Spin (physics) discrete angular momenta despite having no orbital angular momentum. In some ways, spin is like a vector quantity; it has a definite magnitude, and it has a "direction" (but quantization makes this "direction" different from the direction of an ordinary vector). All elementary particles of a given kind have the same magnitude of spin angular momentum, which is indicated by assigning the particle a spin quantum number. The SI unit of spin is the (N·m·s) or (kg·m·s), just as with classical angular momentum. In practice, spin is given as a dimensionless spin quantum number by dividing the spin angular momentum
Magnitude (astronomy) century continued to think of magnitude in terms of the physical size of a star. Johannes Hevelius produced a very precise table of star sizes measured telescopically, but now the measured diameters ranged from just over six "seconds" of arc for first magnitude down to just under 2 seconds for sixth magnitude.<ref name="Graney/Grayson"> </ref> By the time of William Herschel astronomers recognized that the telescopic disks of stars were spurious and a function of the telescope as well as the brightness of the stars, but still spoke in terms of a star's size more than its brightness. Even well into