RELATED TERMS: Design and General Economic Anti-Epistemology; Uncertainty
Karen Barad (2007: 19-20), through a discussion of Michael Frayn’s play Copenhagen, analyses the disagreement between Werner Heisenberg and Niels Bohr concerning the former’s uncertainty principle. She summarises the difference between their views in the following way.
For Bohr, what is at stake is that particles do not have determinate values of position and momentum simultaneously. The issue for Bohr is not that we cannot know both the position and momentum simultaneously. Heisenberg’s point is that in measuring any of the characteristics of a particle, we necessarily disturb its pre-measurement values, so that the more we know about a particle’s position, the less we will know about its momentum, and vice versa.
Bohr is making a point about the nature of reality, not simply our knowledge of it. He is calling into question the belief that the world is made up of individual things with their independent sets of determinate properties. The lesson that Bohr derives from quantum physics is that the world is not constituted by things drifting aimlessly in the void that possess the complete set of properties that Newtonian physics assumes, such as, for example, position and momentum.
Rather, it is in the nature of measurement interactions that, given a particular measurement apparatus, certain properties become determinate, while others are excluded. Which properties become determinate is not governed by the desires or will of the experimenter, but by the specificity of the experimental apparatus. Different quantities become determinate using different apparatuses.
It is not possible to have a situation in which all quantities will have definite values at once, because some are always excluded in any one case. Two complementary sets of variables emerge from this. For any given experimental apparatus, those variables that are determinate are said to be complementary to those that are indeterminate, and vice versa. Complementary variables require different and mutually exclusive apparatuses. Heisenberg eventually accepted Bohr’s interpretation that it is complementarity that is at issue, not uncertainty.
The principle of complementarity is defined in the Principia Cybernetica Web as follows:
“Some observations can never be made simultaneously. For example, one cannot see an electron as a particle and a wave at the same time. Two different experimental situations are necessary, and they cannot be realized simultaneously. The principle was first formulated by Niels Bohr. (Lefebvre, 1983, p. xxv) “
References
Barad, K. (2007). Meeting the universe half way: quantum physics and the entanglement of matter and meaning. Durham, NC: Duke University Press.
Originally posted on the Actors/Networks blog on 14 May 2010 by Allan Parsons
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