180 résultats pour "sun"

• Weather.

  hours, and the snow can be much deeper in places where the wind piles it up in drifts. Extraordinarily deep snows sometimes accumulate on the upwind side ofmountain slopes during severe winter storms or on the downwind shores of large lakes during outbreaks of polar air. VI WIND Wind is the horizontal movement of air. It is named for the direction from which it comes—for example, a north wind comes from the north. In most places near theground, the wind speed averages from 8 to 24 km/h (from 5...

• Planetary Science - astronomy.

  III ORIGINS AND COMPOSITIONS OF PLANETS Astronomers believe that planetary systems are formed of elemental materials that were created in the interiors of giant stars. Some of this material comes from giantstars that shed material into space as they age. Most of the matter to form planets, however, comes from stars that explode as supernovas and spread debris enrichedwith the heavier chemical elements into space. According to the currently accepted views, the most likely first stage in the evo...

• Mercury (planet) - astronomy.

  In 1991 powerful radio telescopes on Earth revealed signs of possible deposits of ice in the polar regions of Mercury. These ice deposits occur in areas where sunlightnever falls, such as crater bottoms near both of the planet’s poles. Similar ice deposits may have been found during the 1990s near the poles of the Moon by theClementine and Lunar Prospector spacecrafts. The ice on Mercury likely comes from comets or water-bearing meteorites that have hit Mercury over the planet’s historyup throug...

• Eclipse - astronomy.

  bending of light rays passing close to the sun because of the sun’s gravitational field ( see Relativity). The great brilliance of the solar disk and the sun-induced brightening of the earth’s atmosphere make observations of the corona and nearby stars impossible except during a solar eclipse. The coronagraph, a photographictelescope, permits direct observation of the edge of the solar disk at all times. Today, scientific solar eclipse observations are extremely valuable, particularly when thepa...

• Light - astronomy.

  Each different frequency or wavelength of visible light causes our eye to see a slightly different color. The longest wavelength we can see is deep red at about 700 nm.The shortest wavelength humans can detect is deep blue or violet at about 400 nm. Most light sources do not radiate monochromatic light. What we call white light,such as light from the Sun, is a mixture of all the colors in the visible spectrum, with some represented more strongly than others. Human eyes respond best to greenlight...

• Meteorology.

  to find the corresponding relative humidity and dew-point temperature. III SPECIAL METEOROLOGICAL INSTRUMENTS Meteorologists have developed several sophisticated instruments that measure multiple physical characteristics of the air simultaneously and at more than one location.The most important of these special instruments are radiosondes, Doppler radar, and weather satellites. A Radiosonde A radiosonde measures air temperature, air pressure, and humidity from the earth’s surface up to an alt...

• Neptune (planet) - astronomy.

  The gaseous atmosphere of Neptune contains hydrogen, helium, and about 3 percent methane. It extends about 5,000 km (about 3,000 mi) above the planet’s ocean.Light reflected from Neptune’s deep atmosphere is blue, because the atmospheric methane absorbs red and orange light but scatters blue light. In 1998 astronomersalso identified molecules of methyl in Neptune’s atmosphere. Methyl molecules each contain one carbon atom and three hydrogen atoms. Methyl molecules are knownas hydrocarbon radical...

• Artificial Satellite - astronomy.

  The first stage of a multistage rocket consists of rocket engines that provide a huge amount of force, or thrust. The first stage lifts the entire launch vehicle—with itsload of fuel, the rocket body, and the satellite—off the launch pad and into the first part of the flight. After its engines use all their fuel, the first stage portion of therocket separates from the rest of the launch vehicle and falls to Earth. The second stage then ignites, providing the energy necessary to lift the satellit...

• Extrasolar Planets - astronomy.

