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Astronomical Rings
Astronomical rings (Latin: annuli astronomici), also known as Gemma's rings, are an early astronomical instrument. The instrument consists of three rings, representing the celestial equator, declination, and the meridian. It can be used as a sun dial to tell time, if the approximate latitude and season is known, or to tell latitude, if the time is known or observed (at solar noon). It may be considered to be a simplified, portable armillary sphere, or a more complex form of astrolabe. History Parts of the instrument go back to instruments made and used by ancient Greek astronomers. Gemma Frisius combined several of the instruments into a small, portable, astronomical-ring instrument. He first published the design in 1534, and in Petrus Apianus's ''Cosmographia'' in 1539. These ring instruments combined terrestrial and celestial calculations. Types Fixed astronomical rings Fixed astronomical rings are mounted on a plinth, like armillary spheres, and can be used as sundials. Tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Ring Dial
Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Babylonians, Greeks, Indians, Egyptians, Chinese, Maya, and many ancient indigenous peoples of the Americas. In the past, astronomy included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars. Nowadays, professional ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basel 2012-10-06 Batch Part 5 (118)
, french: link=no, Bâlois(e), it, Basilese , neighboring_municipalities= Allschwil (BL), Hégenheim (FR-68), Binningen (BL), Birsfelden (BL), Bottmingen (BL), Huningue (FR-68), Münchenstein (BL), Muttenz (BL), Reinach (BL), Riehen (BS), Saint-Louis (FR-68), Weil am Rhein (DE-BW) , twintowns = Shanghai, Miami Beach , website = www.bs.ch Basel ( , ), also known as Basle ( ),french: Bâle ; it, Basilea ; rm, label=Sutsilvan, Basileia; other rm, Basilea . is a city in northwestern Switzerland on the river Rhine. Basel is Switzerland's third-most-populous city (after Zürich and Geneva) with about 175,000 inhabitants. The official language of Basel is (the Swiss variety of Standard) German, but the main spoken language is the local Basel German dialect. Basel is commonly considered to be the cultural capital of Switzerland and the city is famous for its many museums, including the Kunstmuseum, which is the first collection of art accessible to the public ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equatorial Ring
An equatorial ring was an astronomical instrument used in the Hellenistic world to determine the exact moment of the spring and autumn equinoxes. Equatorial rings were placed before the temples in Alexandria, in Rhodes, and perhaps in other places, for calendar purposes. The easiest way to understand the use of an equatorial ring is to imagine a ring placed vertically in the east-west plane at the Earth's equator. At the time of the equinoxes, the Sun will rise precisely in the east, move across the zenith, and set precisely in the west. Throughout the day, the bottom half of the ring will be in the shadow cast by the top half of the ring. On other days of the year, the Sun passes to the north or south of the ring, and will illuminate the bottom half. For latitudes away from the equator, the ring merely needs to be placed at the correct angle in the equatorial plane. At the Earth's poles, the ring would be horizontal. The equatorial ring was about one to two cubits (45cm–90cm) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sundial
A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate (the ''dial'') and a gnomon, which casts a shadow onto the dial. As the Sun appears to move through the sky, the shadow aligns with different hour-lines, which are marked on the dial to indicate the time of day. The ''style'' is the time-telling edge of the gnomon, though a single point or ''nodus'' may be used. The gnomon casts a broad shadow; the shadow of the style shows the time. The gnomon may be a rod, wire, or elaborately decorated metal casting. The style must be parallel to the axis of the Earth's rotation for the sundial to be accurate throughout the year. The style's angle from horizontal is equal to the sundial's geographical latitude. The term ''sundial'' can refer to any device that uses the Sun's altitude or azimut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnomon
A gnomon (; ) is the part of a sundial that casts a shadow. The term is used for a variety of purposes in mathematics and other fields. History A painted stick dating from 2300 BC that was excavated at the astronomical site of Taosi is the oldest gnomon known in China. The gnomon was widely used in ancient China from the second century BC onward in order to determine the changes in seasons, orientation, and geographical latitude. The ancient Chinese used shadow measurements for creating calendars that are mentioned in several ancient texts. According to the collection of Zhou Chinese poetic anthologies ''Classic of Poetry'', one of the distant ancestors of King Wen of the Zhou dynasty used to measure gnomon shadow lengths to determine the orientation around the 14th century BC. The ancient Greek philosopher Anaximander (610–546 BC) is credited with introducing this Babylonian instrument to the Ancient Greeks. The ancient Greek mathematician and astronomer Oenopides used the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Elevation
