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. G

    I Gravitational Waves & Gravitational Pull: Explored

    According to the sticky bead argument, gravitational waves do carry energy. As such, are they, like photons (EM waves), subject to the gravitational pull of planetary bodies?
  2. 1

    What Happens to Mass When Black Holes Move?

    I've recently read a new article that said that the recent gravitational waves might have had 2 black holes in a star that gave me a question, because you need masses to move or accelerate to generate gravitational waves, what happens to the mass inside of the star? because black holes's space...
  3. G

    Gravitational Waves: Were They Stronger Long Ago?

    In order to detect gravitational waves at our present time and location, aLIGO has required a mind-boggling sensitivity, if I understand well it can detect variations in length in the order of 1/10,000 of the diameter of a proton. But space has stretched a lot during the universe's history. If...
  4. JK423

    How did LIGO estimate the distance of the black holes?

    As we all know, the LIGO collaboration published a paper recently on the first direct observation of a binary merging black hole system. From the observed signal, they were able to infer the black holes' masses and their distance from Earth. However, the fact that they can estimate masses and...
  5. Cuboctonion

    Q&A: LIGO Gravitational Wave Detection

    I have a couple of questions regarding the new detection of signals believed to be gravitational waves at LIGO 1. Two similar signals were detected at both facilities. Why does the Livingston signal appear to be weaker than the Hanford signal? 2. The signal in Livingston was reported to have...
  6. Jorrie

    How is the redshift of gravitational wave events measured?

    LIGO reported the announced event with a redshift of 0.6 < z < 1.3. With no em radiation event reported (AFAIK), does anyone know how they have determined the redshift? I understand how they could measure the pre-merger, chirp and ring-down frequencies with good accuracy. In order to determine...
  7. Greg Bernhardt

    Coffeeshop Astrophysics Meeting on Gravitational Waves

    In about an hour I'm heading over to a local Coffeeshop Astrophysics meeting put on by researchers and grad students at UW-Milwaukee. The topic is the gravity wave discovery. Apparently some of them contributed to the LIGO project so it will be interesting to hear what they have to say. I'll...
  8. M

    Gravitational Waves: Definition & General Overview

    What are gravitational waves in general, not just in the weak field/linearized theory?
  9. S

    Gravitational Waves and Frame-Dragging

    I'd like to ask whether the Lens-Thirring effect, which is also known as Frame-Dragging, produces any kind of Gravitational Waves which might be detectable by a detector more sensitive than LIGO. There was of course the Gravity Probe B experiment not too long ago, which saw gyroscopes launched...
  10. G

    B Gravitational Waves prediction

    Dear Friends! Q.There was no direct evidence of binary black holes till September 14,2015,when signals coming from about 1.3 billion light years away were captured by LIGO. Now my question is that how in advance we knew about the specific colliding pair.Did we theoretically predict the graph...
  11. Ontophobe

    Questions About Gravitational Waves

    1. If the Michelson-Morley experiment were to be conducted with gravitational waves instead of light waves, would the results be any different? 2. Ought we to expect the existence of "gamma" gravitational waves and "radio" and "microwave," etc. gravitational waves? In principle, could there be...
  12. G

    Many questions about the LIGO Gravity Wave Experiment....

    I'd like to understand the details behind the LIGO experiment a bit better: How do scientists know that the gravitational waves detected by LIGO originated from two specific black holes (located a billion light years away)?Does the LIGO result confirm the existence of black holes?Was it only...
  13. M

    I LIGO Discovery - A question about space-time properties

    A question from a physics laymen to those more advanced: if eLIGO detects gravitational waves by the difference to the combined laser wavelengths (a difference to the destructive interference pattern following curvature of space-time in each individual pathway), how is it that the lasers...
  14. T

    Gravitational waves, distance and space-time

    So the discovery of gravitational waves observed a contraction and stretching of space-time, and I've been trying to understand how the expansion of the universe means that space itself is growing. I want to understand how this actually works in relation to 'things' like a photon and an atom...
  15. T

    I Can Matter Absorb Energy from Gravitational Waves?

    So everyone knows that the energy of a photon is E = hf, I assume this is just because light also has a particle nature. But how do we calculate the energy of a gravitational wave, because from memory classical wave equations have a mass component to calculate 'kinetic' associated energy, and I...
  16. T

    Proper movement, reference frames and gravitational waves

    Hi, So apparently electrons don't orbit the nucleus of atoms so I'm assuming the lack of movement means that no energy from the atom is radiated away from an atom due to minuscule gravitational waves, over the life of the universe. But gravitational waves have got me thinking about reference...
  17. G

    Gravitational waves speed in a medium

    Electromagnetic waves are known to travel a c in a vacuum, but at lower speeds in a material medium. What about gravitational waves? They are also predicted to travel at c in a vacuum, but what about them traveling through material mediums? Do they get slowed down? by which factor? TX
  18. pioneerboy

    EM length of gravitational waves

    Maybe a stupid question and maybe sensless to ask, but as I don't know, I ask anyway: what is the length of the newly found gravitational waves in terms of traditional EM wavelengths?
  19. S

    Gravitational Waves, Gravitons: Does Discovery Change Odds?

    Now that we have confirmed the existence of gravitational waves, have the odds of discovering a force carrying particle changed? With my limited knowledge it kind of seems like if gravity is caused by the warping of space-time, which was confirmed by gravitational waves, would mean that there is...
  20. bcrowell

    Unresolved background of gravitational waves?

    The aLIGO signal is a discrete event. In addition to such events that can be resolved into individual chirps, I would think that there would be a background of gravitational waves that would look like noise, but that could be distinguished from terrestrial noise (trucks passing by, etc.) because...
  21. G

    Gravitational Waves research and Dark Matter

    A lot is being written about the recent aLIGO observations and in general the implications of GW research for our scientific understanding of the universe. We read about mostly 2 grand areas where GW research can provide novel knowledge. The astronomical / astrophysical area (i.e. mapping...
  22. 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...
  23. DaveC426913

    Exploring Gravitational Waves: Feeling 10cm Distortion at 1LY

    Someone has raised an interesting discussion about how one might experience these waves closer to the merging BHs. (Let's assume we're in a heavily-shielded spaceship that will protect us from all EM radiation and other effects except gravity.) First, how big? My back of napkin calculations...
  24. anorlunda

    Damping of Gravitational Waves

    Like many others, LIGO made me curious about gravitational waves. I found the paper: Nonlocal Gravity: Damping of Linearized Gravitational Waves http://arxiv.org/abs/1304.1769 I'm having difficulty understanding. Does that mean that damping is implicit in the terms of the tensors? Does it...
  25. MartinMb

    Gravitational waves, compensate for the Earth's movement

    How is it possible to compensate for LIGO's movement in the recent measurement of Gravitational Waves? I can understand that we are able to measure something to a tiny fraction of a proton when the subject and observer are both moving relative to each other through space but how is it possible...
  26. S

    I Gravitational waves due to Big Bang?

    The recent observed gravitational wave is claimed due to two merging black holes colliding or infusing into each other. Could it be just another local Big Bang? (Of course I am implying Big Bang occurs in various scales). So "our Big Bang" was a large scale Big Bang and was triggered by two...
  27. DaTario

    Oscillating masses and gravitational waves

    Let me ask one simple question. For less than a thousand dollars one can buy an apparatus which can provide experimental evidence for the gravitational attraction between two masses of one kilogram each, placed at distances of the order of ## 10^{-1} m ##. By making one of these masses to...
  28. D

    Hasn't Gravitational Lensing Already Proved Einstein? (LIGO)

    The news out of LIGO is being heralded as one of the most important experimental verifications of physics in decades, as it provides experimental support to the General Theory. The news makes it seem as though it were like the Higgs Boson was; theoretically concrete, but up in the air until...
  29. T

    Question about cause of gravitational waves

    Hello, I've been doing some research on gravitational waves since their discovery, and I found that all of the places I looked were missing an important piece of information, that is: What is the mechanism by which angular momentum is being conserved. All of places that I've searched will...
  30. Densedog

    A Perception of time, gravitational waves.

    Two stones being dropped into a calm body of water at different times and sizes. The smaller one drops first, sending ripples out. Progressing in time. The second larger stone drops later, creating its own gravitational ripple which is larger than the first. Can the perception of time be altered...
  31. RandAlthor

    B Gravitational Waves & Space-Time: Is There Proof?

    The original question title was too long, so i changed it. My question is: Does the detection of gravitational waves prove the existence of space time? The question may sound odd. I had an argument with one of my friends, who says space time is only a mathematical concept, space does not exist...
  32. G

    Gravitational Waves vs Tidal Effects: Exploring Nature & Inflation

    My simple description of gravitational waves is that they are due to the relativistic principle of locality, i.e. the fact that the action of gravity is not instantaneous, something that you can’t see from the tidal effects in Newtonian physics. Is it correct? I've also found a comment...
  33. R

    Questions About Spatial Orientation of Event w/ Respect to LIGO

    I didn't see these areas addressed, my apologies if I missed them. If there was no delay in the detection of the signals at the two sites, would that mean that the location of the event was 'directly overhead' or 'directly below'? Was the delay, compared to the speed of light and distance...
  34. D

    Release of gravitational waves, with small collistions?

    I just wanted to ask a question, since it went through my mind after hearing about 'gravitational waves' after they have now, apparently, been identified. does everything realease gravitational waves when it collides? Since everything with a mass has gravity, wouldn't that mean that even when...
  35. Javier Zapater

    Question on gravitational waves and redshift in BH coalesce

    Dear Sirs My question relates to the recent observation of gravitational waves by LIGO. The paper PRL 116 "Observation of Gravitational Waves from a Binary Black Hole Merger -B.P Abbott et al"" depicts the chirp signal of the wave detected, where it is seen how both frequency and amplitude...
  36. G

    Does LIGO Ruling Out Linear Gravity Theories?

    As the discovery matches templates based on GR, and the regime is of very strong gravitational fields and very high speeds (relativistic speeds), and there is a 90% match between model and measured data, this does rule out linear or quasi linear alternative theories of gravity?
  37. F

    Duration of recently measured gravitational waves

    Hello, I have a basic question about the temporal duration of these newly measured gravitational waves. How long is the duration of these gravitational waves? Two black holes collided and created these gravitational waves a while ago. How long can we "listen" to these waves? When did they...
  38. SuperGadger

    B Gravitational Waves and Gravitons

    Does the discovery/confirmation of the existence of Gravitational Waves change or add to current theory in regard to Gravitons?
  39. P

    Is the Media Hype Around Gravitational Waves Beneficial or Harmful to Physics?

    There seems to be considerable interest in the recent detection of gravitational waves. For the physics community this interest is fully justified. But in the popular press it seems to me to be reaching unjustified and perhaps harmful levels. When one reads overblown hype like: " A giant...
  40. S

    LIGO discovery on gravitational waves.

    Could someone please describe the recent LIGO project, gravitational waves and their detection in simple terms. PLEASE.
  41. A

    Gravitational waves: who gets the Nobel Prize?

    The deadline for nominations for the 2016 Nobel Prize was the end of January. Since the detection and peer-review of the paper was most certainly done beforehand, who do you think is in line for the 2016 Nobel? My bets are on the three gents who spoke/got mention this morning in Washington...
  42. T

    Gravitational Waves: Speed, Catching Up & Rules

    Could I catch-up to a gravitational wave? Do the same rules apply as with light -- meaning the speed of GRs are frame independent, etc? Thanks.
  43. S

    Gravitational Waves: Exploring What They Are

    What are gravitational waves exactly?
  44. Isaac0427

    Theoretical Understanding of Gravitational Waves

    Following the new discovery of gravitational waves by LIGO, I just want to make sure I understand the concept of these waves. I believe I currently have a novice understanding of gravitational waves: when a large, fairly sudden change happens to the position of a particle (acceleration or its...
  45. bcrowell

    Dispersion of gravitational waves

    The LIGO paper https://dcc.ligo.org/LIGO-P150914/public puts limits on the dispersion of gravitational waves, which can be interpreted as an upper limit of 10^-22 eV on the mass of the graviton. We all know that low-amplitude gravitational waves are supposed to propagate at c according to the...
  46. Dr. Courtney

    A Experimental detection of gravitational waves confirmed

    http://news.mit.edu/2016/ligo-first-detection-gravitational-waves-0211
  47. ujjwal3097

    I LIGO [ meeting on Thursday on 11 feb 2016]

    Does anyone know where we can watch the live stream of the conference held at Washington DC on 11 feb 2016 10:00 am
  48. Math Amateur

    MHB Gravitational Waves Detected at LIGO?

    There are rumours that scientists at Advanced LIGO have detected gravitational waves ... it is about 100 years after Einstein predicted they were there in his mathematical theory of general relativity ... Anyone know more about this rumour ...? Peter
  49. CharlesJQuarra

    Einstein tensor of a gravitational source

    In section 4.4 of gravitational radiation chapter in Wald's general relativity, eq.4.4.49 shows the far-field generated by a variable mass quadrupole: \gamma_{\mu \nu}(t,r)=\frac{2}{3R} \frac{d^2 q_{\mu \nu}}{dt^2} \bigg|_{t'=t-R/c} I have the following field from a rotating binary...
  50. G

    Gravitational Waves & Multidimensional Spacetime: Experiments & Detection

    So I saw that claims are being made that LIGO may have detected gravitational waves. http://www.nature.com/news/has-giant-ligo-experiment-seen-gravitational-waves-1.18449 My question is, if the universe were in fact multidimensional as string theory predicts, would gravitational waves propagate...
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