What is Gravitational waves: Definition and 330 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. P

    Gravitational Waves and Entropy

    I'm learning about gravitational waves and associated matters (detectors etc.). I don't do much maths, but physics is in my bones. Totally at home with classical physics and SR; as for GR- well, I'm O.K. as long as you stay on the 'friendly' side of event horizons... I'm comfortable with the...
  2. S

    What is the speed of gravitational waves?

    I was wandering through the net when I came to know that the Newtonian gravitation suffers discrepancies at some regions of space. On further reading I came to know about gravitational waves. Fundamentally matter has mass and mass is responsible for gravity. Then it may be anything from small...
  3. A

    Gravitational waves and Tidal forces

    Anybody could explain me the difference between tidal forces and gravitational waves? My question emerges from the fact that gravitational waves has never been detected and also considering that tidal forces are very well understood by current physicist. Thanks AG
  4. C

    Does the producing process of gravitational waves produce gravitation?

    Gravitational waves are generated when the mass quadrupole moment changes in time. We also know motion of mass contributes to its gravitation. Does the producing process of gravitational waves, which involves mass in accelerated motion, produce gravitation as well? If so, is it of less, equal...
  5. B

    Question regarding gravitational waves

    Homework Statement A star 10 light-years away explodes and produces gravitational waves. How long will it take these waves to reach the earth? Homework Equations The problem is, I don't know what equations to use or if it's just a matter of simple math. The Attempt at a Solution...
  6. haael

    Could GPS satellites be used to detect gravitational waves?

    To detect gravitational waves, we set up some probe masses in laboratories far from each other and measure distance between them. Why not use GPS satellites for that? I mean: they have precise atomic clocks, they constantly measure their position relative to each other and they are as far away...
  7. B

    Does an accelerated particle emit gravitational waves?

    Does a massive particle that is accelerated emit gravitational waves? What if the acceleration is due to a gravitational field?
  8. S

    What can gravitational waves teach us about the universe?

    Helo everybody..good evening sir .. this ismy first post and i just finish High school and thinking about going to a college.. i'm just wondering what are gravitational waves./thx.
  9. D

    Gravitational Waves: Have They Been Directly Detected?

    Have gravitational waves been directly detected yet?
  10. A

    Progress on detection of gravitational waves?

    Does anyone know how the progress is on the attempts to detect gravitational waves with interferometry? As far as I know there are only null-results up to this date, but maybe I am misinformed? The recent supernova in the galaxy Messier 101, should it generate gravitational waves of...
  11. N

    Why don't gravitational waves get distorted?

    In BLACK HOLES AND TIME WARPS Kip Thorne writes: So why is it that gravitational waves alone are "not at all distorted"?? For example, don't they combine [maybe even non linearly] with other gravitational waves?...they must interact with matter, otherwise we wouldn't be able to detect...
  12. R

    Cosmic inflation and gravitational waves.

    After the big bang, did the cosmic inflation of space occur as a gravitational wave?
  13. F

    Energy-momentum of gravitational waves

    Hello, I was wondering, since gravitational waves carry energy-momentum, would it be possible to find them in regions where the components of the metric tensor vanish? That is to say, empty space (non-quantum) is described by a vanishing energy-momentum tensor - but then, if gravitational waves...
  14. MTd2

    12 min orbit white dwarfs found Best target for gravitational waves

    I'd like to share with you people this great discovery! http://arxiv.org/abs/1107.2389 A 12 minute Orbital Period Detached White Dwarf Eclipsing Binary Warren R. Brown (1), Mukremin Kilic (1), J. J. Hermes (2), Carlos Allende Prieto (3), Scott J. Kenyon (1), D. E. Winget (2) ((1) SAO...
  15. BruceW

    Gravitational waves predicted by Einstein

    I've read a newspaper article which claims: "If the search for gravitational waves succeeds, then Einstein's theory of general relativity may have to be revised" But I thought that Einstein predicted gravitational waves, so surely if they are found, it would confirm general relativity. I don't...
  16. W

    Quantum view of gravitational waves

    In case of electromagnetic fields i think it is like this: A electromagnetic wave is caused by an accelerating charge, this causes a temporal change in the electric and magnetic field around it which propagates through space at the velocity of light. If we have a transmitter and multiple...
  17. Drakkith

    Gravitational Waves: Interfering, Diffracting & More

    Would gravitational waves act just like other types of waves? IE can they interfere, diffract, etc? I would assume no to some of those, as I don't think there is anything that would cause them to diffract as they aren't EM waves or waves through a materiel. But I don't know really. Any thoughts?
  18. E

    Christoffel symbols for gravitational waves

    Homework Statement Determine the Christoffel symbol \Gamma^{t}_{xx} for the metric ds^2 = -c^2dt^2 + (1+h\sin(\omega t))dx^2 + (1-h\sin(\omega t))dy^2 + dz^2 The answer should be: \frac{h\omega}{2} \cos(\omega t) Homework Equations For the evaluation we have to use...
  19. M

    Gravitational Waves: Is Gravity a Force in GR?

