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	Gravitational radiation - Wikipedia, the free encyclopedia
		Gravitational waves should not be confused with gravity waves in hydrodynamics.
		A sufficiently strong sea of primordial gravitational radiation, with an energy density exceeding that of the big bang electromagnetic radiation by a few orders of magnitude, would shorten the life of the universe, violating existing data that show it is at least 13 billion years old.
		Their paper, entitled "Study of the coincidences between the gravitational wave detectors EXPLORER and NAUTILUS in 2001", is based on a statistical analysis of the results from their detectors which shows that the number of coincident detections is greatest when both of their detectors are pointing into the center of our Milky Way galaxy.
	en.wikipedia.org /wiki/Gravitational_wave (1265 words)

	The Astrophysics Spectator: Gravitational Waves
		Gravitational waves are similar to their counterpart in electromagnetism.
		As with electromagnetic waves, gravitational waves exist because changes in the gravitational field can propagate no faster than the speed of light, and as with electromagnetic waves, the energy carried by the gravitational wave falls-off as the inverse of the distance-squared from the source of the waves.
		A gravitational wave acts on matter as a tidal force, so a solid body would be squeezed in one direction and stretched in another, with both actions occurring perpendicular to the wave's direction of motion.
	www.astrophysicsspectator.com /background/survey/physics/GravitationalWaves.html (801 words)

	ESA Science & Technology: Gravitational Waves
		It was 188 years later, in 1993, that Hulse and Taylor were awarded the Nobel Prize for Physics for their indirect proof of the existence of gravitational waves using exactly this kind of observation of the binary pulsar PSR 1913+16.
		While electromagnetic waves, created by the acceleration of electrical charges, propagate in the framework of space and time, gravitational waves, created by the acceleration of masses, are waves of the spacetime fabric itself.
		A gravitational wave passing through the Solar System creates a time-varying strain in space that periodically changes the distances between all bodies in the Solar System in a direction that is perpendicular to the direction of wave propagation.
	hubble.esa.int /science-e/www/object/index.cfm?fobjectid=31417 (771 words)

	LIGO Livingston Observatory Home Page
		LIGO will search for gravitational waves created in supernova collapses of stellar cores (which form neutron stars and fl holes), collisions and coalescences of neutron stars or fl holes, rotations of neutron stars with deformed crusts and the remnants of gravitational radiation created by the birth of the universe.
		Gravitational waves that originated hundreds of millions of light years from earth are expected to distort the 4 kilometer mirror spacing by about a thousandth of a Fermi (less than one trillionth of the diameter of a human hair).
		These waves were first predicted by Einstein's Theory of General Relativity in 1916, when the technology necessary for their detection did not yet exist.
	www.ligo-la.caltech.edu (223 words)

	LIGO Fact Sheet
		Gravitational waves are ripples in the fabric of space and time produced by violent events in the distant universe, for example by the collision of two fl holes or by the cores of supernova explosions.
		Test general relativity's prediction that the forces the waves exert on matter are perpendicular to the waves' direction of travel, and stretch matter along one perpendicular direction while squeezing it along the other; and also, thereby, test general relativity's prediction that the graviton has twice the rate of spin as the photon.
		Gravitational waves are ripples in the fabric of space-time.
	www.ligo.caltech.edu /LIGO_web/about/factsheet.html (1319 words)

	ESA - Science - Home - Gravitational waves — ‘dents’ in space-time
		However, gravitational waves, which are created by the acceleration of masses, are waves of the space-time ‘fabric’ itself.
		In 1993, indirect proof was found for the existence of gravitational waves by observing the binary pulsar PSR 1913+16.
		A gravitational wave passing through the Solar System creates a time-varying strain in space that periodically changes the distances between all bodies in the Solar System (this strain changes distances perpendicularly to the direction in which the wave moves).
	www.esa.int /esaSC/SEMLY2T1VED_index_0.html (641 words)

	Ripples in SpaceTime
		Predicted in Einstein's General Theory of Relativity, gravitational waves are disturbances in the curvature of spacetime caused by the motions of matter.
		Though gravitational waves pass straight t hrough matter, their strength weakens proportionally to the distance traveled from the source.
		For starters, gravitational waves, though weakening with distance, are thought to be unchanged by any material they pass through and, therefore, should carry signals unalt ered across the vast reaches of space.
	archive.ncsa.uiuc.edu /Cyberia/NumRel/GravWaves.html (605 words)

