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comets | A Wisdom Archive on comets | | comets A selection of articles related to comets | |
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comets, Comet, Comet - Comet nomenclature, Comet - Comets in fiction, Comet - Great comets, Comet - History of comet study, Comet - Orbital characteristics, Comet - Peculiar comets, Comet - Physical characteristics, Comet - Debate over comet composition, Comet - Early observations and thought, Comet - Orbital studies, Comet - Studies of physical characteristics, List of periodic comets, List of non-periodic comets, Torino Scale for categorizing the impact hazard
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| ARTICLES RELATED TO comets | | | |  comets: Encyclopedia II - Moon - Occultation of starsDuring the year, the Moon occults - or passes over and hides for a period of time - stars and planets. Because the Moon is close to Earth, occultations of stars are not visible everywhere, where the Moon is at occultation time over the horizon. Because of the moving nodes of the Moon, in each years other stars are occulted.
The contact times can be used for the validation of the theory of lunar orbit.
...
See also:Moon, Moon - The two sides of the Moon, Moon - Orbit, Moon - Earth & Moon, Moon - Tidal Effects, Moon - Double-planet hypotheses, Moon - Origin and history, Moon - Physical characteristics, Moon - Composition, Moon - Selenography, Moon - Presence of water, Moon - Magnetic field, Moon - Atmosphere, Moon - Eclipses, Moon - Occultation of stars, Moon - Observation of the Moon, Moon - Exploration of the Moon, Moon - Human understanding of the Moon, Moon - Myth and folk culture, Moon - The Moon as muse, Moon - Astrology, Moon - Scientific understanding, Moon - Meteor impact on the Moon, Moon - Legal status, Moon - Satellites, Moon - Surface installations, Moon - Lunar location listings Read more here: » Moon: Encyclopedia II - Moon - Occultation of stars |
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| | | | | comets: Encyclopedia II - Moon - Eclipses The angular diameters of the Moon and the Sun as seen from Earth overlap in their variation, so that both total and annular solar eclipses are possible. In a total eclipse, the Moon completely covers the disc of the Sun and the solar corona becomes visible to the naked eye.
Since the distance between the Moon and the Earth is very slightly increasing over time, the angular diameter of the Moon is decreasing. This means that several million years ago the Moon always completely covered the Sun on solar eclipses so that no annular eclipses occurred. Likewise, in several million years the Moon will no longer cover the Sun completely ...
See also:Moon, Moon - The two sides of the Moon, Moon - Orbit, Moon - Earth & Moon, Moon - Tidal Effects, Moon - Double-planet hypotheses, Moon - Origin and history, Moon - Physical characteristics, Moon - Composition, Moon - Selenography, Moon - Presence of water, Moon - Magnetic field, Moon - Atmosphere, Moon - Eclipses, Moon - Occultation of stars, Moon - Observation of the Moon, Moon - Exploration of the Moon, Moon - Human understanding of the Moon, Moon - Myth and folk culture, Moon - The Moon as muse, Moon - Astrology, Moon - Scientific understanding, Moon - Meteor impact on the Moon, Moon - Legal status, Moon - Satellites, Moon - Surface installations, Moon - Lunar location listings Read more here: » Moon: Encyclopedia II - Moon - Eclipses |
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| | | | | comets: Encyclopedia II - Skygazing - Binocular gazing Binoculars are very useful when you wish to observe bright, large astronomical objects. Thanks to them it is possible to see lunar craters. In spite of the distance between us and the Moon, one can observe the relief of these craters along the terminator, the separation line between the illuminated and darkened parts of the Moon. Lunar features are emphasized in this zone where sunlight strikes at a low angle and casts long shadows. This spectacle ...
See also:Skygazing, Skygazing - Naked eye skygazing, Skygazing - Diurnal observation, Skygazing - Nocturnal observation, Skygazing - Binocular gazing, Skygazing - Choice of binoculars, Skygazing - Advice on observational techniques, Skygazing - Observations with a refracting telescope, Skygazing - Choice of the refracting telescope, Skygazing - Advice of usage, Skygazing - The observation with a reflecting telescope, Skygazing - Types of reflecting telescope Read more here: » Skygazing: Encyclopedia II - Skygazing - Binocular gazing |
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| | | | | comets: Encyclopedia II - Vulcan planet - Vulcan revived Observing a planet inside the orbit of Mercury would be extremely difficult, since the telescope must be pointed very close to the Sun, where the sky is never black. Also, an error in pointing the telescope can result in damage for the optics, and injury to the observer. The huge amount of light present even quite away from the Sun can produce false reflections inside the optics, thus fooling the observer into seeing things that do not exist.
