Take the tour ×  This may seem like a slightly trite question,
but it is one that has long intrigued me.  Since I formally
learned classical (Newtonian) mechanics, it has often struck me
that angular momentum (and generally rotational dynamics) can be
fully derived from normal (linear) momentum and dynamics. Simply
by considering circular motion of a point mass and introducing
new quantities, it seems one can describe and explain angular
momentum fully without any new postulates. In this sense, I am
lead to believe only ordinary momentum and dynamics are
fundamental to mechanics, with rotational stuff effectively
being a corollary.  Then at a later point I learned quantum
mechanics. Alright, so orbital angular momentum does not really
disturb my picture of the origin/fundamentality, but when we
consider the concept of spin, this introduces a problem in this
proposed (philosophical) understanding. Spin is apparently
intrinsic angular momentum; that is, it applies to a point
particle. Something can possess angu