1.
Czech language
–
Czech, historically also Bohemian, is a West Slavic language of the Czech–Slovak group. It is spoken by over 10 million people and is the language of the Czech Republic. Czech is closely related to Slovak, to the point of being intelligible to a very high degree. In the later 18th to mid-19th century, the written standard was codified in the context of the Czech National Revival. The main vernacular, known as Common Czech, is based on the vernacular of Prague, the Moravian dialects spoken in the eastern part of the country are mostly also counted as Czech, although some of their eastern variants are closer to Slovak. The Czech phoneme inventory is moderate in size, comprising five vowels, words may contain uncommon consonant clusters, including one consonant represented by the grapheme ř, or lack vowels altogether. Czech orthography is simple, and has used as a model by phonologists. Czech is classified as a member of the West Slavic sub-branch of the Slavic branch of the Indo-European language family and this branch includes Polish, Kashubian, Upper and Lower Sorbian and Slovak. Slovak is by far the closest genetic neighbor of Czech, the West Slavic languages are spoken in an area classified as part of Central Europe. Around the 7th century, the Slavic expansion reached Central Europe, the West Slavic polity of Great Moravia formed by the 9th century. The Christianization of Bohemia took place during the 9th and 10th centuries, the Bohemian language is first recorded in writing in glosses and short notes during the 12th to 13th centuries. Literary works written in Czech appear in the early 14th century, the first complete Bible translation also dates to this period. Old Czech texts, including poetry and cookbooks, were produced outside the university as well, literary activity becomes widespread in the early 15th century in the context of the Bohemian Reformation. There was no standardization distinguishing between Czech and Slovak prior to the 15th century, the publication of the Kralice Bible between 1579 and 1593 became very important for standardization of the Czech language in the following centuries. In 1615, the Bohemian diet tried to declare Czech to be the official language of the kingdom. After the Bohemian Revolt which was defeated by the Habsburgs in 1620 and this emigration together with other consequences of the Thirty Years War had a negative impact on the further use of the Czech language. In 1627, Czech and German became official languages of the Kingdom of Bohemia and in the 18th century German became dominant in Bohemia and Moravia, the modern standard Czech language originates in standardization efforts of the 18th century. Changes include the shift of í to ej and é to í and the merging of í
Czech language
–
The
Bible of Kralice was the first complete
translation of the Bible into the Czech language. Its six volumes were first published between 1579 and 1593.
Czech language
–
regions where Czech is the language of the majority
Czech language
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Jan Hus
Czech language
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Josef Dobrovský, whose writing played a key role in reviving Czech as a written language
2.
Medieval
–
In the history of Europe, the Middle Ages or Medieval Period lasted from the 5th to the 15th century. It began with the fall of the Western Roman Empire and merged into the Renaissance, the Middle Ages is the middle period of the three traditional divisions of Western history, classical antiquity, the medieval period, and the modern period. The medieval period is subdivided into the Early, High. Population decline, counterurbanisation, invasion, and movement of peoples, the large-scale movements of the Migration Period, including various Germanic peoples, formed new kingdoms in what remained of the Western Roman Empire. In the seventh century, North Africa and the Middle East—once part of the Byzantine Empire—came under the rule of the Umayyad Caliphate, although there were substantial changes in society and political structures, the break with classical antiquity was not complete. The still-sizeable Byzantine Empire survived in the east and remained a major power, the empires law code, the Corpus Juris Civilis or Code of Justinian, was rediscovered in Northern Italy in 1070 and became widely admired later in the Middle Ages. In the West, most kingdoms incorporated the few extant Roman institutions, monasteries were founded as campaigns to Christianise pagan Europe continued. The Franks, under the Carolingian dynasty, briefly established the Carolingian Empire during the later 8th, the Crusades, first preached in 1095, were military attempts by Western European Christians to regain control of the Holy Land from Muslims. Kings became the heads of centralised nation states, reducing crime and violence, intellectual life was marked by scholasticism, a philosophy that emphasised joining faith to reason, and by the founding of universities. Controversy, heresy, and the Western Schism within the Catholic Church paralleled the conflict, civil strife. Cultural and technological developments transformed European society, concluding the Late Middle Ages, the Middle Ages is one of the three major periods in the most enduring scheme for analysing European history, classical civilisation, or Antiquity, the Middle Ages, and the Modern Period. Medieval writers divided history into periods such as the Six Ages or the Four Empires, when referring to their own times, they spoke of them as being modern. In the 1330s, the humanist and poet Petrarch referred to pre-Christian times as antiqua, leonardo Bruni was the first historian to use tripartite periodisation in his History of the Florentine People. Bruni and later argued that Italy had recovered since Petrarchs time. The Middle Ages first appears in Latin in 1469 as media tempestas or middle season, in early usage, there were many variants, including medium aevum, or middle age, first recorded in 1604, and media saecula, or middle ages, first recorded in 1625. The alternative term medieval derives from medium aevum, tripartite periodisation became standard after the German 17th-century historian Christoph Cellarius divided history into three periods, Ancient, Medieval, and Modern. The most commonly given starting point for the Middle Ages is 476, for Europe as a whole,1500 is often considered to be the end of the Middle Ages, but there is no universally agreed upon end date. English historians often use the Battle of Bosworth Field in 1485 to mark the end of the period
Medieval
–
The
Cross of Mathilde, a
crux gemmata made for
Mathilde, Abbess of Essen (973–1011), who is shown kneeling before the Virgin and Child in the
enamel plaque. The body of Christ is slightly later. Probably made in
Cologne or
Essen, the cross demonstrates several medieval techniques:
cast figurative sculpture,
filigree, enamelling, gem polishing and setting, and the reuse of Classical
cameos and
engraved gems.
Medieval
–
A late Roman statue
depicting the four Tetrarchs, now in
Venice
Medieval
–
Coin of
Theodoric
Medieval
–
Mosaic showing
Justinian with
the bishop of
Ravenna, bodyguards, and courtiers
3.
Astronomical clock
–
The term is loosely used to refer to any clock that shows, in addition to the time of day, astronomical information. The term should not be confused with astronomical regulator, a high precision, Astronomical clocks usually represent the solar system using the geocentric model. The center of the dial is marked with a disc or sphere representing the earth. The sun is represented by a golden sphere, shown rotating around the earth once a day around a 24-hour analog dial. This view accords both with daily experience and with the world view of pre-Copernican Europe. Research in 2011 and 2012 led a group of researchers to posit that European astronomical clocks are descended from the technology of the Antikythera mechanism. In the 11th century, the Song Dynasty Chinese horologist, mechanical engineer, Su Song is noted for having incorporated an escapement mechanism and earliest known endless power-transmitting chain drive for his clock-tower and armillary sphere to function. They no longer exist, but detailed descriptions of their design and construction survive, wallingfords clock may have shown the sun, moon, stars and planets, and had, in addition, a wheel of fortune and an indicator of the state of the tide at London Bridge. De Dondis clock was a construction with 107 moving parts, showing the positions of the sun, moon. Both these clocks, and others like them, were less accurate than their designers would have wished. The gear ratios may have been calculated, but their manufacture was somewhat beyond the mechanical abilities of the time. Astronomical clocks were built as demonstration or exhibition pieces, to impress as much as to educate or inform, the challenge of building these masterpieces meant that clockmakers would continue to produce them, to demonstrate their technical skill and their patrons wealth. The philosophical message of an ordered, heavenly-ordained universe, which accorded with the Gothic era view of the world, the Science Museum has a scale model of the Cosmic Engine, which Su Sung, a Chinese polymath, designed and constructed in China in 1092. A full-sized working replica of Su Sungs clock exists in the Republic of China s National Museum of Natural Science and this full-scale, fully functional replica, approximately 12 meters in height, was constructed from Su Sungs original descriptions and mechanical drawings. The most sophisticated water-powered astronomical clock was Al-Jazaris castle clock, considered to be an example of a programmable analog computer. It was a device that was about 33 meters high. The Strasbourg Cathedral has housed three different astronomical clocks since the 14th century, the first clock was built between 1352 and 1354 and stopped working sometime at the beginning of the 16th century. A second clock was built by Herlin, Conrad Dasypodius, the Habrecht brothers
Astronomical clock
–
Face of the
Astronomical Clock, in
Old Town Square,
Prague.
Astronomical clock
–
Richard of Wallingford is shown measuring with a pair of compasses in this 14th-century miniature.
Astronomical clock
–
Strasbourg astronomical clock
Astronomical clock
–
Prague Astronomical Clock
4.
