1.
Italy
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Italy, officially the Italian Republic, is a unitary parliamentary republic in Europe. Located in the heart of the Mediterranean Sea, Italy shares open land borders with France, Switzerland, Austria, Slovenia, San Marino, Italy covers an area of 301,338 km2 and has a largely temperate seasonal climate and Mediterranean climate. Due to its shape, it is referred to in Italy as lo Stivale. With 61 million inhabitants, it is the fourth most populous EU member state, the Italic tribe known as the Latins formed the Roman Kingdom, which eventually became a republic that conquered and assimilated other nearby civilisations. The legacy of the Roman Empire is widespread and can be observed in the distribution of civilian law, republican governments, Christianity. The Renaissance began in Italy and spread to the rest of Europe, bringing a renewed interest in humanism, science, exploration, Italian culture flourished at this time, producing famous scholars, artists and polymaths such as Leonardo da Vinci, Galileo, Michelangelo and Machiavelli. The weakened sovereigns soon fell victim to conquest by European powers such as France, Spain and Austria. Despite being one of the victors in World War I, Italy entered a period of economic crisis and social turmoil. The subsequent participation in World War II on the Axis side ended in defeat, economic destruction. Today, Italy has the third largest economy in the Eurozone and it has a very high level of human development and is ranked sixth in the world for life expectancy. The country plays a prominent role in regional and global economic, military, cultural and diplomatic affairs, as a reflection of its cultural wealth, Italy is home to 51 World Heritage Sites, the most in the world, and is the fifth most visited country. The assumptions on the etymology of the name Italia are very numerous, according to one of the more common explanations, the term Italia, from Latin, Italia, was borrowed through Greek from the Oscan Víteliú, meaning land of young cattle. The bull was a symbol of the southern Italic tribes and was often depicted goring the Roman wolf as a defiant symbol of free Italy during the Social War. Greek historian Dionysius of Halicarnassus states this account together with the legend that Italy was named after Italus, mentioned also by Aristotle and Thucydides. The name Italia originally applied only to a part of what is now Southern Italy – according to Antiochus of Syracuse, but by his time Oenotria and Italy had become synonymous, and the name also applied to most of Lucania as well. The Greeks gradually came to apply the name Italia to a larger region, excavations throughout Italy revealed a Neanderthal presence dating back to the Palaeolithic period, some 200,000 years ago, modern Humans arrived about 40,000 years ago. Other ancient Italian peoples of undetermined language families but of possible origins include the Rhaetian people and Cammuni. Also the Phoenicians established colonies on the coasts of Sardinia and Sicily, the Roman legacy has deeply influenced the Western civilisation, shaping most of the modern world
2.
Messina
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Messina is the capital of the Italian Metropolitan City of Messina. It is located near the northeast corner of Sicily, at the Strait of Messina, opposite Villa San Giovanni on the mainland, according to Eurostat the FUA of the metropolitan area of Messina has, in 2014,277,584 inhabitants. The citys main resources are its seaports, cruise tourism, commerce, the city has been a Roman Catholic Archdiocese and Archimandrite seat since 1548 and is home to a locally important international fair. The city has the University of Messina, founded in 1548 by Ignatius of Loyola, Messina has a light rail system, Tranvia di Messina, that was opened on 3 April 2003. This line is 7.7 kilometres and links the central railway station with the city centre. The city is home to a significant Greek-speaking minority, rooted in its history, founded by Greek colonists in the 8th century BC, Messina was originally called Zancle, from the Greek ζάγκλον meaning scythe because of the shape of its natural harbour. A comune of its Metropolitan City, located at the entrance of the Strait of Messina, is to this day called Scaletta Zanclea. In the early 5th century BC, Anaxilas of Rhegium renamed it Messene in honour of the Greek city Messene, the city was sacked in 397 