What is Gravitational wave: Definition and 89 Discussions

Gravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light. They were proposed by Henri Poincaré in 1905 and subsequently predicted in 1916 by Albert Einstein on the basis of his general theory of relativity. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Newton's law of universal gravitation, part of classical mechanics, does not provide for their existence, since that law is predicated on the assumption that physical interactions propagate instantaneously (at infinite speed) – showing one of the ways the methods of classical physics are unable to explain phenomena associated with relativity.
The first indirect evidence for the existence of gravitational waves came from the observed orbital decay of the Hulse–Taylor binary pulsar, which matched the decay predicted by general relativity as energy is lost to gravitational radiation. In 1993, Russell A. Hulse and Joseph Hooton Taylor Jr. received the Nobel Prize in Physics for this discovery. The first direct observation of gravitational waves was not made until 2015, when a signal generated by the merger of two black holes was received by the LIGO gravitational wave detectors in Livingston and in Hanford. The 2017 Nobel Prize in Physics was subsequently awarded to Rainer Weiss, Kip Thorne and Barry Barish for their role in the direct detection of gravitational waves.
In gravitational-wave astronomy, observations of gravitational waves are used to infer data about the sources of gravitational waves. Sources that can be studied this way include binary star systems composed of white dwarfs, neutron stars, and black holes; and events such as supernovae, and the formation of the early universe shortly after the Big Bang.

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  1. B

    Thought experiments about Gravitational Waves

    Imagine a mass that disappeared from space. I know that it is impossible, but imagine it is sucked by a wormhole or it just disapperars. Will we detect ONE gravitational wave only? Like a pulse and nothing else? Now the other way around. A mass appears from nothing. Then we will detect one...
  2. DiracPool

    Gravitational Wave Shapes: 3D Oscillations, Creepy Earthworms & More

    We've seen the peculiar oscillating shape of the "squeeze-stretch" effect that a gravitational wave (GW) imparts on space and matter. What I am unsure of, however, is how does this wave manifest itself in three dimensions, as well as a few other questions.. 1) Does it spread out spherically...
  3. A

    I Gravitational wave time variation

    I have tried to discover if the local time as well as the local space is varied by the passage of a gravitational wave. I have seen animations and discussion of the effects of gravitational wave on space and test particles but can't find a reference to the changes in the time component of...
  4. philton

    Exploring What If: ER = EPR and Gravitational Wave = Quantum Wave

    Homework Statement If ER==EPR Then IsPossible(gravitational wave == projection of quantum wave) In other words: If the conjecture of "ER = EPR" is true, is it possible that "gravitational wave = 3+1 dimensional part of quantum wave" is also true? 2. Homework Equations The quantum source...
  5. phyzguy

    A Rumors of Gravitational Wave Inspiral at Advanced LIGO | Sept 2015 Launch

    There is a rumor going around that a gravitational wave inspiral has been seen at advanced LIGO. The web sites say it went on line in Sept, 2015, so I guess this is possible. Has anyone here heard anything?
  6. Garth

    Primordial gravitational wave constraints from Planck 2015

    In today's Physics ArXiv: New constraints on primordial gravitational waves from Planck 2015. Authors Luca Pagano, Laura Salvati, and Alessandro Melchiorri of the Physics Department and INFN, Universita di Roma. Primordial gravitational waves from the universe exiting Inflation get more and...
  7. K

    Surfing a Gravitational Wave: Is It Possible?

    Is it possible to pulse Alcubiere drive once to catch up a gravitational wave to surf it, then pulse again to stop?
  8. Chronos

    Using atomic clocks for gravitational wave detection

    This paper, http://arxiv.org/abs/1501.00996, proposes using atomic clocks for gravitational wave detection. It sounds similar to other ideas involving pulsar timing experiments. The twist here is utilizing satellites to provide a wide base for improved sensitivity. Sounds like an inexpensive...
  9. P

    Does wormhole create gravitational wave?