Prague
–
Prague is the capital and largest city of the Czech Republic. It is the 14th largest city in the European Union and it is also the historical capital of Bohemia. Situated in the north-west of the country on the Vltava river, the city has a temperate climate, with warm summers and chilly winters. Prague has been a political, cultural, and economic centre of central Europe with waxing and waning fortunes during its history and it was an important city to the Habsburg Monarchy and its Austro-Hungarian Empire. Prague is home to a number of cultural attractions, many of which survived the violence. Main attractions include the Prague Castle, the Charles Bridge, Old Town Square with the Prague astronomical clock, since 1992, the extensive historic centre of Prague has been included in the UNESCO list of World Heritage Sites. The city has more than ten major museums, along with theatres, galleries, cinemas. An extensive modern public transportation system connects the city, also, it is home to a wide range of public and private schools, including Charles University in Prague, the oldest university in Central Europe. Prague is classified as an Alpha- global city according to GaWC studies, Prague ranked sixth in the Tripadvisor world list of best destinations in 2016. Its rich history makes it a popular tourist destination, and the city more than 6.4 million international visitors annually. Prague is the fifth most visited European city after London, Paris, Istanbul, the region was settled as early as the Paleolithic age. In the last century BC, the Celts were slowly driven away by Germanic tribes, around the area where present-day Prague stands, the 2nd century map of Ptolemaios mentioned a Germanic city called Casurgis. In the following century, the Czech tribes built several fortified settlements in the area, most notably in Levý Hradec, Butovice and in the Šárka valley. The construction of what came to be known as the Prague Castle began near the end of the 9th century, the first masonry under Prague Castle dates from the year 885 at the latest. The other prominent Prague fort, the Přemyslid fort Vyšehrad, was founded in the 10th century, Prague Castle is dominated by the cathedral, which was founded in 1344, but completed in the 20th century. The legendary origins of Prague attribute its foundation to the 8th century Czech duchess and prophetess Libuše and her husband, Přemysl, legend says that Libuše came out on a rocky cliff high above the Vltava and prophesied, I see a great city whose glory will touch the stars. She ordered a castle and a town called Praha to be built on the site, a 17th century Jewish chronicler David Solomon Ganz, citing Cyriacus Spangenberg, claimed that the city was founded as Boihaem in c.1306 BC by an ancient king, Boyya. The region became the seat of the dukes, and later kings of Bohemia, under Roman Emperor Otto II the area became a bishopric in 973
Prague
–
Montage of Prague, clockwise from top: Panorama of
Prague Castle and
Charles Bridge,
Dancing House,
Star Villa,
Old Town Square,
Wenceslas Square,
Wallenstein Palace, Royal Garden at Prague Castle,
St. Vitus Cathedral and
Municipal House.
Prague
–
The mythological princess
Libuše prophesies the glory of Prague.
Prague
–
The
Prague astronomical clock was first installed in 1410, making it the third-oldest astronomical clock in the world and the oldest one still working.
Prague
–
A view of one of the bridge towers of the Charles Bridge
5.
Czech Republic
–
The Czech Republic, also known as Czechia, is a nation state in Central Europe bordered by Germany to the west, Austria to the south, Slovakia to the east and Poland to the northeast. The Czech Republic covers an area of 78,866 square kilometres with mostly temperate continental climate and it is a unitary parliamentary republic, has 10.5 million inhabitants and the capital and largest city is Prague, with over 1.2 million residents. The Czech Republic includes the territories of Bohemia, Moravia. The Czech state was formed in the late 9th century as the Duchy of Bohemia under the Great Moravian Empire, after the fall of the Empire in 907, the centre of power transferred from Moravia to Bohemia under the Přemyslid dynasty. In 1002, the duchy was formally recognized as part of the Holy Roman Empire, becoming the Kingdom of Bohemia in 1198 and reaching its greatest territorial extent in the 14th century. Following the Battle of Mohács in 1526, the whole Crown of Bohemia was gradually integrated into the Habsburg Monarchy alongside the Archduchy of Austria, the Protestant Bohemian Revolt against the Catholic Habsburgs led to the Thirty Years War. After the Battle of the White Mountain, the Habsburgs consolidated their rule, reimposed Roman Catholicism, the Czech part of Czechoslovakia was occupied by Germany in World War II, and was liberated in 1945 by the armies of the Soviet Union and the United States. The Czech country lost the majority of its German-speaking inhabitants after they were expelled following the war, the Communist Party of Czechoslovakia won the 1946 elections. Following the 1948 coup détat, Czechoslovakia became a one-party communist state under Soviet influence, in 1968, increasing dissatisfaction with the regime culminated in a reform movement known as the Prague Spring, which ended in a Soviet-led invasion. Czechoslovakia remained occupied until the 1989 Velvet Revolution, when the communist regime collapsed, on 6 March 1990, the Czech Socialistic Republic was renamed to the Czech Republic. On 1 January 1993, Czechoslovakia peacefully dissolved, with its constituent states becoming the independent states of the Czech Republic and the Slovak Republic. The Czech Republic joined NATO in 1999 and the European Union in 2004, it is a member of the United Nations, the OECD, the OSCE, and it is a developed country with an advanced, high income economy and high living standards. The UNDP ranks the country 14th in inequality-adjusted human development, the Czech Republic also ranks as the 6th most peaceful country, while achieving strong performance in democratic governance. It has the lowest unemployment rate in the European Union, the traditional English name Bohemia derives from Latin Boiohaemum, which means home of the Boii. The current name comes from the endonym Čech, spelled Cžech until the reform in 1842. The name comes from the Slavic tribe and, according to legend, their leader Čech, the etymology of the word Čech can be traced back to the Proto-Slavic root *čel-, meaning member of the people, kinsman, thus making it cognate to the Czech word člověk. The country has traditionally divided into three lands, namely Bohemia in the west, Moravia in the southeast, and Czech Silesia in the northeast. Following the dissolution of Czechoslovakia at the end of 1992, the Czech part of the former nation found itself without a common single-word geographical name in English, the name Czechia /ˈtʃɛkiə/ was recommended by the Czech Ministry of Foreign Affairs
Czech Republic
–
Přemysl Ottokar II,
King of Bohemia (1253–1278) and
Duke of Austria (1251–1278)
Czech Republic
–
Flag
Czech Republic
–
The
Crown of Saint Wenceslas is the 4th oldest in Europe
Czech Republic
–
The
Defenestration of Prague sparked the
Thirty Years' War
6.
Old Town Hall (Prague)
–
The Old Town Hall in Prague, the capital of the Czech Republic, is one of the citys most noteworthy monuments. It is located in Old Town Square, in 1338 the councilors of the Old Town bought a magnificent patrician house by the family of Volflin and adapted it for their purposes. The burghers of the Old Town extended their original Town Hall towards the west by buying the adjoining house, the tower, which was the highest in the city in the Middle Ages, was completed in 1364 and the following centuries hardly left any traces on the structure. The Town Hall is one very unusual historical object, because it is out of many different smaller houses. The expansion continued in 1458 when so called Mikes house was added to the west side, the Council Chamber in the east wing was vaulted with the net vault, which was supported with 2 pillars, at the end of the 15th century. The Gothic Cock house was bought in 1835 and the Minute house was sold to the council for the extension of the Town Hall in 1896. Mikes house was rebuilt in Neo-Renaissance style in 1879–1880, the author of the project was Antonín Baum. This wing was destroyed in last days of the World War II during Prague uprising, many architectural competitions were declared during the 20th century. They were supposed to find the right architectonic design for expanding and rebuilding the Old Town Hall, all of the competitions either did not have a winner or the winning projects were not built. The architectural development of the Old Town Hall in the Middle Ages was far from completed after finishing of the tower, there was an interruption due to Hussite movement. In 1458 another house was bought on the west side and it made possible extensive adaptations of the interior of the object. New halls were established in the wing, but only the council room on the upper floor has preserved in its original appearance. Internal adaptations reflected in the reconstruction work can be seen on the south facade to this day. The Gothic arch of the portal has archivolts rich in stone ornaments, decorated brackets support the outer arch which is a typical late-Gothic ogee arch crowned by an imposing finial. The brackets on either side of the portal terminate in slender pinnacles, the structure dates from the close of the 15th century, but the wooden double door itself dates as late as from the year 1652. The window on the left of the portal was completed a few years later, the builder gave up the traditional Gothic arch in favor of a rectangular window, adoring the thickness of the walls with panelled pilasters. A moulded stone cross divides the window four lights, the upper two of which are decorated with the amorial bearing of the Old Town of Prague and the Czech lion. Between and slightly above them may be seen the symbol W representing the initial of the Bohemian king Vladislaus II of Hungaryfrom Jagiellon dynasty
Old Town Hall (Prague)
–
The Old Town Hall is a complex of several ancient houses in the
Old Town Square,
Prague. The houses were connected one by one to a single unit for the purpose of administration of the Old Town of Prague.
Old Town Hall (Prague)
–
A magnificent late Gothic door in the house adjacent to the tower serves as the main entrance to the Old Town Hall.
Old Town Hall (Prague)
–
The Town Hall chapel in the tower, consecrated in 1381.
Old Town Hall (Prague)
–
LEGEND TO THE SECOND-FLOOR PLAN OF THE OLD TOWN HALL: 1.Entrance Hall, 2.Session Chamber, 3.Jiřík Hall, 4.Old Council Chamber, 5.Public Hall, 6.Town Hall Chapel, 7.Torso of destroyed East Wing
7.
