Refraction is the change in direction of wave propagation due to a change in its transmission medium. The phenomenon is explained by the conservation of energy and the conservation of momentum, due to the change of medium, the phase velocity of the wave is changed but its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any other than 0° from the normal. In optics, refraction is a phenomenon that occurs when waves travel from a medium with a given refractive index to a medium with another at an oblique angle. At the boundary between the media, the phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases, but its frequency remains constant, for example, a light ray will refract as it enters and leaves glass, assuming there is a change in refractive index. A ray traveling along the normal will change speed, but not direction, refraction still occurs in this case. Understanding of this led to the invention of lenses and the refracting telescope.
Refraction can be seen looking into a bowl of water. Air has a index of about 1.0003. If a person looks at an object, such as a pencil or straw, which is placed at a slant, partially in the water. This is due to the bending of light rays as they move from the water to the air, once the rays reach the eye, the eye traces them back as straight lines. The lines of sight intersect at a position than where the actual rays originated. This causes the pencil to appear higher and the water to appear shallower than it really is, the depth that the water appears to be when viewed from above is known as the apparent depth. This is an important consideration for spearfishing from the surface because it will make the fish appear to be in a different place. Conversely, an object above the water has a higher apparent height when viewed from below the water, the opposite correction must be made by an archer fish. For small angles of incidence, the ratio of apparent to real depth is the ratio of the indexes of air to that of water.
But, as the angle of incidence approaches 90o, the apparent depth approaches zero, albeit reflection increases, the diagram on the right shows an example of refraction in water waves
In fluid dynamics, wind waves, or wind-generated waves, are surface waves that occur on the free surface of bodies of water. They result from the wind blowing over an area of fluid surface, Waves in the oceans can travel thousands of miles before reaching land. Wind waves on Earth range in size from small ripples, to waves over 100 ft high, when directly generated and affected by local winds, a wind wave system is called a wind sea. After the wind ceases to blow, wind waves are called swells, more generally, a swell consists of wind-generated waves that are not significantly affected by the local wind at that time. They have been generated elsewhere or some time ago, wind waves in the ocean are called ocean surface waves. Wind waves have an amount of randomness, subsequent waves differ in height, duration. The key statistics of wind waves in evolving sea states can be predicted with wind wave models, although waves are usually considered in the water seas of Earth, the hydrocarbon seas of Titan may have wind-driven waves.
The great majority of large breakers seen at a result from distant winds. Water depth All of these work together to determine the size of wind waves. Further exposure to that wind could only cause a dissipation of energy due to the breaking of wave tops. Waves in an area typically have a range of heights. For weather reporting and for analysis of wind wave statistics. This figure represents an average height of the highest one-third of the waves in a time period. The significant wave height is the value a trained observer would estimate from visual observation of a sea state, given the variability of wave height, the largest individual waves are likely to be somewhat less than twice the reported significant wave height for a particular day or storm. Wave formation on a flat water surface by wind is started by a random distribution of normal pressure of turbulent wind flow over the water. This pressure fluctuation produces normal and tangential stresses in the surface water and it is assumed that, The water is originally at rest.
There is a distribution of normal pressure to the water surface from the turbulent wind. Correlations between air and water motions are neglected, the second mechanism involves wind shear forces on the water surface
A missionary is a member of a religious group sent into an area to proselytize and/or perform ministries of service, such as education, social justice, health care, and economic development. The word mission originates from 1598 when the Jesuits sent members abroad, derived from the Latin missionem, meaning act of sending or mittere, meaning to send. The word was used in light of its usage, in the Latin translation of the Bible. The term is most commonly used for Christian missions, but can be used for any creed or ideology, a Christian missionary can be defined as one who is to witness across cultures. The Lausanne Congress of 1974, defined the term, related to Christian mission as, Missionaries can be found in many countries around the world. Jesus instructed the apostles to make disciples of all nations and this verse is referred to by Christian missionaries as the Great Commission and inspires missionary work. The New Testament-era missionary outreach of the Christian church from the time of St Paul expanded throughout the Roman Empire and beyond to Persia, in 596, Pope Gregory the Great sent the Gregorian Mission into England.