    I've seen many sci-fi that they said wormhole could be detected by its gravitational wave ? Does wormhole actually create gravitational wave ? And how could a pair of black hole spinning around each other create such thing as gravity wave ? I am sorry for lacking knowledge about general relativity.
  10. G

    Gravitational Wave Observatories: Testing & Feasibility

    This may be a stupid question, but have the various gravitational wave observatories around the world been tested by seeing if they can detect man-made gravitational waves, and thus work as expected? Or would it be too unfeasible to make them, even given the extreme sensitivity that the...
  11. wolram

    Can Pulsar Timing Arrays Detect Gravitational Wave Bursts with Memory?

    arXiv:1404.5682 arXiv:1404.5682 [pdf, ps, other] Assessing Pulsar Timing Array Sensitivity to Gravitational Wave Bursts with Memory D. R. Madison, J. M. Cordes, S. Chatterjee Comments: Submitted to ApJ Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for...
  12. D

    Would we feel the effects of a strong gravitational wave?

    So I created an account here just so I could ask this burning question. I keep looking online and through other resources but can't really find any details on this. Apologize if I didn't post on the right forum. So I know gravitational waves are still being studied and as far as I know any...
  13. S

    Derivation of the quadrupole moment of gravitational wave

    Hi, Can anyone give a derivation of the quadrupole moment in the TT gauge ( Equation metioned below ) of the gravitational wave ? QijTT(x) = ∫ρ(xixj-1/3δijr2)d3x Where ρ is the matter density Thanks In Advance
  14. C

    Gravitational wave solution boundary conditions

    In linearized gravity we can one sets $$(1) \ \ g_{\mu \nu} = \eta_{\mu \nu} + h_{\mu \nu}$$ where h is taken to be a small perturbation about the flat space metric. One common decomposition of h is to write the spatial part as $$ h_{i j} = 2 s_{ij} - 2\psi \delta_{ij} \ h_{0i} \equiv...
  15. T

    Why does gravitational wave research get DoD funding?

    Question in the subject. I have no idea what the DoD's interest is in this. Sorry is this is the wrong forum.
  16. wolram

    If a strong gravitational wave hit Earth would clocks record it?

    If a strong gravitational wave hit Earth would clocks record it? as if i understand it it is space time that is oscillating so the time component must be changing.
  17. C

    Direct Measurement of Gravitational Wave Velocity

    http://www.spacedaily.com/reports/Chinese_scientists_find_evidence_for_speed_of_gravity_999.html Done by the Institute of Geophysics at the Chinese Academy of Sciences using Earth tide measurements. The conclusion is that it is the speed of light. http://en.wikipedia.org/wiki/Earth_tide...
  18. S

    Gravitational Wave: Mechanical Waves & Space-Time Continuum

    I have a question: Would Gravity (or gravitational) waves be considered mechanical waves? Wouldn't the Medium be the space-time continuum itself for these waves?
  19. S

    Gravitational wave data analysis. More of Signal processing techniques

    I am using the matched filtering technique to extract the data from a heavy noise background in the process of detection of gravitational waves. I calculate the correlation between the experimental data and a theoretical template. I have been told that the maximum of the correlation function...
  20. alemsalem

    Gravitational Wave Local Energy: Not Gauge Invariant?

    I'm reading wald page 85, and he defines a stress-energy tensor for the linearized gravitational field. he mentions that it not gauge invariant as a problem. but isn't that a general property of any tensor (except scalars). so any stress-energy tensor will not be gauge invariant (change of...
  21. W

    Observation of gravitational wave strain.

    Hello, I have a question or two about gravitational waves. My current job is basically to measure atomic strains using x-ray diffraction. I have managed to reduce the error in measurement low enough to reveal an annual sine wave in my data for a sample which should not contain any strain. I...
  22. V

    Can Interferometers Measure Gravitational Waves Despite Being Made of Matter?

    I'm currently reading the chapter in Schutz about gravitational waves (though knowledge of/access to Schutz shouldn't be necessary to answer my question). After demonstrating how a passing gravitational wave will cause the proper distance between two points to change temporarily, he says: "A...
  23. J

    Gravitational Wave Propagation

    Would gravitational waves propagating through space-time at the speed of light be affected by the curvature? Or are they independent? Why does the spinning of a binary pulsar cause a gravitational wave when there is no change in mass other than the loss of photon energy? Doesn't this object...
  24. P

    Gravitational Wave Disbursement

    Have a question related to this quote from Wikipedia: "The amplitude of a spherical wave will fall off as the inverse square of the distance from the source." Is it correct to think that the energy of the whole of the wave is maintained but that it's the disbursement of the wave which results...
  25. M

    Most power gravitational wave sources

    In reality what do you expect to be the first detection with GW detectors? Closest pulsars?
  26. C

    Structure of a gravitational wave?

