Jang Yeong-sil! Jang Yeong-sil was a prominent Korean scientist and astronomer during the Joseon Dynasty (1392–1910). Although Jang was born as a peasant, King Sejong's (r. 1418–1450) new policy of breaking class barriers placed on the national civil service allowed Jang to work at the royal palace. Jang's inventions, such as the Cheugugi (the rain gauge) and the water gauge, highlight the technological advancements of the Joseon Dynasty. Image * Image Sejong's first assignment to Jang was to build a celestial globe to measure astronomical objects. Books obtained from Arabian and Chinese schola ...... Celestial Globe * Image Self-striking water clocks had already been invented by the Arabians and the Chinese (in 1091), and a more primitive form was in use by the Koreans. WaterClock * Image Jang's invention of the water clock saw its infusion throughout the country. Yet, these were very costly, and the cheaper and more manageable alternative ..... Sundial Love Jang! Telephone. : 12345678-90 Fax : 23456789-01 Email : ask@lovejang.com Get Social with us! Share your thoughts! Copyright © 2012 Lovejang Incorporated LRP 727 6783 83839 All rights reserved Jang Yeong-sil! Jang Yeong-sil was a prominent Korean scientist and astronomer during the Joseon Dynasty (1392–1910). Although Jang was born as a peasant, King Sejong's (r. 1418–1450) new policy of breaking class barriers placed on the national civil service allowed Jang to work at the royal palace. Jang's inventions, such as the Cheugugi (the rain gauge) and the water gauge, highlight the technological advancements of the Joseon Dynasty. Image * Image Sejong's first assignment to Jang was to build a celestial globe to measure astronomical objects. Books obtained from Arabian and Chinese schola ...... Celestial Globe * Image Self-striking water clocks had already been invented by the Arabians and the Chinese (in 1091), and a more primitive form was in use by the Koreans. WaterClock * Image Jang's invention of the water clock saw its infusion throughout the country. Yet, these were very costly, and the cheaper and more manageable alternative ..... Sundial Early Years Jang Yeong-sil's birth is recorded only in the genealogy of the Jang family and in the Annals of the Joseon Dynasty. According to these records, his father, Jang Seong-hwi, was the 8th generation of the Jang family who came from China. Jang Seong-hwi was the 3rd of 5 brothers and all of the brothers previously were ministers of Goryeo. There are many historical records about his elder brother, Jang Seong-bal, who was born in 1344 and his grave located at Ui-seong in the province of Gyeongbuk. The Annals state that his mother was a gwangi (gisaeng), thereby their (Yeong-sil's and their mother) social status was a gwanno, (a servant in civil service district courts). Yeong-sil's talent was so excellent that he was sent to the royal court. From above, we may infer that Yeong-sil was born in a family of high official status but when General Yi Song-gye unleashed a coup d'etat, which gave rise to the Joseon Dynasty, Jang Seong-hwi became a political prisoner and Yeong-sil and his mother became gwannos. Jang's extraordinary accomplishments earned him much trust of the king. Some government officials were very jealous of Jang, especially when he had achieved so much regardless of his common origin. Furthermore, as Joseon's society was rooted in Korean Confucianism, scientists and engineers were held in low esteem in parallel with craftsmen. In 1442, King Sejong ordered Jang to build a gama, an elaborately decorated Korean sedan chair. The gama broke while the king was traveling, and Jang was held responsible. Although the king was against the decree, Jang was jailed for a long time, and was expelled from the royal palace. Later events of his life, including the date of his death, were not recorded. Jang Yeong-sil! Jang Yeong-sil was a prominent Korean scientist and astronomer during the Joseon Dynasty (1392–1910). Although Jang was born as a peasant, King Sejong's (r. 1418–1450) new policy of breaking class barriers placed on the national civil service allowed Jang to work at the royal palace. Jang's inventions, such as the Cheugugi (the rain gauge) and the water gauge, highlight the technological advancements of the Joseon Dynasty. Image * Image Sejong's first assignment to Jang was to build a celestial globe to measure astronomical objects. Books obtained from Arabian and Chinese schola ...... Celestial Globe * Image Self-striking water clocks had already been invented by the Arabians and the Chinese (in 1091), and a more primitive form was in use by the Koreans. WaterClock * Image Jang's invention of the water clock saw its infusion throughout the country. Yet, these were very costly, and the cheaper and more manageable alternative ..... Sundial Celestial Globe WaterClock Sundial Celestial globes show the apparent positions of the stars in the sky. Image Sejong's first assignment to Jang was to build a celestial globe to measure astronomical objects. Books obtained from Arabian and Chinese scholars were not complete in their instructions, for these devices could also be used for military purposes. After two months of study, he made a spherical device that could perform with mediocre accuracy. One year after his first attempt, in 1433, Young Sil made the honcheonui (혼천의, 渾天儀). Honcheonui depended on a waterwheel to rotate the internal globe to indicate time. Whether day or night, this allowed the instrument to be updated on the positions of the sun, moon, and the stars. Later celestial globes (i.e. gyupyo (규표)) could measure time changes according to the seasonal variations. These instruments, along with the sundials and water clocks, were stationed around the Kyonghoeru Pond in Kyongbok Palace and made