A Student's Guide Through the Great Physics Texts pp 443-456 | Cite as

# The Quantum Paradox

## Abstract

One of the most striking and significant features of the new quantum mechanics is the formulation of *Heisenberg’s uncertainty (*or *indeterminacy) principle*, which appeared in his 1927 publication “On the Perceptual Content of Quantum Theoretical Kinematics and Mechanics.” Heisenberg’s *indeterminacy principle* places a numerical limit on the precision with which one may simultaneously determine the values of certain pairs of observable quantities.

The reading selection that follows was one of Heisenberg’s Gifford Lectures delivered at the University of Saint Andrews in the winter of 1955–1956. Herein, he describes the *Copenhagen Interpretation* of quantum theory. This interpretation takes the indeterminacy principle as the cornerstone, so to speak, of quantum theory. In other words, it assumes that our inability to simultaneously know the position and momentum of a sub-atomic particle with unlimited precision is not simply an artifact of one particular method of measurement. Rather, it is an essential feature of nature itself, and hence cannot be circumvented under any conceivable circumstances. As you explore the following text, you might consider the following questions: what (if any) are the philosophical and scientific implications of accepting the indeterminacy principle? In particular, does the Copenhagen interpretation of quantum theory retain the notion of causality? Do you think that Heisenberg’s conclusions are correct?