Rotation can be described as a vector, pointing along the axis of rotation. You could imagine writing down the vectors for all of the objects in a planetary sys

Rotation can be described as a vector, pointing along the axis of rotation. You could imagine writing down the vectors for all of the objects in a planetary system, and doing some kind of statistics on the numbers to see if there was a preference for a particular axis. You could use a sign convention such as the right hand rule. The rotation vector is associated with another, which is angular momentum. The reason why there's all kinds of spinny stuff in a solar system, or a galaxy, is that the massive objects jointly conserve the total angular momentum of the blob of dust that the system coalesced from. Neutrinos are another beast, they have a preference for one direction of their spin quantum number: https://neutrinos.fnal.gov/mysteries/handedness/ https://neutrinos.fnal.gov/mysteries/handedness/ In fact you could use the spin of neutrinos to say that the sign convention for rotation is not arbitrary.