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	Gravitational lens - Wikipedia, the free encyclopedia
		A gravitational lens is formed when the light from a very distant, bright source (such as a quasar) is "bent" around a massive object (such as a massive galaxy) between the source object and the observer.
		The process is known as gravitational lensing, and is one of the predictions of Albert Einstein's general relativity theory.
		This gravitational lens was discovered accidentally by Dennis Walsh, Bob Carswell, and Ray Weymann using the Kitt Peak National Observatory 2.1 meter telescope.
	en.wikipedia.org /wiki/Gravitational_lens (1562 words)

	Gravitation Encyclopedia Article, Information, History and Biography @ NaturalResearch.org (Site not responding. Last check: 2007-11-07)
		The gravitational force is one of the four fundamental forces in nature, the other three being the electromagnetic force, the weak nuclear force, and the strong nuclear force.
		Newton’s conception and quantification of gravitation held until the beginning of the 20th century, when the notion of instantaneous action at a distance, which it entailed, was recognized as being untenable from the viewpoint of relativity.
		In common usage "gravity" and "gravitation" are either used interchangeably, or the distinction is sometimes made that "gravity" is specifically the attractive force of the earth, while "gravitation" is the general property of mutual attraction between bodies of matter.
	www.naturalresearch.org /encyclopedia/Gravitation (1853 words)

	gravitational lens
		Gravitational lenses arise from the warping of spacetime around a massive object, as described by Einstein's general theory of relativity and first discussed by Einstein in 1936.
		Depending on the geometry of the gravitational lens, the resulting image of the lensed object may be an arc, a complete circle (known as an Einstein ring), or a series of multiple images.
		Gravitational lensing also occurs on a smaller scale, known as microlensing, when a dark object in our Galaxy passes directly in front of a more distant star (for example, one of the stars in the Magellanic Clouds) and makes its image brighten briefly.
	www.daviddarling.info /encyclopedia/G/gravlens.html (368 words)

	Gravitational Lensing
		The arcs are actually distorted images of very distant galaxies that are being imaged by the gravitational lens: The cluster is so massive and compact that light rays passing through it are deflected by its enormous gravitational field, much as an optical lens bends light to form an image.
		Gravitational lensing was actually discovered for quasars before it was found for galaxies.
		This interpretation was bolstered by the discovery of a galaxy nearly in front of one of the images and a surrounding cluster of galaxies that are candidates for the intervening mass causing the lens effect.
	csep10.phys.utk.edu /astr162/lect/galaxies/lensing.html (403 words)

	Gravitational Lenses - Picture Gallery (Site not responding. Last check: 2007-11-07)
		The gravitational lens is produced by the cluster's tremendous gravitational field that bends light to magnify, brighten and distort the image of a more distant object.
		A gravitational lens is produced by the enormous gravitational field of a massive object which bends light to magnify, brighten and distort the image of a more distant object.
		The gravitational lens action is also magnifying the background object by a factor of ten, providing an unparalleled view of this very distant galaxy which is in a stage of active star-formation.
	astro.hi.is /lens/pict_th.html (3346 words)

	[No title]
		In the gravitational lens 2237+0305 the four lensed images of a single background quasar are seen in a cross formation superimposed on the barred spiral lensing galaxy, so that theoretical lens models and the observed structure and dynamics of the galaxy can be compared.
		Gravitational lensing by a spiral galaxy occurs when the line-of-sight to a background quasar passes within a few kpc from the center of the galactic disk.
		Gravitational lensing by the cluster potential leads to a systematic deficit in the residual intensity of unresolved sources behind the cluster core relative to a control field far from the cluster center.
	www-astro-theory.fnal.gov /Conferences/Texas96/glens-abs.html (4126 words)

	Benjamin Granett
		The physics behind gravitational lensing is general relativity, a field invented and developed by Einstein at the beginning of the 20th century.
		Astronomers use gravitational lenses to “weigh” the lensing body, and to infer the existence and measure the mass of a body, like a planet or a fl hole, from its gravitational effect even if it cannot be seen.
		Gravitational lenses hint that dark matter exists in our galaxy and others; they suggest new estimates of the age and size of the universe; and over the next decade they will provide powerful tools for contributing to astronomical research.
	www.its.caltech.edu /~sciwrite/journal03/A-L/granett.html (4112 words)

