Lecture: Quantum mechanics. Classical physics

Lecture: Quantum mechanics.
Classical physics.

Classical physics consists of Newtonian Mechanics, Maxwell’s Electrodynamics and Einstein’s Theory of Relativity. The main point of classical physics is principle of determinism.

The Newtonian world picture is now the common sense of most educated people. Both materialism and mechanism are embedded in the Newtonian world picture and few ideas can have had greater philosophical influence. The great success of Newtonian mechanics in describing the motions of the planets, the tides, and the behavior of things on the surface of the Earth in the years following the publication of the Principia in 1678, gave Newton and his corpuscular philosophy immense credit. The force laws which operated between the particles in an isolated system influences specified for that system a unique evolution in time.

The physical world is determinate: things consist of separate corpuscles each of which endures through time, the variable physical quantities of dynamical variables used to describe bodies – energy, momentum, angular momentum – all take a continuous range of possible values, each possible value being definite. The machinery of the physical world operates on these particles through the laws of conservation of energy, momentum, and angular momentum.

In 1873 Maxwell created electromagnetic field theory which added the field to matter. The electromagnetic field solved the problem of action-at-a-distance. Solutions to Maxwell’s equations showed that the electromagnetic field propagated through space with a fixed speed as radiation in the form of waves. Maxwell had shown that light was nothing more than electromagnetic radiation of a particular range of wavelengths.

The tension between Newtonian mechanics and Maxwellian electromagnetism produced Einstein’s theory of relativity. Through the theories of relativity – the special theory of 1905 and the general theory of 1915 – physics revolutionized ideas of space and time. These are now thought of as aspects of a single entity called space-time. General relativity tells that space-time is not only a unity but also that it is warped.

Relativity – special and general – preserves the determinateness of reality.