In physics, spin is a fundamental property of elementary particles, such as electrons, protons, and neutrons. It is often described as a form of intrinsic angular momentum. However, it is important to note that spin is not the same as the classical notion of spinning objects like planets or tops. It is a quantum mechanical property that cannot be visualized in the same way.
Spin is quantized, meaning it can only take certain discrete values. For example, particles can have a spin of 1/2, 1, 3/2, and so on. The spin of a particle is usually represented by the symbol "s."
Regarding your second question, there are indeed massive particles with spin. For instance, protons and neutrons, which are the building blocks of atomic nuclei, have spin 1/2. Many other particles, known as fermions, also have half-integer spin, such as electrons, quarks, and neutrinos.
However, it is true that no particles with a non-zero rest mass have been observed to have spin greater than 2. This observation is known as the spin-statistics theorem, which is a fundamental result in quantum field theory. It states that particles with integer spin, called bosons, have symmetric wave functions and follow Bose-Einstein statistics. On the other hand, particles with half-integer spin, called fermions, have antisymmetric wave functions and follow Fermi-Dirac statistics.
As for the possibility of massive particles with no spin, such particles have not been observed in nature so far. All known elementary particles with mass have some degree of spin. However, it is theoretically possible for particles to exist that have no spin. These hypothetical particles are known as spin-zero particles or scalar particles. Examples of spin-zero particles include the Higgs boson, which was discovered in 2012, and the hypothetical graviton, which is a proposed particle associated with the gravitational force.