analyzed as being the superposition of a discrete series of comparatively simple proper vibrations, each of which goes on with a quite definite frequency.'194 For Schrddinger the great question always was to understand the meaning of 'discreteness.' After all, the quantum systems could be described with the continuous wave equation,...

## Between Scylla and Charybdis

In a lecture on 'Experiment and Theory in Physics,' Max Born said 'It is natural that a man should consider the work of his hands or his brain to be useful and important. Therefore nobody will object to an ardent experimentalist boasting of his measurements and rather looking down on the paper and ink physics of his theoretical friend, who on his part is proud of his lofty ideas and despises the dirty fingers of the other. But in recent years this kind of friendly rivalry has changed into...

## The Probability Interpretation of the Wave Function

Max Born wrote The matrix form of quantum mechanics founded by Heisenberg and developed by him together with Jordan and the author of this report, starts from the idea that an exact description of the phenomena in space and time is not possible at all and therefore is satisfied in obtaining relations between observable quantities, which can be interpreted only in the classical limit as properties of motions. Schodinger, on the other hand, seems to ascribe to the waves which he considers with de...