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Quantum physics

Quantum Spin

An intrinsic form of angular momentum carried by particles, quantised in units of the reduced Planck constant and unrelated to any literal spinning. Spin divides particles into fermions and bosons and, through the Pauli exclusion principle, into the electron shells of atoms; the spin-flip of hydrogen produces the 21-centimetre radio line that maps neutral gas across the Galaxy.

Highlights

  • Behind the Pauli principle and the 21-cm hydrogen line

Across fundamental physics

Knowledge connections

Sources

The primary and reference sources this topic draws on.

  • NASANational Aeronautics and Space Administration

    Mission data, planetary science, space telescopes, and public-domain imagery.

    Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.