Classical mechanics

In physics, classical mechanics is one of the two major sub-fields of study in the science of mechanics, which is concerned with the motions of bodies, and the forces that cause them. The other sub-field is quantum mechanics. Roughly speaking, classical mechanics was developed in the 400 years since the groundbreaking works of Brahe, Kepler, and Galileo, while quantum mechanics developed within the last 100 years, starting with similarly decisive discoveries by Planck, Einstein, and Bohr.

History

The Greeks, and Aristotle in particular, were the first to propose that there are abstract principles governing nature.

Related Topics:
Greeks - Aristotle

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One of the first scientists who suggested abstract laws was Galileo Galilei who may have performed the famous experiment of dropping two cannon balls from the tower of Pisa. (The theory and the practice showed that they both hit the ground at the same time.) Though the reality of this experiment is disputed, he did carry out quantitative experiments by rolling balls on an inclined plane; his correct theory of accelerated motion was apparently derived from the results of the experiments.

Related Topics:
Galileo Galilei - Tower of Pisa - Inclined plane

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Sir Isaac Newton was the first to propose the three laws of motion (the law of inertia, his second law mentioned above, and the law of action and reaction), and to prove that these laws govern both everyday objects and celestial objects.

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Newton and most of his contemporaries, with the notable exception of Christiaan Huygens hoped that classical mechanics would be able to explain all entities, including (in the form of geometric optics) light. When he discovered Newton's rings, Newton's own explanation avoided wave principles and resembled more the explanation for the decay of the neutral Kaons, K0 and K0 bar. That is, he supposed that the light particles were altered or excited by the glass and resonated.

Related Topics:
Christiaan Huygens - Newton's rings - Kaon

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Newton also developed the calculus which is necessary to perform the mathematical calculations involved in classical mechanics. However it was Gottfried Leibniz who developed the notation of the derivative and integral which are used to this day.

Related Topics:
Calculus - Gottfried Leibniz - Derivative - Integral

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After Newton the field became more mathematical and more abstract.

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Although classical mechanics is largely compatible with other "classical physics" theories such as classical electrodynamics and thermodynamics, some difficulties were discovered in the late 19th century that could only be resolved by more modern physics. When combined with classical thermodynamics, classical mechanics leads to the Gibbs paradox in which entropy is not a well-defined quantity. As experiments reached the atomic level, classical mechanics failed to explain, even approximately, such basic things as the energy levels and sizes of atoms. The effort at resolving these problems led to the development of quantum mechanics. Similarly, the different behaviour of classical electromagnetism and classical mechanics under velocity transformations led to the theory of relativity.

Related Topics:
Classical physics - Electrodynamics - Thermodynamics - Gibbs paradox - Entropy - Quantum mechanics - Electromagnetism - Theory of relativity

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By the end of the 20th century, the place of classical mechanics in physics is no longer that of an independent theory. Along with classical electromagnetism, it has become imbedded in relativistic quantum mechanics or quantum field theory. It is the non-relativistic, non-quantum mechanical limit for massive particles.

Related Topics:
Physics - Electromagnetism - Relativistic - Quantum mechanics - Quantum field theory

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