Old Town Square
–
Old Town Square is a historic square in the Old Town quarter of Prague, the capital of the Czech Republic. It is located between Wenceslas Square and the Charles Bridge, Prague Orloj is a medieval astronomical clock located on the Old Town Hall. The clock was first installed in 1410, making it the third-oldest astronomical clock in the world, the Baroque St. Nicholas Church is another church located in the square, while the tower of the Old Town Hall offers a panoramic view of Old Town. An art museum of the Czech National Gallery is located in Kinský Palace, the squares center is home to a statue of religious reformer Jan Hus, who for his beliefs was burned at the stake in Constance, this led to the Hussite Wars. The statue known as the Jan Hus Memorial was erected on July 6,1915 to mark the 500th anniversary of his death. In front of the Old Town Hall is also a memorial to martyrs beheaded on that spot during the Old Town Square execution by Habsburgs, twenty-seven crosses mark the pavement in their honour. The crosses were installed during the repairs of Old Town Hall after the WW2, on November 3,1918, a Marian Column that had been erected in the square shortly after the Thirty Years War was demolished in celebration of independence from the Habsburg empire. At Christmas and Easter, markets are held on the square, a tall decorated tree and a musical stage are set up. The Christmas Markets on the Old Town Square are the largest Christmas markets in the Czech Republic and are visited by hundreds of thousands of visitors from the Czech Republic, the markets are mostly visited by Germans, Russians, Italians and British. In 2016, CNN rates Prague’s Christmas Markets among the world’s best, Old Town Square execution Old Town Square Live WebCam
Old Town Square
–
The Old Town Hall and the Church of Our Lady before Týn
Old Town Square
–
Jan Hus monument
Old Town Square
–
The Church of St Nicholas
Old Town Square
–
Old Town Square
8.
Sun
–
The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
Sun
–
The Sun in visible wavelength with filtered white light on 8 July 2014. Characteristic
limb darkening and numerous
sunspots are visible.
Sun
–
During a total
solar eclipse, the solar
corona can be seen with the naked eye, during the brief period of totality.
Sun
–
Taken by
Hinode 's Solar Optical Telescope on 12 January 2007, this image of the Sun reveals the filamentary nature of the plasma connecting regions of different magnetic polarity.
Sun
–
Visible light photograph of sunspot, 13 December 2006
9.
Moon
–
The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
Moon
–
Full moon as seen from Earth's
northern hemisphere
Moon
–
The Moon, tinted reddish, during a
lunar eclipse
Moon
–
Near side of the Moon
Moon
–
Far side of the Moon
10.
Hour
–
An hour is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3, 599–3,601 seconds, depending on conditions. The seasonal, temporal, or unequal hour was established in the ancient Near East as 1⁄12 of the night or daytime, such hours varied by season, latitude, and weather. It was subsequently divided into 60 minutes, each of 60 seconds, the modern English word hour is a development of the Anglo-Norman houre and Middle English ure, first attested in the 13th century. It displaced the Old English tide and stound, the Anglo-Norman term was a borrowing of Old French ure, a variant of ore, which derived from Latin hōra and Greek hṓrā. Like Old English tīd and stund, hṓrā was originally a word for any span of time, including seasons. Its Proto-Indo-European root has been reconstructed as *yeh₁-, making hour distantly cognate with year, the time of day is typically expressed in English in terms of hours. Whole hours on a 12-hour clock are expressed using the contracted phrase oclock, Hours on a 24-hour clock are expressed as hundred or hundred hours. Fifteen and thirty minutes past the hour is expressed as a quarter past or after and half past, respectively, fifteen minutes before the hour may be expressed as a quarter to, of, till, or before the hour. Sumerian and Babylonian hours divided the day and night into 24 equal hours, the ancient Egyptians began dividing the night into wnwt at some time before the compilation of the Dynasty V Pyramid Texts in the 24th century BC. By 2150 BC, diagrams of stars inside Egyptian coffin lids—variously known as diagonal calendars or star clocks—attest that there were exactly 12 of these. The coffin diagrams show that the Egyptians took note of the risings of 36 stars or constellations. Each night, the rising of eleven of these decans were noted, the original decans used by the Egyptians would have fallen noticeably out of their proper places over a span of several centuries. By the time of Amenhotep III, the priests at Karnak were using water clocks to determine the hours and these were filled to the brim at sunset and the hour determined by comparing the water level against one of its twelve gauges, one for each month of the year. During the New Kingdom, another system of decans was used, the later division of the day into 12 hours was accomplished by sundials marked with ten equal divisions. The morning and evening periods when the failed to note time were observed as the first and last hours. The Egyptian hours were closely connected both with the priesthood of the gods and with their divine services, by the New Kingdom, each hour was conceived as a specific region of the sky or underworld through which Ras solar bark travelled. Protective deities were assigned to each and were used as the names of the hours, as the protectors and resurrectors of the sun, the goddesses of the night hours were considered to hold power over all lifespans and thus became part of Egyptian funerary rituals. The Egyptian for astronomer, used as a synonym for priest, was wnwty, the earliest forms of wnwt include one or three stars, with the later solar hours including the determinative hieroglyph for sun
Hour
–
Key concepts
Hour
–
Midnight on a 24-hour digital clock
11.
Twelve Apostles
–
In Christian theology and ecclesiology, the apostles, particularly the Twelve Apostles, were the primary historical disciples of Jesus, the central figure in Christianity. During the life and ministry of Jesus in the 1st century AD, the word disciple is sometimes used interchangeably with apostle, for instance, the Gospel of John makes no distinction between the two terms. In modern usage, prominent missionaries are often called apostles, a practice which stems from the Latin equivalent of apostle, i. e. missio, for example, Saint Patrick was the Apostle of Ireland, and Saint Boniface was the Apostle to the Germans. The commissioning of the Twelve Apostles during the ministry of Jesus is recorded in the Synoptic Gospels, after his resurrection, Jesus sent 11 of them by the Great Commission to spread his teachings to all nations. This event is called the Dispersion of the Apostles. There is also an Eastern Christian tradition derived from the Gospel of Luke of there having been as many as 70 apostles during the time of Jesus ministry. Prominent figures in early Christianity, notably Paul, were called apostles. The period of early Christianity during the lifetimes of the apostles is called the Apostolic Age, during the 1st century AD, the apostles established churches throughout the territories of the Roman Empire and, according to tradition, through the Middle East, Africa, and India. In his writings, the epistles to Christian churches throughout the Levant, Paul did not restrict the term apostle to the Twelve, the restricted usage appears in the Revelation to John. By the 2nd century AD, association with the apostles was esteemed as an evidence of authority, Churches which are believed to have been founded by one of the apostles are known as apostolic sees. Pauls epistles were accepted as scripture, and two of the four gospels were associated with apostles, as were other New Testament works. Various Christian texts, such as the Didache and the Apostolic Constitutions, were attributed to the apostles, bishops traced their lines of succession back to individual apostles, who were said to have dispersed from Jerusalem and established churches across great territories. Christian bishops have traditionally claimed authority deriving, by apostolic succession, early Church Fathers who came to be associated with apostles, such as Pope Clement I with St. Peter, are referred to as the Apostolic Fathers. The Apostles Creed, popular in the West, was said to have composed by the apostles themselves. The word apostle comes from the Greek word ἀπόστολος, formed from the prefix ἀπό- and root στέλλω and originally meaning messenger and it has, however, a stronger sense than the word messenger, and is closer to a delegate. The Greek-English Lexicon of the New Testament argues that its Christian use translated a Jewish position known in Hebrew as the sheliach and this ecclesiastical meaning of the word was later translated into Latin as missio, the source of the English missionary. In the New Testament, the names of the majority of the apostles are Hebrew names, Mark 6, 7-13 states that Jesus initially sent out these twelve in pairs to towns in Galilee. The text states that their initial instructions were to heal the sick and their carrying of just a staff is sometimes given as the reason for the use by Christian bishops of a staff of office in those denominations that believe they maintain an apostolic succession
Twelve Apostles
–
The Last Supper, a late 1490s mural painting by Leonardo da Vinci, is a depiction of the last supper of Jesus and his twelve apostles on the eve of his crucifixion.
Twelve Apostles
–
Jesus and his twelve apostles, fresco with the
Chi-Rho symbol ☧,
Catacombs of Domitilla,
Rome.
Twelve Apostles
–
The
Synaxis of the Twelve Apostles. Russian, 14th century, Moscow Museum.
Twelve Apostles
–
Jesus and the 12 apostles in
Domus Galilaeae,
Israel.
12.
