The Maxwell conjecture was a conjecture in theoretical physics (though not a particularly important one)
replyThe fundamental obstacle is that we have no conceivable way to produce the energy levels to test the predictions that new theoretical physics would produce. We are like over a dozen orders of magnitude off.
replyThere's a lot of everyday stuff in physics which is unexplained like the particle masses we have.
replyAnd a lot of condensed matter physics. Type II superconductivity is a well-known one, but there are a lot of more less well-known ones
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