Question 13: Do you understand quantum mechanics?

Reinhard Scherm, former PTB-Department "Fundamentals of Physics and Metrology": No. In the course of evolution, our brain developed to survive in a world with and . Consequently, how could we really understand RelT or QMech in a microscopic non-relativistic world? Nevertheless, I have often tried my best and meanwhile I am even in a position to separate the Hamiltonian H from the dose rate H₁₀.

Gesine Grosche, PTB Working Group "Unit of Length": What do you understand by “understand”? We understand hardly anything. But if “understand” means: being able to predict new observations on the basis of a model, then quantum mechanics is nothing special. One has to accept certain things. Then the consequences can be “understood” without difficulty. By the way: Just quantum mechanics has effects which can be directly recognized in a great many experiments. Quantum mechanics has, for example, become “touchable” in optics and solid-state physics.

Albert Einstein (1897 - 1955): “The idea that an electron exposed to a beam freely decides on the moment and on the direction in which it wants to jump away is intolerable for me. In that case I would rather be a shoemaker or an employee of a casino than a physicist.” Nevertheless, Einstein studied quantum theory for all his life, was not, however, certain as to its significance.

Ernst O. Göbel, President of the PTB: No, but I got used to it.

Andreas Bauch, PTB Working Group "Unit of Time": “I think I can safely say that nobody today understands quantum mechanics.” (Richard Feynman, The Character of Physical Law 1965). I am not presumptuous...

Uwe Keyser, former PTB Department "Focal Points of Experimental Research": I can work with it - but I don't know any person who understands it.

Annette Paul, PTB Working Group"Environmental radioactivity": I understand that I know something about it.

Werner Heisenberg (1901 - 1976): "Wolfram once asked me – I think it was in the course of an evening we spent at a pub at Grainau – whether I had understood Einstein’s theory of relativity which played such an important part in the Sommerfeld seminar. I could only answer him that I didn’t know, as I was not sure to understand the meaning of the word "understand" in natural science. I did not have any difficulties in understanding the mathematical structure of the theory of relativity, but that did not mean that I had understood why the word "time" has a different meaning for an observer in motion than for an observer at rest. For me, this confusion around the term of "time" was weird and insofar I did not understand this term."