Death (personification)
–
Death, also known as the Grim Reaper, is a common element in culture and history. As a personified force it has been imagined in many different ways, in some mythologies, the Grim Reaper causes the victims death by coming to collect him. In turn, people in some stories try to hold on to life by avoiding Deaths visit, in many mythologies, Death is personified in male form, while in others, Death is perceived as female. Mot was personified to Canaanites as a god of death and he was considered a son of the king of the gods, El. His contest with the storm god Baʿal forms part of the myth cycle discovered in the 1920s in the ruins of Ugarit, lacunae obscure some of the details, but Mot apparently consumes Baʿal before being split open and mutilated by that gods sister, the warrior Anat. After a time, both gods are restored and resume battle before the sun goddess Shapash prompts a truce by warning Mot that, if forced to, El would intervene on Baʿals behalf. The Phoenicians also worshipped death under the name Mot and a version of Mot later became Maweth, Ancient Greece found Death to be inevitable, and therefore, he is not represented as purely evil. He is often portrayed as a bearded and winged man, but has also portrayed as a young boy. Death, or Thanatos, is the counterpart of life, death being represented as male and he is the twin brother of Hypnos, the god of sleep. He is typically shown with his brother and is represented as being just and his job is to escort the dead to the underworld, Hades. He then hands the dead over to Charon, who mans the boat that carries them over the river Styx, which separates the land of the living from the land of the dead. It was believed if the ferryman did not receive some sort of payment. Thanatos sisters, the Keres, were the spirits of violent death and they were associated with deaths from battle, disease, accident, and murder. The sisters were portrayed as evil, often feeding on the blood of the body after the soul had been escorted to Hades and they had fangs and talons, and would be dressed in bloody garments. Breton folklore shows us a spectral figure portending death, the Ankou, the Ankou drives a deathly wagon or cart with a creaking axle. The cart or wagon is piled high with corpses and a stop at a cabin means instant death for those inside. In Ireland there was a known as a dullahan, whose head would be tucked under his or her arm, and the head was said to have large eyes. The dullahan would ride a horse or a carriage pulled by black horses, and stop at the house of someone about to die, and call their name
Death (personification)
–
A Western depiction of Death as a skeleton wielding a
scythe.
Death (personification)
–
Thanatos as a winged youth, c. 325–300 BC, at
Temple of Artemis,
Ephesos
Death (personification)
–
Yama, the Hindu lord of death, presiding over his court in hell
Death (personification)
–
Santa Muerte
13.
Charles University
–
Charles University, known also as Charles University in Prague or historically as the University of Prague, is the oldest and largest university in the Czech Republic. Founded in 1348, it was the first university in Central Europe and it is one of the oldest universities in Europe in continuous operation and ranks in the upper 1.5 percent of the world’s best universities. Its seal shows its protector Emperor Charles IV, with his coats of arms as King of the Romans and King of Bohemia, kneeling in front of St. Wenceslas and it is surrounded by the inscription, Sigillum Universitatis Scolarium Studii Pragensis. The establishment of a university in Prague was inspired by Holy Roman Emperor Charles IV. He asked his friend and ally, Pope Clement VI, to do so, on 26 January 1347 the pope issued the bull establishing a university in Prague, modeled on the University of Paris, with the full number of faculties, that is including theological. This was caused by a shift in the 19th century. The university was opened in 1349, the university was sectioned into parts called nations, the Bohemian, Bavarian, Polish and Saxon. Ethnically Czech students made 16–20% of all students, archbishop Arnošt of Pardubice took an active part in the foundation by obliging the clergy to contribute and became a chancellor of the university. The first graduate was promoted in 1359, the lectures were held in the colleges, of which the oldest was named for the king the Carolinum, established in 1366. In 1372 the Faculty of Law became an independent university, in 1402 Jerome of Prague in Oxford copied out the Dialogus and Trialogus of John Wycliffe. The dean of the faculty, Jan Hus, translated Trialogus into the Czech language. In 1403 the university forbade its members to follow the teachings of Wycliffe, in the Western Schism, the Bohemian natio took the side of king Wenceslaus and supported the Council of Pisa. The other nationes of the university declared their support for the side of Pope Gregory XII, Hus and other Bohemians, though, took advantage of Wenceslaus opposition to Gregory. By the Decree of Kutná Hora on 18 January 1409, the king subverted the university constitution by granting the Bohemian masters three votes, only a single vote was left for all other three nationes combined, compared to one vote per each natio before. The result of this coup was the emigration of foreign professors and students, in the autumn of 1409, Hus was elected rector of the now Czech-dominated rump university. Thus, the Prague university lost the largest part of its students, from then on the university declined to a merely regional institution with a very low status. Soon, in 1419, the faculties of theology and law disappeared, the faculty of arts became a centre of the Hussite movement, and the chief doctrinal authority of the Utraquists. No degrees were given in the years 1417–30, at times there were eight or nine professors
Charles University
–
Monument to the
protector of the university,
Emperor Charles IV in
Prague (built in 1848)
Charles University
–
Charles University in Prague
Charles University
–
Carolinum – the oldest building of Charles University built in the 14th century
Charles University
–
Baroque library hall in Clementinum, which originally belonged to the university, today part of
Czech National Library
14.
Gothic architecture
–
Gothic architecture is a style of architecture that flourished in Europe during the high and late medieval period. It evolved from Romanesque architecture and was succeeded by Renaissance architecture and its characteristics include the pointed arch, the ribbed vault and the flying buttress. Gothic architecture is most familiar as the architecture of many of the cathedrals, abbeys. It is also the architecture of many castles, palaces, town halls, guild halls, universities and to a less prominent extent, private dwellings, for this reason a study of Gothic architecture is largely a study of cathedrals and churches. A series of Gothic revivals began in mid-18th-century England, spread through 19th-century Europe and continued, largely for ecclesiastical and university structures, the term Gothic architecture originated as a pejorative description. Hence, François Rabelais, also of the 16th century, imagines an inscription over the door of his utopian Abbey of Thélème, Here enter no hypocrites, slipping in a slighting reference to Gotz and Ostrogotz. Authorities such as Christopher Wren lent their aid in deprecating the old medieval style, the Company disapproved of several of these new manners, which are defective and which belong for the most part to the Gothic. Gothic architecture is the architecture of the medieval period, characterised by use of the pointed arch. As an architectural style, Gothic developed primarily in ecclesiastical architecture, the greatest number of surviving Gothic buildings are churches. The Gothic style is most particularly associated with the cathedrals of Northern France. At the end of the 12th century, Europe was divided into a multitude of city states, norway came under the influence of England, while the other Scandinavian countries and Poland were influenced by trading contacts with the Hanseatic League. Angevin kings brought the Gothic tradition from France to Southern Italy, throughout Europe at this time there was a rapid growth in trade and an associated growth in towns. Germany and the Lowlands had large flourishing towns that grew in comparative peace, in trade and competition with other, or united for mutual weal. Civic building was of importance to these towns as a sign of wealth. England and France remained largely feudal and produced grand domestic architecture for their kings, dukes and bishops, the Catholic Church prevailed across Europe at this time, influencing not only faith but also wealth and power. Bishops were appointed by the lords and they often ruled as virtual princes over large estates. The early Medieval periods had seen a growth in monasticism, with several different orders being prevalent. Foremost were the Benedictines whose great abbey churches vastly outnumbered any others in France, a part of their influence was that towns developed around them and they became centers of culture, learning and commerce
Gothic architecture
–
Façade of
Reims Cathedral, France
Gothic architecture
–
The interior of the western end of Reims Cathedral
Gothic architecture
–
Overview of Reims Cathedral from north-east
Gothic architecture
–
South side of
Chartres Cathedral.
15.
Prague Uprising
–
The Prague uprising was an attempt by the Czech resistance to liberate the city of Prague from German occupation during World War II. Events began on May 5,1945, in the last moments of the war in Europe, the uprising went on until May 8,1945, ending in a ceasefire between the Czech resistance and the German army, which decided to quit Prague on the same day. Next morning, the Red Army entered the liberated city. The most important task of the Czechs was to stop the Germans from disturbing what Czechoslovak territory they occupied as well as to stop them from continuing the war on Czech soil. The goal of the resistance was to force the German occupants to retreat to Germany, the Czech Resistance needed the support and help of the Red Army in order to become fully liberated. As the end of the war came closer, it had an effect on the residents all over Czechoslovakia. In fact, it strengthened their longing to explicitly demonstrate their bitter hatred toward the German occupants, during the German occupation of Czechoslovakia, tensions had built up because of oppression. This would later lead to the expulsion of three million Sudeten Germans from their homes of 800 years, in the spring of 1945 throughout Czechoslovakia, there were both many large and small partisan groups that totaled about 7,500 people. For example, there were some lines the Germans could use only in the daytime, on the eve of the uprising, the propaganda activities of the group called the Communist Youth, were in full swing, but didn’t last long. The communist groups whose solidarity had been broken by arrests in March were somehow able to work under the circumstances of illegality. From 30 April-1 May 1945, the Waffen-SS Senior Group Leader, as rumors of an impending Allied approach reached Prague, the people of Prague streamed into the streets to welcome the victors. Frank ordered the streets to be cleared and instructed the German army, on 5 May, the uprising was triggered in the morning by a broadcast on Czech radio. In a mixture of Czech and German, the broadcast announced, with the sounds of combat in the background, the radio station continued to broadcast messages of defiance, encouraging citizens to revolt. The Prague radio broadcast an appeal to all Czechs to come to the radio buildings defence, it was the beginning of five days of fighting in Prague. The radio was during this time led by Otakar Matousek, a director of scientific programmes at the radio before the war. At about 1,00 pm on May 5,1945, the radio announcer broadcast a call to the Czech nation to rise up and asked the people in the streets of Prague to build barricades. Elsewhere, Czech resistance fighters occupied the Gestapo and Sipo Headquarters, in the afternoon of May 5, the Prague mayor formally switched allegiance to the National Committee in the City Hall. The Czechs in the streets tore down the German road traffic signs, the insurgents attacked any Germans within sight and seized their weapons
Prague Uprising
–
Residents and defenders of the Prague Uprising barricades greet the
Red Army tanks on May 9, 1945
Prague Uprising
–
An ROA T-34 tank in Prague.
