Spin (physics)

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In physics, spin is the angular momentum of a particle.

For large visible objects like the earth, spin is the angular momentum of the turning of the earth around its axis. This tells the amount of rotation that it has. Angular momentum changes with the mass and shape of the object, and with how fast it is turning.

For tiny particles that obey the laws of quantum physics, spin measures the amount of angular momentum even though the particle does not actually turn. For tiny particles that obey quantum physics the spin is always a number that is an integer (1,2,3…) or half-integer (1/2, 3/2, 5/2…).