Questions tagged [gravitational-waves]
For questions about the propagation of waves carried by space-time, for instance as described by general relativity. Not to be confused with gravity waves, such as ocean surface waves.
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questions
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Graph Interpretation of Gravitational Waves
In the image is the data recorded by the LIGO's 2 observatories in USA. What is its interpretation? I mean what does the zig zag lines represent? Similarly, what does the blond red and blue lines (...
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3answers
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What would the wavelength of the Cosmic Background Gravitational Wave radiation be?
Considering electromagnetic CMB can only see light as old as 380,000 years after the Big Bang, whilst theoretically those being gravitational should be formed from the beginning, what would their ...
2
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2answers
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Would the 2 orbiting black holes emit gravitational waves?
Would the 2 orbiting black holes emit gravitational waves even if they are moving at a constant speed in orbits? Here, can we consider the changing direction of black holes in their orbits as ...
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1answer
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About Oscillation in Gravitational wave [duplicate]
I am a high school student studying about gravitational waves. I hope they are similar to other waves like sound waves, etc. So I what to know exactly what oscillates in a gravitational wave. Like in ...
2
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1answer
69 views
Are gravitons produced in an atomic transition?
Atomic transitions produce photons. You can create beams of photons with a laser. In lasers rays of light are produced. Will rays of gravitons (or small directed gravitational waves) be produced also?
68
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7answers
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Does gravity bend gravity?
Let's say that there is a large mass $M$ a light-year or so away from a black hole merger, which causes a very large gravitational wave to be produced. When the gravitational wave reaches $M$, does it ...
3
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1answer
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Quadrupole formula in TT gauge
In weak gravity limit, we can derive the celebrated quadrupole formula in Lorenz gauge $\partial^{\mu} \bar{h}_{\mu \nu} = 0$:
$$
\bar{h}_{ij} = \frac{2G}{r}\frac{d^2}{dt^2}I_{ij}(t_r)
$$
To get $h^{...
0
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1answer
120 views
Are gravitational waves produced only when a mass accelerates? [duplicate]
Why? They are not a form of EMR, are they.
Or are the rapidly changing ones the only ones we can detect?
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2answers
161 views
Why do gravitational waves move at the speed of light? [duplicate]
They are not a form of electromagnetic radiation, are they? So, why do gravitational waves move at the speed of light?
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2answers
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Does a Photon take longer to reach me when travelling in the “trough” of a gravitational Wave?
I'm struggling for a while with this question and I'm not knowledgeable enough in SRT/GRT, so I'll ask here:
Suppose some big cosmic event like a Black Hole Merger that generates significant ...
0
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2answers
42 views
How does LIGO detect accurate time differences if gravitational waves are also compressing and stretching the light waves-specific confusion below [duplicate]
I was watching this veritaserum which explains my question at 5:55 https://www.youtube.com/watch?v=iphcyNWFD10 saying that the speed of light is much faster so will pass through the arms multiple ...
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3answers
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Could the Michelson-Morley experiment have detected gravitational waves?
If everything went perfectly and they had no outside noise while conducting the experiment, could they have detected gravitational waves? What would it have looked like to them?
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1answer
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Derivation of Bondi metric
I was trying to understand the BMS formalism from the beginning. The whole formalism depends on the expression of the Bondi metric. I don't understand how this expression of the metric was derived. ...
2
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1answer
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Projection on transverse traceless Gauge
I am reading this book about Gravitational waves.
On page 10 and 11 Maggiore says that
Given a plane wave solution $h_{\mu\nu}$ propagating in the direction $\hat{n}$, outside the sources, already in ...
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2answers
72 views
Claims of detection of gravitational waves with an accelerometer
Is this claim:
https://earthscience.stackexchange.com/q/21236/
of detection of gravitational waves with accelerometers legitimate?
I do not know much about this, but given how gravitational waves form ...
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0answers
35 views
Why is AdS equipped with a Lorentzian metric not geodesically connected and static?
Consider AdS $M=]-\pi/2,\pi/2[\times R$ equipped with a Lorentzian metric geodesically complete, but not geodesically connected? Does this mean that gravitational waves don't exist in AdS? Then how ...