Prague Uprising
–
Mass grave of two generals and 187 unknown soldiers of the Russian Liberation Army in Prague cemetery
16.
Armoured vehicle
–
An armoured fighting vehicle is a combat vehicle, protected by strong armour and generally armed with weapons, which combines operational mobility, tactical offensive, and defensive capabilities. AFVs can be wheeled or tracked and it is not uncommon for AFVs to be simply referred to as armour. Armoured fighting vehicles are classified according to their role on the battlefield. This classification is not absolute, at different times different countries will classify the vehicle in different roles. For example, armoured carriers were generally replaced by infantry fighting vehicles in a similar role. Modern armoured fighting vehicles are the realization of an ancient concept, War machines with rudimentary armour have been used in battle for millennia. These designs historically struggled between the paradox of exposed-mobility, effective-firepower and cumbersome-protection, Siege engines, such as battering rams and trebuchets, would often be armoured in order to protect the crews from the defenders. Very large movable siege towers, helepolis were developed by Polyidus of Thessaly, the idea of a vehicle with a tortoise like cover has been known since antiquity. Frequently cited is Leonardo da Vincis 15th century sketch of a mobile, protected gun platform, the machine was to be mounted on four wheels which would be turned by the crew through a system of hand cranks and cage gears. Leonardo quoted I will build armored wagons which will be safe, there will be no obstacle which it cannot overcome. Modern replicas have demonstrated that the crew would have been able to move it over only short distances. The war wagon were medieval weapon-platforms developmed during the Hussite Wars around 1420 by Hussite forces rebelling in Bohemia. These heavy wagon were given protective sides with firing slits and heavy firepower from either a cannon or a force of hand-gunners and crossbowmen, supported by infantry using pikes, heavy arquebuses mounted on wagons were called arquebus à croc. These carried a ball of about 3.5 ounces, the first modern AFVs were armed cars, dating back virtually to the invention of the motor car. The Motor Scout was designed and built by British inventor F. R. Simms in 1898 and it was the first armed petrol engine powered vehicle ever built. The vehicle was a De Dion-Bouton quadricycle with a mounted Maxim machine gun on the front bar, an iron shield offered some protection for the driver from the front, but it lacked all-around protective armour. The armoured car was the first modern fully armoured fighting vehicle, the first of these was the Simms Motor War Car, designed by Simms and built by Vickers, Sons & Maxim in 1899. The vehicle had Vickers armour 6 mm thick and was powered by a four-cylinder 3. 3-litre 16 hp Cannstatt Daimler engine giving it a speed of around 9 miles per hour
Armoured vehicle
–
A
M1128 Mobile Gun System firing its 105 mm cannon
Armoured vehicle
–
An
MRAP Cougar HE in testing with land mines set off around it
Armoured vehicle
–
Model of a vehicle sketched by
Leonardo da Vinci
Armoured vehicle
–
Hittite chariot (drawing of an
Egyptian relief)
17.
Google Doodle
–
A Google Doodle is a special, temporary alteration of the logo on Googles homepage that is intended to celebrate holidays, events, achievements and people. The first Google Doodle was in honor of the Burning Man Festival of 1998, subsequent Google Doodles were designed by an outside contractor, until Page and Brin asked public relations officer Dennis Hwang to design a logo for Bastille Day in 2000. From that point onward, Doodles have been organized and published by a team of employees termed Doodlers, initially, Doodles were neither animated nor hyperlinked. They were simply images linked to the theme, Doodles increased in both frequency and complexity by the beginning of the 2010s, and in January 2010 the first animated Doodle was posted honoring Isaac Newton. The first interactive Doodle appeared shortly thereafter celebrating Pac-Man, and hyperlinks also began to be added to Doodles, by 2014, Google had published over 2,000 regional and international Doodles throughout its homepages, often featuring guest artists, musicians and personalities. The featuring of Lowells logo design coincided with the launch of another Google product, Google doodles are also used to depict major events at Google, such as the companys own anniversary. The celebration of events is another common topic of Google Doodles including a Lego brick design in celebration of the interlocking Lego blocks 50th anniversary. Some Google Doodles are limited to Googles country-specific home pages while others appear globally, in May 2010, on the 30th anniversary of the arcade game Pac-Man, Google unveiled worldwide their first interactive logo, created in association with Namco. Anyone who visited Google could play Pac-Man on the logo, which featured the letters of the word Google on the Pac-Man maze, the logo also mimicked the sounds the original arcade game made. The Im Feeling Lucky button was replaced with an Insert Coin button, pressing this once enabled you to play the Pac-Man logo. Pressing it once more added a second player, Ms. Pac-Man, enabling two players to play at once, controlled using the W, A, S, D keys, pressing it for a third time performed an Im Feeling Lucky search. It was then removed on May 23,2010, initially replacing Pac-Man with the normal logo, later on that day, Google released a permanent Google Pac-Man site, due to the popular user demand for the playable logo. Similarly, Freddie Mercurys 65th birthday was celebrated on September 5,2011, on April 15,2011, Google sported the first video doodle, commemorating Charlie Chaplins 122nd birthday. This doodle was a black and white YouTube video that, when clicked upon, all parts in this short film were played by the Google doodle team, and special behind-the-scenes footage was to be found on the Google blog. Google displayed an electric guitar doodle starting June 9,2011. The doodle still maintained some resemblance to the Google logo, in the U. S, the doodle also allowed the user to record a 30-second clip, after which a URL is created and can be sent to others. The doodle remained on the site a day due to popularity in the US. It now has its own page linked to the Google Doodles archives, on June 23,2012, in commemoration of Alan Turings 100th birthday, Googles logo became an interactive Turing Machine
Google Doodle
–
Google conference room in
New York featuring 2005's Doodle for
Leonardo da Vinci
Google Doodle
–
Artist and "Doodler" Jennifer Hom has designed many Doodles throughout the years
18.
Astrolabe
–
An astrolabe is an elaborate inclinometer, historically used by astronomers and navigators, to measure the inclined position in the sky of a celestial body, day or night. It can thus be used to identify stars or planets, to determine local latitude given local time and vice versa, to survey and it was used in classical antiquity, the Islamic Golden Age, the European Middle Ages and the Renaissance for all these purposes. While the astrolabe is effective for determining latitude on land or calm seas, the mariners astrolabe was developed to solve that problem. OED gives the translation star-taker for the English word astrolabe and traces it, through medieval Latin, to the Greek word astrolabos from astron star, in the medieval Islamic world the word asturlab was given various etymologies. In Arabic texts, the word is translated as akhdh al-kawakib which corresponds to an interpretation of the Greek word, al-Biruni quotes and criticizes the medieval scientist Hamzah al-Isfahani who had stated, asturlab is an arabization of this Persian phrase. In medieval Islamic sources, there is also a fictional and popular etymology of the words as lines of lab, in this popular etymology, Lab is a certain son of Idris. This etymology is mentioned by a 10th-century scientist named al-Qummi but rejected by al-Khwarizmi, Lab in Arabic also means sun and black stony places. An early astrolabe was invented in the Hellenistic world by Apollonius of Perga, a marriage of the planisphere and dioptra, the astrolabe was effectively an analog calculator capable of working out several different kinds of problems in spherical astronomy. Theon of Alexandria wrote a treatise on the astrolabe. Some historians attribute the invention to Hypatia, the daughter of Theon of Alexandria, noting that Synesius. Astrolabes continued in use in the Greek-speaking world throughout the Byzantine period, about 550 AD the Christian philosopher John Philoponus wrote a treatise on the astrolabe in Greek, which is the earliest extant Greek treatise on the instrument. In addition, Severus Sebokht, a bishop who lived in Mesopotamia, Astrolabes were further developed in the medieval Islamic world, where Muslim astronomers introduced angular scales to the astrolabe, adding circles indicating azimuths on the horizon. It was widely used throughout the Muslim world, chiefly as an aid to navigation and as a way of finding the Qibla, the first person credited with building the astrolabe in the Islamic world is reportedly the 8th-century mathematician Muhammad al-Fazari. The mathematical background was established by the Muslim astronomer Albatenius in his treatise Kitab az-Zij, the earliest surviving dated astrolabe is dated AH315. In the Islamic world, astrolabes were used to find the times of sunrise and the rising of fixed stars, to help schedule morning prayers. In the 10th century, al-Sufi first described over 1,000 different uses of an astrolabe, in areas as diverse as astronomy, astrology, navigation, surveying, timekeeping, prayer, Salat, Qibla, etc. The spherical astrolabe, a variation of both the astrolabe and the sphere, was invented during the Middle Ages by astronomers and inventors in the Islamic world. The earliest description of the spherical astrolabe dates back to Al-Nayrizi, in the 12th century, Sharaf al-Dīn al-Tūsī invented the linear astrolabe, sometimes called the staff of al-Tusi, which was a simple wooden rod with graduated markings but without sights
Astrolabe
–
A modern astrolabe, made in
Tabriz, Iran in 2013.
