Cosimo I orig. Cosimo de' Medici (b. June 12, 1519—d. April 21, 1574, Castello, near Florence) Second duke of Florence (1537-74) and first grand duke of Tuscany (1569-74). The son of Giovanni de’ Medici, Cosimo became head of the Florentine republic in 1537 after the assas¬ sination of his distant cousin Alessandro de’ Medici. He continued Alessan¬ dro’s tyrannical rule and defeated attempts to oust him with aid from Emperor Charles V. Seeking to expand his power, he attacked Siena in 1554 and brought nearly all of Tuscany under his control. He used his despotic power to improve the government’s efficiency and to sponsor artistic projects. Far advanced for the time as an administrator, he united all public services into one building, the Uffizi (“Offices”), designed by Giorgio Vasari. He promoted the talents of such artists as II Bronzino and Bartolommeo Ammannati, sponsored archaeological excavations of Etrus¬ can sites, and established the Florentine Academy for linguistic studies. In 1569 he was given the title of grand duke of Tuscany.
Cosimo, Piero di See Piero di Cosimo Cosimo the Elder See Cosimo de’ Medici cosine See trigonometric function
Cosmati \'kaz-,ma-te\ work Type of decorative inlay or mosaic used by Roman decorators and architects in the 12th—13th centuries. Small pieces of coloured stone and glass were combined with strips and disks of white marble arranged in geometric patterns. Cosmati work was used for architectural decoration and church furnishings. The term derives from craftsmen of several families named Cosmatus.
cosmetics Any of several preparations (excluding soap) applied to the human body for beautifying, preserving, or altering the appearance or for cleansing, colouring, conditioning, or protecting the skin, hair, nails, lips, eyes, or teeth. The earliest known cosmetics were in use in Egypt in the 4th millennium bc. Cosmetics were in wide use in the Roman Empire, but they disappeared from much of Europe with the fall of the Roman Empire (5th century ad) and did not reappear until the Middle Ages, when Cru¬ saders returned from the Middle East with cosmetics and perfumes. By the 18th century they had come into use by nearly all social classes. Modem cosmetics include skin-care preparations; foundation, face powder and rouge (blusher); eye makeup; lipstick; shampoo; hair curling and straight¬ ening preparations; hair colours, dyes, and bleaches; and nail polish. Related products include antiperspirants, mouthwashes, depilatories, astringents, and bath crystals.
cosmic background radiation Electromagnetic radiation, mostly in the microwave range, believed to be the highly redshifted residual effect (see redshift) of the explosion billions of years ago from which, accord¬ ing to the big-bang model, the universe was created. It was discovered by accident in 1964 by Robert W. Wilson and Arno Penzias; its presence sup¬ ports the predictions of big-bang cosmology.
cosmic ray High-speed particle (atomic nucleus or electron) that trav¬ els through the Milky Way Galaxy. Some cosmic rays originate from the Sun, but most come from outside the solar system. Primary cosmic rays that reach Earth’s atmosphere collide with nuclei in it, creating secondar¬ ies. Because lower-energy primaries are strongly influenced by the inter¬ planetary magnetic field and Earth’s magnetic field (see geomagnetic field), most of those detected near Earth have very high energy, corresponding to speeds about 87% that of light or more. Observations from spacecraft indicate that most cosmic rays come from the Galaxy’s disk, but the highest-energy ones are probably extragalactic. Details of their produc¬ tion and acceleration remain unclear, but apparently expanding shock waves from supernovas can accelerate particles. From the early 1930s to the 1950s, cosmic rays were the only source of high-energy particles used in studying the atomic nucleus and its components. Short-lived subatomic particles were discovered through cosmic-ray collisions, leading to the rise of particle physics. Even powerful particle accelerators cannot impart energy anywhere near that of the highest-energy cosmic rays. See also Victor Francis Hess.
cosmogony See creation myth
cosmological argument Form of argument used in natural theology to prove the existence of God. Thomas Aquinas, in his Summa theologiae, presented two versions of the cosmological argument: the first-cause argu¬
ment and the argument from contingency. The first-cause argument begins with the fact that there is change in the world, and a change is always the effect of some cause or causes. Each cause is itself the effect of a further cause or set of causes; this chain moves in a series that either never ends or is completed by a first cause, which must be of a radically different nature in that it is not itself caused. Such a first cause is an important aspect, though not the entirety, of what Christianity means by God. The argument from contingency follows by another route a similar basic movement of thought from the nature of the world to its ultimate ground.
cosmological constant Term reluctantly added by Albert Einstein to his equations of general relativity in order to obtain a solution to the equa¬ tions that described a static universe, as he believed it to be at the time. The constant has the effect of a repulsive force that acts against the gravi¬ tational attraction of matter in the universe. When Einstein heard of the evidence that the universe is expanding, he called the introduction of the cosmological constant the “biggest blunder” of his life. Recent develop¬ ments suggest that in the early universe there may well have been a cos¬ mological constant with a nonzero value.
cosmology Field of study that brings together the natural sciences, especially astronomy and physics, in an effort to understand the physical universe as a unified whole. The first great age of scientific cosmology began in Greece in the 6th century bc, when the Pythagoreans introduced the concept of a spherical Earth and, unlike the Babylonians and Egyp¬ tians, hypothesized that the heavenly bodies moved according to the har¬ monious relations of natural laws. Their thought culminated in the Ptolemaic model (see Ptolemy) of the universe (2nd century ad). The Copernican revolution (see Copernican system) of the 16th century ush¬ ered in the second great age. The third began in the early 20th century, with the formulation of special relativity and its development into general relativity by Albert Einstein. The basic assumptions of modern cosmology are that the universe is homogeneous in space (on the average, all places are alike at any time) and that the laws of physics are the same every¬ where.
cosmonaut See astronaut
cosmos Vkaz-m3s\ Any of the garden plants that make up the genus Cosmos (composite family), containing about 20 species native to the tropi¬ cal New World. Heads of flowers are borne along long flower stalks or together in an open cluster. The disk flowers are red or yellow; the ray flowers, sometimes notched, may be white, pink, red, purple, or other col¬ ors. Most annual ornamental varieties have been developed from the com¬ mon garden cosmos (C. bipinnatus).
Cossacks Peoples dwelling in the northern hinterlands of the Black and Caspian seas. The term (from the Turkic kazak, “free person”) originally referred to semi-independent Tatar groups, which formed in the Dnieper River region. Later it was also applied to peasants who had fled from serfdom in Poland, Lithuania, and Muscovy to the Dnieper and Don regions. The Cossacks had a tradition of independence and received privi¬ leges from the Russian government in return for military services. They were used as defenders of the Russian frontier and advance guards for imperial territorial expansion. Attempts in the 17th—18th century to reduce their privileges caused revolts, led by Stenka Razin and Yemelyan Pugachov, and the Cossacks gradually lost their autonomous status.
cost Monetary value of goods and services that producers and consum¬ ers purchase. In a basic economic sense, cost is the measure of the alter¬ native opportunities forgone in the choice of one good or activity over others (see opportunity cost). For consumers, cost describes the price paid for goods and services. For producers, cost has to do with the relation¬ ship between the value of production inputs and the level of output. Total cost refers to all the expenses incurred in reaching a particular level of output; if total cost is divided by the quantity produced, average or unit cost is obtained. A portion of the total cost known as fixed cost (e.g., the costs of building rental or of heavy machinery) does not vary with the quantity produced and, in the short run, cannot be altered by increasing or decreasing production. Variable costs, like the costs of labour or raw materials, change with the level of output. Economic decisions are based on marginal cost, the additional cost of an incremental unit of production or consumption.