	Gravitational Waves (Part 1)
		To summarize the characteristics of gravitons and gravitational waves, a graviton or several gravitons (usually 6 gravitons) resides in a quark, which is supposed to be the smallest particle in physics so far.
		Now gravitational waves, tiny vertical waves control the horizontal electro magnetic waves and produce mixed waves that give you different feelings, bringing back your part of your brain to function to produce moderate amount of melatonin which will keep you young and try to give you enough sleep.
		It is interesting to see that electro magnetic waves (horizontal waves) had been discovered by a western person and that the importance of gravitational waves (vertical waves) has been discovered by an oriental person.
	www.rialian.com /rnboyd/karita1.htm (2992 words)

	Gravitational Waves
		Gravitational waves, like scalar fields, obey the Klein-Gordon equation in a flat universe and their amplitudes begin oscillating and decaying once the perturbation crosses the horizon.
		Because gravitational waves cause a quadrupole temperature anisotropy at the end of recombination, they also generate a polarization.
		-component presents a promising means of measuring the gravitational waves from inflation and hence the energy scale of inflation (see Figure 4, right panel).
	background.uchicago.edu /~whu/araa/node23.html (362 words)

	The Space Place :: LISA Looks for Gravity Waves!
		The biggest gravitational waves would be caused by huge events--for example, two huge stars orbiting each other, or a massive star orbiting a fl hole, or two fl holes orbiting each other.
		However, gravitational waves from even these cosmic happenings are very weak by the time they reach us from some far away star system, just as a loud sound that is far away can be very faint.
		Gravitational waves are very hard to detect, so we have never before been able to measure them.
	spaceplace.nasa.gov /en/kids/lisa_fact2.shtml (804 words)

	Gravitational Waves,1997
		Gravitational waves - waves in the curvature of space-time - are a prediction of General Relativity.
		Gravitational wave detectors: Potential sources of gravitational waves include the collapse of massive stars in supernova explosions and the coalescence of two compact stars such as neutron stars in binary systems.
		At present we are working on a prototype detector fitted with ultra-low loss optics, and much of the work of the group is devoted to developing precision interferometric techniques, and to understanding and minimising noise sources such as seismic and thermal noise in delicate optical and mechanical systems.
	www.physics.gla.ac.uk /gradschool/w3gw.html (651 words)

	Gravitational waves (Site not responding. Last check: 2007-11-07)
		Existence of gravitational waves is generally accepted, at least since their indirect observation via energy and angular momentum losses in binary pulsars, like in the Hulse-Taylor pulsar.
		Gravitation being the weakest of all interactions, gravitational waves are difficult to generate and detect in the laboratory.
		Gravitational waves are characterised by a dimensionless amplitude — a measure of the strain in space they cause as they pass through.
	www.europhysicsnews.com /full/12/article14/article14.html (1894 words)

	PSR 1913+16 (Site not responding. Last check: 2007-11-07)
		When they are closer together, near apastron, the gravitational field is stronger, so that the pasage of time is slowed down -- the time between pulses (ticks) lengthens just as Einstein predicted.
		The pulsar clock is slowed down when it is travelling fastest and in the strongest part of the gravitational field; it regains time when it is travelling more slowly and in the weakest part of the field.
		Such a merger might produce strong enough gravitational radiation to be detected by instruments like the Laser Inteferometer Gravitational-Wave Observatory now under contruction.
	astrosun.tn.cornell.edu /courses/astro201/psr1913.htm (1149 words)

	Gravitational waves (Site not responding. Last check: 2007-11-07)
		Gravitational waves (GWs) are ripples in space-time and can come from sources like fl holes and/or neutron stars spiraling into each other, from the formation of fl holes, from rotation of neutron stars, and other things.
		Gravitational wave astronomy is an entirely different way of looking at the universe than previous electromagnetic radiation observations (various forms of light), so it will provide information we have not had before.
		The reason for this is that in general the energy per unit area carried by waves is proportional to the inverse square of the distance of the source, whereas the wave amplitude is inversely proportional to the distance.
	www.johnstonsarchive.net /relativity/gravwave.html (1223 words)

	Press Release - PRESS WELCOME TO ATTEND GRAVITATIONAL WAVES MEETING, APRIL 24-26 - 03-42 (Site not responding. Last check: 2007-11-07)
		According to Einstein's theory of general relativity, gravitational waves are ripples in the four-dimensional fabric of space-time created by massive objects in motion or undergoing an extreme event.
		The waves hardly interact with matter, however, altering the distance of objects as far apart as the Earth and the Moon by less than the width of an atom.
		Gravitational wave astronomy is poised to open a new observational window on the Universe through both ground-based, high-frequency detectors (LIGO and LIGO II) and space-based, low-frequency detectors (LISA), according Dr. Joan Centrella, a theoretical astrophysicist in the Goddard Laboratory for High Energy Astrophysics and chair of the meeting.
	www.gsfc.nasa.gov /news-release/releases/2003/03-42.htm (523 words)

