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Hoba Meteorite
The Hoba ( ) meteorite, short for Hoba West, is a meteorite that lies on the farm of the same name, not far from Grootfontein, in the Otjozondjupa Region of Namibia. It has been uncovered, but because of its large mass, has never been moved from where it fell. The main mass is estimated at more than 60 tonnes. It is the largest known intact meteorite (as a single piece) and about twice as massive as the largest fragment of either the Cape York meteorite's 31-tonne Ahnighito kept in Manhattan or the Campo del Cielo's 31-tonne Gancedo in Argentina. It is also the most massive naturally occurring piece of iron (actually ferronickel) known on Earth's surface. The name "Hoba" comes from a Khoekhoegowab word meaning "gift". Following donation to the government in 1987, a visitor centre was constructed with a circular stone access and seating area. Impact The Hoba meteorite impact is thought to have occurred less than 80,000 years ago. It is inferred that the Earth's atmosphere slowed t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteorite
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a fireball, also known as a shooting star; astronomers call the brightest examples " bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater. Meteorites that are recovered after being observed as they transit the atmosphere and impact the Earth are called meteorite falls. All others are known as meteorite finds. Meteorites have traditionally been divided into three broad categories: stony meteorites that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal. Cobalt-based blue pigments (cobalt blue) have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was for a long time thought to be due to the known metal bismuth. Miners had long used the name '' kobold ore'' (German for ''goblin ore'') for some of the blue-pigment-producing minerals; they were so named because they were poor in known metals, and gave poisonous arsenic-containing fumes when smelted. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the ''kobold''. Today, some cobalt is produced specifically from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bonhams
Bonhams is a privately owned international auction house and one of the world's oldest and largest auctioneers of fine art and antiques. It was formed by the merger in November 2001 of Bonhams & Brooks and Phillips Son & Neale. This brought together two of the four surviving Georgian auction houses in London, Bonhams having been founded in 1793, and Phillips in 1796 by Harry Phillips, formerly a senior clerk to James Christie. Today, the amalgamated business handles art and antiques auctions. It operates two salerooms in London—the former Phillips sale room at 101 New Bond Street, and the old Bonham's sale room at the Montpelier Galleries in Montpelier Street, Knightsbridge—with a smaller sale room in Edinburgh. Sales are also held around the world in New York, Hong Kong, Los Angeles, Paris, San Francisco, Sydney, and Singapore. Bonhams holds more than 280 sales a year in more than 60 collecting areas, including Asian art, Pictures, motor cars and jewelry. Bonh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Republic Of Namibia
Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and east. Although it does not border Zimbabwe, less than 200 metres (660 feet) of the Botswanan right bank of the Zambezi River separates the two countries. Namibia gained independence from South Africa on 21 March 1990, following the Namibian War of Independence. Its capital and largest city is Windhoek. Namibia is a member state of the United Nations (UN), the Southern African Development Community (SADC), the African Union (AU) and the Commonwealth of Nations. The driest country in sub-Saharan Africa, Namibia has been inhabited since pre-historic times by the San, Damara and Nama people. Around the 14th century, immigrating Bantu peoples arrived as part of the Bantu expansion. Since then, the Bantu groups, the largest being the Ovambo, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tripartite Accord (1988)
The Agreement among the People's Republic of Angola, the Republic of Cuba, and the Republic of South Africa (also known as the Tripartite Accord, Three Powers Accord or New York Accords) granted independence to Namibia from South Africa and ended the direct involvement of foreign troops in the Angolan Civil War. The accords were signed on 22 December 1988 at the United Nations Headquarters in New York City by the Foreign Ministers of People's Republic of Angola ( Afonso Van-Dunem), Republic of Cuba ( Isidoro Malmierca Peoli) and Republic of South Africa ( Roelof F. Botha). Negotiations In 1981 Chester Crocker, U.S. assistant secretary of state for African affairs for newly elected United States President Ronald Reagan, had developed a linkage policy. It tied apartheid South Africa's agreement to relinquish control of Namibia, in line with United Nations Security Council Resolution 435, and to retreat from Angola, to Cuba's withdrawing its troops from Angola.Tvedten, Ing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South African Border War
