Fowler_NottinghamUni said:
Hi, I am a student at Nottingham University England. I am currently studying for a degree in Physics, doing a second year module in Quantum Mechanics. I was just wondering if anyone could explain the indistinguishability of particles.
Indistinguishability is the foundation of quantum statistics. In QM, particles (and sometime even LARGE partices) can be described by the Schrodinger wave equation. This means that these are not classical particles, but can have some "spread", both in real space and momentum space.
Now, if these particles are, on average, far enough apart, the "spreading" of what or who they are doesn't come into play. We can accurately describe them as classical particles. However, if they interact with each other very often, or are in very close proximity to each other so much so that their wavefunctions begin to overlap significantly, then something unusual happens. QM says that in this situation, you can no longer identify one from the other, and your ability to track one particle unambiguously is gone.
Now this is different than, let's say, having 20 identical-looking red balls. While they all look the same, you can STILL make out that they are twenty DISTINCT red balls. If you have a good eye, you can still follow one red ball as I shake all of them. In the QM indistinguishable case, you don't even see 20 read balls, but rather a fuzzy red glob. Their individuality is no longer there. When this happens, a whole set of quantum statistics kicks in, and this is where you get the fermi-dirac and bose-einstein statistics.
Zz.