In their turn, Christians from Ireland and from Britain became prominent in converting the inhabitants of central Europe, about the same time, missionaries such as Francis Xavier as well as other Jesuits, Augustinians and Dominicans started moving into Asia and the Far East. The Portuguese sent missions into Africa and these are some of the most well-known missions in history. While some missions accompanied imperialism and oppression, others were relatively peaceful, contemporary Christian missionaries argue that working for justice forms a constitutive part of preaching the Gospel, and observe the principles of inculturation in their missionary work. Over time, the Vatican gradually established a church structure in the mission areas, often starting with special jurisdictions known as apostolic prefectures. The two 9th-century saints Cyril and Methodius had extensive success in central Europe. The Byzantines expanded their work in Ukraine after a mass baptism in Kiev in 988. The Serbian Orthodox Church had its origins in the conversion by Byzantine missionaries of the Serb tribes when they arrived in the Balkans in the 7th century, Orthodox missionaries worked successfully among the Estonians from the 10th to the 12th centuries, founding the Estonian Orthodox Church.
The Russian St. Nicholas of Japan took Eastern Orthodoxy to Japan in the 19th century, the Russian Orthodox Church sent missionaries to Alaska beginning in the 18th century, including Saint Herman of Alaska, to minister to the Native Americans. Quaker publishers of truth visited Boston and other mid-17th century colonies, the Danish government began the first organized Protestant mission work through its College of Missions, established in 1714. This funded and directed Lutheran missionaries such as Bartholomaeus Ziegenbalg in Tranquebar, India and he got to know a slave from the Danish colony in the West Indies. Within thirty years, Moravian missionaries had become active on every continent, and they are famous for their selfless work, living as slaves among the slaves and together with the Native Americans, the Delaware and Cherokee Indian tribes
The Marshall Islands, officially the Republic of the Marshall Islands, is an island country located near the equator in the Pacific Ocean, slightly west of the International Date Line. Geographically, the country is part of the island group of Micronesia. The countrys population of 53,158 people is spread out over 29 coral atolls, comprising 1,156 individual islands and islets. The islands share maritime boundaries with the Federated States of Micronesia to the west, Wake Island to the north, Kiribati to the south-east, about 27,797 of the islanders live on Majuro, which contains the capital. Micronesian colonists gradually settled the Marshall Islands during the 2nd millennium BC, Islands in the archipelago were first explored by Europeans in the 1520s, with Spanish explorer Alonso de Salazar sighting an atoll in August 1526. Other expeditions by Spanish and English ships followed, the islands derive their name from British explorer John Marshall, who visited in 1788. The islands were known by the inhabitants as jolet jen Anij.
The European powers recognized Spanish sovereignty over the islands in 1874 and they had been part of the Spanish East Indies formally since 1528. Later, Spain sold the islands to the German Empire in 1884, in World War I the Empire of Japan occupied the Marshall Islands, which in 1919 the League of Nations combined with other former German territories to form the South Pacific Mandate. In World War II, the United States conquered the islands in the Gilbert, along with other Pacific Islands, the Marshall Islands were consolidated into the Trust Territory of the Pacific Islands governed by the US. Self-government was achieved in 1979, and full sovereignty in 1986, Marshall Islands has been a United Nations member state since 1991. The country uses the United States dollar as its currency, the majority of the citizens of the Marshall Islands are of Marshallese descent, though there are small numbers of immigrants from the United States, China and other Pacific islands. The two official languages are Marshallese, which is a member of the Malayo-Polynesian languages, and English, micronesians settled the Marshall Islands in the 2nd millennium BC, but there are no historical or oral records of that period.
Over time, the Marshall Island people learned to navigate over long distances by canoe using traditional stick charts. Spanish explorer Alonso de Salazar was the first European to see the islands in 1526, commanding the ship Santa Maria de la Victoria, on August 21, he sighted an island at 14°N that he named San Bartolome. On September 21,1529, Álvaro de Saavedra Cerón commanded the Spanish ship Florida and he stood off a group of islands from which local inhabitants hurled stones at his ship. These islands, which he named Los Pintados, may have been Ujelang, on October 1, he found another group of islands where he went ashore for eight days, exchanged gifts with the local inhabitants and took on water. These islands, which he named Los Jardines, may have been Enewetak or Bikini Atoll
The Pacific Ocean is the largest and deepest of the Earths oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west, the Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres. Both the center of the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean, the oceans current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favourable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means peaceful sea, important human migrations occurred in the Pacific in prehistoric times. Long-distance trade developed all along the coast from Mozambique to Japan and therefore knowledge, extended to the Indonesian islands but apparently not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of trade was controlled by Arabs or Muslims.