into use by the astronomers. The success of Jang Yeong-sil's astronomical machines was marked in 1442 AD when the Korean astronomers compiled their computations on the courses of the seven heavenly objects (five visible planets, the sun, and moon) in Chiljeongsan (칠정산).Celestial globes show the apparent positions of the stars in the sky. They omit the Sun, Moon and planets because the positions of these bodies vary relative to those of the stars, but the ecliptic, along which the Sun moves, is indicated. A potential issue arises regarding the "handedness" of celestial globes. If the globe is constructed so that the stars are in the positions they actually occupy on the imaginary celestial sphere, then the star field will appear back-to-front on the surface of the globe (all the constellations will appear as their mirror images). This is because the view from Earth, positioned at the centre of the celestial sphere, is of the inside of the celestial sphere, whereas the celestial globe is viewed from the outside. For this reason, celestial globes may be produced in mirror image, so that at least the constellations appear the "right way round". Some modern celestial globes address this problem by making the surface of the globe transparent. The stars can then be placed in their proper positions and viewed through the globe, so that the view is of the inside of the celestial sphere, as it is from Earth. The sphericity of the Earth was established by f7c Hellenistic astronomy in the 3rd century BC, and the earliest terrestrial globe appeared from that period. The earliest known example is the one constructed by Crates of Mallus in Cilicia (now Cukurova in modern-day Turkey), in the mid-2nd century BC.[1] No terrestrial globes from Antiquity or the Middle Ages have survived. An example of a surviving celestial globe is part of a Hellenistic sculpture, called the Farnese Atlas, surviving in a 2nd century AD Roman copy in the Naples Museum, Italy.[2] Early terrestrial globes depicting the entirety of the Old World were constructed in the Islamic world.[3][4] According to David Woodward, one such example was the terrestrial globe introduced to Beijing by the Persian astronomer, Jamal ad-Din, in 1267.[5] The oldest surviving terrestrial globe is the Erdapfel, created by Martin Behaim in Nuremberg, Germany, in 1492.[2] A facsimile globe showing America was made by Martin Waldseemueller in 1507. Another early globe, the Hunt-Lenox Globe, ca. 1507, is thought to be the source of the phrase "Here be dragons". Another "remarkably modern-looking" terrestrial globe of the Earth was constructed by Taqi al-Din at the Istanbul observatory of Taqi al-Din during the 1570s.[6] An unusually high proportion of vintage 20th century world globes feature the Australian town of Birdum, which no longer exists but once held an important position at the end of the Northern Australian Railway. Globus IMP electro-mechanical devices including five-inch globes have been used in Soviet and Russian spacecraft from 1961 to 2002 as navigation instruments. In 2001, the TMA version of the Soyuz spacecraft replaced this instrument with a virtual globe.Traditionally, globes were manufactured by gluing a printed paper map onto a sphere, often made from wood. The most common type has long, thin gores (strips) of paper that narrow to a point at the poles,[8] small disks cover over the inevitable irregularities at these points. The more gores there are, the less stretching and crumpling is required to make the paper map fit the sphere. From a geometric point of view, all points on a sphere are equivalent ? one could select any arbitrary point on the Earth, and create a paper map that covers the Earth with strips that come together at that point and the antipodal point. A thermoplastic globe hemisphere, before the excess plastic has been trimmed off. Modern globes are often made from thermoplastic. Flat, plastic disks are printed with a distorted map of one of the Earth's Hemispheres. This is placed in machine which molds the disk into a hemispherical shape. The hemisphere is united with its opposite counterpart to form a complete globe. A globe is usually mounted at a 23.5° angle on bearings. In addition to making it easy to use this mounting also represents the angle of the planet in relation to its sun and the spin of the planet. This makes it easy to visualize how days and seasons change. Osmosis beats is the fastest, safest, and most ecological means of energy generation. Image Jang's invention of the water clock saw its infusion throughout the country. Yet, these were very costly, and the cheaper and more manageable alternative came about to be the sundial. Jang, Ichun, Kimjo, and other scientists made Korea's first sundial, Angbu Ilgu (앙부일구) (仰釜日晷), which meant "pot-shaped sun clock staring at the sky". Angbu Ilgu was bronze in composition, and consisted of a bowl marked with 13 meters to indicate time and four legs jointed by a cross at the base. 7 lines crossed the 13 meters in different curves to compensate for the seasonal changes of the course of the sun. Angbu Ilgu and other variants, such as the Hyunjoo Ilgu and the Chunpyung Ilgu, were implemented in strategic spots, such as the main streets with heavy traffic, so that the people could be well informed of the time. To compensate for the high illiteracy rate among the commoners, 12 shapes of animals, such as mouse, tiger, and cow, were engraved in juxtaposition with the meters. No extant Joseon Dynasty sundials today were made during King Sejong's reign, none known to have survived past Imjin wars (임진왜란).There are different types of sundials: Some sundials use a line of light to indicate the time. Others use the edge of a shadow. The spot of light may be formed by allowing the sun's rays