For the wreath used in heraldry, see torse. A wreath is an assortment of flowers, fruits, twigs, or various materials, constructed to form a ring. In English-speaking countries, wreaths are used as household ornaments, most as an Advent and Christmas decoration, they are used in ceremonial events in many cultures around the globe. They can be worn as a garland around the neck. Wreaths have much symbolism associated with them, they are made from evergreens and symbolize strength, as evergreens last throughout the harshest winters. Bay laurel may be used; the word wreath comes from Old English writha, band. Wreaths were a design used in ancient times in southern Europe; the most well-known are pieces of Etruscan civilization jewelry, made of gold or other precious metals. Symbols from Greek myths appear in the designs, embossed in precious metal at the ends of the wreath. Ancient Roman writers referred to Etruscan corona sutilis, which were wreaths with their leaves sewn onto a background; these wreaths resemble a diadem, with thin metal leaves being attached to an ornamental band.
Wreaths appear stamped into Etruscan medallions. The plants shown making the wreaths in Etruscan jewelry include ivy, olive leaves, laurel and vines. Wreaths were worn as crowns by Etruscan rulers; the Etruscan symbolism continued to be used in Ancient Rome. Roman magistrates wore golden wreaths as crowns, as a symbolic testament to their lineage back to Rome's early Etruscan rulers. Roman magistrates used several other prominent Etruscan symbols in addition to a golden wreath crown: fasces, a curule chair, a purple toga, an ivory rod. In the Greco-Roman world, wreaths were used as an adornment that could represent a person’s occupation, their achievements and status; the wreath, used was the laurel wreath. The use of this wreath comes from the Greek myth involving Apollo, Zeus’ son and the god of life and light, who fell in love with the nymph Daphne; when he pursued her she asked the river god Peneus to help her. Peneus turned her into a laurel tree. From that day, Apollo wore a wreath of laurel on his head.
Laurel wreaths became associated with what Apollo embodied. Laurel wreaths were used to crown victorious athletes at the original Olympic Games and are still worn in Italy by university students who just graduated. Other types of plants used to make wreath crowns had symbolic meaning. For example, oak leaves symbolized wisdom, were associated with Zeus, who according to Greek mythology made his decisions while resting in an oak grove; the Twelve Tables, dating to 450 BC, refer to funeral wreaths as a long-standing tradition. Olive wreath was the prize for the winner at the ancient Olympic Games. Harvest wreaths, a common household decoration today, are a custom with ancient roots in Europe; the creation of harvest wreaths in Europe can be traced back to ancient times, is associated with animistic spiritual beliefs. In Ancient Greece, the harvest wreath was a sacred amulet, using wheat or other harvested plants, woven together with red and white wool thread; the harvest wreath would be hung by the door year-round.
Harvest wreaths were an important symbol to the community in Ancient Greece, not to the farmer and his family. The festivals devoted to Dionysus, the Oschophoria and Anthesteria, included a ritual procession called the eiresîonê. A harvest wreath was carried to Pyanopsia and Thargelia by young boys, who would sing during the journey; the laurel or olive wreath would be hung at the door, offerings were made to Helios and the Hours. It was hoped. In Poland, the harvest wreath is a central symbol of the Harvest Dozynki. Wreaths are made of different shapes and sizes, using harvested grain plants and nuts; the wreath is brought to a church for a blessing by a priest. The tradition includes a procession to the family home from the church, with a girl or young woman leading the procession and carrying the wreath; the procession is followed with a feast. Ukraine and other Eastern Europe cultures have similar rituals that began as part of pre-Christian culture. In Christianity, wreaths are used to observe the Advent season, in preparation for Christmastide and Epiphanytide, as well as to celebrate the latter two liturgical seasons.
