Huallaga \wa-'ya-ga\ River River, western and northern Peru. It rises in the Andes Mountains and descends north, carving a valley between the Cordillera Central and the Cordillera Azul and joining the Maranon River in the Amazon River basin. The Huallaga is estimated to be 700 mi (1,100 km) long and is mostly unnavigable.
Huang Chao Vhwaq-'chaiA or Huang Ch'ao (d. 884, China) Chi¬ nese rebel leader whose revolt against the Tang dynasty, though ultimately defeated, so weakened the dynasty that it collapsed shortly thereafter. A salt smuggler turned rebel, Huang captured Guangzhou (Canton) in 879 and the Tang capital of Chang'an in 881. There he proclaimed himself emperor but was driven out by an alliance of government troops and Turkish nomads. One of his generals overthrew the Tang (907) and founded the first of the short-lived Five Dynasties.
Huang Hai See Yellow Sea
Huang He or Huang Ho English Yellow River River, northern, central, and eastern China. The second longest river in China and one of the world’s longest, it flows 3,395 mi (5,464 km) from the Plateau of Tibet generally east to the Yellow Sea (Huang Hai). In its lower reaches it has often overflowed its banks, flooding vast areas of rich farmland. Its out¬ let has shifted over the years to enter the Yellow Sea at points as far apart as 500 mi (800 km). Irrigation and flood-control works have been main¬ tained for centuries, and dams, begun in the mid-1950s, exploit the riv¬ er’s hydroelectric potential.
Huang-Lao Vhwaq-'lauX Political ideology based on the tenets attrib¬ uted to the Yellow Emperor Huangdi and on the Daoist teachings of Laozi. This method of governance, which stressed the principles of reconcilia¬ tion and noninterference, became the dominant ideology of the imperial court in the early Western Han (206 bc-ad 25). The Huang-Lao masters believed that Laozi’s Daodejing perfectly described the art of rulership, and they venerated the legendary Yellow Emperor as the founder of a golden age. Their teachings constitute the earliest Daoist movement for which there is clear historical evidence. See also Daoism.
Huangdi or Huang-ti Vhwaq-'de\ Chinese Yellow Emperor Third of ancient China’s mythological emperors and a patron saint of Daoism. According to legend, he was bom in 2704 bc and became emperor in 2697. He is remembered as a paragon of wisdom who established a golden age, seeking to create an ideal kingdom in which his people would live in keeping with natural law. Tradition holds that his reign saw the introduc¬ tion of wooden houses, carts, boats, the bow and arrow, writing, and gov¬ ernmental institutions. His wife was reputed to have taught women how to breed silkworms and weave silk.
Hubble, Edwin P(owell) (b. Nov. 20, 1889, Marshfield, Mo., U.S.—d. Sept. 28, 1953, San Marino, Calif.) U.S. astronomer. He earned a degree in mathematics and astronomy at the University of Chicago, then made a brief foray into law before returning to astronomy. After earning his Ph.D., he began working at Mount Wilson Observatory. In 1922-24 he discovered that certain nebulae contained Cepheid variable stars; he determined that these were several hundred thousand light-years away (outside the Milky Way Galaxy) and that the nebulae they were in were actually other galaxies. In studying those galaxies, he made his second remarkable discovery (1927): that the galaxies were receding from the Milky Way at rates that increased with distance. This implied that the uni¬ verse, long considered unchanging, was expanding (see expanding uni¬ verse); even more remarkable, the ratio of the galaxies’ speed to their distance was a constant (see Hubble's constant). Hubble’s original calcu¬ lation of the constant was incorrect; it made the Milky Way larger than
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904 I Hubble Space Telescope ► Hudson's Bay Co.
all other galaxies and the entire universe younger than the surmised age of Earth. Later astronomers determined that galaxies were systematically more distant, resolving the discrepancy.
Hubble Space Telescope (HST) Most sophisticated optical obser¬ vatory ever placed into orbit around Earth. Because it is above Earth’s obscuring atmosphere, it can obtain images much brighter, clearer, and more detailed than ground-based telescopes can. Named for Edwin Hub¬ ble, it was built under NASA supervision and deployed on a 1990 space- shuttle mission. The reflector telescope’s mirror optics gather light from celestial objects and direct it to an array of cameras and spectrographs (see spectroscopy). A defect in the primary mirror initially caused it to pro¬ duce fuzzy images; in 1993 another shuttle mission corrected this and other problems. Subsequent missions to the HST have been for mainte¬ nance, repairs, and instrument upgrades.
Hubble's constant Constant used to relate the velocities of remote galaxies to their distances from Earth. Denoted H and named in honour of Edwin Hubble, it expresses the rate of expansion of the universe. Its actual value has been debated for decades; improved measurements have naiTOwed the range in which it falls to about 10.5-14 mi/second (17-23 km/second) per million light-years. The reciprocal of H gives the time, in seconds, since the galaxies began to separate from each other—i.e., the approximate age of the universe. Hubble used the redshifts of distant gal¬ axies measured by Vesto Slipher (1875-1969) and his own distance esti¬ mates of those galaxies to establish the cosmological velocity-distance law (Hubble law): velocity = H x distance, according to which the greater a galaxy’s distance, the faster it is receding. Derived from theoretical considerations and confirmed by observations, the Hubble law has made secure the concept of an expanding universe.
Hubei \'hu-'ba\ or Hu-pei conventional Hupeh Province (pop., 2002 est.: 59,880,000), east-central China. It lies north of the Yangtze River (Chang Jiang) and is bordered by Shaanxi, Henan, Anhui, Jiangxi, and Hunan provinces and Chongqing municipality. It has an area of 72,400 sq mi (187,500 sq km), and its capital is Wuhan. Part of the kingdom of Chu (3rd century bc), it became part of the Qin dynasty after being sub¬ jugated by Shihuangdi. Until the reign of Kangxi, Hubei and Hunan formed one province; they were divided in the mid-17th century. The area was the scene of battles after the 1850 Taiping Rebellion. The revolution of 1911/12 (see Nationalist Party) began in Hubei. The province was heavily bombed during the Sino-Japanese War of 1937—45. Restoration began after the communist Chinese takeover. In addition to agricultural produc¬ tion, Hubei has important heavy industrial production.
Hubei \'hyu-bol\ / David (Hunter) (b. Feb. 27, 1926, Windsor, Ont., Can.) Canadian-born U.S. neurobiologist. He studied medicine at McGill University and in 1959 joined the faculty of Harvard Medical School. In 1981 he shared a Nobel Prize with Torsten Wiesel and Roger Sperry for investigations of visual perception, one of their achievements being analy¬ sis of the flow of nerve impulses from the retina to the brain’s sensory and motor centres.
Hubertusburg Miu-'ber-tos-.burkV Peace of (1763) Treaty between Prussia and Austria ending the Seven Years' War in Germany. Signed five days after the Treaty of Paris, it guaranteed that Frederick II the Great main¬ tained his possession of Silesia and confirmed Prussia’s stature as a major European power.
huckleberry Small, fruit-bearing, branching shrub of the genus Gay- lussacia, in the heath family, resembling in habit the English bilberry, to which it is closely related. It bears fleshy fruit with 10 nutlike seeds, dif¬ fering in this respect from the blueberry. The common huckleberry of the northern U.S. is G. baccata , also called black, or highbush, huckleberry. The florists’, or evergreen, huckleberry is actually a blueberry. The red huckleberry of the southern U.S. is commonly called the southern cran¬ berry.