Classical physics
Classical physics is a group of physics theories that predate modern, more complete, or more widely applicable theories. If a currently accepted theory is considered to be modern, and its introduction represented a major paradigm shift, then the previous theories, or new theories based on the older paradigm, will often be referred to as belonging to the area of "classical physics".
As such, the definition of a classical theory depends on context. Classical physical concepts are often used when modern theories are unnecessarily complex for a particular situation. Most often, classical physics refers to pre-1900 physics, while modern physics refers to post-1900 physics, which incorporates elements of quantum mechanics and relativity.[1]
Overview
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Classical theory has at least two distinct meanings in physics. In the context of
Depending on point of view, among the branches of theory sometimes included in classical physics are variably:
- Classical mechanics
- Newton's laws of motion
- Classical Lagrangian and Hamiltonian formalisms
- Maxwell's Equations)
- Classical thermodynamics
- Classical nonlinear dynamics
Comparison with modern physics
In contrast to classical physics, "
A physical system can be described by classical physics when it satisfies conditions such that the laws of classical physics are approximately valid.
In practice, physical objects ranging from those larger than
From the point of view of classical physics as being non-relativistic physics, the predictions of general and special relativity are significantly different from those of classical theories, particularly concerning the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light. Traditionally, light was reconciled with classical mechanics by assuming the existence of a stationary medium through which light propagated, the luminiferous aether, which was later shown not to exist.
Mathematically, classical physics equations are those in which
Computer modeling and manual calculation, modern and classic comparison
Today, a computer performs millions of arithmetic operations in seconds to solve a classical differential equation, while Newton (one of the fathers of the differential calculus) would take hours to solve the same equation by manual calculation, even if he were the discoverer of that particular equation.
Computer modeling is essential for quantum and relativistic physics. Classical physics is considered the limit of quantum mechanics for a large number of particles. On the other hand,
Computer modeling would use only the energy criteria to determine which theory to use: relativity or quantum theory, when attempting to describe the behavior of an object. A physicist would use a classical model to provide an approximation before more exacting models are applied and those calculations proceed.
In a computer model, there is no need to use the speed of the object if classical physics is excluded. Low-energy objects would be handled by quantum theory and high-energy objects by relativity theory.[5][6][7]
See also
- Glossary of classical physics
- Semiclassical physics
References
- ^ Weidner and Sells, Elementary Modern Physics Preface p.iii, 1968
- ISBN 9780521876223.
- ISBN 9780486640389.
- ISBN 9780760759219.
- arXiv:quant-ph/0105127
- ^ Wojciech H. Zurek, Decoherence and the transition from quantum to classical, Physics Today, 44, pp 36–44 (1991)
- ^ Wojciech H. Zurek: Decoherence and the Transition from Quantum to Classical—Revisited Los Alamos Science Number 27 2002