The best strategy for observations would be to wait for the planet's transit of the Sun's disk. A small, round dark spot might be seen movi ...
See also:Vulcan planet, Vulcan planet - Argument for Vulcan's existence, Vulcan planet - The search for Vulcan, Vulcan planet - Search conclusion, Vulcan planet - Vulcan revived, Vulcan planet - Vulcan in modern fiction Read more here: » Vulcan planet: Encyclopedia II - Vulcan planet - Vulcan revived |
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| | | | | | comets: Encyclopedia II - Vulcan planet - Search conclusion In 1877 Le Verrier died, still convinced of having discovered another planet. With the loss of its principal proponent, the search for Vulcan cooled down. After many years of searching, astronomers were seriously doubting the planet's existence.
The final act came in 1915, when Einstein's theory of relativity explained the perturbations of Mercury as a mere byproduct of the Sun's gravitational field. His equations predicted slightly different results than classical mechanics, and exactly in ...
See also:Vulcan planet, Vulcan planet - Argument for Vulcan's existence, Vulcan planet - The search for Vulcan, Vulcan planet - Search conclusion, Vulcan planet - Vulcan revived, Vulcan planet - Vulcan in modern fiction Read more here: » Vulcan planet: Encyclopedia II - Vulcan planet - Search conclusion |
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| | | | | comets: Encyclopedia II - Moon - Observation of the Moon During the brightest full moons, the Moon can have an apparent magnitude of about −12.6. For comparison, the Sun has an apparent magnitude of −26.8.
The Moon appears larger when close to the horizon. This is a purely psychological effect (see Moon illusion). The angular diameter of the Moon from Earth is about one half of one degree, and is actually about 1.5% smaller when the Moon is near the horizon than when it is high in the sky (beca ...
See also:Moon, Moon - The two sides of the Moon, Moon - Orbit, Moon - Earth & Moon, Moon - Tidal Effects, Moon - Double-planet hypotheses, Moon - Origin and history, Moon - Physical characteristics, Moon - Composition, Moon - Selenography, Moon - Presence of water, Moon - Magnetic field, Moon - Atmosphere, Moon - Eclipses, Moon - Occultation of stars, Moon - Observation of the Moon, Moon - Exploration of the Moon, Moon - Human understanding of the Moon, Moon - Myth and folk culture, Moon - The Moon as muse, Moon - Astrology, Moon - Scientific understanding, Moon - Meteor impact on the Moon, Moon - Legal status, Moon - Satellites, Moon - Surface installations, Moon - Lunar location listings Read more here: » Moon: Encyclopedia II - Moon - Observation of the Moon |
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| | | | | | | comets: Encyclopedia II - Moon - Earth & Moon
Moon - Tidal Effects.
The tides on Earth are generated by the Moon's gravitation (see tide and tidal force for a more detailed discussion). There are two tidal bulges, one in the direction of the Moon, and one in the opposite direction (figure 1). The buildup of these bulges and their movement around the earth causes an energy loss due to friction. The energy loss decr ...
See also:Moon, Moon - The two sides of the Moon, Moon - Orbit, Moon - Earth & Moon, Moon - Tidal Effects, Moon - Double-planet hypotheses, Moon - Origin and history, Moon - Physical characteristics, Moon - Composition, Moon - Selenography, Moon - Presence of water, Moon - Magnetic field, Moon - Atmosphere, Moon - Eclipses, Moon - Occultation of stars, Moon - Observation of the Moon, Moon - Exploration of the Moon, Moon - Human understanding of the Moon, Moon - Myth and folk culture, Moon - The Moon as muse, Moon - Astrology, Moon - Scientific understanding, Moon - Meteor impact on the Moon, Moon - Legal status, Moon - Satellites, Moon - Surface installations, Moon - Lunar location listings Read more here: » Moon: Encyclopedia II - Moon - Earth & Moon |
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| | | | | comets: Encyclopedia II - Moon - Human understanding of the Moon
Moon - Myth and folk culture.
Main article: Moon (mythology)
Moon - The Moon as muse.
Main article: Moon in art and literature
The Moon has been the subject of many works of art and literature and the inspiration for countless others.
Moon - Astrology.
Main article: Moon (astrology)
Moon - Scientific understanding.
A 5,000 year old rock carving at Knowth, Ireland may represent the ...