Astrolabe
–
Astrolabe quadrant, England, 1388
Astrolabe
–
A 16th-century astrolabe, showing a tulip rete and
rule
Astrolabe
–
A treatise explaining the importance of the astrolabe by
Nasir al-Din al-Tusi, Persian scientist.
19.
Astronomy
–
Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets, while the phenomena include supernovae explosions, gamma ray bursts, more generally, all astronomical phenomena that originate outside Earths atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole, Astronomy is the oldest of the natural sciences. The early civilizations in recorded history, such as the Babylonians, Greeks, Indians, Egyptians, Nubians, Iranians, Chinese, during the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the results and observations being used to confirm theoretical results. Astronomy is one of the few sciences where amateurs can play an active role, especially in the discovery. Amateur astronomers have made and contributed to many important astronomical discoveries, Astronomy means law of the stars. Astronomy should not be confused with astrology, the system which claims that human affairs are correlated with the positions of celestial objects. Although the two share a common origin, they are now entirely distinct. Generally, either the term astronomy or astrophysics may be used to refer to this subject, however, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Few fields, such as astrometry, are purely astronomy rather than also astrophysics, some titles of the leading scientific journals in this field includeThe Astronomical Journal, The Astrophysical Journal and Astronomy and Astrophysics. In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye, in some locations, early cultures assembled massive artifacts that possibly had some astronomical purpose. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye, most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon, the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the model of the Universe, or the Ptolemaic system. The Babylonians discovered that lunar eclipses recurred in a cycle known as a saros
Astronomy
–
A
star -forming region in the
Large Magellanic Cloud, an
irregular galaxy.
Astronomy
–
A giant
Hubble mosaic of the
Crab Nebula, a
supernova remnant
Astronomy
–
19th century
Sydney Observatory,
Australia (1873)
Astronomy
–
19th century
Quito Astronomical Observatory is located 12 minutes south of the
Equator in
Quito,
Ecuador.
20.
Planetarium
–
A planetarium is a theatre built primarily for presenting educational and entertaining shows about astronomy and the night sky, or for training in celestial navigation. Whatever technologies are used, the objective is normally to link together to provide an accurate relative motion of the sky. Typical systems can be set to display the sky at any point in time, past or present, planetaria range in size from the Hayden Planetariums 21-meter dome seating 423 people, to three-meter inflatable portable domes where children sit on the floor. Such portable planetaria serve education programs outside of the permanent installations of museums, the term planetarium is sometimes used generically to describe other devices which illustrate the solar system, such as a computer simulation or an orrery. Planetarium software refers to an application that renders a three-dimensional image of the sky onto a two-dimensional computer screen. The term planetarian is used to describe a member of the staff of a planetarium. The ancient Greek polymath Archimedes is attributed with creating a primitive device that could predict the movements of the Sun and the Moon. The discovery of the Antikythera mechanism proved that such devices already existed during antiquity, campanus of Novara described a planetary equatorium in his Theorica Planetarum, and included instructions on how to build one. The Globe of Gottorf built around 1650 had constellations painted on the inside and these devices would today usually be referred to as orreries. In fact, many planetaria today have what are called projection orreries, the small size of typical 18th century orreries limited their impact, and towards the end of that century a number of educators attempted some larger scale simulations of the heavens. The efforts of Adam Walker and his sons are noteworthy in their attempts to fuse theatrical illusions with educational aspirations, walkers Eidouranion was the heart of his public lectures or theatrical presentations. Every Planet and Satellite seems suspended in space, without any support and these devices most probably sacrificed astronomical accuracy for crowd-pleasing spectacle and sensational and awe-provoking imagery. The oldest, still working planetarium can be found in the Dutch town Franeker and it was built by Eise Eisinga in the living room of his house. It took Eisinga seven years to build his planetarium, which was completed in 1781 and this was displayed at the Deutsches Museum in 1924, construction work having been interrupted by the war. The planets travelled along overhead rails, powered by electric motors,180 stars were projected onto the wall by electric bulbs. Atwoods work at the Chicago Academy of Sciences and by the ideas of Walther Bauersfeld, in August 1923, the first Zeiss planetarium projected images of the night sky onto the white plaster lining of a 16 m hemispherical concrete dome, erected on the roof of the Zeiss works. The first official public showing was at the Deutsches Museum in Munich on October 21,1923, when Germany was divided into East and West Germany after the war, the Zeiss firm was also split. Part remained in its headquarters at Jena, in East Germany
Planetarium
–
Inside a planetarium projection hall. (
Belgrade Planetarium,
Serbia)
Planetarium
–
Inside the same hall during projection. (
Belgrade Planetarium,
Serbia)
Planetarium
–
A planetarium under construction in
Nishapur, near the
Mausoleum of Omar Khayyam.
Planetarium
–
The
Eise Eisinga Planetarium
21.
Horizon
–
At many locations, the true horizon is obscured by trees, buildings, mountains, etc. and the resulting intersection of earth and sky is called the visible horizon. When looking at a sea from a shore, the part of the sea closest to the horizon is called the offing. The word horizon derives from the Greek ὁρίζων κύκλος horizōn kyklos, separating circle, from the verb ὁρίζω horizō, to divide, to separate, a pilot can also retain his or her spatial orientation by referring to the horizon. For observers near sea level the difference between this geometrical horizon and the horizon is imperceptible to the naked eye. In astronomy the horizon is the plane through the eyes of the observer. It is the plane of the horizontal coordinate system, the locus of points that have an altitude of zero degrees. While similar in ways to the horizon, in this context a horizon may be considered to be a plane in space. One typically sees further along the Earths curved surface than a simple geometric calculation allows for because of refraction error, the reverse happens if the ground is hotter than the air above it, as often happens in deserts, producing mirages. Examples, For an observer standing on the ground with h =1.70 metres, for an observer standing on the ground with h =2 metres, the horizon is at a distance of 5 kilometres. For an observer standing on a hill or tower of 100 metres in height, for an observer standing at the top of the Burj Khalifa, the horizon is at a distance of 103 kilometres. For an observer atop Mount Everest, the horizon is at a distance of 336 kilometres, with d in miles and h in feet, d ≈1.5 h ≈1.22 h. Examples, assuming no refraction, For an observer on the ground with eye level at h =5 ft 7 in, for an observer standing on a hill or tower 100 feet in height, the horizon is at a distance of 12.2 miles. For an observer on the summit of Aconcagua, the horizon to the west is at a distance of 184 miles. The secant-tangent theorem states that O C2 = O A × O B, the equation can also be derived using the Pythagorean theorem. Since the line of sight is a tangent to the Earth and this sets up a right triangle, with the sum of the radius and the height as the hypotenuse. Another relationship involves the distance s along the surface of the Earth to the horizon, with γ in radians, s = R γ. Solving for s gives s = R cos −1 R R + h, the distances d and s are nearly the same when the height of the object is negligible compared to the radius. If the observer is close to the surface of the earth, then it is valid to disregard h in the term, and the formula becomes d =2 R h
Horizon
–
A water horizon, in northern
Wisconsin, U.S.
Horizon
–
View of Earth's horizon as seen from
Space Shuttle Endeavour, 2002
Horizon
–
A view across a 20-km-wide bay in the coast of
Spain. Note the
curvature of the Earth hiding the base of the buildings on the far shore.
Horizon
–
The curvature of the horizon is easily seen in this photograph, taken from a space shuttle at an altitude of 226 km in 2008.
22.
Latin
–
Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole
Latin
–
Latin inscription, in the
Colosseum
Latin
–
Julius Caesar 's
Commentarii de Bello Gallico is one of the most famous classical Latin texts of the Golden Age of Latin. The unvarnished, journalistic style of this
patrician general has long been taught as a model of the urbane Latin officially spoken and written in the floruit of the
Roman republic.
Latin
–
A multi-volume Latin dictionary in the
University Library of Graz
Latin
–
Latin and Ancient Greek Language - Culture - Linguistics at
Duke University in 2014.
23.
Roman numerals
–
The numeric system represented by Roman numerals originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers in this system are represented by combinations of letters from the Latin alphabet, Roman numerals, as used today, are based on seven symbols, The use of Roman numerals continued long after the decline of the Roman Empire. The numbers 1 to 10 are usually expressed in Roman numerals as follows, I, II, III, IV, V, VI, VII, VIII, IX, Numbers are formed by combining symbols and adding the values, so II is two and XIII is thirteen. Symbols are placed left to right in order of value. Named after the year of its release,2014 as MMXIV, the year of the games of the XXII Olympic Winter Games The standard forms described above reflect typical modern usage rather than a universally accepted convention. Usage in ancient Rome varied greatly and remained inconsistent in medieval, Roman inscriptions, especially in official contexts, seem to show a preference for additive forms such as IIII and VIIII instead of subtractive forms such as IV and IX. Both methods appear in documents from the Roman era, even within the same document, double subtractives also occur, such as XIIX or even IIXX instead of XVIII. Sometimes V and L are not used, with such as IIIIII. Such variation and inconsistency continued through the period and into modern times. Clock faces that use Roman numerals normally show IIII for four o’clock but IX for nine o’clock, however, this is far from universal, for example, the clock on the Palace of Westminster in London uses IV. Similarly, at the beginning of the 20th century, different representations of 900 appeared in several inscribed dates. For instance,1910 is shown on Admiralty Arch, London, as MDCCCCX rather than MCMX, although Roman numerals came to be written with letters of the Roman alphabet, they were originally independent symbols. The Etruscans, for example, used
Roman numerals
–
Entrance to section LII (52) of the
Colosseum, with numerals still visible
Roman numerals
–
Numeral systems
Roman numerals
–
A typical
clock face with Roman numerals in
Bad Salzdetfurth, Germany
Roman numerals
–
An inscription on
Admiralty Arch, London. The number is 1910, for which MCMX would be more usual
24.
