# Classical physics

As classical physics, refers to those physical theories that were elaborated by the end of the 19th century. In the first half of the 20th century, these theories have been supplemented by the conceptual fundamentally new theories of quantum physics and the theory of relativity, which constitute the foundation of modern physics. The theories of classical physics have thus not lost their importance, but they are included as an approximation to the modern theories. In particular, the structure of matter but can only be explained by quantum theory.

For classical physics one expects classical mechanics, electrodynamics, thermodynamics and optics. Since, as Albert Einstein has recognized the special theory of relativity is structurally rooted in electrodynamics, one expects these as part of the electrodynamics sometimes even classical physics.

The following assumptions of classical physics are not universal:

- In classical physics it was assumed that the time was an absolutely measurable parameters. In fact, it depends on the reference frame in which it is measured.
- Furthermore, It was assumed that all physics games in a three dimensional Cartesian space from. In fact, the room is, however, curved, and interwoven with the time.
- It was assumed that light is completely describable as an electromagnetic wave by the Maxwell equations. In fact, light energy occurs only quantized.
- It was believed that the position and momentum of a physical object are both measured simultaneously at any given time basically with arbitrarily high accuracy. In fact, the maximum achievable measurement accuracy is limited. See Heisenberg uncertainty principle.
- Classical physics is deterministic. It was believed that one can predict the behavior of a physical system precisely at sufficiently accurate knowledge of all the parameters and laws of nature. According to the laws of quantum physics, but can only make statements about probabilities (see Copenhagen interpretation )

In the training only classical physics is still largely taught and introduced based on this the broader theories. In practice, studied in physical questions whether a classical treatment is possible or whether due to the required accuracy, or the relevant orders of magnitude quantum and relativistic effects must be considered.

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