Atmosphere, Ionospheric variations

The ionosphere is variable in space and time. Some of the changes are chemical in origin and can be readily understood on the basis of the general considerations outlined above. There is a systematic variation, for example, as a function of time of day. In the early morning the Sun is relatively low in the sky. Radiation must penetrate a large column of air before reaching

Anchovy Pear

(Grias cauliflora), evergreen tree of the family Lecythidaceae, native to the West Indies. The name is also applied to its edible fruit, for which the tree is cultivated. The plant grows to about 15 m (50 feet) tall and bears spear-shaped, glossy leaves about 90 cm long that are produced in palmlike tufts. The fragrant yellow flowers are about 5 cm across. The fruit, which contains one

Evans, Walker

American photographer, important primarily for documenting the effects of economic depression in the American South and photographically interpreting American folk architecture. His approach to photography was largely formed by the documentary photographs of the French photographer Eugène Atget, whose influence

Schaerbeek

Flemish  Schaarbeek  municipality, Brabant province, central Belgium. A village until 1795, it is now an industrial suburb northeast of Brussels and one of the 19 communes that make up Greater Brussels. A rail junction with switch and freight yards, it has an electric power station and manufactures clothing, chemicals, and machinery. The conspicuous domed Church of Sainte-Marie (1845–53) is built in the

Andorra

Andorra's independence is traditionally ascribed to Charlemagne, who recovered the

Wynyard

Town, northern Tasmania, Australia, at the mouth of the River Inglis on Bass Strait. Founded in 1841, it was made a municipality in 1856 and named Table Cape for a high promontory (380 feet [116 m]) to the south. It was gazetted a town in 1861, when its name was changed to honour Major General Edward Wynyard, commander in chief in 1850 of British forces in Van Diemen's Land (now Tasmania). Located on a rail line

Dayton

Following the peace treaty with the Shawnee

Farman, Maurice

A champion bicyclist, he also distinguished himself as an automobile racing driver. With his brother Henri, Maurice made the first circular flight of more than one kilometre in 1908, completing a 1.6-kilometre (one-mile) flight near Paris. The following year he built

Early, Jubal A(nderson)

Confederate general in the American Civil War (1861–65) whose army at one time threatened Washington, D.C., but whose series of defeats during the Shenandoah Valley campaigns of late 1864 and early 1865 led to the final collapse of the South. A West Point graduate, Early served in the Second Seminole War in Florida (1835–42) and the Mexican War (1846–48). In the period

Niuafo'ou

Northernmost island of Tonga, in the southwestern Pacific Ocean. The generally wooded land area of 19 square miles (49 square km) includes a volcanic peak 853 feet (260 m) high, a crater lake, and numerous hot springs. During a particularly violent eruption in 1946, the island's inhabitants were evacuated to 'Eua, several hundred miles to the south. They began returning to Niuafo'ou in 1958. Because

Stuttgart

City, capital (1945) of Baden-Württemberg Land (state), southwestern Germany, astride the Neckar River, in a forested vineyard-and-orchard setting in historic Swabia. It lies between the Black Forest on the west and the Swabian Jura to the south. There were prehistoric settlements and a Roman fort in the area of Bad Cannstatt (a suburb), but Stuttgart itself originated as a Stuotgarten,

Sucking

Drawing of fluids into the mouth by creating a vacuum pressure in the oral cavity. Mammalian infants rely on this method of food ingestion until they are capable of eating more solid substances. A partial vacuum is created in the oral cavity by retracting the tongue to the back of the mouth. The rear portion of the tongue seals against the roof of the mouth, allowing

Bearing

Most bearings support rotating shafts against either transverse (radial) or thrust (axial) loads. To minimize friction, the

Christianity, Moral arguments

Moral theistic argument belongs primarily to the modern world and perhaps reflects the modern lack of confidence in metaphysical constructions. Kant, having rejected the cosmological, ontological, and design proofs, argued in the Critique of Practical Reason (1788) that the existence of God, though not directly provable, is a necessary postulate of the moral life. To