through a small hole or reflecting them from a small circular mirror. A line of light may be formed by allowing the rays through a thin slit or focusing them through a cylindrical lens. When the sundial reads by shadows, the shadow-casting object ? the sundial's gnomon ? may be a thin rod, or any object with a sharp tip or a straight edge. Sundials employ many types of gnomon. The gnomon may be fixed or moved according to the season. It may be oriented vertically, horizontally, aligned with the Earth's axis, or oriented in an altogether different direction determined by mathematics. Sundials also may use many types of surfaces to receive the light or shadow. Planes are the most common surface, but partial spheres, cylinders, cones and other shapes have been used for greater accuracy or beauty. Sundials differ in their portability and their need for orientation. The installation of many dials requires knowing the local latitude, the precise vertical direction (e.g., by a level or plumb-bob), and the direction to true Nor 1130 th. Portable dials are self-aligning; for example, it may have two dials that operate on different principles, such as a horizontal and analemmatic dial, mounted together on one plate. In these designs, their times agree only when the plate is aligned properly. Sundials indicate the local solar time, unless corrected for some other time. To obtain the official clock time, three types of corrections need to be made. First, the orbit of the Earth is not perfectly circular and its rotational axis not perfectly perpendicular to its orbit. The sundial's indicated solar time thus varies from clock time by small amounts that change throughout the year. This correction ? which may be as great as 15 minutes ? is described by the equation of time. A sophisticated sundial, with a curved style or hour lines, may incorporate this correction. Often instead, simpler sundials are used, with a small plaque that gives the offsets at various times of the year. Second, the solar time must be corrected for the longitude of the sundial relative to the longitude of the official time zone. For example, a sundial located west of Greenwich, England but within the same time-zone, shows a later time than the official time. It will show "noon" after the official noon has passed, since the sun passes overhead later. This correction is often made by rotating the hour-lines by an angle equal to the difference in longitudes. Last, to adjust for daylight saving time, the sundial must shift the time away from solar time by some amount, usually an hour. This correction may be made in the adjustment plaque, or by numbering the hour-lines with two sets of numbers.The principles of sundials can be understood most easily from the Sun's apparent motion. Scientists have proven that the Earth rotates on its axis, and revolves in an elliptic orbit about the Sun; however, meticulous observations and experiments were needed. For the purposes of a sundial, an excellent approximation assumes that the Sun revolves around a stationary Earth on the celestial sphere, which rotates every 23 hours and 56 minutes about its celestial axis. The celestial axis is the line connecting the celestial poles. Since the celestial axis is aligned with the axis about which the Earth rotates, the angle of the axis with the local horizontal is the local geographical latitude. Unlike the fixed stars, the Sun changes its position on the celestial sphere, being at a positive declination in summer, at a negative declination in winter, and having exactly zero declination (i.e., being on the celestial equator) at the equinoxes. The Sun's celestial longitude also varies, changing by one complete revolution per year. The path of the Sun on the celestial sphere is called the ecliptic. The ecliptic passes through the twelve constellations of the zodiac in the course of a year. Sundial in Singapore Botanic Gardens. The fact that Singapore is located almost at the equator is reflected in its design. This model of the Sun's motion helps to understand sundials. If the shadow-casting gnomon is aligned with the celestial poles, its shadow will revolve at a constant rate, and this rotation will not change with the seasons. This is the most common design. In such cases, the same hour lines may be used throughout the year. The hour-lines will be spaced uniformly if the surface receiving the shadow is either perpendicular (as in the equatorial sundial) or circular about the gnomon (as in the armillary sphere). In other cases, the hour-lines are not spaced evenly, even though the shadow rotates uniformly. If the gnomon is not aligned with the celestial poles, even its shadow will not rotate uniformly, and the hour lines must be corrected accordingly. The rays of light that graze the tip of a gnomon, or which pass through a small hole, or reflect from a small mirror, trace out a cone aligned with the celestial poles. The corresponding light-spot or shadow-tip, if it falls onto a flat surface, will trace out a conic section, such as a hyperbola, ellipse or (at the North or South Poles) a circle. This conic section is the intersection of the cone of light rays with the flat surface. This cone and its conic section change with the seasons, as the Sun's declination changes; hence, sundials that follow the motion of such light-spots or shadow-tips often have different hour-lines for different times o 10b7 f the year. This is seen in shepherd's dials, sundial rings, and vertical gnomons such as obelisks. Alternatively, sundials may change the angle and/or position of the gnomon relative to the hour lines, as in the analemmatic dial or the Lambert dial. In general, sundials indicate the time by casting a shadow or throwing light onto a surface known as a dial face or dial