BC by the Carthaginians and then reconquered by Dionysius I of Syracuse. In 288 BC the Mamertines seized the city by treachery, killing all the men, the city became a base from which they ravaged the countryside, leading to a conflict with the expanding regional empire of Syracuse. Hiero II, tyrant of Syracuse, defeated the Mamertines near Mylae on the Longanus River, carthage assisted the Mamertines because of a long-standing conflict with Syracuse over dominance in Sicily. When Hiero attacked a second time in 264 BC, the Mamertines petitioned the Roman Republic for an alliance, although initially reluctant to assist lest it encourage other mercenary groups to mutiny, Rome was unwilling to see Carthaginian power spread further over Sicily and encroach on Italy. Rome therefore entered into an alliance with the Mamertines, in 264 BC, Roman troops were deployed to Sicily, the first time a Roman army acted outside the Italian Peninsula. At the end of the First Punic War it was a city allied with Rome. In Roman times Messina, then known as Messana, had an important pharos, Messana was the base of Sextus Pompeius, during his war against Octavian. In 1548 St. Ignatius founded there the first Jesuit college in the world, the Christian ships that won the Battle of Lepanto left from Messina, the Spanish author Miguel de Cervantes, who took part in the battle, recovered for some time in the Grand Hospital. The city reached the peak of its splendour in the early 17th century, under Spanish domination, in 1674 the city rebelled against the foreign garrison. A massive fortress was built by the occupants and Messina decayed steadily, in 1743,48,000 died of plague in the city. In 1783, an earthquake devastated much of the city, and it took decades to rebuild, in 1847 it was one of the first cities in Italy where Risorgimento riots broke out
3.
Reggio Calabria
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Reggio di Calabria, commonly known as Reggio Calabria listen or simply Reggio in Southern Italy, is the biggest city and the most populated comune of Calabria, Southern Italy. It is the capital of the Metropolitan City of Reggio Calabria, Reggio is located on the toe of the Italian Peninsula and is separated from the island of Sicily by the Strait of Messina. It is situated on the slopes of the Aspromonte, a long, about 560,000 people live in the metropolitan area, recognised in 2015 by Italian Republic as a metropolitan city. The region has been subject to earthquakes and it is a major economic center for regional services and transport on the southern shores of the Mediterranean. Reggio, with Naples and Taranto, is home to one of the most important archaeological museums, Reggio is the seat, since 1907, of the Archeological Superintendence of Bruttium and Lucania. The city center, consisting primarily of Liberty buildings, has a development along the coast with parallel streets. The city was an Italian candidate to become the European Capital of Culture. in 2019, during its 3, 500-year history Reggio has often been renamed. Each name corresponds with the major historical phases, Recion. Erythrà, the pre-Greek settlement populated by the Italic people, Rhégion, the Greek city from the archaic age to the Magna Grecia age, from the 8th to the 3rd centuries BC. Febèa, a period under Dionysius II of Syracuse, in the 4th century BC. Regium, its first Latin name, during the 3rd and 2nd centuries BC, rhègium Julium, as a noble Roman city during the Imperial age. Rivàh, Arabic name under the domination by Emirate of Sicily. Rìsa, under the Normans, between the 11th and 12th centuries, regols, Aragonese name under the Crown of Aragon, in the late 13th century. Reggio or Regio, usual Italian name in the Middle and Modern age, règgio di Calàbria, post Italian Unification. The toponym of the city is derived from Chaldean word Rec or maybe from the Greek one régnȳmi referring to the Straits between Calabria and Sicily as a break in the land. The sculptor Léarchos was at Reggio at the end of the 15th century BC, the land around Reggio was first known as Saturnia, or Neptunia, and later Italia, which in Roman times became the name of the whole Italian peninsula. After Cumae, Reggio is one of the oldest Greek colonies in southern Italy, the colony was settled by the inhabitants of Chalcis in 730 or 743 BC on the site of the older settlement, Erythrà, meaning the Red one. This dated back to the 3rd millennium BC and was established by the Ausones
4.
Sicily
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Sicily is the largest island in the Mediterranean Sea. It is an autonomous Region of Italy, along with surrounding minor islands, Sicily is located in the central Mediterranean Sea, south of the Italian Peninsula, from which it is separated by the narrow Strait of Messina. Its most prominent landmark is Mount Etna, the tallest active volcano in Europe, the island has a typical Mediterranean climate. The earliest archaeological evidence of activity on the island dates from as early as 12,000 BC. It became part of Italy in 1860 following the Expedition of the Thousand, a revolt led by Giuseppe Garibaldi during the Italian unification, Sicily was given special status as an autonomous region after the Italian constitutional referendum of 1946. Sicily has a rich and unique culture, especially regard to the arts, music, literature, cuisine. It is also home to important archaeological and ancient sites, such as the Necropolis of Pantalica, the Valley of the Temples, Sicily has a roughly triangular shape, earning it the name Trinacria. To the east, it is separated from the Italian mainland by the Strait of Messina, about 3 km wide in the north, and about 16 km wide in the southern part. The northern and southern coasts are each about 280 km long measured as a line, while the eastern coast measures around 180 km. The total area of the island is 25,711 km2, the terrain of inland Sicily is mostly hilly and is intensively cultivated wherever possible. Along the northern coast, the ranges of Madonie,2,000 m, Nebrodi,1,800 m. The cone of Mount Etna dominates the eastern coast, in the southeast lie the lower Hyblaean Mountains,1,000 m. The mines of the Enna and Caltanissetta districts were part of a leading sulphur-producing area throughout the 19th century, Sicily and its surrounding small islands have some highly active volcanoes. Mount Etna is the largest active volcano in Europe and still casts black ash over the island with its ever-present eruptions and it currently stands 3,329 metres high, though this varies with summit eruptions, the mountain is 21 m lower now than it was in 1981. It is the highest mountain in Italy south of the Alps, Etna covers an area of 1,190 km2 with a basal circumference of 140 km. This makes it by far the largest of the three volcanoes in Italy, being about two and a half times the height of the next largest, Mount Vesuvius. In Greek Mythology, the deadly monster Typhon was trapped under the mountain by Zeus, Mount Etna is widely regarded as a cultural symbol and icon of Sicily. The Aeolian Islands in the Tyrrhenian Sea, to the northeast of mainland Sicily form a volcanic complex, the three volcanoes of Vulcano, Vulcanello and Lipari are also currently active, although the latter is usually dormant
5.
Calabria
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Calabria, known in antiquity as Bruttium and formerly as Italia, is a region in Southern Italy and forms the traditionally conceptualized toe of the Italian Peninsula which resembles a boot. The capital city of Calabria is Catanzaro and its most populated city, and the seat of the Regional Council of Calabria, is Reggio Calabria in the Province of Reggio Calabria. The region is bordered to the north by the Basilicata Region, to the west by the Tyrrhenian Sea, the region covers 15,080 km2 and has a population of just under 2 million. The demonym of Calabria in English is Calabrian, in ancient times Calabria was referred to as Italy. The Romans later extended the name to cover Southern Italy and then the entire peninsula, the region is a long and narrow peninsula which stretches from north to south for 248 km, with a maximum width of 110 km. Some 42% of Calabrias area, corresponding to 15,080 km2, is mountainous, 49% is hilly and it is surrounded by the Ionian and Tyrrhenian seas. It is separated from Sicily by the Strait of Messina, where the narrowest point between Capo Peloro in Sicily and Punta Pezzo in Calabria is only 3.2 km, three mountain ranges are present, Pollino, La Sila and Aspromonte. All three mountain ranges are unique with their own flora and fauna, the Pollino Mountains in the north of the region are rugged and form a natural barrier separating Calabria from the rest of Italy. Parts of the area are heavily wooded, while others are vast and these mountains are home to a rare Bosnian Pine variety, and are included in the Pollino National Park. The highest point is Botte Donato, which reaches 1,928 metres, the area boasts numerous lakes and dense coniferous forests. La Sila also has some of the tallest trees in Italy which are called the Giants of the Sila, the Sila National Park is also known to have the purest air in Europe. The Aspromonte massif forms the southernmost tip of the Italian peninsula bordered by the sea on three sides and this unique mountainous structure reaches its highest point at Montalto, at 1,995 metres, and is full of wide, man-made terraces that slope down towards the sea. In general, most of the terrain in Calabria has been agricultural for centuries. The lowest slopes are rich in vineyards and citrus fruit orchards, the Diamante citron is one of the citrus fruits. Moving upwards, olives and chestnut trees appear while in the regions there are often dense forests of oak, pine, beech. Calabrias climate is influenced by the sea and mountains, mountain areas have a typical mountainous climate with frequent snow during winter. Erratic behavior of the Tyrrhenian Sea can bring heavy rainfall on the slopes of the region, while hot air from Africa makes the east coast of Calabria dry. The mountains that run along the region also influence the climate, the east coast is much warmer and has wider temperature ranges than the west coast
6.
