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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 - Cosmic dust - Introductory MaterialCosmic Dust refers to particles in space which are assemblages of a few molecules to tenth-millimeter-sized grains. Cosmic dust can be further distinguished by its astronomical location; for example: interplanetary dust, interstellar dust, comet dust, circumplanetary dust. This article covers bulk and radiative properties of cosmic dust, the dust particles' origins, end-fates, and specific locations in space.
Historically, cosmic dust used to be an annoyance to astronomers because of the way that the dust obscures the object th ...
See also:Cosmic dust, Cosmic dust - Introductory Material, Cosmic dust - Some bulk properties of cosmic dust, Cosmic dust - Radiative properties of cosmic dust, Cosmic dust - Dust grain formation, Cosmic dust - Dust grain destruction, Cosmic dust - Some dusty clouds in the universe Read more here: » Cosmic dust: Encyclopedia II - Cosmic dust - Introductory Material |
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| | | | | comets: Encyclopedia II - Dust - House dust The dust which collects in houses is composed of atmospheric dust combined with dust generated by the inhabitants, mostly from sloughed skin cells and fibers from clothing and coverings. It can be removed with a broom, dusting cloth, or vacuum cleaner.
House dust mites, often found in fibers like carpets and beds, feed on the organic components of house dust. Their feces, in turn, become part of house dust and can pr ...
See also:Dust, Dust - House dust, Dust - Dust in outer space, Dust - Reference Read more here: » Dust: Encyclopedia II - Dust - House dust |
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| | | | | comets: Encyclopedia II - Extraterrestrial skies - Mars Mars has only a thin atmosphere; however, it is extremely dusty and there is much light that is scattered about. The sky is thus rather bright during the daytime and stars are not visible.
Extraterrestrial skies - The colour of the Martian sky.
Generating accurate true-colour images from Mars' surface is surprisingly complicated [1]. To give but one aspect to consider, there is the Purkinje effect: the human eye's response to colour depends on the level of ambient light — red objects appear to darken fas ...
See also:Extraterrestrial skies, Extraterrestrial skies - Mercury, Extraterrestrial skies - The Sun from Mercury, Extraterrestrial skies - Other planets seen from Mercury, Extraterrestrial skies - Venus, Extraterrestrial skies - The Moon, Extraterrestrial skies - The Sun from the Moon, Extraterrestrial skies - The Earth from the Moon, Extraterrestrial skies - Eclipses from the Moon, Extraterrestrial skies - Mars, Extraterrestrial skies - The colour of the Martian sky, Extraterrestrial skies - The Sun from Mars, Extraterrestrial skies - Mars' moons as seen from Mars, Extraterrestrial skies - Earth from Mars, Extraterrestrial skies - The skies of Mars' moons, Extraterrestrial skies - Asteroids, Extraterrestrial skies - 87 Sylvia and its moons Romulus and Remus, Extraterrestrial skies - Jupiter, Extraterrestrial skies - Jupiter's moons as seen from Jupiter, Extraterrestrial skies - The skies of Jupiter's moons, Extraterrestrial skies - Saturn, Extraterrestrial skies - The skies of Saturn's moons, Extraterrestrial skies - Uranus, Extraterrestrial skies - Neptune, Extraterrestrial skies - The sky of Triton, Extraterrestrial skies - Pluto and Charon, Extraterrestrial skies - Comets, Extraterrestrial skies - Extrasolar planets Read more here: » Extraterrestrial skies: Encyclopedia II - Extraterrestrial skies - Mars |
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| | | | | comets: Encyclopedia II - Planet - Definition and classification of planets Much like "continent", "planet" is a word without a precise definition, with history and culture playing as much of a role as geology and astrophysics. Recent definitions have been vague and imprecise; The American Heritage Dictionary, for instance, formerly defined a planet as:
A nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the Sun, around which it revolves. In the solar system there are nine known planets: Mercury, Venus, Ea ...
See also:Planet, Planet - Planetary formation, Planet - Within our solar system, Planet - Accepted planets, Planet - Other candidates, Planet - Extrasolar planets, Planet - Brown dwarf planets, Planet - Interstellar planets, Planet - Definition and classification of planets, Planet - Suggested wide definitions, Planet - Suggested narrow definitions, Planet - Further classification Read more here: » Planet: Encyclopedia II - Planet - Definition and classification of planets |
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| | | | | comets: Encyclopedia II - Space colonization - Method Building cities in space will require materials, energy, transportation, communications, life support, and radiation protection.