	Gravitational Lens (Site not responding. Last check: 2007-11-07)
		The gravitational lens was observed on April 25 by Nicholas Morgan, a post-doctoral fellow at the Yale Center for Astronomy and Astrophysics, using the 3.5-meter WIYN Telescope at the Kitt Peak National Observatory near Tucson, Arizona.
		The lens is located near the constellation Hercules and is officially known as SDSS 1650+4251.
		The value of finding a gravitational lens, he said, is that it can help in deducing the age of the universe by watching how the light from the quasar changes with time.
	www.yale.edu /ycaa/lens.html (418 words)

	MSN Encarta - Search Results - Gravitational Lens (Site not responding. Last check: 2007-11-07)
		Gravitational Lens, astronomical phenomenon predicted by the relativity theory of Albert Einstein.
		One way to detect such strings would be by their gravitation, which would bend light around them to produce multiple images of objects beyond, such...
		Lens (city), town in northern France, in the Pas-de-Calais Department near Lille.
	uk.encarta.msn.com /Gravitational_Lens.html (118 words)

	The 2dF gravitational lens survey
		Finally, the (hopefully) small set of strong lens candidates would have to be imaged at high resolution (< 1 arcsec) with a view to determining their nature morphologically.
		This is very sensitive to the properties of the lens, but such details need not be treated explicitly as the range of possible weightings can be analysed without knowing the actual image configurations.
		The noise properties of the spectra are certainly correct provided both spectra are kept in their observed frame; the one possible important omission is reddening of the background quasar by dust in the lens.
	www.atnf.csiro.au /pasa/18_2/mortlock2/paper/node4.html (694 words)

	Gravitational Lenses (Site not responding. Last check: 2007-11-07)
		The image may be magnified, distorted, or multiplied by the lens, depending upon the position of the source with respect to the lesnsing mass.
		The characteristics of the gravitationally lensed image depend upon the alignment of the observer, the lens and the background object.
		A gravitational lens is most effective if it is near midway between the observer and the distant object which is being lensed.
	cassfos02.ucsd.edu /public/tutorial/GLens.html (518 words)

	Astronomers Discover Six-Image Gravitational Lens
		The unique configuration is produced by the gravitational effect of three galaxies along the line of sight between the more-distant galaxy and Earth.
		The gravitational lens, called CLASS B1359+154, consists of a galaxy more than 11 billion light-years away in the constellation Bootes, with a trio of galaxies more than 7 billion light-years away along the same line of sight.
		The gravitational effect of the intervening galaxies has caused the light and radio waves from the single, more-distant galaxy to be "bent" to form six images as seen from Earth.
	www.nrao.edu /pr/2001/sixlens (910 words)

	ipedia.com: Gravitational lens Article (Site not responding. Last check: 2007-11-07)
		A gravitational lens is formed when the light from a very distant, bright source is "bent" around a massive object between the source object and the observer.
		In a gravitational lens, the gravity from the massive object bends light as a lens might.
		More commonly, the massive galaxy is off-center, creating different numbers of images according to the relative positions of the source, lens, and observer, and the shape of the gravitational well of the lensing galaxy.
	www.ipedia.com /gravitational_lens.html (985 words)

	Introduction to Gravitational Lenses
		A gravitational lens is an extraordinary astronomical object which is really made up of two separate objects.
		The gravitational lensing phenomena was predicted by Albert Einstein in 1915; it is a direct result of his general theory of relativity.
		Like people, gravitational lenses come in several different shapes and sizes depending on what types of objects are involved, their distances from us and each other, and how close the light from the source passes by the lens.
	www.mira.org /fts0/s_system/161/text/txt001z.htm (553 words)

	APOD: 2005 March 27 - The Einstein Cross Gravitational Lens (Site not responding. Last check: 2007-11-07)
		The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images.
		gravitational lensing, and this specific case is known as the
		Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy.
	antwrp.gsfc.nasa.gov /apod/ap050327.html (154 words)

	JBO Gravitational Lensing Group - CLASS (Site not responding. Last check: 2007-11-07)
		The surviving gravitational lens candidates are then re-observed at higher resolution with MERLIN.
		Some of the lens systems discovered have been monitored to determine the time-delay between the images, allowing a measurement of Hubble's constant to be made.
		Current work is focussed on the modelling the mass profiles of individual lens systems and looking for evidence of sub-structure in the dark matter haloes of the lens galaxy.
	www.jb.man.ac.uk /research/gravlens/class/class.html (433 words)

