Classical physics refers to scientific theories developed predominantly before 1900, encompassing non-quantum and sometimes non-relativistic physics. It includes foundational areas such as classical mechanics (governed by Newton's laws), classical electrodynamics (described by Maxwell's equations), and classical thermodynamics. Unlike "modern physics," which introduced quantum mechanics and relativity after 1900, classical physics is generally characterized by complete determinism and describes systems where quantum effects are negligible.

These classical laws accurately explain the behavior of macroscopic and astronomical objects, but they fundamentally break down at the atomic and subatomic levels, where quantum physics becomes necessary. Interestingly, classical dynamics can emerge as an approximation from quantum physics for larger systems, illustrating the correspondence principle and explaining its continued relevance for everyday phenomena.