plate. Although usually a flat plane, the dial face may also be the inner or outer surface of a sphere, cylinder, cone, helix, and various other shapes. The time is indicated where a shadow or light falls on the dial face, which is usually inscribed with hour lines. Although usually straight, these hour lines may also be curved, depending on the design of the sundial (see below). In some designs, it is possible to determine the date of the year, or it may be required to know the date to find the correct time. In such cases, there may be multiple sets of hour lines for different months, or there may be mechanisms for setting/calculating the month. In addition to the hour lines, the dial face may offer other data?such as the horizon, the equator and the tropics?which are referred to collectively as the dial furniture. The entire object that casts a shadow or light onto the dial face is known as the sundial's gnomon.[1] However, it is usually only an edge of the gnomon (or another linear feature) that casts the shadow used to determine the time; this linear feature is known as the sundial's style. The style is usually aligned with the axis of the celestial sphere, and therefore aligned with the local geographical meridian. In some sundial designs, only a point-like feature, such as the tip of the style, is used to determine the time and date; this point-like feature is known as the sundial's nodus.[1][2] Some sundials use both a style and a nodus to determine the time and date. The gnomon is usually fixed relative to the dial face, but not always; in some designs such as the analemmatic sundial, the style is moved according to the month. If the style is fixed, the line on the dial plate perpendicularly beneath the style is called the substyle,[1] meaning "below the style". The angle the style makes perpendicularly with the dial plate is called the substyle height, an unusual use of the word height to mean an angle. On many wall dials, the substyle is not the same as the noon line (see below). The angle on the dial plate between the noon line and the substyle is called the substyle distance, an unusual use of the word distance to mean an angle. By tradition, many sundials have a Motto. The motto is usually in the form of an epigram: sometimes sombre reflections on the passing of time and the brevity of life, but equally often humorous witticisms of the dial maker.[3] A dial is said to be equiangular if its hour-lines are straight and spaced equally. Most equiangular sundials have a fixed gnomon style aligned with the Earth's rotational axis, as well as a shadow-receiving surface that is symmetrical about that axis; examples include the equatorial dial, the equatorial bow, the armillary sphere, the cylindrical dial and the conical dial. However, other designs are equiangular, such as the Lambert dial, a version of the analemmatic dial with a moveable style. Get in touch with LoveJang! Name: Email: Subject: Message: Subscribe to newsletter I agree to the Terms and Conditions King Sejong the Great instituted a policy of selecting officials based on their talent, not by their wealth nor social class. Jang's fame gained him entry into the royal court at Hanseong (present day Seoul), where selected commoners displayed their talents before the king and his advisers. Sejong saw that Jang met his expectations in crafts and engineering, and allowed Jang to work as a government official in the palace. The talented scientists recruited under King Sejong's new program worked at the Hall of Worthies (집현전; 集賢殿; Jiphyeonjeon). Astronomical Instruments Sejong's first assignment to Jang was to build a celestial globe to measure astronomical objects. Books obtained from Arabian and Chinese scholars were not complete in their instructions, for these devices could also be used for military purposes. After two months of study, he made a spherical device that could perform with mediocre accuracy. One year after his first attempt, in 1433, Young Sil made the honcheonui (혼천의, 渾天儀). Honcheonui depended on a waterwheel to rotate the internal globe to indicate time. Whether day or night, this allowed the instrument to be updated on the positions of the sun, moon, and the stars. Later celestial globes (i.e. gyupyo (규표)) could measure time changes according to the seasonal variations. These instruments, along with the sundials and water clocks, were stationed around the Kyonghoeru Pond in Kyongbok Palace and made into use by the astronomers. The success of Jang Yeong-sil's astronomical machines was marked in 1442 AD when the Korean astronomers compiled their computations on the courses of the seven heavenly objects (five visible planets, the sun, and moon) in Chiljeongsan (칠정산). Iron printing press Although Choe Yun-ui (최윤의) invented the world's first metal printing press in 1234 during the Goryeo Dynasty, Johann Gutenberg is recognized worldwide as the first to pioneer this technology. In general, metal movable type printing blocks surpassed the wooden counterparts in durability, clarity, and longevity. Even then, the king asked the scientists at Jiphyeonjeon to build a better printing press. In 1434, the scientists accomplished in building Gabinja (갑인자, 甲寅字), which was made of copper-zinc and lead-tin alloys. It was said to be twice as fast as the previous printing presses and print the Chinese characters in astounding beauty and clarity. Gabinja was reproduced six times during the next 370 years. [edit] Research on weaponry When King Sejong learned of reports that Korean melee weapons were duller and somewhat heavier than those 9af of the neighboring countries, he sent Jang to Gyeongsang province, where he had spent his earlier life, to develop metal alloys for various weapons and tools. Since Jang used to be a gwan-no, he had already acquired