Gravity wave

Gravity waves referdifferent (but basically similar) conceptsfluid dynamicselectrodynamics.

Tablecontents

1 Fluid dynamics 2 Radiation 2.1 General 2.2 Experiments 3 ReferencesExternal links

Fluid dynamics

Gravity wavesgenerated influid medium (e.g.atmosphere), whenfluid parceldisplaced [e.g. by convection] toregion withdifferent density. Iffluid stratificationstable,parcel will startoscillate aroundpoint where thereno net force. Sincefluid iscontinuous medium,traveling disturbance will result.

Radiation

In physics,Gravity wave iswave ingravitational field. Gravitational radiation isoverall resultgravity wavesbulkrefers toconcept forphenomenon known as gravity. The proposed quantumgravitational radiation isgraviton. Accordinggeneral relativity, gravity can cause oscillations (or waves)spacetime which can transmit energy. If gravity wavesinspace-time,theyproduced by media, itproposed that"waves" will startoscillate around center points. Sincespacecontinuous,traveling disturbance will result.

General

Roughly speaking,strengthgravity will go updown asgravitational wave passes, much assurface ofbodywater will go updown aswater wave passes. More precisely,isstrengthdirectiontidal forces (measured byWeyl tensor) that oscillates, which should cause objects inpath ofwavechange shape (but not size) inpulsating fashion. Similarly, gravitational waves will be emitted by physical objects withpulsating shape, specifically objects withnonzero quadrupole moment.

The existencegravitational radiation, withfeatures described above,predicted byphysical theorygeneral relativity, which describes gravitationgeneral. The equationsthis theorynonlinear, so that:

• The solutions toequations do not formvector spacecannot be superimposed (added together)produce new solutions. This makes solvingequations much harder thanlinear analogues, such astheoryelectromagnetic radiation.
• Gravitational waves interacteach other (not justother physical objects). Thisunlike,instance,interactiontwo wave pulses travelling downstring, which can pass through each other without interference.

However, weak gravitational waves can be described togood approximation by linearised general relativity, whichlinear.

The theory must account foressential difference between gravitationalelectric forces:

[1] Electric forces act statically locally interactingnearby opposite charges.

[2] Gravitational forces have infinite range. ("spooky action atdistance")

Proposed sourcesGravity waves include all bodies on space-time, butcurrently only detectable ongalactic scale. These include:

1. Supernovas or gamma radiation bursts
2. Inspiraling coalescing binary star "chirps"
3. Spherically asymmetric periodic pulsars signals
4. Chaotic cosmic microwave background radiation (CMBR) sources

Scientistseagerfindwaydetect these gravitational waves, sincecould help reveal information aboutvery structure ofuniverse. In contrastelectromagnetic radiation, itnot known what differencepresencegravitational radiation would make forworkings ofuniverse.

Experiments

Physicists Russell HulseJoseph Taylor explained their observations ofbinary neutron star system asresult ofsystem's emitting gravitational wavesaccordancegeneral relativity, an achievementwhichwere awarded1993 Nobel PrizePhysics. However, gravitational radiation has never been directly observed -- that is, no one has yet witnessedphysical object actually changing shape asgravitational wave passes through-- although there have beennumberunconfirmed reports. The confirmed observationgravitational waves would be important further evidence forvaliditygeneral relativity.

One reason forlackdirect detection so farthatgravitational waves that we expectbe producednaturevery weak, so thatsignalsgravitational waves, ifexist,buried under noise generated from other sources. Reportedly, ordinary terrestrial sources would be undetectable, despite their closeness, because ofgreat relative weakness ofgravitational force. It has been proposed that certian conductors, especially superconductors, could be madeemit gravitational waves inlaboratory, but this workstill considered speculative. Seeexternal link listed atend ofarticlemore information.

A numberteamsworking on making more sensitiveselective gravitational wave detectorsanalysing their results. A commonly used techniquereduceeffectsnoise isuse coincidence detectionfilter out events that do not register on both detectors. Theretwo common typesdetectors usedthese experiments:

• laser interferometers, which uselight paths, such as GEO, LIGO, TAMA, VIRGOACIGA;
• resonant mass gravitational wave detectors which use large masses at very low temperatures, such as EXPLORERNAUTILUS.

In November 2002,teamItalian researchers atIstituto Nazionale di Fisica Nucleare andUniversityRome produced an analysistheir experimental results that may be further indirect evidence ofexistencegravitational waves. Their paper, entitled "Study ofcoincidences betweengravitational wave detectors EXPLORERNAUTILUS2001"based onstatistical analysis ofresults from their detectors which shows thatnumbercoincident detectionsgreatest when boththeir detectorspointing intocenterour galaxy,Milky Way.

ReferencesExternal links

Fuild dynamics

• Dr. Steven Koch, Hugh D. Cobb, IIINeil A. Stuart, "Notes on Gravity Waves - Operational ForecastingDetectionGravity Waves WeatherForecasting". NOAA, Eastern Region Site Server.

Radiation

• Sica, R. J., "A Short Primer on Gravity Waves". DepartmentPhysicsAstronomy, The UniversityWestern Ontario. 1999.
• "Gravity waves". Physics central.
• Discussiongravitational radiation onUSENET physics FAQ
• Tablegravitational wave detectors
• Laser Interferometer Gravitational Wave Observatory. LIGO Laboratory, California InstituteTechnology.
• B. Allen, et al., "Observational Limit on Gravitational Waves from Binary Neutron Stars inGalaxy". The American Physical Society, March 31, 1999.
• "Gravitational Radiation". Davis Associates, Inc.
• The Italian researchers' paper analysing data from EXPLORERNAUTILUS
• CenterGravitational Wave Physics. National Science Foundation [PHY 01- 14375].
• Australian International Gravitational Research Center. UniversityWestern Australia.
• TAMA project. Developing advanced techniqueskm-sized interferometer.
• Amos, Jonathan, "Gravity wave detector all set". BBC, February 28, 2003.
• Rickyjames, "Doing(Gravity) Wave". SciScoop, December 8, 2003.
• Could superconductors transmute electromagnetic radiation into gravitational waves? -- Scientific American article