  When a planet passes in a front of the star it orbits—an event called a transit—it causes a small dip in the brightness of the star. Measuring the slight change in thebrightness can be used not only to directly detect a planet, but to determine its size and orbit. However, the planet needs to orbit in a plane that lies in a telescope’sline of sight on the star. Despite long odds, Earth-based telescopes have detected and studied a few exoplanets using this method. The first space telescope design...

• Relativity I INTRODUCTION Albert Einstein In 1905 German-born American physicist Albert Einstein published his first paper outlining the theory of relativity.

  in calculating very large distances or very large aggregations of matter. As the quantum theory applies to the very small, so the relativity theory applies to the verylarge. Until 1887 no flaw had appeared in the rapidly developing body of classical physics. In that year, the Michelson-Morley experiment, named after the American physicistAlbert Michelson and the American chemist Edward Williams Morley, was performed. It was an attempt to determine the rate of the motion of the earth through t...

• Cosmology - astronomy.

  In 1917 American scientist Harlow Shapley measured the distance to several groups of stars known as globular clusters. He measured these distances by using amethod developed in 1912 by American astronomer Henrietta Leavitt. Leavitt’s method relates distance to variations in brightness of Cepheid variables, a class of starsthat vary periodically in brightness. Shapley’s distance measurements showed that the clusters were centered around a point far from the Sun. The arrangement of theclusters was...

• Saturn - astronomy.

  measurements of the magnetic field made by the Voyager space probes in the 1980s. Additional Cassini findings reported in March 2007 suggested that particles originating from geysers on the moon Enceladus may provide a partial explanation for thechange. The neutral gas particles become electrically charged and are captured by Saturn’s magnetic field, forming a disk of hot, ionized gas around the planet’sequator. The charged particles interact with the magnetic field and slow down the rotation of...

• Asteroid - astronomy.

  Asteroids of the S type, related to the stony iron meteorites, make up about 15 percent of the total population of asteroids that can be seen from Earth. Much rarer arethe M-type objects, corresponding in composition to the meteorites known as “irons.” These objects are made up of an iron-nickel alloy and may represent the cores ofbodies that were large enough to differentiate into layers and to melt deep inside. Their rocky outer layers may have been removed by impacts with other asteroids . A...

• Chine de 1910 à 1919 : Histoire

  Disparition d'un symbole rie l'Ancien Régime: les soldatr de l'arm ée rél'olutiomwire de compter sur le soutien des notables, sur le relais du patriotisme populaire et sur une structure étatique unifiée, Yu an Che-k'ai n'impose son bonapartisme qu 'en vertu de son emprise sur l'armée du ord, le Pei­ yang (Bei yang), et de la supériorité de celle-ci sur les armées provinciales. L ors qu 'i l meurt brusq uemen t (1916), la modernisation économi qu e et so...

• Microsoft Corporation (entreprise).

  3.5 Diversification des activités Au milieu des années 1990, Microsoft élargit son activité vers les médias, les loisirs et les industries de la communication en lançant MSN (Microsoft Network) en 1995 etMSNBC en 1996. La même année, la société introduit également Windows CE, un système d’exploitation pour assistants personnels. En 1997, elle achète WebTV Network (fabricant de composants permettant de relier la télévision à l’Internet) pour 425 millions de dollars (soit environ autant d’euros)...

• Ice Ages.

  B Future Ice Ages The record of previous glacial activity is the best indicator for future ice ages. Scientists examine the evidence for the numerous 100,000-year glacial-interglacial cycleswithin the present ice age to attempt a forecast of future ice ages. Since all previous ice ages lasted tens of millions of years, our present ice age will likely continue fora considerable amount of time. Each glaciation begins slowly and may take 80,000 years or more to reach its maximum extent. A rapid me...

• La «Sun Belt» des États-Unis

  connu la plus forte croissance en pourcentage, ce sont en fait les Etats littoraux qui ont absorbé l'essentiel du croît démographique (40% de l'accroissement total de la population américaine pour_ la Californie, le Texas et la Floride réunis de 1970 à 1980 !). La Californie est l'Etat le plus peuplé de l'union avec plus de 26 millions d'habitants. 2. Il existe toutefois des différences de comportements démographiques au sein de la «Sun Belt »:...