In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality, from 1404 to 1433 Zheng He led expeditions into the Indian Ocean. The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and he named it Mar del Sur because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. Later, Portuguese explorer Ferdinand Magellan sailed the Pacific East to West on a Castilian expedition of world circumnavigation starting in 1519, Magellan called the ocean Pacífico because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until the eighteenth century, sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions discovered the Caroline Islands, the Aru Islands, and Papua New Guinea. In 1542–43 the Portuguese reached Japan, in 1564, five Spanish ships consisting of 379 explorers crossed the ocean from Mexico led by Miguel López de Legazpi and sailed to the Philippines and Mariana Islands.
The Manila galleons operated for two and a half centuries linking Manila and Acapulco, in one of the longest trade routes in history, Spanish expeditions discovered Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, and the Admiralty Islands in the South Pacific. In the 16th and 17th century Spain considered the Pacific Ocean a Mare clausum—a sea closed to other naval powers, as the only known entrance from the Atlantic the Strait of Magellan was at times patrolled by fleets sent to prevent entrance of non-Spanish ships. On the western end of the Pacific Ocean the Dutch threatened the Spanish Philippines, Spain sent expeditions to the Pacific Northwest reaching Vancouver Island in southern Canada, and Alaska. The French explored and settled Polynesia, and the British made three voyages with James Cook to the South Pacific and Australia and the North American Pacific Northwest, one of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794.
It sailed vast areas of the Pacific, from Cape Horn to Alaska and the Philippines, New Zealand and the South Pacific. Growing imperialism during the 19th century resulted in the occupation of much of Oceania by other European powers, and later, Japan, in Oceania, France got a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853 respectively. After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro managed to negotiate an incorporation of the island into Chile with native Rapanui in 1888, by occupying Easter Island, Chile joined the imperial nations
A canoe is a lightweight narrow boat, typically pointed at both ends and open on top, propelled by one or more seated or kneeling paddlers facing the direction of travel using a single-bladed paddle. In International Canoe Federation nomenclature used in some European countries such as the United Kingdom the term refers to kayaks. Canoes are used for racing, whitewater canoeing and camping, the intended use of the canoe dictates its hull shape and length and construction material. Historically, canoes were dugouts or made of bark on a wood frame, most modern canoes are made of molded plastic or composites such as fiberglass. Until the mid-1800s the canoe was an important means of transport for exploration and trade, canoeing has been part of the Olympics since 1936. In places where the played a key role in history, such as the northern United States and New Zealand. Canoes can be adapted to many purposes, for example with the addition of sails, outboard motors, the word canoe comes from the Carib kenu, via the Spanish canoa.
Constructed between 8200 and 7600 BC, and found in the Netherlands, the Pesse canoe may be the oldest known canoe, excavations in Denmark reveal the use of dugouts and paddles during the Ertebølle period. Australian Aboriginal people made canoes using a variety of materials, including bark, the indigenous people of the Amazon commonly used Hymenaea trees. Many indigenous peoples of the Americas built bark canoes and they were usually skinned with birch bark over a light wooden frame, but other types could be used if birch was scarce. At a typical length of 4.3 m and weight of 23 kg, although susceptible to damage from rocks, they are easily repaired. When you reach them you load canoe and baggage upon your shoulders and go overland until the navigation is good, and you put your canoe back into the water, and embark again. American painter and traveler George Catlin wrote that the canoe was the most beautiful. Native American groups of the north Pacific coast made dugout canoes in a number of styles for different purposes, from western red-cedar or yellow-cedar, different styles were required for ocean-going vessels versus river boats, and for whale-hunting versus seal-hunting versus salmon-fishing.