Mediterranean Sea
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The sea is sometimes considered a part of the Atlantic Ocean, although it is usually identified as a separate body of water. The name Mediterranean is derived from the Latin mediterraneus, meaning inland or in the middle of land and it covers an approximate area of 2.5 million km2, but its connection to the Atlantic is only 14 km wide. The Strait of Gibraltar is a strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Gibraltar. In oceanography, it is called the Eurafrican Mediterranean Sea or the European Mediterranean Sea to distinguish it from mediterranean seas elsewhere. The Mediterranean Sea has a depth of 1,500 m. The sea is bordered on the north by Europe, the east by Asia and it is located between latitudes 30° and 46° N and longitudes 6° W and 36° E. Its west-east length, from the Strait of Gibraltar to the Gulf of Iskenderun, the seas average north-south length, from Croatia’s southern shore to Libya, is approximately 800 km. The Mediterranean Sea, including the Sea of Marmara, has an area of approximately 2,510,000 square km. The sea was an important route for merchants and travelers of ancient times that allowed for trade, the history of the Mediterranean region is crucial to understanding the origins and development of many modern societies. In addition, the Gaza Strip and the British Overseas Territories of Gibraltar and Akrotiri, the term Mediterranean derives from the Latin word mediterraneus, meaning amid the earth or between land, as it is between the continents of Africa, Asia and Europe. The Ancient Greek name Mesogeios, is similarly from μέσο, between + γη, land, earth) and it can be compared with the Ancient Greek name Mesopotamia, meaning between rivers. The Mediterranean Sea has historically had several names, for example, the Carthaginians called it the Syrian Sea and latter Romans commonly called it Mare Nostrum, and occasionally Mare Internum. Another name was the Sea of the Philistines, from the people inhabiting a large portion of its shores near the Israelites, the sea is also called the Great Sea in the General Prologue by Geoffrey Chaucer. In Ottoman Turkish, it has also been called Bahr-i Sefid, in Modern Hebrew, it has been called HaYam HaTikhon, the Middle Sea, reflecting the Seas name in ancient Greek, Latin, and modern languages in both Europe and the Middle East. Similarly, in Modern Arabic, it is known as al-Baḥr al-Mutawassiṭ, in Turkish, it is known as Akdeniz, the White Sea since among Turks the white colour represents the west. Several ancient civilisations were located around the Mediterranean shores, and were influenced by their proximity to the sea. It provided routes for trade, colonisation, and war, as well as food for numerous communities throughout the ages, due to the shared climate, geology, and access to the sea, cultures centered on the Mediterranean tended to have some extent of intertwined culture and history. Two of the most notable Mediterranean civilisations in classical antiquity were the Greek city states, later, when Augustus founded the Roman Empire, the Romans referred to the Mediterranean as Mare Nostrum
7.