See also:Moon, Moon - The two sides of the Moon, Moon - Orbit, Moon - Earth & Moon, Moon - Tidal Effects, Moon - Double-planet hypotheses, Moon - Origin and history, Moon - Physical characteristics, Moon - Composition, Moon - Selenography, Moon - Presence of water, Moon - Magnetic field, Moon - Atmosphere, Moon - Eclipses, Moon - Occultation of stars, Moon - Observation of the Moon, Moon - Exploration of the Moon, Moon - Human understanding of the Moon, Moon - Myth and folk culture, Moon - The Moon as muse, Moon - Astrology, Moon - Scientific understanding, Moon - Meteor impact on the Moon, Moon - Legal status, Moon - Satellites, Moon - Surface installations, Moon - Lunar location listings Read more here: » Moon: Encyclopedia II - Moon - Human understanding of the Moon |
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| | | | | comets: Encyclopedia II - Moon - The two sides of the Moon The far side is sometimes called the "dark side". In this case "dark" means "unknown and hidden" and not "lacking light" as implied by the name; in fact the far side receives (on average) as much sunlight as the near side, but at opposite times. Spacecraft are cut off from direct radio communication with the Earth when on the far side of the Moon.
One distinguishing feature of the far side is its almost complete lack of maria (singular: ...
See also:Moon, Moon - The two sides of the Moon, Moon - Orbit, Moon - Earth & Moon, Moon - Tidal Effects, Moon - Double-planet hypotheses, Moon - Origin and history, Moon - Physical characteristics, Moon - Composition, Moon - Selenography, Moon - Presence of water, Moon - Magnetic field, Moon - Atmosphere, Moon - Eclipses, Moon - Occultation of stars, Moon - Observation of the Moon, Moon - Exploration of the Moon, Moon - Human understanding of the Moon, Moon - Myth and folk culture, Moon - The Moon as muse, Moon - Astrology, Moon - Scientific understanding, Moon - Meteor impact on the Moon, Moon - Legal status, Moon - Satellites, Moon - Surface installations, Moon - Lunar location listings Read more here: » Moon: Encyclopedia II - Moon - The two sides of the Moon |
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| | | | | comets: Encyclopedia II - Space dust - Analysis The dust that is collected is taken to a clean room. This room has filters to decrease the number of dust particles in the air. The room must have very few particles to avoid contaminating the samples. Space dust is then scanned by an electron microscope, after which the sample is sent to the NASA space dust library for storage. Currently, NASA can only catalog 300 particles a year.
The difference between dust from Earth and dust from space is easily observed. Dust from Earth almost never has Iridium or Osmium, and dust from space has ...
See also:Space dust, Space dust - Types, Space dust - Collection methods, Space dust - Airplanes, Space dust - Spacecraft, Space dust - Terrestrial collection, Space dust - Deep-sea collection, Space dust - Analysis, Space dust - Images Read more here: » Space dust: Encyclopedia II - Space dust - Analysis |
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| | | | | comets: Encyclopedia II - Skygazing - The observation with a reflecting telescope A reflecting telescope is constituted not of lenses but of mirrors. It being less costly to manufacture, one can, for the price of a refracting telescope, acquire an instrument of the more important diameter that gives access to the deep space. Nevertheless, to take advantage of the power of a reflecting telescope, it is necessary to have a good site of observation safe from the lights of the city, otherwise the usage of a good telescope is preferable.
With a 150mm lensed reflecting telescope, the viewer is able to distinguish the spi ...
See also:Skygazing, Skygazing - Naked eye skygazing, Skygazing - Diurnal observation, Skygazing - Nocturnal observation, Skygazing - Binocular gazing, Skygazing - Choice of binoculars, Skygazing - Advice on observational techniques, Skygazing - Observations with a refracting telescope, Skygazing - Choice of the refracting telescope, Skygazing - Advice of usage, Skygazing - The observation with a reflecting telescope, Skygazing - Types of reflecting telescope Read more here: » Skygazing: Encyclopedia II - Skygazing - The observation with a reflecting telescope |
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| | | | | comets: Encyclopedia II - Solar system - Origin and age of the solar system The current hypothesis of solar system formation is the nebular hypothesis, first proposed in 1755 by Immanuel Kant and independently formulated by Pierre-Simon Laplace. It states the solar system was formed from a gaseous cloud called the solar nebula. It had a diameter of 100 AU and was 2-3 times the mass of the Sun. Over time, a disturbance, possibly a nearby supernova, sent shock waves into space, which squeezed the nebula, pushing more and more of its matter inward until gravitational forces overcame its internal gas pressure and it beg ...