	Gravitational waves (from relativity) -- Britannica Student Encyclopedia (Site not responding. Last check: 2007-11-07)
		General relativity predicts the occurrence of gravitational waves, whose properties should resemble in some respects those of electromagnetic waves: they should travel at the same speed, c, and they should be polarized.
		The phenomenon is the result of interference—that is, when waves are superimposed, their energies are either added together or cancelled out.
		In the case of waves moving in the same direction, interference produces a travelling wave; for oppositely moving waves,...
	www.britannica.com /ebi/article-28937 (949 words)

	Brief on gravitational waves (Site not responding. Last check: 2007-11-07)
		Gravitational waves (g.w.) are predicted by General Relativity.
		The effect on matter of the passage of gravitational radiation is a squeezing and stretching, depending on the phase of the wave.
		The effect of the passage of gravitational radiation through a person is sketched in fig.2: well, the effect of squeezing and stretching has been exaggerated a bit!
	www.auriga.lnl.infn.it /auriga/grav_wave.html (308 words)

	www.iop.org News - UK expert takes on bookies over Gravitational Waves (Site not responding. Last check: 2007-11-07)
		Gravitational waves are ripples in the fabric of spacetime and are one of the more exotic predictions of Einstein's theory of gravity — General Relativity.
		Weak gravitational waves are probably passing through us all the time but are too faint to detect.
		Scientists are currently trying to detect the strongest waves, for example those created in violent events such as supernovae but none of the instruments looking for them have yet picked up a clear and definite signal.
	www.iop.org /news/817 (626 words)

	New Scientist Breaking News - Fast-spinning star could test gravitational waves
		One possible mechanism could be gravitational waves - hypothesised ripples in space-time that are yet to be detected.
		Fast-spinning objects that are not perfectly symmetrical are predicted to radiate away energy in gravitational waves, with faster objects unleashing much more energy than slower ones.
		It is possible, says Chakrabarty, that spin rates of 600 times per second allow gravitational waves to siphon away enough energy to prevent pulsars from spinning any faster.
	www.newscientist.com /article.ns?id=dn7052 (723 words)

	ESA - Science - Home - LISA overview
		The most predictable sources of gravitational waves are binary stars in our Galaxy, namely pairs of stars held together by their mutual gravitational pull.
		If gravitational radiation from known binary systems is not detected, or is detected with amplitudes or polarisations not predicted by general relativity, general relativity must be wrong.
		However, to detect the vibrations caused by the passing gravitational waves, all other sources of vibration must be eliminated or damped down to an acceptable level.
	www.esa.int /science/lisa (1478 words)

	NASA - Top Story - EINSTEIN'S GRAVITATIONAL WAVES MAY SET SPEED LIMIT FOR PULSAR SPIN - July 2, 2003
		Gravitational radiation, ripples in the fabric of space predicted by Albert Einstein, may serve as a cosmic traffic enforcer, protecting reckless pulsars from spinning too fast and blowing apart, according to a report published in the July 3 issue of Nature.
		Gravitational waves, analogous to waves upon an ocean, are ripples in four-dimensional spacetime.
		These exotic waves, predicted by Einstein's theory of relativity, are produced by massive objects in motion and have not yet been directly detected.
	www.nasa.gov /centers/goddard/news/topstory/2003/0702pulsarspeed.html (1233 words)

	Gravitational Waves (Site not responding. Last check: 2007-11-07)
		Among all the forces of nature, the gravitational force is the one that has been known to man for the longest time.
		Einstein's theory predicts the existence of gravitational waves, that is, perturbations of the gravitational field, which, as it is for electromagnetic field, spread out through space at the speed fo light.
		The weakness of gravitational force, makes it extremely hard to detect gravitational waves: actually, after 30 years of active research, we only have an indirect proof of their existence obtained from studying a binary pulsar system, but it has not yet been possible to detect directly the gravitational waves.
	www.virgo.infn.it /GravWaves1.html (154 words)

	gravitational waves
		Vibrations in the fabric of spacetime which travel at the speed of light and are predicted by Einstein's general theory of relativity.
		The most intense gravitational waves, resulting from large masses undergoing high accelerations, are expected to be produced when stars collapse or matter falls into a fl hole.
		Although they have yet to be detected, evidence for their existence has come from observations of the only known binary star in which both components are neutron stars.
	www.daviddarling.info /encyclopedia/G/gravwave.html (184 words)

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