    Hello, I have a BA physics but I've never taken GR. My question is whether gravity is a force in GR? the answer i get everywhere is that it isn't a force, but rather the curvature of space. And objects moving under 'gravity' is simply them moving along a geodesic. But then i keep hearing the...
  20. J

    Gravitational waves by analogy with Maxwell's equations

    According to the Wikipedia article on Gravitomagnetism: http://en.wikipedia.org/wiki/Gravitomagnetism There is a gravitational analog of maxwell's field equations that is valid for weak gravitational fields. Basically all you have to do is replace eps_0 in maxwell's equations with -1/4...
  21. TrickyDicky

    Doubt about gravitational waves

    The usual derivation of the wave form equations from the GR field equations is done in the weak field, linearized approximation of the GR theory. In this limit, that ignores non-linear contributions and that gives accurate results when used to predict solutions for problems in the Newtonian...
  22. WannabeNewton

    What Determines the Speed of Gravitational Waves?

    Hey guys. So in the einstein gauge the linear field equations can reduce to the wave equations: \partial^{2} _{t}h_{ab} - \nabla^{2}h_{ab} = 0 where here h_{ab} is the symmetric tensor containing the deviation of the gravitational field from minkowski space for the weak field. How can one...
  23. M

    Gravitomagnetism & Gravitational Waves

    Hi all! I was browsing Wikipedia when I came upon the following article: http://en.wikipedia.org/wiki/Gravitomagnetism It seems here they state a form of the complete linearized Einstein equations that resembles very much (or is mathematically identical to that of) Maxwell's equations...
  24. C

    Gravitational Waves and Speed of Light

    Can you explain for me what part of general relativity says that gravity must go outward from the body at the speed of light, rather than instantly? I realize that Einstein believed nothing could go faster than the speed of light, but is there evidence that this must be so in the case of...
  25. ShayanJ

    Gravitational waves due to acceleration

    As I understood from relativity,for an accelerated object,the space-time is curved.because that curvature needs to be at the place of the object and because the object is moving,the curvature must move too, which I think is called a gravitational wave.So when an accelerated object passes near...
  26. TrickyDicky

    Exploring the Possibility of Gravitational Waves in a Static Spacetime

    Are gravitational waves (where the field varies with time) possible in a static spacetime(no time derivatives)? I would expect them to be predicted only in a expanding spacetime but I'm not totally sure.
  27. Z

    Time Dilation & Black Hole Mergers: Exploring Ringdown Gravitational Waves

    Time dilation and black-hole--black-hole mergers, and ringdown gravitational waves An observer far away from an event horizon never sees a particle cross the event horizon. How does this effect the apparent merger of two black holes? Also, I've seen that the gravitational waves during the...
  28. D

    Gravitational waves are also redshifted?

    I want to confirm one thing. Say, I have an emitter of gravitational waves with frequency f. I throw it into black hole. Is it correct to assume that: 1. frequency f and energy of GR waves are decreased in exactly the same manner as frequency and energy of ordinary light? 2. and GR...
  29. J

    M-theory and gravitational waves

    I've read that the discovery of gravitational waves will further support the big bang theory at the expense of M-theory. What's the specific difference between the two models that relates to gravitational waves? Is it that a brane collision would not produce the waves at the beginning of the...
  30. P

    Will LHC measure gravitational waves?

    Considering they will eventually be colliding gold or lead ions, will they measure or be able to measure the gravitational impact of the collisions? Just curious since the velocity will be so extreme. I would think Tevatron would already have something to say about this, but I'm unsure of...
  31. P

    Laser interferometry and the search for gravitational waves

    When viewing the light coming from distant galaxies, it is my understanding that there are 2 redshifts occurring, the doppler effect from the galaxies' peculiar motions, and the cosmological redshift from space itself expanding. For the cosmological redshift, I visualize a square of space...
  32. C

    Gravitational Waves: Do They Bend Like Light?

    Do Gravitational waves bend like light in the presences of a strong gravitational field.
  33. M

    Do gravitational waves have different frequencies?

