model and modeling, in painting, the use of light and shade to simulate volume in the representation of solids. In sculpture the terms denote a technique involving the use of a pliable material such as clay or wax. As opposed to carving, modeling permits addition as well as subtraction of material and lends itself to freer handling and change of intention. The technique is exemplified also by those works in cast metal and plaster that are made from the mold of a clay original. The mold is made by the process of cire perdue. The noun model is used to describe such an original and also any three-dimensional scale model for a larger or more elaborate project in architecture, landscaping, or industry. It also denotes a person or object used as an aid to representation in painting.

Standard Model, in physics: see elementary particles.

Model Parliament: see Parliament.

Concept of an expanding universe whose average density remains constant, matter being continuously created throughout it to form new stars and galaxies at the same rate that old ones recede from sight. A steady-state universe has no beginning or end, and its average density and arrangement of galaxies are the same as seen from every point. Galaxies of all ages are intermingled. The theory was first put forward by William Macmillan (1861–1948) in the 1920s and modified by Fred Hoyle to deal with problems that had arisen in connection with the big-bang model. Much evidence obtained since the 1950s contradicts the steady-state theory and supports the big-bang model.

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In physics, the combination of two theories of particle physics into a single framework to describe all interactions of subatomic particles except those due to gravity (see gravitation). The two theories, the electroweak theory and the theory of quantum chromodynamics, describe the interactions between particles in terms of the exchange of intermediary particles. The model has proved highly accurate in predicting certain interactions, but it does not explain all aspects of subatomic particles. For example, it cannot say how many particles there should be or what their masses are. The search goes on for a more complete theory, and in particular a unified field theory describing the strong, weak, and electromagnetic forces.

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Model of the origin of the universe, which holds that it emerged from a state of extremely high temperature and density in an explosive expansion 10 billion–15 billion years ago. Its two basic assumptions—that Albert Einstein's general theory of relativity correctly describes the gravitational interaction of all matter and that an observer's view of the universe does not depend on direction of observation or on location—make it possible to calculate physical conditions in the universe back to a very early time called the Planck time (after Max Planck). According to the model proposed by George Gamow in the 1940s, the universe expanded rapidly from a highly compressed early state, with a steady decrease in density and temperature. Within seconds, matter predominated over antimatter and certain nuclei formed. It took another million years before atoms could form and electromagnetic radiation could travel through space unimpeded. The abundances of hydrogen, helium, and lithium and the discovery of cosmic background radiation support the model, which also explains the redshifts of the light from distant galaxies as resulting from the expansion of space.

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Automobile built by the Ford Motor Co. from 1908 until 1927, the first widely affordable mass-produced car. Assembly-line production methods introduced by Henry Ford in 1913 enabled the price of this five-seat touring car to drop from $850 in 1908 to $300 in 1925. Over 15 million Model T's were built. The car was offered in several body styles, all mounted on a standard chassis. Various colors were initially available, but after 1913 its sole color was black. It was replaced by the popular Model A in 1928.

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