The South African Border War, also known as the Namibian War of Independence, and sometimes denoted in South Africa as the Angolan Bush War, was a largely asymmetric conflict that occurred in Namibia (then South West Africa), Zambia, and Angola from 26 August 1966 to 21 March 1990. It was fought between the South African Defence Force (SADF) and the People's Liberation Army of Namibia (PLAN), an armed wing of the South West African People's Organisation (SWAPO). The South African Border War resulted in some of the largest battles on the African continent since World War II and was closely intertwined with the Angolan Civil War. Following several years of unsuccessful petitioning through the United Nations and the International Court of Justice for Namibian independence from South Africa, SWAPO formed the PLAN in 1962 with material assistance from the Soviet Union, China, and sympathetic African states such as Tanzania, Ghana, and Algeria. Fighting broke out between PLAN and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South West Africa
South West Africa ( af, Suidwes-Afrika; german: Südwestafrika; nl, Zuidwest-Afrika) was a territory under South African administration from 1915 to 1990, after which it became modern-day Namibia. It bordered Angola ( Portuguese colony before 1975), Botswana ( Bechuanaland before 1966), South Africa, and Zambia (Northern Rhodesia before 1964). Previously the German colony of South West Africa from 1884–1915, it was made a League of Nations mandate of the Union of South Africa following Germany's defeat in the First World War. Although the mandate was abolished by the United Nations in 1966, South African control over the territory continued despite its illegality under international law. The territory was administered directly by the South African government from 1915 to 1978, when the Turnhalle Constitutional Conference laid the groundwork for semi-autonomous rule. During an interim period between 1978 and 1985, South Africa gradually granted South West Africa a limited ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Find A Grave
Find a Grave is a website that allows the public to search and add to an online database of cemetery records. It is owned by Ancestry.com. Its stated mission is "to help people from all over the world work together to find, record and present final disposition information as a virtual cemetery experience." Volunteers can create memorials, upload photos of grave markers or deceased persons, transcribe photos of headstones, and more. , the site claimed more than 210 million memorials. History The site was created in 1995 by Salt Lake City resident Jim Tipton (born in Alma, Michigan) to support his hobby of visiting the burial sites of celebrities. He later added an online forum. Find a Grave was launched as a commercial entity in 1998, first as a trade name and then incorporated in 2000. The site later expanded to include graves of non-celebrities, in order to allow online visitors to pay respect to their deceased relatives or friends. In 2013, Tipton sold Find a Grave to An ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogenation, C=C (and other) bond ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs '' in situ'' (on site, with little or no movement), and so is distinct from erosion, which involves the transport of rocks and minerals by agents such as water, ice, snow, wind, waves and gravity. Weathering processes are divided into ''physical'' and ''chemical weathering''. Physical weathering involves the breakdown of rocks and soils through the mechanical effects of heat, water, ice, or other agents. Chemical weathering involves the chemical reaction of water, atmospheric gases, and biologically produced chemicals with rocks and soils. Water is the principal agent behind both physical and chemical weathering, though atmospheric oxygen and carbon dioxide and the activities of biological organisms are also important. Chemical weathering by biological action is also known as biolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron Hydroxide
Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of which is rust. Iron oxides and oxyhydroxides are widespread in nature and play an important role in many geological and biological processes. They are used as iron ores, pigments, catalysts, and in thermite, and occur in hemoglobin. Iron oxides are inexpensive and durable pigments in paints, coatings and colored concretes. Colors commonly available are in the "earthy" end of the yellow/orange/red/brown/black range. When used as a food coloring, it has E number E172. Stoichiometries Iron oxides feature as ferrous (Fe(II)) or ferric (Fe(III)) or both. They adopt octahedral or tetrahedral coordination geometry. Only a few oxides are significant at the earth's surface, particularly wüstite, magnetite, and hematite. * Oxides of FeII ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