These wreaths, as with other Advent and Christmas decorations, are set up on the first Sunday of Advent, a custom, sometimes done liturgically, through a hanging of the greens ceremony. The Advent wreath was first used by Lutherans in Germany in the 16th century, in 1839, Lutheran priest Johann Hinrich Wichern used a wreath made from a cart wheel to educate children about the meaning and purpose of Christmas, as well as to help them count its approach, thus giving rise to the modern version of the Advent wreath. For every Sunday of Advent, starting with the fourth Sunday before Christmas, he would put a white candle in the wreath and for every day in between he would use a red candle; the use of the Advent wreath has since spread from the Lutheran Church to many Christian denominations, some of these traditions, such as the Catholic Church and Moravian Church, have introduced unique variations to it. All of the Advent wreaths, have four candles, many of them have a white candle in the centre, the Christ candle, lit on Christmas Day.
Advent and Christmas wreaths are con
Snow refers to forms of ice crystals that precipitate from the atmosphere and undergo changes on the Earth's surface. It pertains to frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size and accumulate on surfaces metamorphose in place, melt, slide or sublimate away. Snowstorms develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a variety of shapes, basic among these are platelets, needles and rime; as snow accumulates into a snowpack, it may blow into drifts. Over time, accumulated snow metamorphoses, by sintering and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form. Otherwise, snow melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the polar regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture and cold temperatures.
In the Southern Hemisphere, snow is confined to mountainous areas, apart from Antarctica. Snow affects such human activities as transportation: creating the need for keeping roadways and windows clear. Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds; the physics of snow crystal development in clouds results from a complex set of variables that include moisture content and temperatures. The resulting shapes of the falling and fallen crystals can be classified into a number of basic shapes and combinations, thereof; some plate-like and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Snow clouds occur in the context of larger weather systems, the most important of, the low pressure area, which incorporate warm and cold fronts as part of their circulation. Two additional and locally productive sources of snow are lake-effect storms and elevation effects in mountains.
Mid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemisphere's fall and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall. In the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side. A cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface; the strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall lasts less than 30 minutes at any point along its path but the motion of the line can cover large distances. Frontal squalls may form a short distance ahead of the surface cold front or behind the cold front where there may be a deepening low pressure system or a series of trough lines which act similar to a traditional cold frontal passage.
In situations where squalls develop post-frontally it is not unusual to have two or three linear squall bands pass in rapid succession only separated by 25 miles with each passing the same point in 30 minutes apart. In cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder, dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air and creates precipitation at the boundary. Snow transitions to rain in the warm sector behind the front. Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water, warming the lower layer of air which picks up water vapor from the lake, rises up through the colder air above, freezes and is deposited on the leeward shores; the same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the moving air mass is uplifted by the orographic influence of higher elevations on the downwind shores.
This uplifting can produce narrow but intense bands of precipitation, which deposit at a rate of many inches of snow each hour resulting in a large amount of total snowfall. The areas affected by lake-effect snow are called snowbelts; these include areas east of the Great Lakes, the west coasts of northern Japan, the Kamchatka Peninsula in Russia, areas near the Great Salt Lake, Black Sea, Caspian Sea, Baltic Sea, parts of the northern Atlantic Ocean. Orographic or relief snowfall is caused when masses of air pushed by wind are forced up the side of elevated land formations, such as large mountains; the lifting of air up the side of a mountain or range results in adiabatic cooling, condensation and precipitation. Moisture is removed by orographic lift, leaving drier, warmer air on the leeward side; the resulting enhanced productivity of snow fall and the decrease in temperature with elevation means that snow depth
Nynorsk is one of the two written standards of the Norwegian language, the other being Bokmål. Nynorsk was established in 1929 as one of two state sanctioned fusions of Ivar Aasen's standard Norwegian language with the Dano-Norwegian written language, the other such fusion being called Bokmål. Nynorsk is a variation, closer to Landsmål, whereas Bokmål is closer to Riksmål. In local communities, one quarter of Norwegian municipalities have declared Nynorsk as their official language form, these municipalities account for about 12% of the Norwegian population. Nynorsk is being taught as a mandatory subject in both high school and elementary school for all Norwegians who don't have it as their own language form. Of the remaining municipalities that don't have Nynorsk as their official language form, half are neutral and half have adopted Bokmål as their official language form. Four of Norway's eighteen counties, Hordaland, Sogn og Fjordane and Møre og Romsdal, have Nynorsk as their official language form.
