![]() that physical laws be invariant under Lorentz transformations. : 19 It was proposed that all physical laws must be the same for observers at different velocities, i.e. New rules, called Lorentz transformations, were given for the way time and space coordinates of an event change under changes in the observer's velocity, and the distinction between time and space was blurred. In the same year as his paper on the photoelectric effect, Einstein published his theory of special relativity, built on Maxwell's electromagnetism. Uniting these scattered ideas, a coherent discipline, quantum mechanics, was formulated between 19, with important contributions from Max Planck, Louis de Broglie, Werner Heisenberg, Max Born, Erwin Schrödinger, Paul Dirac, and Wolfgang Pauli. In 1924, Louis de Broglie proposed the hypothesis of wave–particle duality, that microscopic particles exhibit both wave-like and particle-like properties under different circumstances. The Bohr model successfully explained the discrete nature of atomic spectral lines. In 1913, Niels Bohr introduced the Bohr model of atomic structure, wherein electrons within atoms can only take on a series of discrete, rather than continuous, energies. This implied that the electromagnetic radiation, while being waves in the classical electromagnetic field, also exists in the form of particles. ![]() : Ch.2 Building on this idea, Albert Einstein proposed in 1905 an explanation for the photoelectric effect, that light is composed of individual packets of energy called photons (the quanta of light). This process of restricting energies to discrete values is called quantization. These are known as quantum harmonic oscillators. He treated atoms, which absorb and emit electromagnetic radiation, as tiny oscillators with the crucial property that their energies can only take on a series of discrete, rather than continuous, values. Max Planck's study of blackbody radiation marked the beginning of quantum mechanics. : 19ĭespite the enormous success of classical electromagnetism, it was unable to account for the discrete lines in atomic spectra, nor for the distribution of blackbody radiation in different wavelengths. ![]() Action-at-a-distance was thus conclusively refuted. Maxwell's equations implied the existence of electromagnetic waves, a phenomenon whereby electric and magnetic fields propagate from one spatial point to another at a finite speed, which turns out to be the speed of light. The theory of classical electromagnetism was completed in 1864 with Maxwell's equations, which described the relationship between the electric field, the magnetic field, electric current, and electric charge. This description of fields remains to this day. He argued against "action at a distance", and proposed that interactions between objects occur via space-filling "lines of force". He introduced fields as properties of space (even when it is devoid of matter) having physical effects. Michael Faraday coined the English term "field" in 1845. : 18įields began to take on an existence of their own with the development of electromagnetism in the 19th century. However, this was considered merely a mathematical trick. In an exchange of letters with Richard Bentley, however, Newton stated that "it is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter without mutual contact." : 4 It was not until the 18th century that mathematical physicists discovered a convenient description of gravity based on fields-a numerical quantity (a vector in the case of gravitational field) assigned to every point in space indicating the action of gravity on any particle at that point. The force of gravity as described by Newton is an " action at a distance"-its effects on faraway objects are instantaneous, no matter the distance. The earliest successful classical field theory is one that emerged from Newton's law of universal gravitation, despite the complete absence of the concept of fields from his 1687 treatise Philosophiæ Naturalis Principia Mathematica. : xi A brief overview of these theoretical precursors follows. Quantum field theory results from the combination of classical field theory, quantum mechanics, and special relativity. When a piece of paper is sprinkled with iron filings and placed above a bar magnet, the filings align according to the direction of the magnetic field, forming arcs. Magnetic field lines visualized using iron filings.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |