Relational Approach To Quantum Physics - Background

Background

As is well known, Einstein's theory of relativity, which involves a profound analysis of time and space, introduced radical changes, not only in our basic concepts, but also in our modes of physical reasoning. The essence of Einstein's theory was to adopt a relational approach to the notions of time and space, which mathematically can be expressed through the Lorentz space-time transformations.

Although the mathematical structure of the Lorentz ether theory, which leaves the speed of light in vacuo, c, a universal constant, is equivalent to that of Einstein's, there is nevertheless a drastic difference in the way to conceive it. On the one hand, Lorentz began with retaining the customary concepts of absolute time and space of the older Newtonian mechanics, and by considering changes in the observing instruments. The invariant nature of c, as measured experimentally from the Michelson-Morley experiment, was successfully explained by the so-called 'Lorentz contraction', moving through the hypothetical ether. However, this theory led to the difficulty that the exact values of the 'true' distances and times, with respect to a detection scheme at rest in the ether, became somewhat ambiguous and unknowable. Einstein, on the other hand, by commencing with the observed facts, regarded time and space a priori as a certain class of 'coordinates' merely expressing relationships of an event to the measuring instruments. On the basis of a constant speed of light, both time and space become relative concepts, fundamentally dependent of the observer.

The developments of quantum formulation early this century has also led physicists to question the Newtonian concepts of physical objects, such as 'particle' and 'wave', which are basic ideas in all of classical physics. Subsequently, Heisenberg in his pioneering paper developed a conceptual framework that in a way retained all the classical concepts, and plays a great role in the Copenhagen interpretation. This basic new step was to study the disturbance of observing instruments, and for this purpose, Heisenberg constructed the famous gedanken microscope experiment to measure very accurately the position of an electron. It was found that since the individual quanta of action must be taken into account in the measurement process, the irreducible disturbance rendered it impossible to assign simultaneously the precise values of position and momentum. Consequently, by considering the uncontrollable influence from the observation itself, the notion of particle into quantum mechanics was preserved, and the uncertainty principle was born.