Whirlpool
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A whirlpool is a body of swirling water produced by the meeting of opposing currents. The vast majority of whirlpools are not very powerful and very small whirlpools can easily be seen when a bath or a sink is draining, more powerful ones in seas or oceans may be termed maelstroms. Vortex is the term for any whirlpool that has a downdraft. Smaller whirlpools also appear at the base of waterfalls and can also be observed downstream from manmade structures such as weirs. In the case of waterfalls, like Niagara Falls, these whirlpools can be quite strong. Moskstraumen is a system of whirlpools in the open seas in the Lofoten Islands off the Norwegian coast. It is the second strongest whirlpool in the world with flow currents reaching speeds as high as 32 km/h and it finds mention in several books and movies. The maelstrom of Saltstraumen is the Earths strongest maelstrom, and is located close to the Arctic Circle,33 km round the bay on the Highway 17, south-east of the city of Bodø, Norway. The strait at its narrowest is 150 m in width and water funnels through the four times a day. It is estimated that 400 million cubic meters of water passes the narrow strait during this event, the water is creamy in colour and most turbulent during high tide, which is witnessed by thousands of tourists. It reaches speeds of 40 km/h, with speed of about 13 km/h. As navigation is dangerous in this only a small slot of time is available for large ships to pass through. Its impressive strength is caused by the worlds strongest tide occurring in the location during the new. A narrow channel of 3 km length connects the outer Saltfjord with its extension, the Corryvreckan is a narrow strait between the islands of Jura and Scarba, in Argyll and Bute, on the northern side of the Gulf of Corryvreckan, Scotland. It is the third-largest whirlpool in the world, though it was initially classified as non-navigable by the British navy it was later categorized as extremely dangerous. A documentary team from Scottish independent producers Northlight Productions once threw a mannequin into the Corryvreckan with a life jacket, the mannequin was swallowed and spat up far down current with a depth gauge reading of 262 metres with evidence of being dragged along the bottom for a great distance. Old Sow whirlpool is located between Deer Island, New Brunswick, Canada, and Moose Island, Eastport, Maine and it is given the epithet pig-like as it makes a screeching noise when the vortex is at its full fury. The smaller whirlpools around this Old Sow are known as Piglets. the Naruto whirlpools are located in the Naruto Strait near Awaji Island in Japan, which have speeds of 26 km/h
8.
Scylla
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In Greek mythology, Scylla was a monster that lived on one side of a narrow channel of water, opposite her counterpart Charybdis. The two sides of the strait were within a range of each other—so close that sailors attempting to avoid Charybdis would pass too close to Scylla. Scylla made her first appearance in Homers Odyssey, where Odysseus and his crew encounter her, later myth gave her an origin story as a beautiful nymph who gets turned into a monster. The strait where Scylla dwelled has been associated with the Strait of Messina between Italy and Sicily, the idiom between Scylla and Charybdis has come to mean being forced to choose between two equally dangerous situations. The parentage of Scylla varies according to author, Other authors have Hecate as Scyllas mother. The Hesiodic Megalai Ehoiai gives Hecate and Phorbas as the parents of Scylla, while Acusilaus says that Scyllas parents were Hecate and Phorkys. Perhaps trying to reconcile these accounts, Apollonius of Rhodes says that Crataeis was another name for Hecate. Likewise, Semos of Delos says that Crataeis was the daughter of Hecate and Triton, Stesichorus names Lamia as the mother of Scylla, possibly the Lamia who was the daughter of Poseidon, while according to Hyginus, Scylla was the offspring of Typhon and Echidna. A similar story is found in Hyginus, according to whom Scylla was loved by Glaucus and her body consisted of 12 tentacle-like legs and a cats tail, while four to six dog-heads ringed her waist. In this form, she attacked the ships of passing sailors, in a late Greek myth, recorded in Eustathius commentary on Homer and John Tzetzes, Heracles encountered Scylla during a journey to Sicily and slew her. Her father, the sea-god Phorcys, then applied flaming torches to her body, in Homers Odyssey XII, Odysseus is advised by Circe to sail closer to Scylla, for Charybdis could drown his whole ship, Hug Scyllas crag—sail on past her—top speed. Better by far to lose six men and keep your ship than lose your entire crew, She also tells Odysseus to ask Scyllas mother, the river nymph Crataeis, to prevent Scylla from pouncing more than once. According to Ovid, the fisherman-turned-sea-god Glaucus fell in love with the beautiful Scylla, when he went to Circe to ask for a love potion to win her, the sorceress herself fell in love with him. Meeting with no success, she became jealous of her rival, prepared a vial of poison and poured it in the sea-pool where Scylla bathed. In vain she offers herself to run And drags about her what she strives to shun. The story was adapted into a five-act tragic opera, Scylla et Glaucus. In John Keats loose retelling of Ovids version of the myth of Scylla and Glaucus in Book 3 of Endymion, Glaucus then takes her corpse to a crystal palace at the bottom of the ocean where lie the bodies of all lovers who have died at sea. After a thousand years, she is resurrected by Endymion and reunited with Glaucus, at the Carolingian abbey of Corvey in Westphalia, a unique ninth-century wall painting depicts, among other things, Odysseus fight with Scylla, an illustration not noted elsewhere in medieval arts
9.