• LI SUN-SIN. (résumé)

• Sun Tzu, L’art de la guerre

  Sun Tzu, L’art de la guerre Ecrit au IVe siècle avant Jésus-Christ, L’art de la guerre est le plus ancien traité sur la guerre connu à ce jour. Traduit tardivement par un missionnaire jésuite français peu avant la Révolution, il est, depuis, une référence majeure de la polémologie. C’est que, malgré leur ancienneté, les 13 chapitres qui composent le livre, montrent que Sun Tzu avait compris qu’une guerre ne se gagne pas seulement par la force des armes. Elle est d’abord affaire de psycholo...

• Egyptian Mythology I INTRODUCTION Egyptian Mythology, specifically, the religion of ancient Egypt.

  PtahThe Egyptian god Ptah was, among other things, patron of the arts and of artisans. He was worshipped at Memphis, theancient capital of Egypt. This statue of the deity dates from the 18th dynasty and is in the Egyptian Museum of Turin,Italy.Gianni Dagli Orti/Corbis In addition to those already named, the important divinities included the gods Amon, Thoth, Ptah, Khnemu, and Hapi, and the goddesses Hathor, Mut, Neit, andSekhmet. Their importance increased with the political ascendancy of the lo...

• Odyssey Greek The epic poem by Homer that describes the adventures of Odysseus on his homeward voyage to Ithaca after the Trojan War.

  turn his men back into their human forms. Under her spell, he dallied for a year on the island of the sorceress, who gave him warnings about the perils he would encounter on his way home. Odysseus in the Underworld - Mythology. After suffering under the spell of the witch-goddess Circe for a year, Odysseus and his crew grew restless and wanted to leave. On the advice of Circe, Odysseus and his crew visited the Underworld (1) to consult the ghost of the blind seer Tiresias. Tiresias had many wa...

• Alphabet I INTRODUCTION Bengali Script India developed a number of different writing systems over the course of its history.

  A Pictographic and Ideographic Systems Early systems of writing used pictures to represent things and then to represent the sounds of those things. Pictographic writing, in which a simplified picture of the sunstood for the word sun, was probably the first step toward a written language. Chinese began as a pictographic language. To represent abstract ideas, the Chinese writing system combined pictographs. For example, the pictographs for sun and tree were combined to represent the concept of...

• La Révolution chinoise.

  En 1949, la victoire de Mao Zedong en Chine marque la fin des affrontements incessants qui déchiraient le pays depuis l'effondrement de l'empire.Trente ans après la révolution de 1917, le camp communiste se renforce ainsi d'un nouveau géant, dont l'histoire sera riche en rebondissements. La révolution inachevée Depuis le renversement de la dynastie mandchoue en 191 1, la Chine est dirigée par Yuan Shikai, président de la République ,...

• La Chanson de Roland

  2 III B LANCANDRINS fut des plus saives paiens ; 25 De vasselage fut asez chevaler, Prozdom i out pur sun seignur aider, E dist al rei : « Ore ne vus esmaiez ! Mandez Carlun, a l’orguillus e al fier, Fedeilz servises e mult granz amistez. 30 Vos li durrez urs e leons e chens, Set cenz camelz e mil hosturs muers, D’or e d’argent .IIII.C. muls cargez, Cinquante carre qu’en ferat carier : Ben en purrat luer ses soldeiers. 35 En ceste tere ad asez osteiet ; En France, ad Ais, s’en deit...

• Pluto - astronomy.

  depended on how Pluto was classified. The status of Pluto drew world attention in 2006 when the official body that governs the naming of astronomical objects, the International Astronomical Union (IAU),voted for an official definition of the term planet . According to the standards adopted, a “classical planet” must orbit the Sun, must have a rounded shape from effects of its own gravity, and must be the dominant object in its region of space, having cleared the neighborhood of its orbit of oth...