Space colonization - Materials.
Colonies on the Moon and Mars can use local materials, although the Moon is deficient in carbon and nitrogen. For orbital colonies, launching materials from Earth is very expensive, so bulk materials should come from the Moon or Near-Earth Objects (NEOs - asteroids and comets with orbits near Earth) where gravitational forces are much less, there i ...
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 - Method |
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| | | | | comets: Encyclopedia II - Fred Hoyle - Contribution to cosmogony An early paper of his made an interesting use of the Anthropic Principle. In trying to work out the routes of stellar nucleosynthesis, he observed that one particular nuclear reaction, the Triple-alpha process, which generated carbon, would require the carbon nucleus to have a very specific energy for it to work. The large amount of carbon in the universe, which makes it possible for life to exist, demonstrated that this nuclear reaction must work. Based on this notion, he made a prediction of the energy levels in th ...
See also:Fred Hoyle, Fred Hoyle - Contribution to cosmogony, Fred Hoyle - Rejection of the big bang, Fred Hoyle - Media appearances and scientific honours, Fred Hoyle - Rejection of chemical evolution, Fred Hoyle - Other controversies, Fred Hoyle - Honours, Fred Hoyle - Fiction works, Fred Hoyle - Non-fiction works Read more here: » Fred Hoyle: Encyclopedia II - Fred Hoyle - Contribution to cosmogony |
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| | | | | comets: Encyclopedia II - Death Star - Description The Galactic Empire's ultimate terror weapon, the Death Stars were battle stations (the original being 160 kilometers in diameter, Death Star II 900 kilometers) and mounting a directed superlaser weapon capable of completely destroying an Earth-sized planet with a single shot. Planetary shields that could have held off entire Imperial fleets were ineffective against such a weapon. The first Death Star held 27,048 officers, 774,576 crew including troopers, pilots and crewers, 400,000 support workers and over 25,000 Imperial stormtroopers. It ...
See also:Death Star, Death Star - Description, Death Star - Expanded Universe, Death Star - Physics, Death Star - Cultural impact Read more here: » Death Star: Encyclopedia II - Death Star - Description |
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| | | | | comets: Encyclopedia II - Charge heraldry - Proper charges Heraldic writers have, somewhat arbitrarily, distinguished between "honourable ordinaries" and "sub-ordinaries". It is often said that only nine charges are "honourable ordinaries", but exactly which nine fit into this category is a subject of disagreement. It is sometimes said that only those ordinaries each of whose widths is one-fifth or more of the total width of the escutcheon is "honourable".
Narrower or smaller versions of these ordinaries are called "diminutives". Many have two diminutives, the first with half the width of the original, and the second with quarter the width of the original.
< ...
See also:Charge heraldry, Charge heraldry - Tinctures, Charge heraldry - Proper charges, Charge heraldry - Honourable Ordinaries, Charge heraldry - Sub-Ordinaries, Charge heraldry - Diminutives, Charge heraldry - Common charges, Charge heraldry - Supernatural or Divine beings, Charge heraldry - Humans, Charge heraldry - Animals, Charge heraldry - Plants, Charge heraldry - Inanimate charges Read more here: » Charge heraldry: Encyclopedia II - Charge heraldry - Proper charges |
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| | | | | comets: Encyclopedia II - Deluge prehistoric - The lower Tigris-Euphrates Valley reflooding the Persian Gulf 12000 years ago This is type 1. When sea levels were low, the combined Tigris-Euphrates river flowed through a wide flat marshy landscape. The Persian Gulf today has an average depth of only 35 m. During the most recent glaciation, which ended 12,000 years ago, worldwide sea levels dropped 120 to 130 m, leaving the bed of the Persian Gulf well above sea level during the glacial maximum. It had to have been a swampy freshwater floodp ...
