Scrawled on a toilet stall at Caltech sometime in the early '80s:
"Heisenberg sat here yesterday."
Then, in different handwriting immediately below:
"Pauli was here at the same time."


I was there. It goes:

"Heisenberg might have been here."
"Pauli was here too, but not at the same time."

It refers to the Heisenberg uncertanty principle (one can measure the position
or momentum of a particle, but not both at the same time (*)), and the Pauli
exclusion principle (no two electrons (**) can be in the same state at the same
time)

(*) You can measure them both, but the more accurately you measure one, the
less accurate the other is. It's not too farfetched to say that the concept of
a particle having a precise position and momentum at the same time is
meaningless.

(**) Not just electrons, but an entire class of particles (called Fermions)
behave this way. Common fermions are electrons, protons, and neutrons.
Compare with Bosons, which like to be in the same state. Photons are bosons,
which is why a laser works... all the light waves can line up in step. An
electron laser would be impossible (or would lead to a huge physics advance)

All this is related to aviation in that thinking about it makes one high. g

Jose


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