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	Theory - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-10-07)
		For a given body of theory to be considered part of established knowledge, it is usually necessary for the theory to characterize a critical experiment, that is, an experimental result which cannot be predicted by any established theory.
		Unfortunately, the usage of the term is muddled by cases such as string theory and "theories of everything," each probably better characterized at present as a bundle of competing hypotheses for a protoscience.
		In the humanities, theory is often used as an abbreviation for critical theory or literary theory, referring to continental philosophy's aesthetics or its attempts to understand the structure of society and to conceptualize alternatives.
	www.bexley.us /project/wikipedia/index.php/Theory (1461 words)

	Giant impact theory - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-10-07)
		Big Bang) is the leading scientific theory for the formation of the Moon, which is theorized to have formed as a result of a collision between the young Earth and a hypothetical Mars-sized body sometimes called Theia.
		Shortly after the formation of the Earth 4.45 billion years ago, it is thought that a Mars-sized planetesimal hit the Earth at an oblique angle; destroying the impactor and ejecting most of that body along with a significant portion of the Earth's felsic-rich mantle out into space.
		Evidence for this impact comes from rocks collected during the Apollo Moon landings, which show an oxygen isotope composition that is nearly identical to the Earth's mantle.
	www.bucyrus.us /project/wikipedia/index.php/Giant_impact_theory (627 words)

	Theory (Site not responding. Last check: 2007-10-07)
		For a given body of theory to be considered part of established knowledge, it is usually necessary for the theory to produce a critical experiment, that is, an experimental result which cannot be predicted by any established theory.
		There are two types of theories; a supposition which is not backed by observation is known as a conjecture, and if backed by observation it is a hypothesis.
		Unfortunately, the usage of the term is muddled by cases such as string theory and "theories of everything," each probably better characterized at present as a bundle of competing hypotheses.
	www.bidprobe.com /en/wikipedia/t/th/theory.html (1197 words)

	CONK! Encyclopedia: Theory (Site not responding. Last check: 2007-10-07)
		In various sciences, a theory is a logically self-consistent model or framework for describing the behavior of a certain natural or social phenomenon, thus either originating from observable facts or supported by them (see scientific method).
		For a given body of theory to be considered part of established scientific knowledge, it is usually necessary for it to characterize a critical experiment, namely an experimental result not predicted by any existing established theory.
		Unfortunately, the usage of the term theory is muddled by cases such as string theory and various theories of everything, all of which are better characterized at present as a bundle of competing hypotheses for a protoscience.
	www.conk.com /search/encyclopedia.cgi?q=Theory (1583 words)

	Theory - Open Encyclopedia (Site not responding. Last check: 2007-10-07)
		In mathematics, a theory is a set of statements closed under logical implication.
		In mathematical logic, "theory" is the term for a set of well-formed formulae consisting of certain axioms and all theorems provable from said axioms.
		In sciences, a theory is a model or framework for understanding.
	open-encyclopedia.com /Theory (1179 words)

	[No title] (Site not responding. Last check: 2007-10-07)
		The giant impact theory is the leading scientific theory for the formation of the Moon, which is theorized to have formed as a result of a collision between the young Earth and a hypothetical Mars-sized body sometimes called Theia.
		Shortly after the formation of the Earth 4,450 million years ago, it is thought that a Mars-sized planetesimal hit the Earth at an oblique angle; destroying the impactor and ejecting most of that body along with a significant portion of the Earth's felsic-rich mantle out into space.
		Evidence for this impact comes from rocks collected from Apollo Moon landings which show an Oxygen isotope composition that is nearly identical to the Earth's mantle.
	www.informationgenius.com /encyclopedia/g/gi/giant_impact_theory_1.html (334 words)

	CNN - New evidence supports theory on moon's creation - July 28, 1997
		DENVER (CNN) -- Scientists at the University of Colorado have found new evidence supporting a theory which says that the moon was born of a collision between the Earth and a planet three times larger than Mars.
		Astrophysicist Robin Canup is to present her theory on the moon's birth at a meeting of the American Astronomical Society in Cambridge, Massachusetts, this week.
		Theories abound about where in the universe Earth's moon originated, including that it was traveling through space and was captured by Earth's gravity.
	www2.cnn.com /TECH/9707/28/moon.collision (447 words)

