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Jens Olsen's World Clock
Jens Olsen's World Clock or Verdensur is an advanced astronomical clock which is displayed in Copenhagen City Hall. The clock consists of 12 movements which together have 15,448 parts. The clock is mechanical and must be wound once a week. Displays include lunar and solar eclipses, positions of the stellar bodies, and a perpetual calendar, in addition to the time. The fastest gear completes a revolution every ten seconds and the slowest every axial precession, 25,753 years. History The clock was designed and calculated by Jens Olsen (1872–1945), who was a skilled locksmith, and later learned the trade of clockmaker, clockmaking. He also took part in the beginning of the clock's construction, and died in 1945, 10 years before the clock was completed. The calculations for the clock were made up until 1928, after which they were supervised by the astronomer Elis Strömgren. The drawings for the clock were made between 1934 and 1936, and the actual production of the clock took p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jens Olsens Front
Jens may refer to: * Jens (given name), a list of people with the name * Jens (surname), a list of people * Jens, Switzerland, a municipality * 1719 Jens, an asteroid See also * Jensen (other) Jensen may refer to: People and fictional characters * Jensen (surname), a list of people and fictional characters * Jensen (given name), a list of people * Jensen (gamer), Danish professional ''League of Legends'' player Places * Jensen, Que ... * Jenssi {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escapement
An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to the clock's timekeeping element (usually a pendulum or balance wheel) to replace the energy lost to friction during its cycle and keep the timekeeper oscillating. The escapement is driven by force from a coiled spring (device), spring or a suspended weight, transmitted through the timepiece's gear train. Each swing of the pendulum or balance wheel releases a tooth of the escapement's ''escape wheel'', allowing the clock's gear train to advance or "escape" by a fixed amount. This regular periodic advancement moves the clock's hands forward at a steady rate. At the same time, the tooth gives the timekeeping element a push, before another tooth catches on the escapement's pallet, returning the escapement to its "locked" state. The sudden stoppi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Time
Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day, based on the synodic rotation period. Traditionally, there are three types of time reckoning based on astronomical observations: #Apparent solar time, apparent solar time and #Mean solar time, mean solar time (discussed in this article), and ''sidereal time'', which is based on the apparent motions of stars other than the Sun. Introduction A tall pole vertically fixed in the ground casts a shadow on any sunny day. At one moment during the day, the shadow will point exactly north or south (or disappear when and if the Sun moves directly overhead). That instant is called solar noon, ''local apparent noon'', or 12:00 local apparent time. About 24 hours later the shadow will again point north–south, the Sun seeming to have covered a 360-degree arc around Earth's axis. When the Sun has covered exactly 15 degrees (1/24 of a circle, both a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equation Of Time
The equation of time describes the discrepancy between two kinds of solar time. The two times that differ are the apparent solar time, which directly tracks the diurnal motion of the Sun, and mean solar time, which tracks a theoretical mean Sun with uniform motion along the celestial equator. Apparent solar time can be obtained by measurement of the current position (Hour angle#Solar hour angle, hour angle) of the Sun, as indicated (with limited accuracy) by a sundial. ''Mean'' solar time, for the same place, would be the time indicated by a steady clock set so that over the year its differences from apparent solar time would have a mean of zero. The equation of time is the east or west component of the analemma, a curve representing the angular offset of the Sun from its mean position on the celestial sphere as viewed from Earth. The equation of time values for each day of the year, compiled by astronomical observatory, observatories, were widely listed in almanacs and ephemeri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moveable Feast
A moveable feast is an observance in a Christian liturgical calendar which occurs on different dates in different years. It is the complement of a fixed feast, an annual celebration that is held on the same calendar date every year, such as Christmas. Spring paschal feasts Often considered the most important Christian observance, Spring paschal feasts are a fixed number of days before or after Easter Sunday, which Computus, varies by 35 days since it depends partly on the Lunisolar calendar, phase of the moon and must be Computus, computed each year. In the Hebrew calendar, the new moon of Aviv, spring, is fixed as the Lunar New Year#Middle East/West Asia, Lunar New Year, and the month is called Nisan. The 14 of Nisan is the paschal full moon, the day of the Pesach seder, a ritual meal Haggadah, telling the story of the Exodus from Egypt. It is one of the Three Pilgrimage Festivals, three pilgrimage festivals incumbent on all Jewish males living in the land of Israel. For thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lunar Phase