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3answers
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Can we detect gravitons this way?
First, we shoot a collection of particles (let's exclude gravitons from these, just for the sake of clarity) through a large region of spacetime in which the stress-energy tensor is zero and make them ...
0
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1answer
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Prove of conservation of energy and momentum in linearized Einstein Field Equation
From the Linearized Einstein Field Equation, we have $\Box\bar{h}_{\mu \nu} =-16\pi GT_{\mu \nu}$.
How can I obtain conservation of energy and momentum, $T_{\mu \nu},^{\nu}=0$, from the previous ...
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0answers
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Will Earth's rotation be altered if a circularly polarized gravitational wave passes through it?
I have read this question:
If you rotate a polarized classical electromagnetic wave by 180° about its axis of propagation, you don't get the same wave back; you get the same wave phase-shifted by ...
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0answers
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Inclination of gravitational wave
Without rotating the axis, if we observe the gravitational wave propagating in z direction,
\begin{gather}
h_{ij}
=
\begin{pmatrix}
h_+ & h_x &0\\
h_x & -h_+ &0\\
0&0&0
\end{...
2
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1answer
23 views
Polarization of Gravitational Waves Emitted by Binaries
Are the gravitational waves emitted by binary masses linearly or circularly polarized?
Is there a relationship between the binary rotation axis and the polarization?
Does this change during an ...
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2answers
51 views
Has anyone considered a gradual change in Gravitational Potential across the universe as a cause for cosmic red shift?
Since the formation of fundamental particles at the beginning of the universe (roughly the time of the CMB emission, and after the inflationary epoch of Big Bang theory), the gravity wave front of all ...
1
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1answer
112 views
Hilbert gauge and gravitationl waves
I am studying the gravitational waves as a conseguence of the linearized (vacuum) field equation of general relativity.
I have a problem when we write the linearized field equation in the form $\Box ...
1
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1answer
70 views
Derivation of gravitational wave as quadrupole moment
In Carroll's Spacetime and geometry section 7.5, it is deriving metric $\bar h_{\mu \nu}$ with Lorenz gauge in terms of quadrupole moment of energy density.
In Eq.[7.135],
\begin{equation}
\int d^3y \...
3
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0answers
42 views
How is the phase gain of a Fabry-Perot resonator for gravitational wave detection derived?
I am trying to understand the use of the Fabry-Perot (FP) resonator in the arms of a gravitational wave detector. A typical explanation is that the gain in power in the arms is equal to $\sqrt{F}$ (...
2
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1answer
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When are gravitational waves (for the major part) absorbed?
This question made me think. It was asked why matter is transparent for gravitational waves. it was said (more or less) that because the waves interact with mass very weakly, mass makes them pass ...
4
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1answer
749 views
Why matter is transparent to gravitational waves? [duplicate]
I recently asked a question at Astronomy.SE related to matter-gravitational waves interactions: https://astronomy.stackexchange.com/q/43265
From related question Do gravitational waves disperse/...
3
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0answers
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Consistency condition in the context of gravitational waves
Reference: archive.org/details/GeneralRelativity/page/n250/mode/1up
I am studying the phenomenon of gravitational waves as one of the conseguences of the linearized Einstein field equation.
In order ...
2
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1answer
117 views
Transverse-traceless gauge: Why the traceless condition?
I'm right now following a course on GR and I arrived to the gravitational waves part. Letting the metric be that of the plane Minkowski space with a small perturbation:
$$g_{\mu\nu}=\eta_{\mu\nu}+h_{\...
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2answers
53 views
Amplitude decay of electromagnetic and gravitational waves
I recently got confused by an article that claimed that gravitational waves were interesting because that their amplitude of a gravitational wave falls as $1/r$ in the far field limit. Suggesting this ...
38
votes
4answers
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Did LIGO measurements prove that the speed of gravity equals the speed of light?
This question about the speed of light prompted my own question. In the linked question it is asked if there is experimental proof that the speed of gravity equals the speed of light. I was surprised ...