	An alternative theory of the origin of the Moon
		Although the Giant Impact, or Big Whack theory as it is sometimes called, leaves something to be desired, and does not satisfy all the observations about our natural satellite, it has nevertheless remained supreme for the past 25 years because it comes closer than any of the preceding attempts.
		A new theory was necessary, and the Giant Impact Hypothesis was born.
		The theory requires a colossal collision with a massive planet, (the size of Mars), from elsewhere in the Solar System, travelling in an unusual, probably elliptical, orbit which was nevertheless in the plane of the ecliptic, where all the other major planets revolve in closely circular orbits.
	www.users.bigpond.com /ernestmcfarlane/lunargenesis.html (6512 words)

	GIANT IMPACT THEORY FACTS AND INFORMATION (Site not responding. Last check: 2007-10-07)
		Big_Bang) is the now dominant scientific theory for the formation of the Moon, which is thought to have formed as a result of a collision between the young Earth and a Mars-sized body sometimes called Theia.
		Evidence for this impact comes from rocks collected during the Apollo_Moon_landings, which show an oxygen isotope composition that is nearly identical to the Earth's mantle.
		Simulation work published in 2005 by Robin_Canup suggested that Pluto's moon Charon could also have formed by a giant impact around 4.5 billion years ago, in this case by another Kuiper_belt_object between 1600 and 2000 kilometres in diameter that struck the planet at a speed of 1 kilometre per second.
	www.witwib.com /Giant_impact_theory (551 words)

	PlanetPapers - Theories of The Origin of the Moon
		A major difficulty with this theory is that the angular momentum of the earth, in order to achieve rotational instability, would have to have been much greater than the angular momentum of the present earth-moon system.
		The catastrophic impact blasted portions of the earth and the planetesimal into earth orbit, where debris from the impact eventually coalesced to form the moon.
		Planetesimal Impact Theory (Giant Impact Theory) As the Apollo project progressed, it became noteworthy that few scientists working on the project were changing their minds about which of these three theories they believed was most likely correct, and each of the theories had its vocal advocates.
	www.planetpapers.com /Assets/468.php (1239 words)

	Where did the Moon come from?
		The Fission Theory: This theory proposes that the Moon was once part of the Earth and somehow separated from the Earth early in the history of the solar system.
		The Capture Theory: This theory proposes that the Moon was formed somewhere else in the solar system, and was later captured by the gravitational field of the Earth.
		The giant impact theory emerged from this conference with nearly consensus support by scientists, enhanced by new models of planet formation that suggested large impacts were actually quite common events in the late stages of terrestrial planet formation.
	starchild.gsfc.nasa.gov /docs/StarChild/questions/question38.html (874 words)

	Giant Impact Theory of the Origin of the Moon
		This article summarizes calculations that simulate what may have been the most violent event that has ever occurred to the Earth, its collision with the next largest body that was present in its region of accumulations in the early Solar System.
		At the same meeting, the three classical theories of formation of the Moon were discussed in depth, and it was clear that all continued to present grave difficulties.
		The giant impact theory emerged as the "fashionable" theory, but everyone agreed that it was relatively untested and that it would be appropriate to reserve judgement on it until a lot of testing has been conducted.
	www.windows.ucar.edu /cgi-bin/tour_def/teacher_resources/impact_theory.html (896 words)

	Encyclopedia article on Theory [EncycloZine] (Site not responding. Last check: 2007-10-07)
		In mathematics, theory is used informally to refer to a body of knowledge about mathematics.
		The term "theory" also has a formal usage in mathematics, particularly in mathematical logic and model theory: A theory is set of statements closed under certain rules of inference.
		In the humanities, theory is often used as a synonym of critical theory and refers to an attempt to understand the structure of society and to conceptualize alternatives.
	encyclozine.com /Scientific_theory (1321 words)

	bigsplat
		How these theories — condensation, splitting off, and capture — and a fourth one that was added later were winnowed down to a single, generally accepted hypothesis neatly illustrates how science progresses.
		Another theory came a few decades later from astronomer Thomas Jefferson Jackson See, who postulated that the Moon was a body from outer space that had been captured by Earth’s gravity.
		Kant’s condensation theory was in trouble because the density of the Moon is lower than that of the Earth, which has a heavy iron core.
	scibooks.org /bigsplat.html (780 words)

	Extinction - Giant Impact (Site not responding. Last check: 2007-10-07)
		The crater formed by the impact is estimated to be at least one hundred miles across.
		Thick clouds from the dust thrown up by the impact and clouds of smoke from fires started by the heat of the impact explosion covered the whole Earth for at least six months to a year.
		Algae in the oceans and plants on the land not burned by the fires died due to the lack of sunlight.
	home.comcast.net /~ntal3/dinosaurs/extinctionimpact.html (245 words)