The Quinault of Washington State built shovel-nose canoes, with double bows, the Kootenai of British Columbia province made sturgeon-nosed canoes from pine bark, designed to be stable in windy conditions on Kootenay Lake. The first explorer to cross the North American continent, Alexander Mackenzie, used extensively, as did David Thompson. Its dimensions were, length approximately 11 m, beam 1.2 to 1.8 m and it could carry 60 packs weighing 41 kg, and 910 kg of provisions. With a crew of eight or ten, they could make three knots over calm waters, four to six men could portage it, bottom up
Cartography is the study and practice of making maps. Combining science and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively, the fundamental problems of traditional cartography are to, Set the maps agenda and select traits of the object to be mapped. This is the concern of map editing, traits may be physical, such as roads or land masses, or may be abstract, such as toponyms or political boundaries. Represent the terrain of the object on flat media. This is the concern of map projections, eliminate characteristics of the mapped object that are not relevant to the maps purpose. This is the concern of generalization, reduce the complexity of the characteristics that will be mapped. This is the concern of generalization, orchestrate the elements of the map to best convey its message to its audience. This is the concern of map design, modern cartography constitutes many theoretical and practical foundations of geographic information systems.
The earliest known map is a matter of debate, both because the term map isnt well-defined and because some artifacts that might be maps might actually be something else. A wall painting that might depict the ancient Anatolian city of Çatalhöyük has been dated to the late 7th millennium BCE, the oldest surviving world maps are from 9th century BCE Babylonia. One shows Babylon on the Euphrates, surrounded by Assyria and several cities, all, in turn, another depicts Babylon as being north of the world center. The ancient Greeks and Romans created maps since Anaximander in the 6th century BCE, in the 2nd century AD, Ptolemy wrote his treatise on cartography, Geographia. This contained Ptolemys world map – the world known to Western society. As early as the 8th century, Arab scholars were translating the works of the Greek geographers into Arabic, in ancient China, geographical literature dates to the 5th century BCE. The oldest extant Chinese maps come from the State of Qin, dated back to the 4th century BCE, in the book of the Xin Yi Xiang Fa Yao, published in 1092 by the Chinese scientist Su Song, a star map on the equidistant cylindrical projection.
Early forms of cartography of India included depictions of the pole star and these charts may have been used for navigation. Mappa mundi are the Medieval European maps of the world, approximately 1,100 mappae mundi are known to have survived from the Middle Ages. Of these, some 900 are found illustrating manuscripts and the remainder exist as stand-alone documents, the Arab geographer Muhammad al-Idrisi produced his medieval atlas Tabula Rogeriana in 1154
SMS Bussard was an unprotected cruiser of the Imperial German Navy, built in the 1880s. She was the ship of her class, which included five other vessels. The cruisers keel was laid in 1888, and she was launched in January 1890, intended for overseas duty, Bussard was armed with a main battery of eight 10. 5-centimeter guns, and could steam at a speed of 15.5 knots. Bussard served abroad for the majority of her career, first in the East Asia Division in the mid-1890s and she had a relatively peaceful career, her only major action came while stationed in Asia in 1894. There, she assisted in suppressing a revolt in Samoa. In 1910, she returned to Germany, where she remained in service for two more years, she was stricken in October 1912 and scrapped the following year in Hamburg. Bussard was 82.6 meters long overall and had a beam of 12.5 m and she displaced 1,868 t at full combat load. Her propulsion system consisted of two horizontal 3-cylinder triple-expansion steam engines powered by four coal-fired cylindrical boilers and these provided a top speed of 15.5 kn and a range of approximately 2,990 nautical miles at 9 kn.
She had a crew of 9 officers and 152 enlisted men, the ship was armed with eight 10.5 cm K L/35 guns in single pedestal mounts, supplied with 800 rounds of ammunition in total. They had a range of 8,200 m, two guns were placed side by side forward, two on each broadside in sponsons, and two side by side aft. The gun armament was rounded out by five revolver cannon and she was equipped with two 35 cm torpedo tubes with five torpedoes, both of which were mounted on the deck. Bussard was laid down at the Kaiserliche Werft in Danzig under the contract name C and she was launched on 23 January 1890, fitting-out work was completed quickly, and the new cruiser was ready for commissioning into the Imperial fleet on 7 October 1890. She thereafter served on overseas stations in the German Empire, early in her career, Bussard served on the East Asia Station with the East Asia Division. In July 1893, she and her sister ship Falke assisted in the suppression of a revolt led by Mataafa Iosefo in Samoa. They were joined by the old British corvette HMS Curacao, Mataafa was taken to Apia, the capital, while Bussard remained behind to ensure the demilitarization of his supporters.
