Copenhagen interpretation

Principles

1. A system is completely described by a wave function ψ, representing an observer’s subjective knowledge of the system. (Heisenberg)^{[citation needed]}
2. The description of nature is essentially probabilistic, with the probability of an event related to the square of the amplitude of the wave function related to it. (The Born rule, after Max Born)
3. It is not possible to know the value of all the properties of the system at the same time; those properties that are not known with precision must be described by probabilities. (Heisenberg’s uncertainty principle)
4. Matter exhibits a wave–particle duality. An experiment can show the particle-like properties of matter, or the wave-like properties; in some experiments both of these complementary viewpoints must be invoked to explain the results, according to the complementarity principle of Niels Bohr.
5. Measuring devices are essentially classical devices, and measure only classical properties such as position and momentum.
6. The quantum mechanical description of large systems will closely approximate the classical description. (The correspondence principle of Bohr and Heisenberg.)

Photo:

Description: Niels Bohr and Werner Heisinberg at a Bohr Institute conference, Copenhagen.
Date: 1934 or 1936
Credit: Photograph by Paul Ehrenfest, Jr., courtesy AIP Emilio Segre Visual Archives, Weisskopf Collection
Names: Bohr, Niels Henrik David; Heisenberg, Werner

Copenhagen is a play by Micheal Frayn

(Photo from Teatro Comunale Giuseppe Verdi)

Landau kept a list of names of physicists which he ranked on a logarithmic scale of productivity ranging from 0 to 5. The highest ranking, 0.5, was assigned to Albert Einstein. A rank of 1 was awarded to “historical giants” Isaac Newton, Satyendra Nath Bose, Eugene Wigner, and the founding fathers of quantum mechanics, Niels Bohr, Werner Heisenberg, Paul Dirac and Erwin Schrödinger. Landau ranked himself as a 2.5 but later promoted himself to a 2. David Mermin, writing about Landau, referred to the scale, and ranked himself in the fourth division, in the article My Life with Landau: Homage of a 4.5 to a 2.

(Photo: Niels Bohr and Lev Landau from AIP)

Solvay Conference

awesomepeoplehangingouttogether:

Famous Physicists hanging out together:
A. Piccard, E. Henriot, P. Ehrenfest, Ed. Herzen, Th. De Donder, E. Schrödinger, J.E. Verschaffelt, W. Pauli, W. Heisenberg, R.H. Fowler, L. Brillouin;
P. Debye, M. Knudsen, W.L. Bragg, H.A. Kramers, P.A.M. Dirac, A.H. Compton, L. de Broglie, M. Born, N. Bohr;
I. Langmuir, M. Planck, M. Curie, H.A. Lorentz, A. Einstein, P. Langevin, Ch. E. Guye, C.T.R. Wilson, O.W. Richardson

(reposting for better quality and image caption, thank you Axel!)