Basic experimental observations

Phyllis Chiasson

Chun‐Lei Tang

Basic scientific theories usually start with a set of hypotheses or “postulates.” There is generally no logical reason, apart from internal consistency, that can be given to justify such postulates absolutely. They come from ‘revelations’ in the minds of ‘geniuses,’ most likely with hints from Nature based on extensive careful observations. Their general validity can only be established through experimental verification. If numerous rigorously derived logical consequences of a very small set of postulates all agree with experimental observations without exception, one is inclined to accept these postulates as correct descriptions of the laws of Nature and use them confidently to explain and predict other natural phenomena. Quantum mechanics is no exception. It is based on a few postulates. For the purpose of the present discussion, we begin with three basic postulates involving: the “state functions,” “operators,” and “equations of motion.” In this chapter, this set of basic postulates and some of the corollaries and related definitions of terms are introduced and discussed. We will first simply state these postulates and introduce some of the related mathematical tools and concepts that are needed to arrive at their logical consequences later. To those who have not been exposed to the subject of quantum mechanics before, each of these postulates taken by itself may appear puzzling and meaningless at first. It should be borne in mind, however, that it is the collection of these postulates as a whole that forms the foundations of quantum mechanics.

Carl S. Helrich

А. В. Никулов

It is shown that one of consequences of basic principle of quantum mechanics at the mesoscopic level is violation of the second law of thermodynamics and that an experimental evidence of this violation was obtained long ago.

Jerry B. Marion, J. L. Fowler

Panos A. Ligomenides

Modern science is eliminating the old, unrealistic approach to experimental errors. The Heisenberg principle of uncertainty has effected a fundamental change in the scientific attitude toward experimental errors and toward the degree of exactness in stating physical laws. Quantum physics has brought about the realization that a measurement or a mere observation at the quantum level perturbs the observed system in such a way that corrections cannot be made for the ``loading'' effect of the measuring instrument. There is something more basic and fundamental to our limitations in measurements than the lack of perfection in experimental planning and equipment. This article examines the types of uncertainty in measurements or observations. The interest then focuses on the fundamental importance of the relation between experimental uncertainty in measuring, observing, or in any way identifying a physical quantity, and the energy required to accomplish this in a certain allotted interval of time. This last relation has a direct bearing on the speed limitations of measurements.