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LECTURE 34
     goals and outline

lecture title

    The Uncertainty Principle: Heisenberg

text pages

    Chs 17 and 18, pp 218-233.

lecture goals

  • Learn Heisenberg's (Nobel 1932) Uncertainty Principle and the various uncertainty relations among conjugate quantum variables.
  • See how uncertainty implies loss of predictability, hence loss of determinism in physics.
  • See how tunneling is plausible in terms of uncertainty between energy and time, as well as in terms of probability. You were introduced to tunneling in the nuclear fission and fusion processes, and it is applied in modern electronic devices.
  • Learn Niels Bohr's Pinciple of Complementarity and the so-called Copenhagen (where Bohr lived) Interpretation of quantum physics, which Einstein couldn't accept.
  • Introduce a bit about the quantum theory of measurement: that we disturb any system we measure, so we can't ever expect certainty.

outline of lecture

    1. Heisenberg's Uncertainty Principle -- Predictability

    2. Tunneling

    3. Copenhagen Interpretation -- Determinism is Dead, Measurement

quotes

I was lucky enough to be allowed once to look over the good Lord's shoulder while He was at work.

-- Werner Heisenberg, quoted by his wife

It seems hard to look in God's cards. But I cannot for a moment believe that he plays dice and makes use of ``telepathic'' means (as the current quantum theory alleges He does).

-- Albert Einstein

Do you really believe God resorts to dice--playing?

-- Albert Einstein

Don't you think caution is needed in ascribing attributes to Providence in ordinary language?

-- Niels Bohr

In spite of all divergences of approach and opinion, a most harmonious spirit animated the discussions.

-- Niels Bohr
...all this at Fifth Solvay Conference, October, 1927, subject ``Electrons and Photons,'' with speakers including Schrödinger, Heisenberg, Born, deBroglie

Who is the man with the soft look and the indistinct pronunciation?

-- Emilio Segré (Nobel 1959)

That is Bohr.

-- Enrico Fermi (Nobel 1938)
...this at Como Conference, September, 1927

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Please email any questions, comments, or suggestions to Professor Bernice Durand, bdurand@theory3.physics.wisc.edu.

Revised November 30, 1997.


Content © 1997, Bernice Durand
Images and layout © 1997, Shane Hamilton