• Gravitation I INTRODUCTION Gravitation, the force of attraction between all objects that tends to pull them toward one another.

  precise observations possible, and Galileo was one of the first to use a telescope to study astronomy. In 1609 Galileo observed that moons orbited the planet Jupiter, afact that could not reasonably fit into an earth-centered model of the heavens. The new heliocentric theory changed scientists' views about the earth's place in the universe and opened the way for new ideas about the forces behind planetarymotion. However, it was not until the late 17th century that Isaac Newton developed a theory...

• Gravitation - astronomy.

  precise observations possible, and Galileo was one of the first to use a telescope to study astronomy. In 1609 Galileo observed that moons orbited the planet Jupiter, afact that could not reasonably fit into an earth-centered model of the heavens. The new heliocentric theory changed scientists' views about the earth's place in the universe and opened the way for new ideas about the forces behind planetarymotion. However, it was not until the late 17th century that Isaac Newton developed a theory...

• Supernova - astronomy.

  The term hypernova has been proposed for an extremely massive core-collapse supernova—possibly more than 100 times the mass of the Sun. A hypernova is thought to form a black hole. Just before it explodes, a hypernova may release a huge burst of gamma rays in a jet from the rotating black hole at its center. These jets mayexplain the so-called long gamma-ray bursts detected by astronomers. According to some researchers, massive stars with over 40 solar masses may sometimescollapse directly int...

• Astrobiology - astronomy.

  water to help reactions along. American chemists Stanley Miller and Harold Urey tested part of Oparin and Haldane’s hypothesis in the early 1950s by simulating conditions of the early Earth. In whathas become known as the Miller-Urey experiment, the two scientists connected two flasks with a loop of glass tubing that allowed the gases to pass between the flasks.They filled the upper flask with methane, ammonia, and hydrogen—components thought to have been in the early atmosphere. They filled the...

• Light I INTRODUCTION Light, form of energy visible to the human eye that is radiated by moving charged particles.

  simulates the action of a moving charge upon the electric field. It creates a wave that travels along the rope in a direction that is perpendicular to the initial up anddown movement. Because electromagnetic waves are transverse—that is, the vibration that creates them is perpendicular to the direction in which they travel, they are similar to waveson a rope or waves traveling on the surface of water. Unlike these waves, however, which require a rope or water, light does not need a medium, or su...

• Aztec Empire.

  tribute to the empire in agricultural products, which were used to finance public projects. All able-bodied men owed military service to the empire. Citizens could also bedrafted to work on public lands or build temples, dikes, aqueducts, and roads. Although Aztec society had strict classes, a person’s status could change based on his or her contribution to society. Commoners could improve their rank, especially byperforming well in battle, and become prosperous landowners. Young people of some...

• Aztec Empire - USA History.

  tribute to the empire in agricultural products, which were used to finance public projects. All able-bodied men owed military service to the empire. Citizens could also bedrafted to work on public lands or build temples, dikes, aqueducts, and roads. Although Aztec society had strict classes, a person’s status could change based on his or her contribution to society. Commoners could improve their rank, especially byperforming well in battle, and become prosperous landowners. Young people of some...

• Global Warming.

  some of the warming influence of increasing greenhouse gases. A1 Carbon Dioxide Carbon dioxide is the second most abundant greenhouse gas, after water vapor. Carbon dioxide constantly circulates in the environment through a variety of naturalprocesses known as the carbon cycle. It is released into the atmosphere from natural processes such as eruptions of volcanoes; the respiration of animals, whichbreathe in oxygen and exhale carbon dioxide; and the burning or decay of plants and other organic...

• Excerpt from Love's Labour's Lost - anthology.

