What spin is in quantum mechanics — an intrinsic angular momentum that has no classical analogue

What the Stern-Gerlach experiment showed — angular momentum is quantized, not continuous

The Stern-Gerlach experiment demonstrated that electron spin has quantized angular momentum

Why rotational symmetry gives angular momentum conservation — if physics doesn't change with direction, angular momentum is conserved

Rotational symmetry implies invariance under spatial rotations, leading to conservation of angular momentum

What the spin-statistics theorem connects — integer spin particles are bosons, half-integer spin are fermions

Spin-statistics theorem: Integer spin = bosons, half-integer spin = fermions

What the Schwarzschild solution describes — spacetime geometry around a non-rotating spherical mass

The Schwarzschild solution describes the spacetime geometry around a non-rotating spherical mass

What gauge symmetry is — local phase transformations that leave physics invariant, the basis of all fundamental forces

Gauge symmetry: Local phase transformations preserving physics, underlying fundamental forces

What the Dirac equation predicted — relativistic quantum mechanics requires antimatter to exist

Dirac equation predicted the existence of antimatter in relativistic quantum mechanics