Fata Morgana (mirage)
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A Fata Morgana is an unusual and complex form of superior mirage that is seen in a narrow band right above the horizon. Although the term Fata Morgana is sometimes applied to other, more kinds of mirages. Fata Morgana mirages significantly distort the object or objects on which they are based, a Fata Morgana can be seen on land or at sea, in polar regions or in deserts. It can involve almost any kind of distant object, including boats, islands, a Fata Morgana is often rapidly changing. The mirage comprises several inverted and erect images that are stacked on top of one another, Fata Morgana mirages also show alternating compressed and stretched zones. The optical phenomenon occurs because rays of light are bent when they pass through air layers of different temperatures in a thermal inversion where an atmospheric duct has formed. A Fata Morgana requires a duct to be present, thermal inversion alone is not enough to produce this kind of mirage, while a thermal inversion often takes place without there being an atmospheric duct, an atmospheric duct cannot exist without there first being a thermal inversion. A Fata Morgana is most commonly seen in regions, especially over large sheets of ice which have a uniform low temperature. It can, however, be observed in almost any area, in polar regions the Fata Morgana phenomenon is observed on relatively cold days. However, in deserts, over oceans, and over lakes, to generate the Fata Morgana phenomenon, the thermal inversion has to be strong enough that the curvature of the light rays within the inversion layer is stronger than the curvature of the Earth. Under these conditions, the bend and create arcs. An observer needs to be within or below an atmospheric duct in order to be able to see a Fata Morgana, a Fata Morgana can be observed from any altitude within the Earths atmosphere, from sea level up to mountaintops, and even including the view from airplanes. A Fata Morgana can be described as a very complex superior mirage with more than three distorted erect and inverted images. The sequential image here shows sixteen photographic frames of a mirage of the Farallon Islands as seen from San Francisco, in the first fourteen frames, elements of the Fata Morgana mirage display alternations of compressed and stretched zones. The last two frames were photographed few hours later, around sunset time, at that point in time, the air was cooler while the ocean was probably a little bit warmer, which caused the thermal inversion to be not as extreme as it was few hours before. A mirage was still present at that point, but it was not as complex as few hours before sunset, the mirage was no longer a Fata Morgana, but instead had become a simple superior mirage. Gabriel Gruber and Tobias Gruber, who observed Fata Morgana above Lake Cerknica, were the first to study it in a laboratory setting, la Fata Morgana is the name of Morgan le Fay in Italian. Morgan le Fay, alternately known as Morgane, Morgain, Morgana and other variants, was described as a sorceress and antagonist of King Arthur
10.
Bird
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Birds, a subgroup of Reptiles, are the last living examples of Dinosaurs. Birds live worldwide and range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the class of tetrapods with the most living species, at ten thousand. Birds are the closest living relatives of crocodilians, the fossil record indicates that birds evolved from feathered ancestors within the theropod group of saurischian dinosaurs. True birds first appeared during the Cretaceous period, around 100 million years ago, Birds, especially those in the southern continents, survived this event and then migrated to other parts of the world while diversifying during periods of global cooling. Primitive bird-like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid-Jurassic period, around 170 million years ago. Birds have wings which are more or less developed depending on the species, the digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have evolved for swimming. Many species annually migrate great distances, Birds are social, communicating with visual signals, calls, and bird songs, and participating in such social behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of species are socially monogamous, usually for one breeding season at a time, sometimes for years. Other species have breeding systems that are polygynous or, rarely, Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents, most birds have an extended period of parental care after hatching. Some birds, such as hens, lay eggs even when not fertilised, songbirds, parrots, and other species are popular as pets. Guano is harvested for use as a fertiliser, Birds prominently figure throughout human culture. About 120–130 species have become extinct due to human activity since the 17th century, human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry, the first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae. Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use, Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda, Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria
11.
