[pramodmaths]

we say that the classical mech is the most basic physics.
but even we don't have a classical analogue of the concept of spin.
Also we talk about spining of particle.can only quantum particles spin,
not the classical particles?

[AntonioLao]

Originally Posted by pramodmaths but even we don't have a classical analogue of the concept of spin.

The spin of the Earth around its axis is a continuous spin (meaning that its spinning axis can be arbitrarily oriented at an infinite number of possible directions). And the reason why the Earth continue to spin for a long time is because its angular momentum is conserved. Moreover, in outer space, there is nothing that causes friction for the Earth's spin to slow down.
In the quantum world, the spin is a quantized quantity. In this case, its has only two possible values, say, up or down. This means that the spin axis has only two possible directions for its orientation. Moreover, all elementary particles share the same two directions but not necessarily at the same location unless their spins are opposite. Therefore, only two quantum particles can share the same quantum state if and only if their spins are opposite (Pauli exclusion principle). Nevertheless, this exclusion principle is only true for fermions. Bosons are excluded from obeying this principle. Because bosons are excluded from Pauli exclusion principle, they make LASER principle realizable.