	Media:Luna : European Space Agency's First Lunar Mission Heads Toward Moon, Slowly
		The information will be used to test the "giant impact theory", which suggests that the Moon was created in a collision between Earth and another object not long after our solar system formed.
		The giant impact theory suggests that an object roughly the size of Mars crashed into Earth 4.5 billion years ago, throwing up vast amounts of debris that then aggregated into the Moon.
		This theory, that the Moon's core is less massive than the Earth's, has also been used to explain the Moon's orbit around the Earth, which is inclined by around 10 degrees relative to the equator.
	www.lunarrepublic.com /news/smart1_launch_092703.shtml (739 words)

	4 Free Essays (Site not responding. Last check: 2007-10-07)
		The modern version of this theory proposes that the moon was spun off from the earth when the earth was young and rotating rapidly on its axis.
		According to this theory, independent formation of the earth and moon, as in the above theory, is assumed; but the moon is supposed to have formed at a different place in the solar system, far from earth.
		First published in 1975, this theory proposes that early in the earth's history, well over 4 billion years ago, the earth was struck by a large body called a planetesimal, about the size of Mars.
	www.4freeessays.com /essays/468.shtml (1178 words)

	Theia (planet) - Wikipedia, the free encyclopedia
		Theia is the hypothetical planet that, according to the giant impact theory of the Moon's formation, collided with the Earth over four billion years ago.
		This impact at a glancing angle would have destroyed Theia, its iron core burying itself within the primordial Earth.
		Earth would have gained significant amounts of angular momentum from such a collision, as well as an increase in total mass to its current level.
	en.wikipedia.org /wiki/Theia_(planet) (192 words)

	[No title] (Site not responding. Last check: 2007-10-07)
		One large impact is now thought to have contributed to the quick demise of the dinosaurs about 65 million years ago.
		The theory cannot explain why the ratios of the oxygen isotopes is the same as that on the Earth but every other solar system object has different oxygen isotope ratios.
		The giant impact theory is the only one proposed that can explain the compositional and structural characteristics of the Moon.
	www.butler.edu /physics/as102/homework/homework6/homework5.html (2206 words)

	Book Review
		The "capture" theory, promulgated by Thomas Jefferson Jackson See, stated that the Moon had formed independently of Earth, and that the braking action of a force he nebulously labeled a "resisting medium" depleted the Moon's energy until Earth captured it.
		This theory had been proposed as early as 1946, but it couldn't explain the difference in lunar and terrestrial topography--that would have to wait until Apollo's samples were analyzed.
		Ironically, this theory was a near-amalgam of the theories that preceded it.
	www.aaa.org /aaaeye0408art6.htm (720 words)

	Southwest Research Institute (SwRI) News Release (Site not responding. Last check: 2007-10-07)
		Boulder, Colorado -- August 15, 2001 -- The "giant impact" theory, first proposed in the mid-1970s to explain how the Moon formed, has received a major boost as new results demonstrate for the first time that a single impact could yield the current Earth-Moon system.
		Previous models had shown two classes of impacts capable of producing an iron-poor Moon, but both were more problematic than the original idea of a single Mars-sized impactor in the last stages of Earth's formation.
		One model involved an impact with twice the angular momentum of the Earth-Moon system; this would require that a later event (such as a second large impact) alter the Earth's spin after the Moon's formation.
	www.swri.org /9what/releases/canupmoon.htm (715 words)

	SPACE.com -- Lunar birth theory: The moon formed when a big object whacked Earth.
		Another theory said the moon formed elsewhere and was somehow captured by Earths gravity.
		The giant impact theory proposed that at least 50 million years after the solar system formed, a large protoplanet whacked a perhaps still-molten Earth, heating and ejecting debris from both objects.
		The young moons inclined orbit had been a stumbling block for the impact theory because scientists thought an impact would produce the moon in equatorial orbit.
	www.space.com /scienceastronomy/planetearth/moonwhack_side_000901.html (814 words)

	Making the Moon :: Astrobiology Magazine :: Search for Life in the Universe
		Summary (Jun 02, 2002): The "giant impact" theory, first proposed in the mid-1970s to explain how the Moon formed, has now received a major boost.
		The Giant Impact, as pictured in a painting by William K. Hartmann on the cover of Natural History Magazine in 1981.
		The "giant impact" theory, first proposed in the mid-1970s to explain how the Moon formed, has now received a major boost.
	astrobio.net /news/article178.html (1069 words)

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