## Chapter 12 – Edition 1

**Some notes on Chapter 12: Seeking a Real World, EPR**

Einstein’s quip, “God doesn’t play dice,” is surely his most quoted objection to quantum mechanics. It was even highlighted by a recent (non-physicist) biographer. And we quote it a few times. But reality, not randomness, was Einstein’s serious objection to quantum mechanics from the very beginning, right after the 1927 probability interpretation of the wavefunction and observer creation of real properties. His movable slit diaphragm (page 126) challenged the “observer creation” of the atom’s position or momentum by attempting to show that it had such properties all along.

Incidentally, the algebra Bohr used to show what was wrong with Einstein’s argument is simple enough for a conceptual physics class. But when you think about what that algebra *means* you can get confused. (At least I can.) It’s worth some class discussion to note that Bohr is applying quantum mechanics to an observed macroscopic object, in apparent conflict with at least one version of the Copenhagen interpretation.

The EPR paper