These four together comprise the region of Western Norway. Danish had been the written language of Norway until 1814, Danish with Norwegian intonation and pronunciation was on occasion spoken in the cities. With the independence of Norway from Denmark, Danish became a foreign language and thus lost much of its prestige, a conservative, written form of Norwegian, Landsmål, had been developed by 1850. By this time, the Danish language had been reformed into the written language Riksmål, no agreement was reached on which of the two forms to use. In 1885, the parliament declared the two forms equal. Efforts were made to fuse the two written forms into one language. A result was that Landsmål and Riksmål lost their official status in 1929, were replaced by the written forms Nynorsk and Bokmål, which were intended to be temporary intermediary stages before their final fusion into one hypothesised official Norwegian language known at the time as Samnorsk; this project was abandoned and Nynorsk and Bokmål remain the two sanctioned standards of what is today called the Norwegian language.
Both written languages are in reality fusions between the Norwegian and Danish languages as they were spoken and written around 1850, with Nynorsk closer to Norwegian and Bokmål closer to Danish. The official standard of Nynorsk has been altered during the process to create the common language form Samnorsk. A minor purist fraction of the Nynorsk population has stayed firm with the historical Aasen norm where these alterations of Nynorsk were rejected, known as Høgnorsk. Ivar Aasen-sambandet is an umbrella organization of associations and individuals promoting the use of Høgnorsk, whereas Noregs Mållag and Norsk Målungdom advocate the use of Nynorsk in general; the Landsmål language standard was constructed by the Norwegian linguist Ivar Aasen during the mid-19th century, to provide a Norwegian-based alternative to Danish, written, to some extent spoken, in Norway at the time. The word Nynorsk has another meaning. In addition to being the name of the present, official written language standard, Nynorsk can refer to the Norwegian language in use after Old Norwegian, 11th to 14th centuries, Middle Norwegian, 1350 to about 1550.
The written Norwegian, used until the period of Danish rule resembles Nynorsk. A major source of old written material is Diplomatarium Norvegicum in 22 printed volumes. In 1749, Erik Pontoppidan released a comprehensive dictionary of Norwegian words that were incomprehensible to Danish people, Glossarium Norvagicum Eller Forsøg paa en Samling Af saadanne rare Norske Ord Som gemeenlig ikke forstaaes af Danske Folk, Tilligemed en Fortegnelse paa Norske Mænds og Qvinders Navne, it is acknowledged that the first systematic study of the Norwegian language was made by Ivar Aasen in the mid 19th century. After the dissolution of Denmark–Norway and the establishment of the union between Sweden and Norway in 1814, Norwegians considered that neither Danish, by now a foreign language, nor by any means Swedish, were suitable written norms for Norwegian affairs; the linguist Knud Knudsen proposed a gradual Norwegianisation of Danish. Ivar Aasen, favoured a more radical approach, based on the principle that the spoken language of people living in the Norwegian countryside, who made up the vast majority of the population, should be regarded as more Norwegian than that of upper-middle class city-dwellers, who for centuries had been influenced by the Danish language and culture.
This idea was not unique to Aasen, can be seen in the wider context of Norwegian romantic nationalism. In the 1840s Aasen studied its dialects. In 1848 and 1850 he published the first Norwegian grammar and dictionary which described a standard that Aasen called Landsmål. New versions detailing the written standard were published in 1864 and 1873, in the 20th century by Olav Beito in 1970. During the same period, Venceslaus Ulricus Hammershaimb standardised the orthography of the Faroese language. Spoken Faroese is related to Landsmål and dialects in Norway proper, Lucas Debes and Peder Hansen Resen classified the Faroese tongue as Norwegian in the late 17th century. However, Faroese was established as a separate language. Aasen's work is based on the idea that Norwegian dialects had a common structure that made them a separate language alongside Danish and Swedish; the central point for Aasen therefore became to find and show the structural dependencies between the dialects. In order t
Bokmål is an official written standard for the Norwegian language, alongside Nynorsk. Bokmål is the preferred written standard of Norwegian for 85% to 90% of the population in Norway. Unlike for instance the Italian language, there is no nationwide standard or agreement on the pronunciation of Bokmål. Bokmål is regulated by the governmental Norwegian Language Council. A more conservative orthographic standard known as Riksmål, is regulated by the non-governmental Norwegian Academy for Language and Literature; the written standard is a Norwegianised variety of the Danish language. The first Bokmål orthography was adopted in 1907 under the name Riksmål after being under development since 1879; the architects behind the reform were Jacob Jonathan Aars. It was an adaptation of written Danish, used since the past union with Denmark, to the Dano-Norwegian koiné spoken by the Norwegian urban elite in the capital; when the large conservative newspaper Aftenposten adopted the 1907 orthography in 1923, Danish writing was out of use in Norway.
The name Bokmål was adopted in 1929 after a proposition to call the written language Dano-Norwegian lost by a single vote in the Lagting. The government does not regulate spoken Bokmål and recommends that normalised pronunciation should follow the phonology of the speaker's local dialect. There is a spoken variety of Norwegian that, in the region of South-Eastern Norway, is seen as the de facto standard for spoken Bokmål. In The Phonology of Norwegian, Gjert Kristoffersen writes that Bokmål is in its most common variety looked upon as reflecting formal middle-class urban speech that found in the eastern part of Southern Norway, with the capital Oslo as the obvious centre. One can therefore say that Bokmål has a spoken realisation that one might call an unofficial standard spoken Norwegian, it is in fact referred to as Standard Østnorsk. Standard Østnorsk is the pronunciation most given in dictionaries and taught to foreigners in Norwegian language classes. Standard Østnorsk as a spoken language is not used and does not have any particular prestige outside South-Eastern Norway.
All spoken variations of the Norwegian language are used e.g. in the Storting and in Norwegian national broadcasters such as NRK and TV 2 in cases where the conventions of Bokmål are used. The spoken variation reflects the region the person grew up in. Up until about 1300, the written language of Norway, Old Norwegian, was the same as the other Old Norse dialects; the speech, was differentiated into local and regional dialects. As long as Norway remained an independent kingdom, the written language remained constant. In 1380, Norway entered into a personal union with Denmark. By the early 16th century, Norway had lost its separate political institutions, together with Denmark formed the political unit known as Denmark–Norway until 1814, progressively becoming the weaker member of the union. During this period, the modern Danish and Norwegian languages emerged. Norwegian went through a Middle Norwegian transition, a Danish written language more influenced by Low German was standardised; this process was aided by the Reformation, which prompted Christiern Pedersen's translation of the Bible into Danish.
Remnants of written Old Norse and Norwegian were thus displaced by the Danish standard, which became used for all administrative documents. Norwegians used Danish in writing, but it came to be spoken by urban elites on formal or official occasions. Although Danish never became the spoken language of the vast majority of the population, by the time Norway's ties with Denmark were severed in 1814, a Dano-Norwegian vernacular called the "educated daily speech" had become the mother tongue of elites in most Norwegian cities, such as Bergen and Trondheim; this Dano-Norwegian koiné could be described as Danish with regional Norwegian pronunciation, some Norwegian vocabulary, simplified grammar. With the gradual subsequent process of Norwegianisation of the written language used in the cities of Norway, from Danish to Bokmål and Riksmål, the upper-class sociolects in the cities changed accordingly. In 1814, when Norway was ceded from Denmark to Sweden, Norway defied Sweden and her allies, declared independence and adopted a democratic constitution.
Although compelled to submit to a dynastic union with Sweden, this spark of independence continued to burn, influencing the evolution of language in Norway. Old language traditions were revived by the patriotic poet Henrik Wergeland, who championed an independent non-Danish written language. Haugen indicates that: "Within the first generation of liberty, two solutions emerged and won adherents, one based on the speech of the upper class and one on that of the common people; the former called for Norwegianisation of the Danish writing, the latter for a brand new start." The more conservative of the two language transitions was advanced by the work of writers like Peter Asbjørnsen and Jørgen Moe and agitator for language reform Knud Knudsen, Knudsen's famous disciple, Bjørnstjerne Bjørnson, as well as a more cautious Norwegianisation by Henrik Ibsen. In particular, Knudsen's work on language reform in the mid-19th century was important for the 1907 orthography and a subsequent reform in 1917, so much so that he is now called the "father of Bokmål".
The term Riksmål, meaning National Language, was first proposed by Bjørnstjerne Bjørnson in 1899 as a name for the Norwegian variety of written Da
An aurora, sometimes referred to as polar lights, northern lights, southern lights, is a natural light display in the Earth's sky, predominantly seen in the high-latitude regions. Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind that the trajectories of charged particles in both solar wind and magnetospheric plasma in the form of electrons and protons, precipitate them into the upper atmosphere due to Earth's magnetic field, where their energy is lost; the resulting ionization and excitation of atmospheric constituents emits light of varying color and complexity. The form of the aurora, occurring within bands around both polar regions, is dependent on the amount of acceleration imparted to the precipitating particles. Precipitating protons produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton auroras are observed at lower latitudes; the word "aurora" is derived from the name of the Roman goddess of the dawn, who traveled from east to west announcing the coming of the sun.
Ancient Roman poets used the name metaphorically to refer to dawn mentioning its play of colours across the otherwise dark sky. Most auroras occur in a band known as the "auroral zone", 3° to 6° wide in latitude and between 10° and 20° from the geomagnetic poles at all local times, most seen at night against a dark sky. A region that displays an aurora is called the "auroral oval", a band displaced towards the night side of the Earth. Early evidence for a geomagnetic connection comes from the statistics of auroral observations. Elias Loomis, Hermann Fritz and S. Tromholt in more detail, established that the aurora appeared in the auroral zone. Day-to-day positions of the auroral ovals are posted on the Internet. In northern latitudes, the effect is known as the northern lights; the former term was coined by Galileo in 1619, from the Roman goddess of the dawn and the Greek name for the north wind. The southern counterpart, the aurora australis or the southern lights, has features identical to the aurora borealis and changes with changes in the northern auroral zone.
The Aurora Australis is visible from high southern latitudes in Antarctica, Argentina, New Zealand, Australia. A geomagnetic storm causes the auroral ovals to expand, bring the aurora to lower latitudes; the instantaneous distribution of auroras is different, being centered about 3–5° nightward of the magnetic pole, so that auroral arcs reach furthest toward the equator when the magnetic pole in question is in between the observer and the Sun. The aurora can be seen best at this time, called magnetic midnight. Auroras seen within the auroral oval may be directly overhead, but from farther away, they illuminate the poleward horizon as a greenish glow, or sometimes a faint red, as if the Sun were rising from an unusual direction. Auroras occur poleward of the auroral zone as either diffuse patches or arcs, which can be subvisual. Auroras are seen in latitudes below the auroral zone, when a geomagnetic storm temporarily enlarges the auroral oval. Large geomagnetic storms are most common during the peak of the 11-year sunspot cycle or during the three years after the peak.
An aurora may appear overhead as a "corona" of rays, radiating from a distant and apparent central location, which results from perspective. An electron spirals about a field line at an angle, determined by its velocity vectors and perpendicular to the local geomagnetic field vector B; this angle is known as the "pitch angle" of the particle. The distance, or radius, of the electron from the field line at any time is known as its Larmor radius; the pitch angle increases as the electron travels to a region of greater field strength nearer to the atmosphere. Thus, it is possible for some particles to return, or mirror, if the angle becomes 90° before entering the atmosphere to collide with the denser molecules there. Other particles that do not mirror enter the atmosphere and contribute to the auroral display over a range of altitudes. Other types of auroras have been observed from space, e.g."poleward arcs" stretching sunward across the polar cap, the related "theta aurora", "dayside arcs" near noon.
These are infrequent and poorly understood. Other interesting effects occur such as flickering "black aurora" and subvisual red arcs. In addition to all these, a weak glow observed around the two polar cusps, the field lines separating the ones that close through the Earth from those that are swept into the tail and close remotely; the altitudes where auroral emissions occur were revealed by Carl Størmer and his colleagues, who used cameras to triangulate more than 12,000 auroras. They discovered that most of the light is produced between 90 and 150 km above the ground, while extending at times to more than 1000 km. Images of auroras are more common today than in the past due to the increase in the use of digital cameras that have high enough sensitivities. Film and digital exposure to auroral displays is fraught with difficulties. Due to the different color spectra present, the temporal changes occurring during the exposure, the results are somewhat unpredictable. Different layers of the film emulsion respond differently to lower light levels, choice of a film can be important.
Longer exposures superimpose changing features, blanket the dynamic attribute of a display. Hi
Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments; the most familiar effects occur in ferromagnetic materials, which are attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Only a few substances are ferromagnetic; the prefix ferro- refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4. Although ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, all other materials are influenced to some extent by a magnetic field, by several other types of magnetism. Paramagnetic substances such as aluminum and oxygen are weakly attracted to an applied magnetic field; the force of a magnet on paramagnetic and antiferromagnetic materials is too weak to be felt, can be detected only by laboratory instruments, so in everyday life these substances are described as non-magnetic.
The magnetic state of a material depends on temperature and other variables such as pressure and the applied magnetic field. A material may exhibit more than one form of magnetism as these variables change; as with magnetising a magnet, demagnetising a magnet is possible. "Passing an alternate current, or hitting a heated magnet in an east west direction are ways of demagnetising a magnet", quotes Sreekethav. Magnetism was first discovered in the ancient world, when people noticed that lodestones magnetized pieces of the mineral magnetite, could attract iron; the word magnet comes from the Greek term μαγνῆτις λίθος magnētis lithos, "the Magnesian stone, lodestone." In ancient Greece, Aristotle attributed the first of what could be called a scientific discussion of magnetism to the philosopher Thales of Miletus, who lived from about 625 BC to about 545 BC. The ancient Indian medical text Sushruta Samhita describes using magnetite to remove arrows embedded in a person's body. In ancient China, the earliest literary reference to magnetism lies in a 4th-century BC book named after its author, The Sage of Ghost Valley.
The 2nd-century BC annals, Lüshi Chunqiu notes: "The lodestone makes iron approach, or it attracts it." The earliest mention of the attraction of a needle is in a 1st-century work Lunheng: "A lodestone attracts a needle." The 11th-century Chinese scientist Shen Kuo was the first person to write—in the Dream Pool Essays—of the magnetic needle compass and that it improved the accuracy of navigation by employing the astronomical concept of true north. By the 12th century the Chinese were known to use the lodestone compass for navigation, they sculpted a directional spoon from lodestone in such a way that the handle of the spoon always pointed south. Alexander Neckam, by 1187, was the first in Europe to describe the compass and its use for navigation. In 1269, Peter Peregrinus de Maricourt wrote the Epistola de magnete, the first extant treatise describing the properties of magnets. In 1282, the properties of magnets and the dry compasses were discussed by Al-Ashraf, a Yemeni physicist and geographer.
In 1600, William Gilbert published his De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure. In this work he describes many of his experiments with his model earth called the terrella. From his experiments, he concluded that the Earth was itself magnetic and that this was the reason compasses pointed north. An understanding of the relationship between electricity and magnetism began in 1819 with work by Hans Christian Ørsted, a professor at the University of Copenhagen, who discovered by the accidental twitching of a compass needle near a wire that an electric current could create a magnetic field; this landmark experiment is known as Ørsted's Experiment. Several other experiments followed, with André-Marie Ampère, who in 1820 discovered that the magnetic field circulating in a closed-path was related to the current flowing through the perimeter of the path. James Clerk Maxwell synthesized and expanded these insights into Maxwell's equations, unifying electricity and optics into the field of electromagnetism.
In 1905, Einstein used these laws in motivating his theory of special relativity, requiring that the laws held true in all inertial reference frames. Electromagnetism has continued to develop into the 21st century, being incorporated into the more fundamental theories of gauge theory, quantum electrodynamics, electroweak theory, the standard model. Magnetism, at its root, arises from two sources: Electric current. Spin magnetic moments of elementary particles; the magnetic properties of materials are due to the magnetic moments of their atoms' orbiting electrons. The magnetic moments of the nuclei of atoms are thousands of times smaller than the electro
Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering 9.98 million square kilometres, making it the world's second-largest country by total area. Canada's southern border with the United States is the world's longest bi-national land border, its capital is Ottawa, its three largest metropolitan areas are Toronto and Vancouver. As a whole, Canada is sparsely populated, the majority of its land area being dominated by forest and tundra, its population is urbanized, with over 80 percent of its inhabitants concentrated in large and medium-sized cities, many near the southern border. Canada's climate varies across its vast area, ranging from arctic weather in the north, to hot summers in the southern regions, with four distinct seasons. Various indigenous peoples have inhabited what is now Canada for thousands of years prior to European colonization. Beginning in the 16th century and French expeditions explored, settled, along the Atlantic coast.
As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces; this began an accretion of provinces and territories and a process of increasing autonomy from the United Kingdom. This widening autonomy was highlighted by the Statute of Westminster of 1931 and culminated in the Canada Act of 1982, which severed the vestiges of legal dependence on the British parliament. Canada is a parliamentary democracy and a constitutional monarchy in the Westminster tradition, with Elizabeth II as its queen and a prime minister who serves as the chair of the federal cabinet and head of government; the country is a realm within the Commonwealth of Nations, a member of the Francophonie and bilingual at the federal level. It ranks among the highest in international measurements of government transparency, civil liberties, quality of life, economic freedom, education.
It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries. Canada's long and complex relationship with the United States has had a significant impact on its economy and culture. A developed country, Canada has the sixteenth-highest nominal per capita income globally as well as the twelfth-highest ranking in the Human Development Index, its advanced economy is the tenth-largest in the world, relying chiefly upon its abundant natural resources and well-developed international trade networks. Canada is part of several major international and intergovernmental institutions or groupings including the United Nations, the North Atlantic Treaty Organization, the G7, the Group of Ten, the G20, the North American Free Trade Agreement and the Asia-Pacific Economic Cooperation forum. While a variety of theories have been postulated for the etymological origins of Canada, the name is now accepted as coming from the St. Lawrence Iroquoian word kanata, meaning "village" or "settlement".
In 1535, indigenous inhabitants of the present-day Quebec City region used the word to direct French explorer Jacques Cartier to the village of Stadacona. Cartier used the word Canada to refer not only to that particular village but to the entire area subject to Donnacona. From the 16th to the early 18th century "Canada" referred to the part of New France that lay along the Saint Lawrence River. In 1791, the area became two British colonies called Upper Canada and Lower Canada collectively named the Canadas. Upon Confederation in 1867, Canada was adopted as the legal name for the new country at the London Conference, the word Dominion was conferred as the country's title. By the 1950s, the term Dominion of Canada was no longer used by the United Kingdom, which considered Canada a "Realm of the Commonwealth"; the government of Louis St. Laurent ended the practice of using'Dominion' in the Statutes of Canada in 1951. In 1982, the passage of the Canada Act, bringing the Constitution of Canada under Canadian control, referred only to Canada, that year the name of the national holiday was changed from Dominion Day to Canada Day.
The term Dominion was used to distinguish the federal government from the provinces, though after the Second World War the term federal had replaced dominion. Indigenous peoples in present-day Canada include the First Nations, Métis, the last being a mixed-blood people who originated in the mid-17th century when First Nations and Inuit people married European settlers; the term "Aboriginal" as a collective noun is a specific term of art used in some legal documents, including the Constitution Act 1982. The first inhabitants of North America are hypothesized to have migrated from Siberia by way of the Bering land bridge and arrived at least 14,000 years ago; the Paleo-Indian archeological sites at Old Crow Flats and Bluefish Caves are two of the oldest sites of human habitation in Canada. The characteristics of Canadian indigenous societies included permanent settlements, complex societal hierarchies, trading networks; some of these cultures had collapsed by the time European explorers arrived in the late 15th and early 16th centuries and have only been discovered through archeological investigations.
The indigenous population at the time of the first European settlements is estimated to have been between 200,000