Zodiac
–
The zodiac is an area of the sky centered upon the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year. The paths of the Moon and visible planets also remain close to the ecliptic, within the belt of the zodiac, in western astrology and astronomy, the zodiac is divided into twelve signs, each sign occupying 30° of celestial longitude. Because the signs are regular, they do not correspond exactly to the boundaries of the twelve constellations after which they are named, the English word zodiac derives from zōdiacus, the Latinized form of the Ancient Greek zōidiakòs kýklos, meaning circle of little animals. Zōidion is the diminutive of zōion, the name reflects the prominence of animals among the twelve signs. The construction of the zodiac is described in Ptolemys vast 2nd century AD work, the term zodiac may also refer to the region of the celestial sphere encompassing the paths of the planets corresponding to the band of about eight arc degrees above and below the ecliptic. The zodiac of a planet is the band that contains the path of that particular body, e. g. the zodiac of the Moon is the band of five degrees above. By extension, the zodiac of the comets may refer to the band encompassing most short-period comets, the division of the ecliptic into the zodiacal signs originates in Babylonian astronomy during the first half of the 1st millennium BC. The zodiac draws on stars in earlier Babylonian star catalogues, such as the MUL. APIN catalogue, around the end of the 5th century BC, Babylonian astronomers divided the ecliptic into twelve equal signs, by analogy to twelve schematic months of thirty days each. Each sign contained thirty degrees of longitude, thus creating the first known celestial coordinate system. Because the division was made into equal arcs, 30° each, in Babylonian astronomical diaries, a planet position was generally given with respect to a zodiacal sign alone, less often in specific degrees within a sign. When the degrees of longitude were given, they were expressed with reference to the 30° of the zodiacal sign, in astronomical ephemerides, the positions of significant astronomical phenomena were computed in sexagesimal fractions of a degree. For daily ephemerides, the positions of a planet were not as important as the astrologically significant dates when the planet crossed from one zodiacal sign to the next. The Babylonian star catalogs entered Greek astronomy in the 4th century BC, Babylonia or Chaldea in the Hellenistic world came to be so identified with astrology that Chaldean wisdom became among Greeks and Romans the synonym of divination through the planets and stars. Hellenistic astrology derived in part from Babylonian and Egyptian astrology, horoscopic astrology first appeared in Ptolemaic Egypt. The Dendera zodiac, a dating to ca.50 BC, is the first known depiction of the classical zodiac of twelve signs. The earliest extant Greek text using the Babylonian division of the zodiac into 12 signs of 30 equal degrees each is the Anaphoricus of Hypsicles of Alexandria. Particularly important in the development of Western horoscopic astrology was the astrologer and astronomer Ptolemy, whose work Tetrabiblos laid the basis of the Western astrological tradition. Under the Greeks, and Ptolemy in particular, the planets, Houses, Ptolemy lived in the 2nd century AD, three centuries after the discovery of the precession of the equinoxes by Hipparchus around 130 BC
Zodiac
–
The Earth in its orbit around the
Sun causes the Sun to appear on the celestial sphere moving over the
ecliptic (red), which is tilted with respect to the equator (blue-white).
Zodiac
–
Wheel of the zodiac: This 6th century mosaic pavement in a synagogue incorporates Greek-Byzantine elements,
Beit Alpha,
Israel.
Zodiac
–
The 1st century BC
Dendera zodiac (19th-century engraving)
Zodiac
–
Angers Cathedral South Rose Window of Christ (centre) with elders (bottom half) and Zodiac (top half). Mediaeval stained glass by Andre Robin after the fire of 1451
25.
Ecliptic
–
The ecliptic is the apparent path of the Sun on the celestial sphere, and is the basis for the ecliptic coordinate system. It also refers to the plane of this path, which is coplanar with the orbit of Earth around the Sun, the motions as described above are simplifications. Due to the movement of Earth around the Earth–Moon center of mass, due to further perturbations by the other planets of the Solar System, the Earth–Moon barycenter wobbles slightly around a mean position in a complex fashion. The ecliptic is actually the apparent path of the Sun throughout the course of a year, because Earth takes one year to orbit the Sun, the apparent position of the Sun also takes the same length of time to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward every day, again, this is a simplification, based on a hypothetical Earth that orbits at uniform speed around the Sun. The actual speed with which Earth orbits the Sun varies slightly during the year, for example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days. The variation of orbital speed accounts for part of the equation of time, if the equator is projected outward to the celestial sphere, forming the celestial equator, it crosses the ecliptic at two points known as the equinoxes. The Sun, in its apparent motion along the ecliptic, crosses the equator at these points, one from south to north. The crossing from south to north is known as the equinox, also known as the first point of Aries. The crossing from north to south is the equinox or descending node. Likewise, the ecliptic itself is not fixed, the gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of Earths orbit, and hence of the ecliptic, known as planetary precession. The combined action of two motions is called general precession, and changes the position of the equinoxes by about 50 arc seconds per year. Once again, this is a simplification, periodic motions of the Moon and apparent periodic motions of the Sun cause short-term small-amplitude periodic oscillations of Earths axis, and hence the celestial equator, known as nutation. Obliquity of the ecliptic is the used by astronomers for the inclination of Earths equator with respect to the ecliptic. It is about 23. 4° and is currently decreasing 0.013 degrees per hundred years due to planetary perturbations, the angular value of the obliquity is found by observation of the motions of Earth and other planets over many years. From 1984, the Jet Propulsion Laboratorys DE series of computer-generated ephemerides took over as the ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated, jPLs fundamental ephemerides have been continually updated. J. Laskar computed an expression to order T10 good to 0″. 04/1000 years over 10,000 years, all of these expressions are for the mean obliquity, that is, without the nutation of the equator included
Ecliptic
Ecliptic
26.
Leo (astrology)
–
Leo, is the fifth astrological sign of the zodiac, originating from the constellation of Leo. It comes after Cancer and before Virgo, under the tropical zodiac, the Sun transits this area on average between July 22 and August 23, the sign spans the 120th to 150th degree of celestial longitude. Astrology, in its broadest sense, is the search for meaning in the sky, it seeks to understand general and specific human behavior through the influence of planets. It has been argued that astrology began as a study as soon as human beings made conscious attempts to measure, record, astrology is believed to have originated in China about the 3rd millennium BC. Its system is based on astronomy and calendars and its development is tied to that of astronomy, Leo is a fixed sign along with Taurus, Scorpio, and Aquarius. The symbol of the lion is based on the Nemean lion and it is a northern sign and its opposite southern sign is Aquarius. Hellenistic astrology is a tradition of astrology that was developed and practiced in the late Hellenistic period in and around the Mediterranean region. The texts and technical terminology of this tradition of astrology were largely written in Greek, the tradition originated sometime around the late 2nd or early 1st century BCE, and then was practiced until the 6th or 7th century CE. The conquest of Asia by Alexander the Great exposed the Greeks to the cultures and cosmological ideas of Syria, Babylon, Persia, Greek overtook cuneiform script as the international language of intellectual communication and part of this process was the transmission of astrology from cuneiform to Greek. Sometime around 280 BC, Berossus, a priest of Bel from Babylon, moved to the Greek island of Kos in order to teach astrology, with this, what historican Nicholas Campion calls, the innovative energy in astrology moved west to the Hellenistic world of Greece and Egypt. According to Campion, the astrology that arrived from the Eastern World was marked by its complexity, astrology is believed to have originated in China about the 3rd millennium BC. Its system is based on astronomy and calendars and its development is tied to that of astronomy, astrology was traditionally regarded highly in China, and Confucius is said to have treated astrology with respect saying, Heaven sends down its good or evil symbols and wise men act accordingly. The 60-year cycle combining the five elements with the animal signs of the zodiac has been documented in China since at least the time of the Shang dynasty. Oracles bones have been found dating from that period with the according to the 60-year cycle inscribed on them, along with the name of the diviner. One of the most famous astrologers in China was Tsou Yen who lived in around 300 BC, the dictionary definition of Leo at Wiktionary Media related to Leo at Wikimedia Commons Warburg Institute Iconographic Database
Leo (astrology)
27.