	A Very Special Lecture on Gravitational Lenses - MIRA Quarterly Newsletter - Fall 1997
		On 20 September, Dr. Donna Womble of MIRA told how she participated in the exciting discovery and confirmation of "A Very Special Gravitational Lens" by an international team of 20 astronomers of which she is still a member.
		The LENS alters the appearance of the SOURCE, changing one or more of its shape, location, or brightness, depending on the exact nature and configuration of the two parts of the gravitational lens.
		Because light from a source object takes multiple paths around a lens object, if an astronomer can find the difference in path length, she may be able to calculate the total distance to the lens objects.
	www.mira.org /newsletr/nlfall97/gravlens.htm (1070 words)

	New Scientist Breaking News - Most distant Einstein ring is revealed
		Gravitational lensing occurs because massive objects - ranging from stars to entire galaxies - distort the fabric of space-time, bending the path of light passing near them.
		If the lens lies directly between Earth and the distant background object, the light can be distorted into a ring, named after Einstein because the effect is described by general relativity.
		At seven billion light years away, the gravitational lens is not quite far enough away to set a record.
	www.newscientist.com /article.ns?id=dn7614&feedId=online-news_rss20 (537 words)

	Gravitational Lens
		This effect is similar to the gravitational effect of light rays that are bent by a massive, dark object coming between the observer's view and a star.
		The gravitational lens is then moved into position between the 'star', that is the truck lamp, and the video camera, that is the observers eye.
		When the gravitational lens simulator is imposed between the lamp and the camera, the lamp 'star' will appear like to reshape into an Einstein ring.
	www.physics.brown.edu /physics/demopages/Demo/astro/demo/8c2040.htm (706 words)

	Space Mission Design solar foci gravity lense deep space
		Gravitational lensing is the bending of light due to gravity.
		Investigate the Sun's gravitational lens, or solar foci, provide a deep space astronomical observatory, complete most of the TAU mission objectives, and provide proof of concept for many unflown technologies.
		Gravitational assists could provide a cheap method to change the orbital plane of the spacecraft if orbital plane change was desirable.
	www.tsgc.utexas.edu /archive/design/foci (2890 words)

	BBC News \| SCI/TECH \| Astronomers get six-way vision
		"This is the first gravitational lens with more than four images of the background object that is produced by a small group of galaxies rather than a large cluster of galaxies," said Dr David Rusin, of the University of Pennsylvania, US.
		Gravitational lensing - first predicted by Albert Einstein - is a neat trick that allows scientists to probe distant parts of the Universe in greater detail than would normally be possible (see box).
		The gravitational lens, called CLASS B1359+154, consists of a galaxy more than 11 billion light-years away in the constellation Bootes.
	news.bbc.co.uk /hi/english/sci/tech/newsid_1516000/1516739.stm (749 words)

	HST Gravitational Lens Image Creator
		Same as SIE with the orientation of the lens mass is constrained to be the same as the light of lens galaxy by including an external shear term.
		Same as SIE with the axis ratio and the orientation of the lens mass is constrained to be the same as the light of lens galaxy by including an external shear term.
		The deflection from gravitational lens used in the simulation is defined by the critical radius which is the directly observed quantity.
	mds.phys.cmu.edu /ego_cgi.html (606 words)

	Gravitational Lens (Site not responding. Last check: 2007-11-07)
		Gravitational lensing is caused by the bending of light rays by the gravitational field of an intervening object.
		The gravitational lens of a simple source can be modeled with a 'wineglass base' shaped lens, one whose curvature is circular.
		A couple of objects to look out for are the quasar 0957+561, a double image of one object and the first gravitational lens identified, and MG 1654+1346, an Einstein ring.
	www.fas.harvard.edu /~scdiroff/lds/AstronomyAstrophysics/GravitationalLens/GravitationalLens.html (335 words)

	G-LenS Gravitational Lensing Simulation
		Each stage of the computer model development is covered in the report, from initial ideas, through to testing the model using some of the latest gravitational* lens observations.
		It is my belief that this project has succeeded not only in producing a working simulation of a point mass gravitational lens system, but also in providing a challenge.
		There is great satisfaction to be gained from creating a computer program from scratch, and developing it into a working model, which can not only simulate basic lens theory, but can also reproduce the lensing effects of an, approximated, observed system.
	www.btinternet.com /~boughen/G-LenS (231 words)

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