In 1925, Wolfgang Pauli gave physics his exclusion principle as a way to explain
the arrangement of electrons in an atom. His hypothesis was that only one electron
can occupy a give quantum state. That is, each electron in an atom has a unique
set of quantum numbers (the principle quantum number which gives its energy level,
the magnetic quantum number which gives the direction of orbital angular momentum,
and the spin quantum number which gives the direction of its spin). If this
principle did not hold, all of the electrons in an atom would pile up in the lowest
energy state (the K shell). In fact, we now know that that the Pauli exclusion
principle holds for not just electrons but for any fermions (half-integer spin
particles like electrons, protons, neutrons, muons, and many more.)
Answered by:
Joseph Kozminski, B.S., Physics Grad Student, MSU, East Lansing, MI
'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '