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Ephemeris
In astronomy and celestial navigation, an ephemeris (pl. ephemerides; ) is a book with tables that gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and possibly velocity) over time. Historically, positions were given as printed tables of values, given at regular intervals of date and time. The calculation of these tables was one of the first applications of mechanical computers. Modern ephemerides are often provided in electronic form. However, printed ephemerides are still produced, as they are useful when computational devices are not available. The astronomical position calculated from an ephemeris is often given in the spherical polar coordinate system of right ascension and declination, together with the distance from the origin if applicable. Some of the astronomical phenomena of interest to astronomers are eclipses, apparent retrograde motion/planetary stations, planetary es, sidereal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phases Of The Moon
Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the terminology of the 4 major phases: new moon, first quarter, full moon, last quarter and 4 minor phases: waxing crescent, waxing gibbous, waning gibbous, and waning crescent. The lunar phases gradually change over a synodic month (~29.53 days) as the Moon's orbital positions around Earth and Earth around the Sun shift. The visible side of the Moon is variously sunlit, depending on the position of the Moon in its orbit. Thus, this face's sunlit portion can vary from 0% (at new moon) to 100% (at full moon). Each of the 4 major lunar phases (see below) is ~7.4 days, with +/− 19 hours in variation (6.58–8.24 days) due to the elliptical shape of the Moon's orbit. Phases of the Moon There are four ''principal'' (primary/major) lunar phases: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apparent Retrograde Motion
Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies. While the terms ''direct'' and ''prograde'' are equivalent in this context, the former is the traditional term in astronomy. The earliest recorded use of ''prograde'' was in the early 18th century, although the term is now less common. Etymology The term ''retrograde'' is from the Latin word – "backward-step", the affix meaning "backwards" and "step". ''Retrograde'' is most commonly an adjective used to describe the path of a planet as it travels through the night sky, with respect to the zodiac, stars, and other bodies of the celestial canopy. In this context, the term refers to planets, as they appear from Earth, stopping briefly and reversing direction at certain times, though in reality, of course, we now understa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sidereal Time
Sidereal time (as a unit also sidereal day or sidereal rotation period) (sidereal ) is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it is possible to easily point a telescope to the proper coordinates in the night sky. In short, sidereal time is a "time scale that is based on Earth's rate of rotation measured relative to the fixed stars", or more correctly, relative to the March equinox. Viewed from the same location, a star seen at one position in the sky will be seen at the same position on another night at the same sidereal time. This is similar to how the time kept by a sundial (Solar time) 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 Earth's rotation about its polar axis: solar time following the Sun while, roughly speaking, sidereal time fol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zīj
A zij ( fa, زيج, zīj) is an Islamic astronomical book that tabulates parameters used for astronomical calculations of the positions of the Sun, Moon, stars, and planets. Etymology The name ''zij'' is derived from the Middle Persian term ''zih'' or ''zīg'', meaning cord. The term is believed to refer to the arrangement of threads in weaving, which was transferred to the arrangement of rows and columns in tabulated data. In addition to the term ''zīj'', some were called by the name ''qānūn'', derived from the equivalent Greek word, . Historically significant zijes The Zij-i Sultani published by Ulugh Beg in 1438/9, was utilized as a reference zij throughout Islam during the early modern era. Omar Khayyam's Zij-i Malik Shahi was updated throughout the modern era under various sultanates. Zijes were updated by different empires to suit the interests of that empire, such as the simplified version of Zij-i Sultani by the Mughal Empire. History Some of the early ''zījes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Babylonian Astronomy