  BEROWNE. I could put thee in comfort—not by two that I know.Thou makest the triumviry, the corner-cap of society,The shape of Love's Tyburn, that hangs up simplicity. LONGAVILLE. I fear these stubborn lines lack power to move.(Reading ) “O sweet Maria, empress of my love!”— These numbers will I tear, and write in prose.He tears the paper BEROWNE. O, rhymes are guards on wanton Cupid's hose;Disfigure not his shop. LONGAVILLE. ( taking another paper ) This same shall go: (Reading ) “Did not the he...

• Maya Civilization.

  destruction was directed mostly at temples in the ceremonial precincts; it had little or no impact on the economy or population of a city as a whole. Some city-states didoccasionally conquer others, but this was not a common occurrence until very late in the Classic period when lowland civilization had begun to disintegrate. Until thattime, the most common pattern of Maya warfare seems to have consisted of raids employing rapid attacks and retreats by relatively small numbers of warriors, most o...

• Maya Civilization - History.

  destruction was directed mostly at temples in the ceremonial precincts; it had little or no impact on the economy or population of a city as a whole. Some city-states didoccasionally conquer others, but this was not a common occurrence until very late in the Classic period when lowland civilization had begun to disintegrate. Until thattime, the most common pattern of Maya warfare seems to have consisted of raids employing rapid attacks and retreats by relatively small numbers of warriors, most o...

• Le déclin de la Chine et le combat du guomindang pour la reconstruction de l'unité nationale

  le chef du guomindang Tchang Kaï-chek, « héritier» politique de Sun Vat-sen En août 1912, le parti populaire national (guomindang), né de la fusion de plusieurs groupes révolutionnaires, constitue un important réservoir de réformateurs. Ses chefs devront pourtant rapidement se réfugier dans la clandestinité ou à l'étr anger pour échapper aux persécutions de Yuan Shikai. Étant donné qu'il n'existe pas de pouvoir unique, Sun Yat-sen, à son retour du Japon,...

• NASA - astronomy.

  Challenger shuttle after launch in 1986 and the Columbia shuttle during reentry in 2003, killing both crews. Investigations traced the accidents to design flaws and tomanagement problems. Both accidents led to design and procedure changes, and to a temporary stoppage of shuttle flights. Following the Columbia disaster, NASA alsoannounced plans to retire the shuttle in 2010, after completion of the International Space Station (ISS), a human orbital research facility. The Constellation program is...

• Indian Art and Architecture I INTRODUCTION Art on the Indian Subcontinent This map highlights places in India and Pakistan where prominent examples of Indian art and architecture have been produced.

  Sun Temple of KonarakThis 13th-century relief depicting a wheel of the chariot of Indian sun god Surya is situated in the Konarak temple. Thetemple, dedicated to Surya, is situated at Puri in the Gulf of Bengal.Keren Su/Corbis The arts of India expressed in architecture, sculpture, painting, jewelry, pottery, metalwork, and textiles, were spread throughout the Far East with the diffusion ofBuddhism and Hinduism and exercised a strong influence on the arts of China, Japan, Myanmar (formerly known...

• X-Ray Astronomy - astronomy.

  Some neutron stars have weaker magnetic fields that allow incoming material to settle onto the entire surface of the neutron star. Eventually, so much material buildsup that the surface layer becomes dense enough to set off a vast thermonuclear explosion, called an outburst. The explosion heats gas to produce X rays. Such aneutron star—called an X-ray burster—can increase its X-ray production by a million times during an outburst. The X-ray glow fades over time, and the binary systementers a lon...

• Plato I INTRODUCTION Plato (428?

  one of the individuals escapes from the cave into the light of day. With the aid of the sun, that person sees for the first time the real world and returns to the cave withthe message that the only things they have seen heretofore are shadows and appearances and that the real world awaits them if they are willing to struggle free oftheir bonds. The shadowy environment of the cave symbolizes for Plato the physical world of appearances. Escape into the sun-filled setting outside the cave symbolize...

