Motivation and Goals
With W. Heisenberg's matrix mechanics, E. Schrödinger's eigenvalue equation, and M. Born's statistical interpretation of the wave function occurring within it, quantum mechanics established itself a good 100 years ago as a new, closed theory of physical processes at the atomic level. Yet, the epistemological consequences of this theory continue to be discussed controversially not only among physicists.
Looking at all the publications, YouTube videos, and lectures found across various media on the occasion of the 100th anniversary of quantum mechanics, one is struck by the sheer volume of metaphysical and not infrequently mystical interpretations of quantum mechanics. Examples include discussions surrounding the violation of causality in quantum mechanics, mystical entangled states, and Schrödinger's cat. The latter can be both dead and alive – a creature capable of making any science fiction fan shudder with delight. Two experiments stand at the center of these discussions: the double-slit experiment and the Bell experiment. With the latter – according to a widespread opinion among physicists – the "non-local reality" of quantum mechanics was proven, as discussed in the famous paper by Einstein, Podolsky, and Rosen (the "EPR" paper) to point out the incompleteness of quantum mechanics.
Another faction of physicists feels aligned with the pragmatic viewpoint of shut up and calculate – justified by the enormous successes this new theory has produced, whose results have contributed to rapid technological progress. Today, it has become indispensable to our everyday life.
Why is it, then, that even after more than 100 years, we find it so difficult to integrate this theory into our understanding of physical reality? One aspect certainly lies in the fact that the objects of quantum mechanics are not directly sensorily perceptible to us. This provides ideal breeding ground for speculation and metaphysics, of which Newton already remarked: "Physics, beware of metaphysics".
It is the goal of this website to contrast the many metaphysical and mystical attempts at explanation with a rational perspective. It is an attempt to reconcile classical physics and quantum mechanics on a rational level.
To this end, the next section of this website will first address what is actually meant by physics or physical reality. In the subsequent chapters, the answer given will be demonstrated using the example of two fundamental objects of classical physics with relevance to quantum mechanics. There, we will already discover commonalities between the description of objects in classical physics and quantum mechanics that can hardly be found in mainstream explanatory attempts. Since physics is arguably the natural science closest to the structural science of mathematics, this website also cannot do without mathematics. However, to appeal to laypersons interested in the subject matter treated here as well, the respective chapters are divided into layman and expert sections.
The final two sections of this website then offer readers the opportunity to interactively engage with the aforementioned Bell experiment and the double-slit experiment.
What is Physics? - An Attempt at Definition
Let us first attempt a definition of physics that might represent something like a "lowest common denominator" of understanding among physicists:
Physics refers to a specific domain of human activities in which an attempt is made to express cause-and-effect relationships in or between specified object classes through measure and numerical value. These can involve either real objects – i.e., directly accessible to our sensory perception – or abstract objects. They are defined by their likewise real or abstract properties. On the other hand, causes can be given a priori and justified by our experimental experience. We shall call them imprinted causes/sources. However, there are also induced causes/sources that can be traced back to interactions between identical or different objects. By an effect, we understand that the object under consideration can assume a specific state or that its initial state changes.
According to this understanding, the 8 categories of cause/source, effect, interaction, object, properties, state, measure, numerical value would constitute the fundamental categories of physics. This makes it clear from the outset that physics deals with the uncovering of causal connections, which are coupled particularly closely to mathematics through the two categories of measure and numerical value. We will examine two examples of this from classical physics in the next two chapters.
A fundamental difference between physics and mathematics is that in the former, experimental experience takes precedence. The structures of mathematics are subsequently used to frame this experience – very much in the sense of N. Bohr – in as universally valid a language as possible. A physical theory is successful when it allows experimental results to be confirmed or predicted. If such a prediction is experimentally confirmed by independent physicists and using different methods, this experimental experience, together with the mathematics describing it, reflects an element of our physical reality.
Actually, there should be no serious objections to this understanding of physics. Quantum mechanics can be seamlessly integrated into it if we conceptualize its objects and states as abstract magnitudes. The question remains to be clarified: what would measure and numerical value be here? A possible answer: The measure is probability, and the numerical value is the relative frequency that can be determined from a multitude of identical experimental steps.
However, since M. Born's statistical interpretation of the wave function, not only horror vacui but also horror probabilitatis has spread among physicists. This is often GROWTH accompanied by the notion that quantum mechanics abolishes determinism. But does it really? After all, this is not about arbitrary probabilities that permit no predictions whatsoever in an experiment. On the contrary, certain experiments lead – as we will demonstrate using the example of the Bell experiment – to very specific, predictable probabilities whose cause lies in defined stochastic sources. Horror probabilitatis prompted Einstein to remark "God does not play dice". To this one might counter: It may be that God does not play dice. But the devil certainly does! And such an understanding of quantum mechanics does not rule out the possibility that the stochastic behavior of these sources might be explained at some point in the future. New generations of physicists want to have their fun too. But let us now turn to the mentioned examples from classical physics to make what has been said somewhat more concrete.