much knowledge about metal working and also knew the geography of the area. Jang surveyed the available metals and their characteristics, and presented his research to king and the generals, contributing to the development of Korean weaponry. Rain gauge The Korean economy during the Joseon Dynasty was agriculturally based and was vulnerable to elongated or consecutively occurring droughts. Therefore, there was a need for better ways to manage water. Although rain gauges had been used in ancient Greece and India, Jang invented Korea's first rain gauge in 1441, called cheokugye (측우기), and, by 1442, a standardized rain gauge with dimensions of 42.5 cm (height) and 17 cm (diameter) was introduced throughout the country to gather data on the yearly averages of precipitation throughout the different regions of the country. Water gauge To allow better water management, the king asked the scientists to figure out some ways to inform the farmers of the available amount of water. And, in 1441, Jang invented the world's first water gauge, called Supyo (수표). It was a calibrated stone column placed in the middle of a body of water, connected by a stone bridge. Printing Printing is a process for reproducing text and images, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing. The development of printing was preceded by the use of cylinder seals in Mesopotamia developed in 3500 B.C., and other related stamp seals. The earliest form of printing was woodblock printing, with existing examples from China dating to before 220 A.D. and Egypt to the fourth century. Later developments in printing include the movable type, first developed by Bi Sheng in China, and the printing press, a more efficient printing process for western languages with their more limited alphabets, developed by Johannes Gutenberg in the fifteenth century.By 2005, Digital printing accounts for approximately 9% of the 45 trillion pages printed annually around the world.[13] Printing at home, an office, or an engineering environment is subdivided into: small format (up to ledger size paper sheets), as used in business offices and libraries wide format (up to 3' or 914mm wide rolls of paper), as used in drafting and design establishments. Some of the more common printing technologies are: blueprint ? and related chemical technologies daisy wheel ? where pre-formed chariGen3 and Nexpress use toner particles and the Indigo uses liquid ink. The InfoPrint 5000 is a full-color, continuous forms inkjet drop-on-demand printing system. All handle variable data, and rival offset in quality. Digital offset presses are also called direct imaging p 113c resses, although these presses can receive computer files and automatically turn them into print-ready plates, they cannot insert variable data. Small press and fanzines generally use digital printing. Prior to the introduction of cheap photocopying the use of machines such as the spirit duplicator, hectograph, and mimeograph was common. Sejong the Great Sejong the Great (May 7, 1397 ? May 18, 1450, r. 1418?1450) was the fourth king of the Joseon Dynasty of Korea. During his regency, he reinforced Korean Confucian policies and executed major legal amendments (공법; 貢法). He also used the creation of Hangul and the advancement of technology to expand his territory. He was the third son of King Taejong and Queen Consort Wonkyeong. Sejong is one of only two Korean rulers posthumously honored with the appellation "the Great", the other being Gwanggaeto the Great of Goguryeo. Sejong was born on May 7, 1397, the third son of King Taejong.[3] When he was twelve, he became Grand Prince Chungnyeong As a young prince, Sejong excelled in various studies and was favored by King Taejong over his two older brothers. Sejong's ascension to the throne was different from those of most other kings. Taejong's eldest son, Yangnyeong (양녕대군), viewing himself as lacking in the requisite skills for kingship, believed that his younger brother Sejong was destined to become king. He believed it was his duty to place Sejong as king, so he behaved rudely in court and was soon banished from Seoul. This plot ultimately brought Sejong to the throne. The eldest prince became a wandering traveler and lived in the mountains. The second son traveled to a Buddhist temple, where he became a monk. In August 1418, following Taejong's abdication two months earlier, Sejong ascended the throne. However, Taejong still retained certain powers at court, particularly regarding military matters, until he died in 1422. King Sejong the Great profoundly impacted Korean history with his introduction of hangul, the native phonetic alphabet system for the Korean language.[14] Before the creation of Hangul, only members of the highest class were literate (hanja was typically used to write Korean by using adapted Chinese characters, while Hanmun was sometimes used to write court documents in classical Chinese). One would have to learn the quite complex hanja characters in order to read and write Korean. Further, despite modifications to the Chinese characters, hanja could prove cumbersome when transcribing the Korean language, due to considerable differences in grammar and sentence order.