• Plato.

  one of the individuals escapes from the cave into the light of day. With the aid of the sun, that person sees for the first time the real world and returns to the cave withthe message that the only things they have seen heretofore are shadows and appearances and that the real world awaits them if they are willing to struggle free oftheir bonds. The shadowy environment of the cave symbolizes for Plato the physical world of appearances. Escape into the sun-filled setting outside the cave symbolize...

• Honey Bee - biology.

  B Reproduction and Development The queen controls the sex of her offspring. When an egg passes from her ovary to her oviduct, the queen determines whether the egg is fertilized with sperm from thespermatheca. A fertilized egg develops into a female honey bee, either worker or queen, and an unfertilized egg becomes a male honey bee, or drone. The queen lays the eggs that will develop into more queens in specially constructed downward-pointing, peanut-shaped cells, in which the egg adheres to the...

• Pasiphaë Greek Daughter of Helios (the Sun); wife of Minos, king of Crete; mother with Minos of Ariadne, Androgeus, and Phaedra.

• Tchang Kaï-chek

  Powered by TCPDF (www.tcpdf.org)Tchang Kai-chek 1886-1973 La carrière politique de Tchang Kai-chek, qui a reçu une formation militaire au Japon avant 1911, commence avec l'introduction de la République et se poursuit dans le sillage de Sun Yat-sen, au sein du Guomindang dont il devient le chef après la mort de Sun. Il occupe alors une position d'influence, non pas seulement parce qu'il se réclame du père de la Chine moderne, mais parce qu'il organise l'armée du Guomindang et qu'il commande l'aca...

• CHIANG KAI-SHEK (1887-1975) : le «Gemo».

  Chiang Kai-shek 1 La personnalité du maréchal Chlang Kal-shek éclaire les origines complexes du mouvement révolutionnaire chinois. Leader politique et chef de guerre d'abord heureux, cet anticommuniste, longtemps soutenu par Moscou, fut toq­ jours champion du même nationalisme que Mao Zedong, à plusieurs reprises son allié. Réfugié à Taiwan, après vingt-deux ans de pouvoir (1927·1949), il y instaure un régime népotlque et policier et y entretient l'...

• Theia (Radiant) Greek A first-generation Titan goddess of sight and the shining light of the blue sky; daughter of Gaia and Uranus; mother, with Hyperion, of the gods who brought light to humans: Helios (Sun), Selene (Moon), and Eos (Dawn).

• Le renversement de la monarchie chinoise : une victoire à la Pyrrhus

  La coupe de la tresse est le symbole du commencement d'une nouvelle époque en Chine. Le renvers ement de la mona rchie chinoise : une victoire à la Pyrrhus Depuis le mil ieu du x1x• siècle, il devient de plus en plu s clair que la dynastie mandchoue au pouvo ir, contrairement au Meiji Tenno au Japon, n'est ni en mesure d'identifier les défis de l'époque moderne ni même de s'y prépa rer. A u XIX' siècle, la Chine connaît un déclin imprévu. Ell...

• Astronomy - astronomy.

  Telescopes may use either lenses or mirrors to gather visible light, permitting direct observation or photographic recording of distant objects. Those that use lenses arecalled refracting telescopes, since they use the property of refraction, or bending, of light ( see Optics: Reflection and Refraction ). The largest refracting telescope is the 40-in (1-m) telescope at the Yerkes Observatory in Williams Bay, Wisconsin, founded in the late 19th century. Lenses bend different colors of light by d...

• Chiang Kai-shek - History.

  Even one of Chiang's allied commanders, Zhang Xueliang, who had been expelled from Manchuria after the Mukden Incident, came to doubt the wisdom of Chiang'sapproach. In 1936 Zhang held Chiang prisoner in Xi'an until Chiang agreed to join the Communists in an allied front against Japan. Chiang later denied making anyagreement. On July 7, 1937, near the Marco Polo Bridge on the outskirts of Beijing, a Chinese patrol and Japanese troops on a training exercise clashed, and full-scalewar broke out be...