Babylonian astronomy was the study or recording of celestial objects during the early history of Mesopotamia. Babylonian astronomy seemed to have focused on a select group of stars and constellations known as Ziqpu stars. These constellations may have been collected from various earlier sources. The earliest catalogue, ''Three Stars Each'', mentions stars of the Akkadian Empire, of Amurru, of Elam and others. A numbering system based on sixty was used, a sexagesimal system. This system simplified the calculating and recording of unusually great and small numbers. The modern practices of dividing a circle into 360 degrees, of 60 minutes each, began with the Sumerians. During the 8th and 7th centuries BC, Babylonian astronomers developed a new empirical approach to astronomy. They began studying and recording their belief system and philosophies dealing with an ideal nature of the universe and began employing an internal logic within their predictive planetary systems. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions. Time has long been an important subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. 108 pages. Time in physics is operationally defined as "what a clock reads". The physical nature of time is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tables Of Toledo
The ''Toledan Tables'', or ''Tables of Toledo'', were astronomical tables which were used to predict the movements of the Sun, Moon and planets relative to the fixed stars. They were a collection of mathematic tables that describe different aspects of the cosmos including prediction of calendar dates, times of cosmic events, and cosmic motion. Origins The Toledan Tables were completed around 1080 by a group of Arabic astronomers at Toledo, Spain. They had started as preexisting Arabic tables made elsewhere, and were numerically adjusted to be centered on the location of Toledo. The Tables of Toledo were partly based on the work of al-Zarqali (known to the West as Arzachel), an Arab mathematician, astronomer, astronomy instrument-maker, and astrologer, who lived in Toledo. The tables were produced by a team whose membership is largely unknown, with the exception of al-Zarqali. Toledo came under Christian Spanish rule in the mid-1080s, shortly after the tables were completed. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muḥammad Ibn Mūsā Al-Khwārizmī
Muhammad ( ar, مُحَمَّد; 570 – 8 June 632 CE) was an Arab religious, social, and political leader and the founder of Islam. According to Islamic doctrine, he was a prophet divinely inspired to preach and confirm the monotheistic teachings of Adam, Abraham, Moses, Jesus, and other prophets. He is believed to be the Seal of the Prophets within Islam. Muhammad united Arabia into a single Muslim polity, with the Quran as well as his teachings and practices forming the basis of Islamic religious belief. Muhammad was born approximately 570CE in Mecca. He was the son of Abdullah ibn Abd al-Muttalib and Amina bint Wahb. His father Abdullah was the son of Quraysh tribal leader Abd al-Muttalib ibn Hashim, and he died a few months before Muhammad's birth. His mother Amina died when he was six, leaving Muhammad an orphan. He was raised under the care of his grandfather, Abd al-Muttalib, and paternal uncle, Abu Talib. In later years, he would periodically seclude h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ibrāhīm Al-Fazārī
Ibrahim ibn Habib ibn Sulayman ibn Samura ibn Jundab al-Fazari () (died 777 CE) was an 8th-century Muslim mathematician and astronomer at the Abbasid court of the Caliph Al-Mansur (r. 754–775). He should not to be confused with his son Muḥammad ibn Ibrāhīm al-Fazārī, also an astronomer. He composed various astronomical writings ("on the astrolabe", "on the armillary spheres", "on the calendar"). The Caliph ordered him and his son to translate the Indian astronomical text, The ''Sindhind'' along with Yaʿqūb ibn Ṭāriq, which was completed in Baghdad about 750 CE, and entitled ''Az-Zīj ‛alā Sinī al-‛Arab''. This translation was possibly the vehicle by means of which the Hindu numeral system (i.e. modern number notation) was transmitted from India to Iran. At the end of the eighth century, while at the court of the Abbasid Caliphate, this Muslim geographer mentioned Ghana, "the land of gold." See also * His son, Muḥammad ibn Ibrāhīm al-Fazārī *List of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ptolemy
Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importance to later Byzantine, Islamic, and Western European science. The first is the astronomical treatise now known as the ''Almagest'', although it was originally entitled the ''Mathēmatikē Syntaxis'' or ''Mathematical Treatise'', and later known as ''The Greatest Treatise''. The second is the ''Geography'', which is a thorough discussion on maps and the geographic knowledge of the Greco-Roman world. The third is the astrological treatise in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. This is sometimes known as the ''Apotelesmatika'' (lit. "On the Effects") but more commonly known as the '' Tetrábiblos'', from the Koine Greek meaning "Four Books", or by its Latin equivalent ''Qua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tablas Alfonsies
Tablas may refer to: * Tablas Island, an island in Romblon Province, Philippines * Tablas Strait, a strait in the Philippines * Tablas Airport or Tugdan Airport, an airport in Romblon Province, Philippines * Tabla A tabla, bn, তবলা, prs, طبلا, gu, તબલા, hi, तबला, kn, ತಬಲಾ, ml, തബല, mr, तबला, ne, तबला, or, ତବଲା, ps, طبله, pa, ਤਬਲਾ, ta, தபலா, te, తబల ..., a hand drum used in Indian classical music * Dupuș village (''Táblás'' in Hungarian), Ațel Commune, Sibiu County, Romania {{Disambiguation, geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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