[15] King Sejong presided over the introduction of the 28-letter Korean alphabet, with the explicit goal being that Koreans from all classes would read and write. He also attempted to establish a cultural identity for his people through its unique script. While creating the alphabet, King Sejong encountered opposition of courtiers. First published in 1446, anyone could learn Hangul in a matter of days. Persons previously unfamiliar with Hangul can typically pronounce Korean script accurately after only a few hours study. Each hangul letter is based on a simplified diagram of the patterns made by the mouth, tongue and teeth when making the sound related to the character. Morphemes are built by writing the characters in syllabic blocks. The blocks of letters are then strung together linearly. Hwacha Hwacha or Hwach'a (화차; 火車) (fire cart) was a multiple rocket launcher developed and used in Korea during the Joseon Dynasty (1392-1897). It had the ability to fire up to 100 Singijeon, a type of fire arrow rocket at one time. The hwacha consisted of a two-wheeled cart carrying a board filled with holes into which the singijeon were inserted. . Some East Asian historians believe this technological breakthrough alongside the turtle ship in the mid-16th century had a distinctive effect during the Imjin War; however, sources on both the turtle ship and hwacha are too scarce to really say much about this. Today, hwacha appear in Korean museums, national parks, and popular culture.Long before the development of the hwacha, China imposed severe restrictions on exporting gunpowder to Korea, fiercely guarding a military asset. Y 1137 et, gunpowder weapons were key to the Koreans in maintaining a predominant navy in the Sea of Japan (East Sea) to protect fishermen and merchants against the increasing numbers of invading Japanese and Waegu pirates. In response, there was an effort by Koreans to develop gunpowder on their own. Between the years of 1374 to 1376,[6] Korea began its first productions of gunpowder. In 1377 a Korean scholar named Choe Mu-seon, discovered a way to obtain gunpowder by extracting potassium nitrate from the soil and subsequently invented the Juhwa, Korea's very first rocket.[7] Further developments led to the birth of the family of singijeons. The hwacha was a brainchild of its predecessors, the Juhwa and the Singijeon. The first hwacha was develeoped in Korea in 1409 during the Joseon Dynasty by several Korean scientists, including Yi Do (이도) and Choi Hae-san (최해산).[notes 1] During the rule of Sejong the Great, hwachas were further developed and extensively made. Records show that during this time 90 hwachas were in use. King Sejong, famous for his contribution to Hangul, made efforts to improve the hwacha and by the end of his rule a single hwacha could fire 200 rocket arrows at one time. Stronger and more effective hwachas were made in 1451 under the decree of King Munjong.[notes 1] At the time, 50 units were deployed in Hanseong (present-day Seoul), and another 80 on the northern border. By the end of 1451, hundreds of hwachas were deployed throughout the peninsula The hwacha's structure was very similar to a hand cart with a mobile wooden launchpad on the top filled with 100 to 200 cylindrical holes, into which the ignitors like sajeonchongtong (사전총통) were placed.[notes 1] The ammunition, similar to the Chinese fire arrow, consisted of a 1.1 m long arrow with the addition of a paper tube filled with gunpowder attached to the shaft just below the head. Approximately 100 projectiles were loaded and launched in one volley,[notes 1] and were effective up to a range of 500 meters. One variant had 5 rows of 10 gun barrels in the launchpad, each of which could fire a bundle of four arrow-like projectiles. The back side of the hwacha featured two parallel arms that allowed the operator to push and pull the machine, and a vertical strip designed for in-line attacks or stand ground-sentry positions.[notes 3] The wagon-like wheels were usually fastened by wood pivots and iron axles. In order to reduce friction between the wheels and the axles, tar oil was used. Hwachas were usually made of pine wood, although there are some versions made of oak. Ropes used within were usually made of hemp. The Korean army carried siege engineers and blacksmiths in order to make repairs to the Hwacha if poor road conditions, bad weather, or battle damaged the machinery History of science and technology in Korea Like most other regions in the world, science and technology in Korea has experienced periods of intense growth as well as long periods of stagnation. Past kingdoms and dynasties in Korea were often invaded and the aftermath of these conflicts caused the various governments to divert funds to reconstruction rather than cultural or scientific development. During the Joseon Dynasty Korea was under the effects of Neo-Confucianism and had a status system which prevented most citizens from being educated or even literate. Moreover, Joseon society had a negative view toward scientists and gave them no formal support. The exception to this is the reign of Sejong the Great and a few other sovereigns of Joseon who realized that Korea's isolationist Hermit kingdom policy was a failure and prevented the flow of new ideas and technology to Korea. The production of hard-fired stoneware ceramics, in which clay is vitrified in kilns at >1000°C, occurred first in the Korean Peninsula during the Three Kingdoms Period. This period is notable for the establishment of industrial-scale production of pottery and roof tiles. This involved the adoption of climbing kiln or 'dragon kiln' technology sometime between AD 100-300. One of very few examples of science and technology during the Three Kingdoms of Korea that has survived until this day is the Cheomseongdae, which means "star gazing platform" and is one of the oldest observatories in 1130 stalled on Earth. It was built during Queen Seondeok's rule. The tower is built out of 366 pieces of cut granite which some claim represent the 366 days of the lunar year and has 12 base stones which supposedly represent the twelve months of the year. The design is said to be strongly influenced by Buddhism. The nine-story wooden pagoda of Hwangnyongsa, which was commissioned by Queen Seondeok after the main temple was finished, is reputed to be the largest premodern Korean stupa ever built. It was reported to be 80 metres in height. Only its foundation stones remain today but they attest to the mammoth proportions of the original structure. At the end of the Palaeolithic, people of the Korean Peninsula adopted microlithic stone tool technology, a highly efficient and useful way of making and maintaining a flexible prehistoric toolkit. The Palaeolithic also marks the beginning of a long period of plant and human interaction in which people undoubtedly adopted a number of wild plants for medicinal use. Archaeological evidence from Gosan-ri in Jeju-do indicates that pottery was first made c. 8500-8000 BC.