Good catch, Bill.
More on Niels Bohr's elusive complementarity:
....In Bohr's words, the wave and particle pictures, or the visual and causal representations, are "complementary" to each other. That is, they are mutually exclusive, yet jointly essential for a complete description of quantum events. Obviously in an experiment in the everyday world an object cannot be both a wave and a particle at the same time; it must be either one or the other, depending upon the situation. In later refinements of this interpretation the wave function of the unobserved object is a mixture of both the wave and particle pictures until the experimenter chooses what to observe in a given experiment. (Remember that, according to Heisenberg, the path of an object first comes into existence when we observe it.) By choosing either the wave or the particle picture, the experimenter disturbs untouched nature. Such favoritism unleashes a limitation in what one can learn about nature "as it really is." This limitation is expressed by Heisenberg's uncertainty relations, which, for Bohr, were related to what he was now calling "complementarity." Complementarity, uncertainty, and the statistical interpretation of Schrödinger's wave function were all related. Together they formed a logical interpretation of the physical meaning of quantum mechanics known as the "Copenhagen interpretation."
aip.org
In the city of Como, Italy, most of the leading scientists of the world gathered in 1927 to commemorate the 100th anniversary of Alessandro Volta’s death. Only Einstein was conspicuous by his absence. It at in this meeting that Niels Bohr, for the first time, introduced in a public lecture his concept of complementarity. As it was meant to be a public lecture, Bohr used only a few and simple mathematical equations in his formulation of the theme of complementarity. What Bohr tried to stress in his lecture was the need to recognise the profound and persistent difference between the classical and quantum descriptions of physical phenomena.
It may, however, be mentioned here that any phenomenon in nature, whether it refers to the phenomenon of daily life or to atomic physics, has to be described in the language of classical physics. In the classical description, causality is taken for granted, whereas in the quantum description one has to accept indeterminacy and probability as inherent aspects of natural description. What Bohr was pointing to in that historical lecture was the strange realisation that in the quantum world, the only way the observer (including his apparatus) could be uninvolved was if he observed nothing at all. In other words the object and the tools of observation form an inseparable whole.
In order to characterise the relation between a phenomenon observed under different experimental conditions, Bohr introduced the term ‘complementarity’, to emphasise that such phenomena together exhaust all definable information about the atomic objects. The notion of complementarity in the physical world refers directly to our position as observers in a domain of experience where experimental conditions play a major role in the description of the physical phenomenon. One experience may reveal, for example, the particle nature of electron, another the wave nature. It is for the scientific observer to decide which facet of the electron to expose by his choice of experiment. Whether an electron is a wave or a particle has the same status as the question: Is America above or below India? The answer would be ‘neither and both’.
Bohr dedicated 30 years of his life to spreading the message of complementarity in fields outside of physics. Not only in quantum physics but also in other fields of human knowledge do we come across situations which remind us of situations as is in quantum physics. For example, the characteristics of individual persons and human cultures present features of wholeness, the account of which (according to Bohr) implies a typical complementary mode of description. Niels Bohr developed the idea of complementarity in sociological and political contexts as he was well aware of the need to promote mutual understanding between nations with very different cultural backgrounds.
The theme of the complementarity approach is that the apparently paradoxical, contradictory accounts of events should not divert out attention from the essential wholeness. We should attempt not to reconcile the dichotomies but rather to realise the complementarity of representation of events in two quite different languages. The separateness of the descriptions only confirms the fact that in the normal language that we human beings have developed for communicating the results of our experiments, we can express the wholeness of nature only through a complementary mode of description. Bohr’s favorite aphorism was Schiller’s: "Nur die Fülle führt zur Klarheit" (Only wholeness leads to clarity).
here-now4u.de |