    I'm wondering if gravitational waves can have a wide range of frequencies and wavelengths much like EM waves, or if they are more uniform and only vary in amplitude. Also, should gravitational waves experience a Doppler shift?
  34. bcrowell

    Very close binary, strongest steady source of gravitational waves

    This paper http://arxiv.org/abs/1003.0658 nails down the interpretation of a binary white dwarf system with an orbital period of only 5.4 minutes, versus 8 hours for the celebrated Hulse-Taylor binary neutron star system. This would probably be the strongest source in the sky of steady...
  35. M

    Gravitational waves and quantum physics

    If gravitational waves have such tiny amplitudes (typically several orders of magnitude smaller than a proton), then why do we model them entirely in terms of general relativity? Aren't quantum effects important at this scale?
  36. Ranku

    Orbital period decay and gravitational waves

    We know that the orbital period of binary stars decay due to the emission of gravity waves that carry away energy from the system. What is the form of the energy loss of the system: kinetic energy or potential energy?
  37. Ranku

    Orbital period decay and gravitational waves

    We know that the orbital period of binary stars decay due to the emission of gravity waves that carry away energy from the system. What is the form of the energy loss of the system: kinetic energy or potential energy?
  38. Ranku

    Detection of gravitational waves

    What is the state-of-the-art of detecting gravity waves. Are the instruments available now sufficiently sensitive to detect gravity waves? Have we identified 'low-hanging' sources from which gravity waves should have been detectable. Have we yet reached the point where doubts are arising as to...
  39. Ranku

    Detection of gravitational waves

    What is the state-of-the-art of detecting gravity waves. Are the instruments available now sufficiently sensitive to detect gravity waves? Have we identified 'low-hanging' sources from whom gravity waves should have been detectable. Have we yet reached that point where serious questions are...
  40. Ranku

    Gravitational waves and gravitation

    Gravitational waves are generated when the mass quadrupole moment changes in time. We also know motion of mass contributes to its gravitation. Does the producing process of gravitational waves, which involves mass in accelerated motion, produce gravitation as well? If so, is it of less, equal...
  41. Ranku

    How Do Gravitational Waves Impact a Solid Sphere of Mass?

    What effect would a train of gravitational waves have when it hits a solid sphere of mass? We know about its expected effect on a dust sphere where it is ellipsed alternately in x and y direction. I would like to know how would an isolated solid sphere be affected when it is hit by a train of...
  42. E

    Could gravitational waves form interference patterns?

    If gravitational waves formed interference patterns, or just simply interfere as normal waves, couldn't that result in gravitational anomalies in absence of mass? Destructive interference could be thought of as negative gravity(dark energy), leading to expansive "forces", whilst constructive...
  43. haushofer

    SR and GR in a medium, gravitational waves

    A little question which I thought of today. I thought about what happened in a medium with Lorentz transformation. With a refraction index n, the speed of light is altered to c/n. However, as far as I can see now this shouldn't influence the Lorentztransformations, right? It's tempting to put...
  44. E

    String theory and gravitational waves imprint on microwave background

    What does string theory have to say about this and how has string theory changed cosmology in terms of verifiable observational predictions?
  45. F

    Hopefully not too stupid question about gravitational waves

    I've been trying to get my head around relativity etc and struggling :-( However there's one thing that I can't find much information about at an interested-layman level - gravitational waves. They're described as having a frequency etc (being waves) and traveling at light speed. But if they...
  46. M

    GR textbook to prepare for gravitational waves

    I've been given Gravitational Waves: Theory and Experiments Volume I to read for a project. The problem is, I haven't learned General Relativity to a high enough level and the book is proving very difficult for me. The book dives straight into linearised gravity in the first chapter, and the...
  47. M

    Black Holes and Gravitational Waves

    As far as I know, a black hole is a singularity in the space-time. The space-time becomes so curved that the geodesics can't get out, i.e., the gravitational field becomes so strong that information can not get out. OK! But what about gravitational waves? As far as I know, gravitational waves...
  48. T

    Gravitational waves - second question

    Gravitational "waves" - second question Assuming our concept of the universe expanding (perhaps) and that the fabric of space time is expanding at the same rate as our galaxy and solar system (velocity equal, so relatively motionless), would we still be able to detect gravitational waves when a...
  49. M

    Are gravitational waves bent by gravity?

    Gravitational waves travel at the speed of light. So do they also bend around massive objects? If we had an extremely sensitive differential accelerometer, would we "feel" a distant star to be where we saw it? This would seem logical if you consider the curved path of light to really be a...
  50. T

    Gravitational Waves: Constant Motion Through Spacetime

    Gravitational "waves" First, I confess that I am not a physicist by training; I work for an RF engineering firm. However, I study theoretical and astrophysics from those who have the extensive math background, and attempt to conceptualize their theories. I am not a conspiratist, and I certainly...
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