[1] People depended on gathering, hunting, and fishing as the main source of food until the Middle Jeulmun Period (c. 3500 to 2000 BC) when small-scale cultivation of plants began.[2][3] Farmers of the Mumun Period began to use multiple cropping systems of agriculture some time after 1500 BC.[2] This sophisticated technological advance in food production irrevocably altered the subsistence systems of the Mumun and hastened the beginnings of intensive agriculture in the Korean Peninsula. Korea and adjacent areas of East Asia seem to have been a part of the domestication region of soybean (Glycine max) between 1500 and 500 BC.[2]Paddy-field agriculture, a highly complex system of wet-rice cultivation, was also introduced into the southern Korean Peninsula during this period. Widespread archaeological evidence shows that after 850 BC the technology for heating homes changed. Before 850 BC pit-houses were heated using fire from various kinds of hearths that were dug into the floor of the pit-house. After 850 BC, hearths disappeared from the interior of pit-house architecture and was likely replaced with some kind of brazier-like technology in Hoseo, Honam, and western Yeongnam. Bronze objects were exchanged into the Korean Peninsula from the outside before 900 BC. However, the moulds for bronze casting from Songguk-ri and an increased number of bronze artifacts indicates that people in the southern part of the peninsula engaged in bronze metallurgical production starting from c. 700 BC. Several hundred years later iron production was adopted, and Korean-made iron tools and weaponry became increasingly common after approximately 200 BC. Iron tools facilitated the spread of intensive agriculture into new areas of the Korean Peninsula. Until recened in the Goryeo Dynasty. The new model was of even higher qua e8c lity and was twice as fast. Other inventions were the sight glass, and the udometer. Also during the Joseon Dynasty Heo Jun, a court physician wrote a number of medical texts, but his most significant achievement is Dongeui Bogam, which is often noted as the defining text of Traditional Korean medicine. The work spread to China and Japan, where it is still regarded as one of the classics of Oriental medicine[disambiguation needed ] today. The highpoint of Korean astronomy was during the Joseon period, where men such as Jang created celestial globes which could, whether day or night, allow the instrument to be updated on the positions of the sun, moon, and the stars among other devices[11] Later celestial globes (Gyupyo, 규표) could measure time changes according to the seasonal variations. The apex of astronomical and calendarial advances made under King Sejong was the Chiljeongsan, made up of compiled computations on the courses of the seven heavenly objects (five visible planets, the sun, and moon) developed in 1442. This work made it possible for scientists to calculate and accurately predict all the major heavenly phenomena, such as solar eclipses and other stellar movements.[12] Honcheonsigye is an astronomical clock created by Song I-yeong in 1669. The clock has an armillary sphere with a diameter of 40 cm. The sphere is activated by a working clock mechanism, showing the position of the universe at any given time. Kangnido, a Korean made map of the world was created in 1402, by Kim Sa-hyeong (김사형, 金士衡), Yi Mu (이무, 李茂) and Yi Hoe (이회, 李撓). The map was created in the second year of the reign of Taejong of Joseon. The map was made by combining Chinese, Korean and Japanese maps. Hangul, the only featural alphabet in current use for a national language, was promulgated by Sejong in 1444 * Jang Yeoung Sil: http://cheonmun.culturecontent.com/data/svc/cp0421034001/cp0421034001_00001.pdf * Sejong Great : http://www.koreanhero.net/kingsejong/content/en/King_Sejong_en.pdf * Korean Secret : http://www.koreanhero.net/kingsejong/content/korean_secret.pdf A water clock or clepsydra is any timepiece in which time is measured by the regulated flow of liquid into or out from a vessel where the amount is then measured. Image Self-striking water clocks had already been invented by the Arabians and the Chinese (in 1091), and a more primitive form was in use by the Koreans. Although it is believed, Samguk Sagi records that an office overseeing the use of water clocks had been established during the Three Kingdoms Period. The Korean version consisted of two stacked jars of water, with water dropping from the top to the bottom at a measured rate. The level of the water indicated the time of the day. This was very inconvenient because a person had to be always be on guard, so that at each hour he or she could bang a drum to inform the public. Upon hearing about the usage of self-striking water clocks in foreign countries, Sejong assigned Jang and other scientists to build a clock emulating such automatic devices. They failed in developing an operational water clock. Therefore, Jang went to China to study the various designs of water clocks. When he returned in 1434, Jang created Korea's first water clock, Jagyeokru (자격루). This water clock did not survive; however, reconstructions of the Jagyeokru based on text descriptions have been made. Circling the clock were 12 wooden figures that served as indicators of time. There were four water containers, 2 jars that received the water, and 12 arrows floating inside the lower container. As the water from the upper containers seeped down the pipe to the lower container, one of the arrows would tilt a board filled with small iron balls; a ball would roll down a pipe to a container of larger iron balls. The collision would cause the larger balls to travel down a lower pipe and hit a giant cymbal, announcing the time to the community. Then, the ball would land on another container, which is part of a complex of levers and pulleys that activates the motions of the wooden figures to indicate time visually. A water clock or clepsydra (Greek κλ?