Volt
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The volt is the derived unit for electric potential, electric potential difference, and electromotive force. One volt is defined as the difference in potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can also be expressed as amperes times ohms, watts per ampere, or joules per coulomb, for the Josephson constant, KJ = 2e/h, the conventional value KJ-90 is used, K J-90 =0.4835979 GHz μ V. This standard is typically realized using an array of several thousand or tens of thousands of junctions. Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc. in the water-flow analogy sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage is likened to difference in water pressure. Current is proportional to the diameter of the pipe or the amount of water flowing at that pressure. A resistor would be a reduced diameter somewhere in the piping, the relationship between voltage and current is defined by Ohms Law. Ohms Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems, the voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell. Cells can be combined in series for multiples of that voltage, mechanical generators can usually be constructed to any voltage in a range of feasibility. High-voltage electric power lines,110 kV and up Lightning, Varies greatly. Volta had determined that the most effective pair of metals to produce electricity was zinc. In 1861, Latimer Clark and Sir Charles Bright coined the name volt for the unit of resistance, by 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission and they made the volt equal to 108 cgs units of voltage, the cgs system at the time being the customary system of units in science. At that time, the volt was defined as the difference across a conductor when a current of one ampere dissipates one watt of power. The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell and this definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of reproducible units was abandoned in 1948. Prior to the development of the Josephson junction voltage standard, the volt was maintained in laboratories using specially constructed batteries called standard cells
12.
Overhead power line
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An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy along large distances. It consists of one or more conductors suspended by towers or poles, since most of the insulation is provided by air, overhead power lines are generally the lowest-cost method of power transmission for large quantities of electric energy. Towers for support of the lines are made of wood, steel or aluminum, concrete, the bare wire conductors on the line are generally made of aluminum, though some copper wires are used in medium-voltage distribution and low-voltage connections to customer premises. Today overhead lines are operated at voltages exceeding 765,000 volts between conductors, with even higher voltages possible in some cases. Medium voltage – between 1000 volts and 69 kV, used for distribution in urban and rural areas, high voltage, used for sub-transmission and transmission of bulk quantities of electric power and connection to very large consumers. Extra high voltage – over 230 kV, up to about 800 kV, used for long distance, ultra high voltage – higher than 800 kV. Structures for overhead lines take a variety of shapes depending on the type of line, tubular steel poles are typically used in urban areas. High-voltage lines are carried on lattice-type steel towers or pylons. For remote areas, aluminum towers may be placed by helicopters, concrete poles have also been used. Poles made of reinforced plastics are available, but their high cost restricts application. Each structure must be designed for the loads imposed on it by the conductors, the weight of the conductor must be supported, as well as dynamic loads due to wind and ice accumulation, and effects of vibration. Where conductors are in a line, towers need only resist the weight since the tension in the conductors approximately balances with no resultant force on the structure. Flexible conductors supported at their ends approximate the form of a catenary, depending on the design criteria for a particular line, semi-flexible type structures may rely on the weight of the conductors to be balanced on both sides of each tower. More rigid structures may be intended to remain standing even if one or more conductors is broken, such structures may be installed at intervals in power lines to limit the scale of cascading tower failures. Foundations for tower structures may be large and costly, particularly if the conditions are poor. Each structure may be stabilized considerably by the use of guy wires to counteract some of the forces applied by the conductors, Power lines and supporting structures can be a form of visual pollution. In some cases the lines are buried to avoid this, but this undergrounding is more expensive, for a single wood utility pole structure, a pole is placed in the ground, then three crossarms extend from this, either staggered or all to one side. The insulators are attached to the crossarms, for an H-type wood pole structure, two poles are placed in the ground, then a crossbar is placed on top of these, extending to both sides