See also:Deluge prehistoric, Deluge prehistoric - The Black Sea around 7600 years ago, Deluge prehistoric - The lower Tigris-Euphrates Valley reflooding the Persian Gulf 12000 years ago, Deluge prehistoric - Great Sunda wetlands Indonesia, Deluge prehistoric - The Carpenteria plain 12000 to 10000 years ago, Deluge prehistoric - The Aegean Basin, Deluge prehistoric - Doggerland, Deluge prehistoric - North America, Deluge prehistoric - The refilling of the Mediterranean, Deluge prehistoric - The Caspian Sea Sea of Azov Black Sea Sea of Marmara and the Aegean Sea around 11600 years ago and about 5600 BC, Deluge prehistoric - Tollmann's hypothetical bolide Read more here: » Deluge prehistoric: Encyclopedia II - Deluge prehistoric - The lower Tigris-Euphrates Valley reflooding the Persian Gulf 12000 years ago |
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| | | | | | | comets: Encyclopedia II - List of alternative speculative and disputed theories - Theories
List of alternative speculative and disputed theories - Biology.
See also Medicine below.
Creationism is the belief that the origin of everything in the universe is the result of a first cause, which was creation brought about by a creator God. 'Creationism' generally refers to the version of this concept of cosmology that is opposed to the theory of Evolution. See creation science.
Creation biology is the subset of creation science that tries to explain bio ...
See also:List of alternative speculative and disputed theories, List of alternative speculative and disputed theories - Theories, List of alternative speculative and disputed theories - Biology, List of alternative speculative and disputed theories - Divination, List of alternative speculative and disputed theories - Geology, List of alternative speculative and disputed theories - Medicine, List of alternative speculative and disputed theories - Physics, List of alternative speculative and disputed theories - Psychology, List of alternative speculative and disputed theories - Sociology, List of alternative speculative and disputed theories - Xenology, List of alternative speculative and disputed theories - Miscellaneous Read more here: » List of alternative speculative and disputed theories: Encyclopedia II - List of alternative speculative and disputed theories - Theories |
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| | | | | comets: Encyclopedia II - History of the world - Hunter-Gatherers The earliest available evidence places the origin of modern Homo sapiens in Africa about 200,000 years ago during the Palaeolithic period. This occurred after a long period of evolution. Ancestors of humans, such as Homo erectus, had been using simple tools for many millennia, but as time progressed, tools became far more refined and complex. Humans also developed language sometime during the Paleolithic period, as well as a conceptual repertoire that included systematic burial of the dead and adornment of the living. During this period, all huma ...
See also:History of the world, History of the world - Hunter-Gatherers, History of the world - Agriculture, History of the world - State, History of the world - City and trade, History of the world - Bronze and Iron Ages, History of the world - The classical empires, History of the world - Age of kingdoms, History of the world - Rise of Europe, History of the world - Age of Discovery, History of the world - Twentieth century Read more here: » History of the world: Encyclopedia II - History of the world - Hunter-Gatherers |
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| | | | | | | comets: Encyclopedia II - Near-Earth asteroid - The NEA threat The general acceptance of the Alvarez hypothesis, explaining the Cretaceous-Tertiary extinction event as the result of a large asteroid or comet impact event, has raised the awareness of the possibility of future Earth impacts with asteroids that cross the Earth's orbit.
The threat of an Earth impact was emphasized by the collision of the comet Shoemaker-Levy 9 with Jupiter on July 16, 1994, resulting in explosive impacts that would have been catastrophic on Earth. To be sure, Jupiter is far larger and more massive than the Earth and so undergoes far more impacts, but the event still illustrates that such ...
See also:Near-Earth asteroid, Near-Earth asteroid - NEA classification, Near-Earth asteroid - The NEA threat, Near-Earth asteroid - Projects to ameliorate the threat, Near-Earth asteroid - An example of a recent asteroid impact, Near-Earth asteroid - External link Read more here: » Near-Earth asteroid: Encyclopedia II - Near-Earth asteroid - The NEA threat |
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| | | | | comets: Encyclopedia II - Kuiper belt - Origins Modern computer simulations show the Kuiper belt to have been formed by the work of Jupiter, the young Jupiter having used its considerable gravity to eject smaller bodies which didn't all escape completely, and also having been formed in-situ. The same simulations and other theories predict there should be bodies of significant mass in the belt, Mars-sized or Earth-sized.
The first astronomers to suggest the existence of this belt were Frederick C. Leonard in 1930 and Kenneth E. Edgeworth in 1943. In 1951 Gerard Kuiper suggested that ...