The solar zenith angle is the zenith angle of the sun, i.e., the angle between the sun’s rays and the vertical direction. It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between the sun’s rays and a horizontal plane. At solar noon, the zenith angle is at a minimum and is equal to latitude minus solar declination angle. This is the basis by which ancient mariners navigated the oceans. Solar zenith angle is normally used in combination with the solar azimuth angle to determine the position of the Sun as observed from a given location on the surface of the Earth. Formula : \cos \theta_s = \sin \alpha_s = \sin \Phi \sin \delta + \cos \Phi \cos \delta \cos h where * \theta_s is the ''solar zenith angle'' * \alpha_s is the ''solar altitude angle'', \alpha_s = 90° – \theta_s * h is the hour angle, in the local solar time. * \delta is the current declination of the Sun * \Phi is the local lati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axis Of Rotation
Rotation around a fixed axis is a special case of rotational motion. The fixed-axis hypothesis excludes the possibility of an axis changing its orientation and cannot describe such phenomena as wobbling or precession. According to Euler's rotation theorem, simultaneous rotation along a number of stationary axes at the same time is impossible; if two rotations are forced at the same time, a new axis of rotation will appear. This article assumes that the rotation is also stable, such that no torque is required to keep it going. The kinematics and dynamics of rotation around a fixed axis of a rigid body are mathematically much simpler than those for free rotation of a rigid body; they are entirely analogous to those of linear motion along a single fixed direction, which is not true for ''free rotation of a rigid body''. The expressions for the kinetic energy of the object, and for the forces on the parts of the object, are also simpler for rotation around a fixed axis, than for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plumb Bob
A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertical datum. It is typically made of stone, wood, or lead, but can also be made of other metals. If it is used for decoration, it may be made of bone or ivory. The instrument has been used since at least the time of ancient EgyptDenys A. Stocks. Experiments in Egyptian archaeology: stoneworking technology in ncient Egypt'. Routledge; 2003. . p. 180. to ensure that constructions are "plumb", or vertical. It is also used in surveying, to establish the nadir with respect to gravity of a point in space. It is used with a variety of instruments (including levels, theodolites, and steel tapes) to set the instrument exactly over a fixed survey marker or to transcribe positions onto the ground for placing a marker. Etymology The ''plu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Variation
Magnetic declination, or magnetic variation, is the angle on the horizontal plane between magnetic north (the direction the north end of a magnetized compass needle points, corresponding to the direction of the Earth's magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole). This angle varies depending on position on the Earth's surface and changes over time. Somewhat more formally, Bowditch defines variation as “the angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north. The angle between magnetic and grid meridians is called grid magnetic angle, grid variation, or grivation.” By convention, declination is positive when magnetic north is east of true north, and negative when it is to the west. '' Isogonic lines'' are lines on the Earth's surface along which the declination has the same constant value, and li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edward Wright (mathematician)
Edward Wright (baptism, baptised 8 October 1561; died November 1615) was an English mathematician and cartographer noted for his book ''Certaine Errors in Navigation'' (1599; 2nd ed., 1610), which for the first time explained the mathematical basis of the Mercator projection by building on the works of Pedro Nunes, and set out a reference table giving the linear scale multiplication factor as a function of latitude, calculated for each minute of arc up to a latitude of 75°. This was in fact a table of values of the integral of the secant function, and was the essential step needed to make practical both the making and the navigational use of Mercator charts. Wright was born at Garvestone, Garveston in Norfolk and educated at Gonville and Caius College, Cambridge, where he became a Oxford fellow, fellow from 1587 to 1596. In 1589 the College granted him leave after Elizabeth I of England, Elizabeth I requested that he carry out navigational studies with Azores Voyage of 1589, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bronze Compass Sundial 005
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such as arsenic or silicon. These additions produce a range of alloys that may be harder than copper alone, or have other useful properties, such as strength, ductility, or machinability. The archaeological period in which bronze was the hardest metal in widespread use is known as the Bronze Age. The beginning of the Bronze Age in western Eurasia and India is conventionally dated to the mid-4th millennium BCE (~3500 BCE), and to the early 2nd millennium BCE in China; elsewhere it gradually spread across regions. The Bronze Age was followed by the Iron Age starting from about 1300 BCE and reaching most of Eurasia by about 500 BCE, although bronze continued to be much more widely used than it is in modern times. Because historical artworks wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