In 1898, Bussard returned to Germany, arriving in the Elbe River in March, on the return voyage, she carried several tropical birds for the Berlin Zoological Garden. After her arrival, Bussard went into drydock at the Kaiserliche Werft in Danzig for reconstruction, the barque rig was cut down to a top-sail schooner rig. A new, larger conning tower structure was built, work was completed by 1900, when Bussard returned to service
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, an island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, an island may be described as such, despite the presence of an artificial land bridge. Example and its causeway, or the various Dutch delta islands, there are two main types of islands in the sea and oceanic. The word island derives from Middle English iland, from Old English igland, Old English ieg is actually a cognate of Swedish ö and German Aue, and related to Latin aqua. There is a difference between islands and continents in terms of geology, continents sit on continental lithosphere which is part of tectonic plates floating high on Earths mantle. Oceanic crust is part of tectonic plates, but it is denser than continental lithosphere, Islands are either extensions of the oceanic crust or geologically they are part of some continent sitting on continental lithosphere.
This holds true for Australia, which sits on its own continental lithosphere, continental islands are bodies of land that lie on the continental shelf of a continent. A special type of island is the microcontinental island, which is created when a continent is rifted. Examples are Madagascar and Socotra off Africa, the Kerguelen Islands, New Caledonia, New Zealand, another subtype is an island or bar formed by deposition of tiny rocks where water current loses some of its carrying capacity. While some are transitory and may disappear if the volume or speed of the current changes, others are stable, oceanic islands are islands that do not sit on continental shelves. The vast majority are volcanic in origin, such as Saint Helena in the South Atlantic Ocean, the few oceanic islands that are not volcanic are tectonic in origin and arise where plate movements have lifted up the ocean floor above the surface. Examples are Saint Peter and Paul Rocks in the Atlantic Ocean, one type of volcanic oceanic island is found in a volcanic island arc.
These islands arise from volcanoes where the subduction of one plate under another is occurring, examples are the Aleutian Islands, the Mariana Islands, and most of Tonga in the Pacific Ocean. The only examples in the Atlantic Ocean are some of the Lesser Antilles, another type of volcanic oceanic island occurs where an oceanic rift reaches the surface. There are two examples, which is the second largest volcanic island, and Jan Mayen. A third type of oceanic island is formed over volcanic hotspots. A hotspot is more or less stationary relative to the tectonic plate above it
World War II
World War II, known as the Second World War, was a global war that lasted from 1939 to 1945, although related conflicts began earlier. It involved the vast majority of the worlds countries—including all of the great powers—eventually forming two opposing alliances, the Allies and the Axis. It was the most widespread war in history, and directly involved more than 100 million people from over 30 countries. Marked by mass deaths of civilians, including the Holocaust and the bombing of industrial and population centres. These made World War II the deadliest conflict in human history, from late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Finland and the Baltic states. In December 1941, Japan attacked the United States and European colonies in the Pacific Ocean, and quickly conquered much of the Western Pacific.
The Axis advance halted in 1942 when Japan lost the critical Battle of Midway, near Hawaii, in 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained all of its territorial losses and invaded Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in South Central China and Burma, while the Allies crippled the Japanese Navy, thus ended the war in Asia, cementing the total victory of the Allies. World War II altered the political alignment and social structure of the world, the United Nations was established to foster international co-operation and prevent future conflicts. The victorious great powers—the United States, the Soviet Union, the United Kingdom, the Soviet Union and the United States emerged as rival superpowers, setting the stage for the Cold War, which lasted for the next 46 years. Meanwhile, the influence of European great powers waned, while the decolonisation of Asia, most countries whose industries had been damaged moved towards economic recovery.
Political integration, especially in Europe, emerged as an effort to end pre-war enmities, the start of the war in Europe is generally held to be 1 September 1939, beginning with the German invasion of Poland and France declared war on Germany two days later. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or even the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred simultaneously and this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935. The British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the forces of Mongolia and the Soviet Union from May to September 1939, the exact date of the wars end is not universally agreed upon.
It was generally accepted at the time that the war ended with the armistice of 14 August 1945, rather than the formal surrender of Japan