See also:Kuiper belt, Kuiper belt - Origins, Kuiper belt - Name, Kuiper belt - Kuiper belt objects, Kuiper belt - Discoveries thus far, Kuiper belt - Orbital trajectories, Kuiper belt - Term kuiper belt object, Kuiper belt - Largest KBOs Read more here: » Kuiper belt: Encyclopedia II - Kuiper belt - Origins |
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| | | | | comets: Encyclopedia II - Celestial mechanics - History of celestial mechanics Although modern analytic celestial mechanics starts 400 years ago with Isaac Newton, prior studies addressing the problem of planetary positions are known going back perhaps 3,000 years.
Celestial mechanics - Ancient Civilizations.
The Ancient Babylonians had no mechanistic theories regarding celestial motions, but recognized repeating patterns in the motion of the sun, moon, and planets. They used tabulated positions during similar pas ...
See also:Celestial mechanics, Celestial mechanics - History of celestial mechanics, Celestial mechanics - Ancient Civilizations, Celestial mechanics - Claudius Ptolemy, Celestial mechanics - Johannes Kepler, Celestial mechanics - Isaac Newton, Celestial mechanics - Albert Einstein, Celestial mechanics - Open problems, Celestial mechanics - Examples of problems, Celestial mechanics - Perturbation theory, Celestial mechanics - External link Read more here: » Celestial mechanics: Encyclopedia II - Celestial mechanics - History of celestial mechanics |
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| | | | | comets: Encyclopedia II - Interplanetary medium - Composition and physical characteristics The interplanetary medium includes interplanetary dust, cosmic rays and hot plasma from the solar wind. The temperature of the interplanetary medium is approximately 10,000 K, and its density is very low at about 5 particles per cubic centimeter in the vicinity of the Earth; it decreases with increasing distance from the sun, in proportion with the inverse square of the distance.
The density is variable, and may be affected by magnetic fields and ev ...
See also:Interplanetary medium, Interplanetary medium - Composition and physical characteristics, Interplanetary medium - Extent of the interplanetary medium, Interplanetary medium - Interaction with planets, Interplanetary medium - Observable phenomena of the interplanetary medium, Interplanetary medium - History Read more here: » Interplanetary medium: Encyclopedia II - Interplanetary medium - Composition and physical characteristics |
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| | | | | comets: Encyclopedia II - Iapetus moon - Physical characteristics The low density of Iapetus indicates that it is primarily composed of ice, with only a small amount of rocky materials.
Furthermore, the overall shape of Iapetus is neither spherical nor ellipsoid—unusual for a large moon; parts of its globe appear to be squashed flat, and its unique equatorial ridge (see below) is so high that it visibly distorts the moon's shape even when viewed from a distance. Scientists are currently unable to describe Iapetus's shape perfectly as the Cas ...
See also:Iapetus moon, Iapetus moon - Name, Iapetus moon - Orbit, Iapetus moon - Physical characteristics, Iapetus moon - Two-tone coloration, Iapetus moon - The equatorial ridge, Iapetus moon - Speculation that Iapetus is artificial, Iapetus moon - Iapetus in fiction Read more here: » Iapetus moon: Encyclopedia II - Iapetus moon - Physical characteristics |
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| | | | | comets: Encyclopedia II - Kepler's laws of planetary motion - Connection to Newton's laws and conservation laws Kepler did not understand why his laws were correct; it was Isaac Newton who discovered the answer to this more than fifty years later. The second law can also be seen as a statement of conservation of angular momentum, which is a logical consequence of Newton's laws in the special case of a force that acts along the line connecting two objects.
Kepler's laws of planetary motion - Kepler's first law.
Newton said that "every object in the universe attracts every other object along a line of the centres of the objects, proportiona ...
See also:Kepler's laws of planetary motion, Kepler's laws of planetary motion - Kepler's first law, Kepler's laws of planetary motion - Kepler's second law, Kepler's laws of planetary motion - Kepler's third law, Kepler's laws of planetary motion - Accuracy and limitations, Kepler's laws of planetary motion - Connection to Newton's laws and conservation laws, Kepler's laws of planetary motion - Kepler's first law, Kepler's laws of planetary motion - Kepler's second law, Kepler's laws of planetary motion - Kepler's third law, Kepler's laws of planetary motion - Solution for the motion as a function of time Read more here: » Kepler's laws of planetary motion: Encyclopedia II - Kepler's laws of planetary motion - Connection to Newton's laws and conservation laws |
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