Sunday, December 9, 2001

Werner Heisenberg

Heisenberg’s uncertainty principle, one of the central tenets of quantum mechanics, maintains that you cannot pin down all the physical properties of a particle at the same time. Among other curiosities, this leads to the startling idea (which has been proved experimentally) that a vacuum is not empty space. Instead, it is filled with pairs of “virtual” particles and their antiparticles, which pop into existence for a fraction of a second before recombining with one another and disappearing again. --The Economist, Dumb insolence: Black holes on a desktop, June 18, 2009

Until Heisenberg's breakthrough -- which soon came to be called matrix mechanics, because it manipulated matrices, or lattices, of numbers, with weird but satisfying results -- there was no real connection between Niels Bohr's semiclassical picture of quantum physics and the ground.

Two years later, Heisenberg came up with his now-famous (and widely co-opted by philosophers and playwrights) uncertainty principle, which in essence says you can't simultaneously pin down the location and momentum of a subatomic particle. It is one of the pillars of the so-called Copenhagen interpretation of quantum theory, which upended classical Newtonian physics and revealed matter and energy as fundamentally discontinuous and unpredictable. --Sara Lippincott, Los Angeles Times, March 8, 2009, review of Beyond Uncertainty, by David C. Cassidy (via Arts & Letters Daily)

With the declassification of important wartime documents, it is now clear from private statements made by Werner Heisenberg, German's leading theorist, that Heisenberg and his colleagues made several key mistakes in calculating what would be needed for a bomb, contributing to pessimism and poor progress in their fission research. In particular, Heisenberg's calculation of the critical mass--the amount of uranium necessary to sustain a nuclear chain reaction--was based on a faulty premise and flawed by arithmetical mistakes. --Jonothan Logan, The Critical Mass, American Scientist, May-June 1996

Other works online: A scientist's case for the classics by Werner Heisenberg, Harper's, May 1958 (via Center for the Study of The Great Ideas)