See also:Solar system, Solar system - Structure and layout of the solar system, Solar system - Origin and age of the solar system, Solar system - Regions of the solar system, Solar system - Interplanetary medium, Solar system - The inner planets, Solar system - The asteroid belt, Solar system - The outer planets, Solar system - The trans-Neptunian region, Solar system - And beyond, Solar system - Galactic orbit of the solar system, Solar system - Planetary system formation, Solar system - Discovery of the solar system, Solar system - Exploration of the solar system, Solar system - Attributes of major planets, Solar system - Attributes of the largest minor planets, Solar system - Other facts Read more here: » Solar system: Encyclopedia II - Solar system - Origin and age of the solar system |
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| | | | | comets: Encyclopedia II - Planetary orbit - Scaling in gravity The gravitational constant G is measured to be:
(6.6742 ± 0.001) × 10−11 N·m2/kg2
(6.6742 ± 0.001) × 10−11 m3/(kg·s2)
(6.6742 ± 0.001) × 10−11 (kg/m3)-1s-2.
Thus the constant has dimension density-1 time-2. This corresponds to the following properties.
Scaling of distances (including sizes of bodies, while keeping the densities the same) gi ...
See also:Planetary orbit, Planetary orbit - History, Planetary orbit - Planetary orbits, Planetary orbit - Understanding orbits, Planetary orbit - Newton's laws of motion, Planetary orbit - Analysis of orbital motion, Planetary orbit - Orbital parameters, Planetary orbit - Orbital period, Planetary orbit - Orbital decay, Planetary orbit - Earth orbits, Planetary orbit - Scaling in gravity, Planetary orbit - Role in the evolution of atomic theory Read more here: » Planetary orbit: Encyclopedia II - Planetary orbit - Scaling in gravity |
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| | | | | comets: Encyclopedia II - Solar system - Structure and layout of the solar system The Sun (astronomical symbol ☉) is a main sequence G2 star that contains 99.86% of the system's known mass. Its two largest orbiting bodies, Jupiter and Saturn, account for 91% of the remainder (the Oort Cloud might hold a substantial percentage, but as yet its existence is unconfirmed).
In broad terms, the charted regions of our solar system consist of the Sun and its planetary system: the eight bodies in relatively unique orbits (commonly called planets or major planets) and two belts of smaller objects (which can be called minor ...
See also:Solar system, Solar system - Structure and layout of the solar system, Solar system - Origin and age of the solar system, Solar system - Regions of the solar system, Solar system - Interplanetary medium, Solar system - The inner planets, Solar system - The asteroid belt, Solar system - The outer planets, Solar system - The trans-Neptunian region, Solar system - And beyond, Solar system - Galactic orbit of the solar system, Solar system - Planetary system formation, Solar system - Discovery of the solar system, Solar system - Exploration of the solar system, Solar system - Attributes of major planets, Solar system - Attributes of the largest minor planets, Solar system - Other facts Read more here: » Solar system: Encyclopedia II - Solar system - Structure and layout of the solar system |
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| | | | | comets: Encyclopedia II - Space colonization - Location Location is a frequent point of contention between space colonization advocates.
The location of colonization can be:
On a planet, natural satellite, or asteroid
In orbit around the Earth, Sun, Lagrangian point or other object
Main article: Colonization of Mars
Mars is a frequent topic of discussion. Its overall surface area is similar to the dry land surface Earth, it may have large water reserves, and has carbon (locked as carbon dioxide in the atmosphere). It may have gone t ...
See also:Space colonization, Space colonization - Method, Space colonization - Materials, Space colonization - Energy, Space colonization - Transportation, Space colonization - Communication, Space colonization - Life support, Space colonization - Radiation protection, Space colonization - Self-replication, Space colonization - Population size, Space colonization - Location, Space colonization - Orbit, Space colonization - Asteroid, Space colonization - Terrestrial analogues, Space colonization - Mercury, Space colonization - Venus, Space colonization - Europa, Space colonization - Gas Giants, Space colonization - Space habitats, Space colonization - Spaceship, Space colonization - Justification, Space colonization - Advocacy, Space colonization - Objections Read more here: » Space colonization: Encyclopedia II - Space colonization - Location |
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| | | | | comets: Encyclopedia II - Terraforming - In fiction
Terraforming - Prose.
