lobster Any of numerous species of marine shrimplike decapods that are bottom-dwellers and mostly noctur¬ nal. Lobsters scavenge for dead ani¬ mals but also eat live fish, small mollusks and other bottom-dwelling invertebrates, and seaweed. One or more pairs of legs are often modified into pincers, usually larger on one side than the other. True lobsters have a distinct snout on the upper body shell. The American lobster (Homarus americanus) and SCAMPI are the most commercially impor¬ tant, being highly prized as food. The American lobster, found from Labra¬ dor to North Carolina, weighs about 1 lb (0.5 kg) and is about 10 in. (25 cm) long when caught in shallow water. Most deepwater specimens weigh about 5.5 lbs (2.5 kg); some may weigh 40 lbs (20 kg). See also shellfish.
local area network (LAN) Communications network consisting of many computers within a local area, such as a single building or company complex. Individual users can share data or files on a LAN as if the data or files resided on their respective computers; a central computer used for this purpose is called a server. Laser printers and other peripheral equip¬ ment can be connected to a LAN for common use. Coaxial and fibre-optic cables are popular communication lines for LANs because they provide fast data transmission and are easy to install. See also computer network.
Local Group Concentration of about 40 galaxies to which the Milky Way Galaxy belongs. Nearly half are dwarf elliptical galaxies, but the six larg¬ est are spiral or irregular galaxies. They are probably kept from separat¬ ing by mutual gravitational attraction. The Milky Way system is near one end of the group; the great Andromeda Galaxy is near the other end, about two million light-years away.
Locarno, Pact of (1925) Multilateral treaty signed in Locarno, Switz., intended to guarantee peace in western Europe. Its signatories were Bel¬ gium, Britain, France, Germany, and Italy. Germany’s borders with France and Belgium as set by the Treaty of Versailles were decreed inviolable, but its eastern borders were not. Britain promised to defend Belgium and France. Other provi¬ sions included mutual defense pacts between France and Poland and between France and Czechoslovakia.
The treaty led to the Allied troops’ departure from the Rhineland by 1930, five years ahead of schedule.
See also Kellogg-Briand Pact.
Loch Leven See Loch Leven Loch Lomond See Loch Lomond Loch Ness See Loch Ness
Lochner \'16k-nor\, Stefan (b. c.
1400, Meersburg am Bodensee,
Bishopric of Constance—d. 1451,
Cologne) German painter. Nothing is
known of his early life, but he may have studied in The Netherlands before settling in Cologne c. 1430, for Flemish influence is evident in his atten¬ tion to minute details. Jan van Eyck’s influence is seen in The Adoration of the Magi, his altarpiece for Cologne’s great cathedral, but Lochner adds his own naturalistic observation and masterly sense of colour and design. Known for his highly mystical religious paintings, he is considered the greatest representative of the school of Cologne.
lock Mechanical or electronic device for securing a door or receptacle so that it cannot be opened except by a key or a code. The lock originated in the Middle East; the oldest known example was found near Nineveh. Possibly 4,000 years old, it is of the pin tumbler type, otherwise known as an Egyptian lock. The Romans were the first to use metal locks and to make small keys for them. They also invented wards, projections in the keyhole that prevent a key from turning unless it has slots that avoid the projections. Probably the most familiar lock today is the cylinder lock, a pin tumbler lock opened by a flat key with a serrated edge; the serrations raise pins in the cylinder to the proper heights, allowing the cylinder to turn. Also common are the unit lock, housed within a rectangular notch cut into the edge of a door, and the mortise lock, housed in a mortise cut into the door edge, the lock mechanism being covered on both sides. Other types include lever and combination locks. Electronic locks that open with a magnetic card key are popular for banks, hotel rooms, and offices.
A cylinder lock's tumbler consists of a series of pins arranged in pairs. The pins are spring-loaded to press against the contours of the inserted key. A wrong key will cause one or more of the pins to block the cylinder from turning; only when the tops of all the lower pins line up with the edge of the cylinder can the cylinder turn.
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Locke, John (b. Aug. 29, 1632, Wrington, Somerset, Eng.—d. Oct. 28, 1704, Oates, Essex) English philosopher. Educated at Oxford, principally in medicine and science, he later became physician and adviser to the future 3rd earl of Shaftesbury (1667-72). He moved to France, but after Shaftesbury’s fall in 1683 he fled to the Netherlands, where he supported the future William III. Locke returned to England after the Glorious Revo¬ lution (1688) to become commissioner of appeals, a post he held until his death. In his major philosophical work, Essay Concerning Human Under¬ standing (1690), he argued that knowledge begins in sensation or intro¬ spection rather than in innate ideas, as the philosophers of rationalism held. From sensation and reflection the mind receives “ideas,” which are the material of knowledge. Some ideas represent actual qualities of objects (such as size, shape, or weight) and others perceived qualities, which do not exist in objects except as they affect observers (such as colour, taste, or smell); Locke called the former qualities “primary” and the latter “sec¬ ondary.” Ideas that are given directly in sensation or reflection are simple, and simple ideas may be “compounded” to form complex ideas. Locke did not succeed in giving a clear account of the origin of the idea of sub¬ stance (it is “a something-I-know-not-what”) or the idea of the “self,” though his account of personal identity in terms of memory was influen¬ tial. In the philosophy of language, he identified the meanings of words
"Madonna of the Rose Bower," paint¬ ing on wood by Stefan Lochner; in the Wallraf-Richartz-Museum, Cologne.
COURTESY OF THE WALLRAF-RICHARTZ-MUSEUM, COLOGNE
© 2006 Encyclopaedia Britannica, Inc.
Lockheed Martin Corp. ► Lodge I 1129
with ideas rather than things. In Two Treatises of Government (1690), he defended a doctrine of natural rights and a conception of political author¬ ity as limited and conditional on the ruler’s fulfillment of his obligation to serve the public good. A classic formulation of the principles of politi¬ cal liberalism, this work influenced the American and French revolutions and the Constitution of the U.S. He is considered the founding figure of British empiricism.
Lockheed Martin Corp. U.S. diversified company that is one of the world’s largest aerospace manufacturers. It was established in 1995 through the merger of Lockheed Corp. (formed 1926 as Lockheed Air¬ craft Co.) and Martin Marietta Corp. (formed 1961 from the merger of Martin Co. and American-Marietta Co.). During World War II, Lockheed established a secret division (“Skunk Works”) that became the leading U.S. developer of military aircraft (e.g., F-104 fighter, U-2 and SR-71 spy planes, and F-117A stealth fighter). In the early 1970s its financially troubled production of the L-1011 TriStar commercial jetliner necessitated its rescue from bankruptcy by massive U.S. government aid. Lockheed’s work in missile development resulted in the Polaris, Poseidon, and Trident submarine-launched ballistic missile systems; in the space sector its activities included the construction and systems integration of the Hubble Space Telescope. In the early 1990s, in partnership with Boeing Co., it con¬ tracted to build the F-22 Raptor stealth fighter (first flown 1997). Martin Co.’s major business after World War II was the development of rockets (e.g., Titan) and electronics systems for the U.S. government. Later, as Martin Marietta, it constructed the Viking Mars landers and the Magellan spacecraft to Venus and designed and produced the external fuel tank for the space shuttle. In the mid-1990s Lockheed Martin formed a joint ven¬ ture, International Launch Services, with the Russian firms Energia and Khrunichev to market commercial space launch services.