|
Solar Hijri Calendar
The Solar Hijri calendar is the official calendar of Iran. It is a solar calendar, based on the Earth's orbit around the Sun. Each year begins on the day of the March equinox and has years of 365 or 366 days. It is sometimes also called the Shamsi calendar, Khorshidi calendar or Persian calendar. It is abbreviated as SH, HS, AP, or, sometimes as AHSh, while the lunar Hijri calendar (commonly known in the West as the 'Islamic calendar') is usually abbreviated as AH. The epoch (very first day) of the Solar Hijri calendar was the day of the spring equinox, March 19, 622 CE. The calendar is a "Hijri calendar" because that was the year that Mohammed is believed to have left from Mecca to Medina, which event is referred to as the Hijrah. Since the calendar uses astronomical observations and calculations for determining the vernal equinox, it theoretically has no intrinsic error in matching the vernal equinox year. According to Iranian studies, it is older than the lunar Hijri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordibehesht 1383 Calendar
Ordibehesht or Ardibehesht (, ) is the second month of the Zoroastrian calendar, which is used officially in Iran and Afghanistan. It has 31 days and spans the months of April and May in the Gregorian calendar. The Dari name for the month is Saur or Sowr. Its associated astrological sign in the Zodiac, tropical zodiac is Taurus (astrology), Taurus. Ordibehesht is the second month of the spring season (), and is followed by the month of Khordad. Events * 13, S.H. 1265 – Haymarket affair (first police confrontation against workers' groups in Chicago) * 4, S.H. 1294 – Landing at Anzac Cove (part of the Gallipoli campaign of World War I) * 19. S.H. 1299 - Kiev Victory Parade (1920) * 5, S.H. 1324 – National Liberation Committee declares war against the Nazi Germany, Nazi-backed Italian Social Republic * 18, S.H. 1324 – End of World War II in Europe * 1, S.H. 1346 – Greek junta#Coup d'état of 21 April, Coup d'état in the Kingdom of Greece * 3, S.H. 1353 – Carnation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Era
Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the original Anno Domini (AD) and Before Christ (BC) notations used for the same calendar era. The two notation systems are numerically equivalent: " CE" and "AD " each describe the current year; "400 BCE" and "400 BC" are the same year. The expression can be traced back to 1615, when it first appears in a book by Johannes Kepler as the (), and to 1635 in English as " Vulgar Era". The term "Common Era" can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish religious scholars. Since the late 20th century, BCE and CE have become popular in academic and scientific publications on the grounds that BCE and CE are religiously neutral terms. They have been promoted as more sensitive to non-Christia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can use Conditional (computer programming), conditionals to divert the code execution through various routes (referred to as automated decision-making) and deduce valid inferences (referred to as automated reasoning). In contrast, a Heuristic (computer science), heuristic is an approach to solving problems without well-defined correct or optimal results.David A. Grossman, Ophir Frieder, ''Information Retrieval: Algorithms and Heuristics'', 2nd edition, 2004, For example, although social media recommender systems are commonly called "algorithms", they actually rely on heuristics as there is no truly "correct" recommendation. As an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropical Year
A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth or another celestial body of the Solar System – thus completing a full cycle of astronomical seasons. For example, it is the time from vernal equinox to the next vernal equinox, or from summer solstice to the next summer solstice. It is the type of year used by tropical solar calendars. The tropical year is one type of astronomical year and particular orbital period. Another type is the sidereal year (or sidereal orbital period), which is the time it takes Earth to complete one full orbit around the Sun as measured with respect to the fixed stars, resulting in a duration of 20 minutes longer than the tropical year, because of the precession of the equinoxes. Since antiquity, astronomers have progressively refined the definition of the tropical year. The entry for "year, tropical" in the '' Astronomical Almanac Onlin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apsidal Precession
In celestial mechanics, apsidal precession (or apsidal advance) is the precession (gradual rotation) of the line connecting the apsis, apsides (line of apsides) of an orbiting body, astronomical body's orbit. The apsides are the orbital points farthest (apoapsis) and closest (periapsis) from its primary (astronomy), primary body. The apsidal precession is the first time derivative of the argument of periapsis, one of the six main orbital elements of an orbit. Apsidal precession is considered positive when the orbit's axis rotates in the same direction as the orbital motion. An apsidal period is the time interval required for an orbit to precess through 360°, which takes the Earth about 112,000 years and the Moon about 8.85 years. History The ancient Greek astronomer Hipparchus noted the apsidal precession of the Moon's orbit (as the revolution of the Moon's apogee with a period of approximately 8.85 years); it is corrected for in the Antikythera Mechanism (circa 80 BC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axial Precession