The term first appeared in a science-fiction novel, Seetee Shock (1949) by Jack Williamson, but the concept pre-dates that work. Olaf Stapledon's Last and First Men (1930) provides the first example in fiction in which Venus is modified, after a long and destructive war with the original inhabitants, who naturally object to the process.
Even earlier, H. G. Wells alludes to xeno-terraforming - alien life altering Earth for their own benefit - in his 1898 novel The War of the Worlds. When the Martians arrive they bring with them a red weed that spreads an ...
See also:Terraforming, Terraforming - History of scholarly study, Terraforming - Ethical issues, Terraforming - Theoretical methods of terraforming, Terraforming - Mars, Terraforming - Venus, Terraforming - Other worlds, Terraforming - Paraterraforming, Terraforming - In fiction, Terraforming - Prose, Terraforming - Television and film, Terraforming - Miscellanea Read more here: » Terraforming: Encyclopedia II - Terraforming - In fiction |
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| | | | | comets: Encyclopedia II - Samuel of Nehardea - Relations with the Persian Court It was due to Mar Samuel's influence with the Persian king that the Jews were granted many privileges. On one occasion Samuel even made his love for his own people subsidiary to his loyalty to the Persian king and to his strict view of the duties of a citizen; for when the news came that the Persians, on capturing Mazaca (Cæsarea), in Cappadocia, had killed 12,000 Jews who had obstinately opposed them, Samuel refrained from displaying any sorrow (M. Ḳ. 26a). But he had a great love for his people, and he loyally cherished the memory of th ...
See also:Samuel of Nehardea, Samuel of Nehardea - Birth, Samuel of Nehardea - Youth, Samuel of Nehardea - His Training, Samuel of Nehardea - As Gaon, Samuel of Nehardea - His Halakha, Samuel of Nehardea - Aggadah, Samuel of Nehardea - Relations with the Persian Court, Samuel of Nehardea - Bibliography Read more here: » Samuel of Nehardea: Encyclopedia II - Samuel of Nehardea - Relations with the Persian Court |
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| | | | | comets: Encyclopedia II - Solar system - Galactic orbit of the solar system The solar system is located in the Local Fluff of the Milky Way galaxy, a spiral galaxy with a diameter of about 100,000 light years containing approximately 200 billion stars, of which our Sun is rather large and bright. (The vast majority of stars are red dwarfs; our Sun is placed near the middle of the Hertzsprung-Russell diagram, but stars larger and hotter than it are rare, whereas stars dimmer and cooler than it are very common, although we can observe on ...
See also:Solar system, Solar system - Structure and layout of the solar system, Solar system - Origin and age of the solar system, Solar system - Regions of the solar system, Solar system - Interplanetary medium, Solar system - The inner planets, Solar system - The asteroid belt, Solar system - The outer planets, Solar system - The trans-Neptunian region, Solar system - And beyond, Solar system - Galactic orbit of the solar system, Solar system - Planetary system formation, Solar system - Discovery of the solar system, Solar system - Exploration of the solar system, Solar system - Attributes of major planets, Solar system - Attributes of the largest minor planets, Solar system - Other facts Read more here: » Solar system: Encyclopedia II - Solar system - Galactic orbit of the solar system |
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| | | | | comets: Encyclopedia II - Moon - Exploration of the Moon The first leap in Lunar observation was caused by the invention of the telescope. Especially Galileo Galilei made good use of this new instrument and observed mountains and craters on the Moon's surface.
The Cold War-inspired space race between the Soviet Union and the United States of America led to an acceleration. What was the next big step depends on the political viewpoint: In the US (and the West in general) the landing of the first humans on the moon in 1969 is seen as a culmination, indeed of the space race in general. On the ...
See also:Moon, Moon - The two sides of the Moon, Moon - Orbit, Moon - Earth & Moon, Moon - Tidal Effects, Moon - Double-planet hypotheses, Moon - Origin and history, Moon - Physical characteristics, Moon - Composition, Moon - Selenography, Moon - Presence of water, Moon - Magnetic field, Moon - Atmosphere, Moon - Eclipses, Moon - Occultation of stars, Moon - Observation of the Moon, Moon - Exploration of the Moon, Moon - Human understanding of the Moon, Moon - Myth and folk culture, Moon - The Moon as muse, Moon - Astrology, Moon - Scientific understanding, Moon - Meteor impact on the Moon, Moon - Legal status, Moon - Satellites, Moon - Surface installations, Moon - Lunar location listings Read more here: » Moon: Encyclopedia II - Moon - Exploration of the Moon |
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