  Classical physics is approached from quantum mechanics in the macroscopic
limit. The technical device to achieve this goal is the quantum version of the
central limit theorem, derived for an observable at a given time and for the
time-dependent expectation value of the coordinate. The emergence of the
classical trajectory can be followed for the average of an observable over a
large set of independent microscopical systems, and the deterministic classical
laws can be recovered in all practical purposes, owing to the largeness of
Avogadro's number. This result refers to the observed system without
considering the measuring apparatus. The emergence of a classical trajectory is
followed qualitatively in Wilson's cloud chamber.