A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. Because the Moon is tidally locked with the Earth, the same hemisphere is always facing the Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days. The appearance of the Moon (its phase) gradually changes over a lunar month as the relative orbital positions of the Moon around Earth, and Earth around the Sun, shift. The visible side of the Moon is sunlit to varying extents, depending on the position of the Moon in its orbit, with the sunlit portion varying from 0% (at new moon) to nearly 100% (at full moon). Phenomenon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Cycle
The Solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a periodic 11-year change in the Sun's activity measured in terms of Modern Maximum, variations in the number of observed sunspots on the Sun's surface. Over the period of a solar cycle, levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation from a Solar minimum, period of minimum activity to a Solar maximum, period of a maximum activity back to a period of minimum activity. The magnetic field of the Sun flips during each solar cycle, with the flip occurring when the solar cycle is near its maximum. After two solar cycles, the Sun's magnetic field returns to its original state, completing what is known as a Hale cycle. This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as aurora but was not clearly identified un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epact
The epact (, from () = added days) used to be described by medieval computists as the age of a phase of the Moon in days on 22 March; in the newer Gregorian calendar, however, the epact is reckoned as the age of the ecclesiastical moon on 1 January. Its principal use is in determining the date of Easter by computistical methods. It varies (usually by 11 days) from year to year, because of the difference between the solar year of 365366 days and the lunar year of 354355 days. Lunar calendar Epacts can also be used to relate dates in the lunar calendar to dates in the common solar calendar. Solar and lunar years A solar calendar year has 365 days (366 days in leap years). A lunar calendar year has 12 lunar months which alternate between 30 and 29 days for a total of 354 days (in leap years, one of the lunar months has a day added; since a lunar year lasts a little over days, a leap year arises every second or third year rather than every fourth.) If ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dominical Letter
Dominical letters or Sunday letters are a method used to determine the day of the week for particular dates. When using this method, each year is assigned a letter (or pair of letters for leap years) depending on which day of the week the year starts with. The Dominical letter for the current year 2025 is E. Dominical letters are derived from the Roman practice of marking the repeating sequence of eight letters A–H (commencing with A on January 1) on stone calendars to indicate each day's position in the eight-day market week ('' nundinae''). The word is derived from the number nine due to their practice of inclusive counting. After the introduction of Christianity a similar sequence of seven letters A–G was added alongside, again commencing with January 1. The dominical letter marks the Sundays. Nowadays they are used primarily as part of the computus, which is the method of calculating the date of Easter. A common year is assigned a single dominical letter, indicating which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jewel Bearing
A jewel bearing is a plain bearing in which a metal spindle (tool), spindle turns in a gemstone, jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter. The jewels are typically made from the mineral corundum, usually either synthetic sapphire or Ruby#Synthesis and imitation, synthetic ruby. Jewel bearings are used in precision instruments where low friction, long life, and dimensional accuracy are important. Their main use is in mechanical watches. History Jewel bearings were invented in 1704 for use in watches by Nicolas Fatio de Duillier, Peter Debaufre, and Jacob Debaufre, who received an English patent for the idea. Originally natural jewels were used, such as diamond, sapphire, ruby, and garnet. In 1902, Verneuil process, a process to make synthetic sapphire and ruby (crystalline aluminium oxide, also known as corundum) was invented by Auguste Verneuil, making jewelled bearings much cheaper. Today most jewelled ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name ''sapphire'' is derived from the Latin word ', itself from the Greek language, Greek word (), which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called ruby, rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on the locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewellery, jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large boule (crystal), crystal boules. Because of the remarkable hardness of sapphires 9 on the Mohs scale of miner ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Invar
Invar, also known generically as FeNi36 (64FeNi in the US), is a nickel–iron alloy notable for its uniquely low coefficient of thermal expansion (CTE or α). The name ''Invar'' comes from the word ''invariable'', referring to its relative lack of expansion or contraction with temperature changes, and is a registered trademark of ArcelorMittal. The discovery of the alloy was made in 1895 by Swiss physicist Charles Édouard Guillaume for which he received the Nobel Prize in Physics in 1920. It enabled improvements in scientific instruments. Properties Like other nickel/iron compositions, Invar is a solid solution; that is, it is a Phase (matter), single-phase alloy. In one commercial grade called Invar 36 it consists of approximately 36% nickel and 64% iron, has a melting point of , a density of and a resistivity of . The invar range was described by Westinghouse scientists in 1961 as "30–45 Mole fraction, atom per cent nickel". Common grades of Invar have a coefficient o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