    Questions concerning GW's are very common on PF, but I think I have a new question on the concept. Maxwell explains that EM waves(photons) propagate in space due to a relationship between the sinusoidal representations of the electric and magnetic fields of the wave. Namely that these...
  27. J

    Gravitational Wave Detection: Understanding Interferometers

    My understanding of how interferometers work is that they detect gravitational waves because they alter the distance between two mirrors as they pass through. They do this by using the wavelength of a laser beam passing through this space. However, shouldn't this always fail to detect anything...
  28. P

    When will LIGO be sensitive enough to detect gravitational wave background?

    Advanced LIGO, scheduled to start in 2014, is believed to be able to detect gravitational waves from stellar sources. According to our best current models, does Advanced LIGO stand any chances of detecting the stochastic GW wave background? And even measure its temperature? (No more than 0.9K...
  29. E

    Building Gravitational Wave Experiment

    I have recently come up with an idea about trying to build an apparatus to run some gravitational wave experiments. Now I am still a novice so I wrote Professor Scott Hughes about my idea, he provided me with the mathematical equations that basically show the experiment is impossible. I will...
  30. Truecrimson

    Macroscopic quantum effects and gravitational wave detector

    My first thread here. Please bear with my lack of knowledge. I talked to a physics grad student about whether it's fair to describe QM as a theory applied only to microscopic objects. Although the definition of "fair" is ambiguous, at least he told me that, from his understanding, he wouldn't...
  31. D

    Caltech Gravitational Wave theory - videos included

    http://elmer.caltech.edu/ph237/CourseMaterials.html Enjoy
  32. C

    Can Gravitational Waves Actually Harm Us or Destroy Planets?

    I was just wondering what it would feel like if I was hit by a decently powerful gravitational wave. Would I feel pulled to the source of the wave? Is there tidal forces present that might stretch me? Could a gravitational wave actually kill me? Or destroy things like planets?
  33. S

    Maxwell's Equations and Path of light & Gravitational wave

    Maxwell's Equations say about the velocity of electromagnetic wave..Does Maxwell's equations also say about path of the electromagnetic wave i.e. light? I want to know how to find the path of light from Maxwell's equations? Or it says only about velocity? One more question, what is the path...
  34. V

    What is Gravitational Wave Astronomy?

    What an ambitious emerging field of research! Anyone else as into this as I am? http://en.wikipedia.org/wiki/Gravitational_wave_astronomy The LISA and LIGO projects are MIND-BLOWING. I can't believe I am so lucky as to be alive in this age. There's never been a better time to be alive. I...
  35. S

    Gravitational wave physics and numerical relativity ?

    What do you think about Gravitational wave physics and numerical relativity ? Will it expand much in future? Now few universities are giving research facilities on these two. Why ? But i really like these two.
  36. CJames

    How does the Gravitational Wave Rocket work?

    Here's the paper I'm talking about http://arxiv.org/PS_cache/gr-qc/pdf/9702/9702005v1.pdf It's times like this I wish I'd gone to class... I've been trying to find a method of propulsion that falls within the realms of accepted physics but is convenient in terms of *storytelling*. I...
  37. E

    Speed of photons inside a very powerful gravitational wave

    could a strong gravitational wave speed up the speed of photons traveling inside it?
  38. D

    Gravitational Wave Detection Project Help

    I am doing a project on Gravitational Wave Detection Techniques, and I am already done with preparing the apparatus for that , its kid of Michelson Interferometer with some minor additions , the wave detection is based on the same basic principle of fringe shift due to path difference in two...
  39. N

    Blackhole decay and gravitational wave

    hi i have few unclear things but I'm not sure if this is the correct thread. 1.can anyone explain me how does a black hole deacy. please include no mathematics and only logic. 2.is gravity wave something like electromagnetic wave transmitted by gravitons instead of a photon?but i heard; by...
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