Stereographic projection
–
In geometry, the stereographic projection is a particular mapping that projects a sphere onto a plane. The projection is defined on the sphere, except at one point. Where it is defined, the mapping is smooth and bijective and it is conformal, meaning that it preserves angles. It is neither isometric nor area-preserving, that is, it preserves neither distances nor the areas of figures, intuitively, then, the stereographic projection is a way of picturing the sphere as the plane, with some inevitable compromises. In practice, the projection is carried out by computer or by using a special kind of graph paper called a stereographic net, shortened to stereonet. The stereographic projection was known to Hipparchus, Ptolemy and probably earlier to the Egyptians and it was originally known as the planisphere projection. Planisphaerium by Ptolemy is the oldest surviving document that describes it, one of its most important uses was the representation of celestial charts. The term planisphere is still used to refer to such charts, in the 16th and 17th century, the equatorial aspect of the stereographic projection was commonly used for maps of the Eastern and Western Hemispheres. It is believed that already the map created in 1507 by Gualterius Lud was in stereographic projection, as were later the maps of Jean Roze, Rumold Mercator, in star charts, even this equatorial aspect had been utilised already by the ancient astronomers like Ptolemy. François dAguilon gave the stereographic projection its current name in his 1613 work Opticorum libri sex philosophis juxta ac mathematicis utiles, in 1695, Edmond Halley, motivated by his interest in star charts, published the first mathematical proof that this map is conformal. He used the recently established tools of calculus, invented by his friend Isaac Newton and this section focuses on the projection of the unit sphere from the north pole onto the plane through the equator. Other formulations are treated in later sections, the unit sphere in three-dimensional space R3 is the set of points such that x2 + y2 + z2 =1. Let N = be the pole, and let M be the rest of the sphere. The plane z =0 runs through the center of the sphere, for any point P on M, there is a unique line through N and P, and this line intersects the plane z =0 in exactly one point P′. Define the stereographic projection of P to be this point P′ in the plane, in Cartesian coordinates on the sphere and on the plane, the projection and its inverse are given by the formulas =, =. In spherical coordinates on the sphere and polar coordinates on the plane, here, φ is understood to have value π when R =0. Also, there are ways to rewrite these formulas using trigonometric identities. In cylindrical coordinates on the sphere and polar coordinates on the plane, the projection is not defined at the projection point N =
Stereographic projection
–
Illustration by
Rubens for "Opticorum libri sex philosophis juxta ac mathematicis utiles", by
François d'Aiguillon. It demonstrates how the projection is computed.
Stereographic projection
–
The sphere, with various
loxodromes shown in distinct colors
Stereographic projection
–
Two points P 1 and P 2 are drawn on a transparent sheet tacked at the origin of a Wulff net.
28.
Vernal equinox
–
An equinox is the moment in which the plane of Earths equator passes through the center of the Sun, which occurs twice each year, around 20 March and 23 September. On an equinox, day and night are of equal duration all over the planet. They are not exactly equal, however, due to the size of the sun. To avoid this ambiguity, the word equilux is sometimes used to mean a day in which the durations of light, see Length of equinoctial day and night for further discussion. The word is derived from the Latin aequinoctium, aequus and nox, the equinoxes are the only times when the solar terminator is perpendicular to the equator. As a result, the northern and southern hemispheres are equally illuminated, the word comes from Latin equi or equal and nox meaning night. In other words, the equinoxes are the times when the subsolar point is on the equator. The subsolar point crosses the equator moving northward at the March equinox, the equinoxes, along with solstices, are directly related to the seasons of the year. In the southern hemisphere, the equinox occurs in September. When Julius Caesar established the Julian calendar in 45 BC, he set 25 March as the date of the spring equinox. Because the Julian year is longer than the tropical year. By 1500 AD, it had drifted backwards to 11 March and this drift induced Pope Gregory XIII to create a modern Gregorian calendar. However, the leap year intervals in his calendar were not smooth and this causes the equinox to oscillate by about 53 hours around its mean position. This in turn raised the possibility that it could fall on 22 March, the astronomers chose the appropriate number of days to omit so that the equinox would swing from 19 to 21 March but never fall on the 22nd. Vernal equinox and Autumnal equinox, these names are direct derivatives of Latin. The equivalent common language English terms spring equinox and autumn equinox are even more ambiguous, March equinox and September equinox, names referring to the months of the year they occur, with no ambiguity as to which hemisphere is the context. They are still not universal, however, as not all use a solar-based calendar where the equinoxes occur every year in the same month. Northward equinox and southward equinox, names referring to the apparent direction of motion of the Sun
Vernal equinox
–
Bas-relief in
Persepolis – a symbol
Iranian/Persian Nowruz – on the day of an equinox, the power of an eternally fighting bull (personifying the
Earth) and that of a lion (personifying the
Sun) are equal.
Vernal equinox
–
Illustration of astronomical calculations of northward equinox and
Nowruz
Vernal equinox
–
Chichen Itza pyramid during the spring equinox –
Kukulkan, the famous descent of the snake
29.
Sidereal time
–
Sidereal time /saɪˈdɪəriəl/ is a time-keeping system that astronomers use to locate celestial objects. Using sidereal time it is possible to point a telescope to the proper coordinates in the night sky. Briefly, sidereal time is a scale that is based on Earths rate of rotation measured relative to the fixed stars rather than the Sun. From a given point, a star found at one location in the sky will be found at the same location on another night at the same sidereal time. This is similar to how the time kept by a sundial can be used to find the location of the Sun, just as the Sun and Moon appear to rise in the east and set in the west due to the rotation of Earth, so do the stars. Both solar time and sidereal time make use of the regularity of Earths rotation about its polar axis, a mean sidereal day is 23 hours,56 minutes,4.0916 seconds, the time it takes Earth to make one rotation relative to the vernal equinox. The longer true sidereal period is called a day by the International Earth Rotation. It is also referred to as the period of rotation. Maps of the stars in the night sky use declination and right ascension as coordinates and these correspond to latitude and longitude respectively. In the sky, the meridian is the north to south line that goes through the point directly overhead. Solar time is measured by the apparent diurnal motion of the Sun, a mean solar day is the average time between local solar noons. Earth makes one rotation around its axis in a sidereal day, so after a sidereal day has passed, Earth still needs to rotate slightly more before the Sun reaches local noon according to solar time. A mean solar day is, therefore, nearly 4 minutes longer than a sidereal day, the stars are so far away that Earths movement along its orbit makes nearly no difference to their apparent direction, and so they return to their highest point in a sidereal day. Another way to see this difference is to notice that, relative to the stars, therefore, there is one fewer solar day per year than there are sidereal days. This makes a sidereal day approximately 365. 24/366.24 times the length of the 24-hour solar day, Earths rotation is not a simple rotation around an axis that would always remain parallel to itself. Earths rotational axis itself rotates about an axis, orthogonal to Earths orbit. This phenomenon is called the precession of the equinoxes, because of this precession, the stars appear to move around Earth in a manner more complicated than a simple constant rotation. In this reference frame, Earths rotation is close to constant and it is also in this reference frame that the tropical year, the year related to Earths seasons, represents one orbit of Earth around the Sun
Sidereal time
–
Key concepts
Sidereal time
–
Sidereal time vs solar time. Above left: a distant star (the small red circle) and the Sun are at
culmination, on the local meridian. Centre: only the distant star is at culmination (a mean
sidereal day). Right: a few minutes later the Sun is on the local meridian again. A
solar day is complete.
30.
Schwabacher
–
The German word Schwabacher refers to a specific blackletter typeface which evolved from Gothic Textualis under the influence of Humanist type design in Italy during the 15th century. Schwabacher typesetting was the most common typeface in Germany, until it was replaced by Fraktur from the mid 16th century onwards, the term derives from the Franconian town of Schwabach, where in 1529 the Articles of Schwabach, a Lutheran creed, were adopted. They became the basis of the 1530 Confessio Augustana and possibly also promoted the use of Schwabacher types, similar to Rotunda, the rounded Schwabacher type was nearer to handwriting than the former Textualis style, though it also includes sharp edges. The lower case g and the upper case H have particularly distinctive forms, in the context of German language texts, Schwabacher appeared vibrant and popular. While the Latin Gutenberg Bible was still set in Textualis type, Schwabacher became widely known with the spread of Luther Bibles from 1522. After Schwabacher was displaced by Fraktur as the most-used German language typeface from about 1530 and it was still used occasionally until the mid 20th century. Actually, there is no evidence of any connection between Jews and the Schwabacher typeface, at the time of its origin the ownership of printing houses was reserved for Christian citizens. The German sentence in the reads, Beispiel Alte Schwabacher. This is a sentence meaning Victor chases twelve boxers across the great dam of Sylt. Friedrich Beck, „Schwabacher Judenlettern“ - Schriftverruf im Dritten Reich, in, Die Kunst des Vernetzens, Verlag für Berlin-Brandenburg,2006, ISBN 3-86650-344-X Philipp Luidl, Die Schwabacher – Die ungewöhnlichen Wege der Schwabacher Judenletter. ISBN 3-87512-415-4 Vergessen und verdrängt Schwabach 1918-1945, Ausstellungskatalog Stadtmuseum Schwabach, archived from the original on March 18,2009
Schwabacher
–
A page from the
Schedelsche Weltchronik, 1493
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