πτειν kleptein, 'to steal'; ?δωρ hudor, 'water') is any timepiece in which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel where the amount is then measured. Water clocks, along with sundials, are likely to be the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and the day-counting tally stick.[1] Whe 1130 re and when they were first invented is not known, and given their great antiquity it may never be. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, claim that water clocks appeared in China as early as 4000 BC.[2] The Greeks and Romans further advanced water clock design to include the inflow clepsydra with an early feedback system, gearing, and escapement mechanism, which were connected to fanciful automata and resulted in improved accuracy. Further advances were made in Byzantium and particularly the Islamic world, where increasingly accurate water clocks incorporated complex segmental and epicyclic gearing, water wheels, and programmability, advances which eventually made their way to Europe. Independently, the Chinese developed their own advanced water clocks, incorporating gears, escapement mechanisms, and water wheels, passing their ideas on to Korea and Japan[citation needed]. Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. These early water clocks were calibrated with a sundial. While never reaching a level of accuracy comparable to today's standards of timekeeping, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by more accurate pendulum clocks in 17th century Europe. In 1434 during the Choson (or Joseon) Dynasty, Chang Yongsil (or Jang Young Sil), Palace Guard and later Chief Court Engineer, constructed the Jagyeongnu (self-striking water clock or striking clepsydra) for King Sejong. What made the Jagyeongnu self-striking (or automatic) was the use of jack-work mechanisms, by which three wooden figures (jacks) struck objects to signal the time. This innovation no longer required the reliance of human workers, known as "rooster men", to constantly replenish it. By 554, the water clock spread from Korea to Japan. Water clocks were used and improved upon throughout Asia well into the 15th century. In the medieval Islamic world (632-1280), the use of water clocks has its roots from Archimedes during the rise of Alexandria in Egypt and continues on through Byzantium. The water clocks by Al-Jazari, however, are credited for going "well beyond anything" that had preceded them. In al-Jazari's 1206 treatise, he describes one of his water clocks, the elephant clock. The clock recorded the passage of temporal hours, which meant that the rate of flow had to be changed daily to match the uneven length of days throughout the year. To accomplish this, the clock had two tanks, the top tank was connected to the time indicating mechanisms and the bottom was connected to the flow control regulator. Basically, at daybreak the tap was opened and water flowed from the top tank to the bottom tank via a float regulator that maintained a constant pressure in the receiving tank.[31] Water-powered automatic castle clock of Al-Jazari, 12th century. The most sophisticated water-powered astronomical clock was Al-Jazari's castle clock, considered by some to be an early example of a programmable analog computer, in 1206.[32] It was a complex device that was about 11 feet (3.4 m) high, and had multiple functions alongside timekeeping. It included a display of the zodiac and the solar and lunar orbits, and a pointer in the shape of the crescent moon which traveled across the top of a gateway, moved by a hidden cart and causing automatic doors to open, each revealing a mannequin, every hour.[33][34] It was possible to re-program the length of day and night in order to account for the changing lengths of day and night throughout the year, and it also featured five musician automata who automatically play music when moved by levers operated by a hidden camshaft attached to a water wheel.[32] Other components of the castle clock included a main reservoir with a float, a float chamber and flow regulator, plate and valve trough, two pulleys, crescent disc displaying the zodiac, and two falcon automata dropping balls into vases.[35] The first water clocks to employ complex segmental and epicyclic gearing was invented earlier by the Arab engineer Ibn Khala 86a f al-Muradi in Islamic Iberia circa 1000. His water clocks were driven by water wheels, as was also the case for several Chinese water clocks in the 11th century.[36] Comparable water clocks were built in Damascus and Fez. The latter (Dar al-Magana) remains until today and its mechanism has been reconstructed. The first European clock to employ these complex gears was the astronomical clock created by Giovanni de Dondi in circa 1365. Like the Chinese, Arab engineers at the time also developed an escapement mechanism which they employed in some of their water clocks. The escapement mechanism was in the form of a constant-head system, while heavy floats were used as weights.