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In particular, axial precession can refer to the gradual shift in the orientation of Earth's axis of rotation in a cycle of approximately 26,000 years.Hohenkerk, C.Y., Yallop, B.D., Smith, C.A., & Sinclair, A.T. "Celestial Reference Systems" in Seidelmann, P.K. (ed.) ''Explanatory Supplement to the Astronomical Almanac''. Sausalito: University Science Books. p. 99. This is similar to the precession of a spinning top, with the axis tracing out a pair of cones joined at their apices. The term "precession" typically refers only to this largest part of the motion; other changes in the alignment of Earth's axis— nutation and polar motion—are much smaller in magnitude. Earth's precession was historically called the precession of the equinoxes, b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Eccentricity
In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit (or capture orbit), and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the Galaxy. Definition In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit. The eccentricity of this Kepler orbit is a non-negative number that defines its shape. The eccentricity may take the following values: * Circular orbit: * Elliptic orbit: * Parabolic trajectory: * Hyperbolic trajectory: The eccentricity is given by e = \sqrt where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
September Equinox
The September equinox (or southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward. Because of differences between the calendar year and the tropical year, the September equinox may occur from September 21 to 24. At the equinox, the Sun as viewed from the equator rises due east and sets due west. Before the Southward equinox, the Sun rises and sets more northerly, and afterwards, it rises and sets more southerly. The equinox may be taken to mark the end of astronomical summer and the beginning of astronomical autumn (autumnal equinox) in the Northern Hemisphere, while marking the end of astronomical winter and the start of astronomical spring (vernal equinox) in the Southern Hemisphere. Occurrences The September equinox is one point in time commonly used to determine the length of the tropical year. The dates and times of the September equinoxes that occur from the year 2018 to 2028 (UTC) are listed as follows: Const ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jalali Calendar
The Jalali calendar, also referred to as ''Malikshahi'' and ''Maliki'', is a solar calendar compiled during the reign of Jalaluddin Malik-Shah I, the Sultan of the Seljuk Empire (1072–1092 CE), by the order of Grand Vizier Nizam al-Mulk, using observations made in the cities of Isfahan (the capital of the Seljuks), Rey, and Nishapur. Variants of the Jalali calendar are still in use today in Iran and Afghanistan. In Iran, the Persian names of the zodiac are used, while in Afghanistan the original Arabic names are used. The Jalali calendar gains approximately 1 day on the Julian calendar every 128 years. The tropical Jalali calendar (), which inherited some aspects from the Yazdgerdi calendar, was adopted on 15 March 1079 by the Sultan, based on the recommendations of a committee of astronomers, including Omar Khayyam, at the imperial observatory in the capital city of Isfahan. It was Khayyam who positioned Isfahan as the prime meridian, otherwise known as the nasf. Month co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lunar Hijri Calendar
The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the annual fasting and the annual season for the great pilgrimage. In almost all countries where the predominant religion is Islam, the civil calendar is the Gregorian calendar, with Syriac month-names used in the Levant and Mesopotamia (Iraq, Syria, Jordan, Lebanon and Palestine), but the religious calendar is the Hijri one. This calendar enumerates the Hijri era, whose epoch was established as the Islamic New Year in 622 CE. During that year, Muhammad and his followers migrated from Mecca to Medina and established the first Muslim community (''ummah''), an event commemorated as the Hijrah. In the West, dates in this era are usually denoted AH (). In Muslim countries, it is also sometimes denoted as H from its Arabic form (, abbreviated ) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Central Asia
Central Asia is a region of Asia consisting of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian language, Persian suffix "-stan" (meaning ) in both respective native languages and most other languages. The region is bounded by the Caspian Sea to the southwest, European Russia to the northwest, China and Mongolia to the east, Afghanistan and Iran to the south, and Siberia to the north. Together, the five Central Asian countries have a total population of around million. In the pre-Islamic and early Islamic eras ( and earlier) Central Asia was inhabited predominantly by Iranian peoples, populated by Eastern Iranian-speaking Bactrians, Sogdians, Khwarezmian language, Chorasmians, and the semi-nomadic Scythians and Dahae. As the result of Turkic migration, Central Asia also became the homeland for the Kazakhs, Kyrgyzs, Volga Tatars, Tatars, Turkmens, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balkans
The Balkans ( , ), corresponding partially with the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throughout the whole of Bulgaria. The Balkan Peninsula is bordered by the Adriatic Sea in the northwest, the Ionian Sea in the southwest, the Aegean Sea in the south, the Turkish straits in the east, and the Black Sea in the northeast. The northern border of the peninsula is variously defined. The highest point of the Balkans is Musala, , in the Rila mountain range, Bulgaria. The concept of the Balkan Peninsula was created by the German geographer August Zeune in 1808, who mistakenly considered the Balkan Mountains the dominant mountain system of southeastern Europe spanning from the Adriatic Sea to the Black Sea. In the 19th century the term ''Balkan Peninsula'' was a synonym for Rumelia, the parts of Europe that were provinces of the Ottoman E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