1
vote
2answers
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Specific gravitational wave polarisation direction for “edge-on” binary system
The gravitational wave signal from a binary system approaching merger consists of a mixture of the two $h_+$ and $h_\times$ orthogonal polarisation states.
If the binary is "face-on" (with ...
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2answers
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GWs from Kerr BHs
A rotating neutron star can emit GW radiation if it has some ellipticity (Maggiore Gravitational Waves Vol I for example), even if we neglect spindown. I would think that a Kerr BH is not a spherical ...
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0answers
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Could mesuring particles in double slit experiment with gravitational waves work?
From my basic knowledge of quantum physics I know that what makes the double slit experiment hard to understand is the mesurement part. Once you mesure a particle you become part of the wave function ...
2
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1answer
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Amplitude of gravitational waves at emission and how they decay
I am a bit confused with some aspects of gravitational waves (GW).
GW we observe here on Earth with LIGO/Virgo have an amplitude of $\approx 10^{-21}$ with peak frequency $\nu = 150\, Hz$. If we ...
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0answers
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Gravitational Waves, Dipole Radiations and Momentum
I am trying to understand Gravitational Waves and and going through MTW's book. They state that there can be no dipole radiation because of the conservation of momentum but gravitational waves also ...
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1answer
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Original reference for Binary star system orbital seperation decay rate due to GW emission
Could someone please point me in the direction of who first derived the equation for the orbital separation decay rate of two point masses in a binary system due to the emission of gravitational waves:...
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0answers
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Could gravitational waves have their origin in collision of true and false vacuum?
Could the gravitational waves the consequence of the collision between a true vacuum bubble and a false vacuum bubble, at the beginning of the universe?
(as they try to explain there:
https://www....
15
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1answer
1k views
Do objects absorb or reflect gravitational waves?
We all know that objects can absorb and reflect electromagnetic waves. It stands to reason the same might be true for gravitational waves.
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Could LIGO detect an Alcubierre drive being used within 10 light-years of the Solar system? [closed]
Maybe this question is too speculative... But is it possible that LIGO would detect the ramp-up and ramp-down of an Alcubierre drive being used within 10 light-years of the Solar system? Also, if the ...
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2answers
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How does LIGO work?
LIGO is described as working as an interferometer, like a Michelson-Morley interferometer but with many reflections along the arms to increase the sensitivity. In MMs work it was assumed that the ...
1
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1answer
66 views
Can gravitational waves escape a black hole? [duplicate]
I know that one of the defining features of a black hole is that all matter, including light, cannot escape a black hole. I was wondering if gravitational waves can. If this is true perhaps we could ...
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2answers
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Is there a gravitational analogue of a classical Rutherford-atom?
In a Rutherford-atom, the electron classically emits EM radiation on an average rate of,
$$
-\frac{dE}{dt}=\frac {\omega^4 e^2 R_0^2}{3c^3(4π\epsilon_0)}
$$
Where $\omega$ is the angular frequency, $...
0
votes
1answer
48 views
Can we use flat space coordinates in linearized gravity?
I am studying the production of gravitational waves in linearized general relativity. While it is not mentioned anywhere, I am convinced, that the coordinates used in the derivations I have seen, are ...
4
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1answer
462 views
In what medium do Gravitational waves propagate?
I am having a hard time understanding how gravitational waves move.
The only reasonable thing that comes to my mind would be the aether but that idea was scrapped.
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0answers
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Are gravitons possible in 2+1 spacetime dimensions?
Spin-1 massless particles are transverse waves, so they need at least three space-time dimensions to exists. As for gravitons, I think they are still not possible in three dimensions, and to reveal ...
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2answers
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Why gravitational waves are hard to detect?
I just started to learn general theory of relativity by Hartle's gravity textbook. In a section on gravitational wave I encountered following statement 'Gravitational waves are hard to detect due to ...
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2answers
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Frequency sensitivity of gravitational wave interferometer with its armlength and with mass of the mergers
To the best of my knowledge, LIGO is capable of observing gravitational waves (GW) from stellar mass black hole (BH) mergers but not mergers of supermassive black holes. In order to detect the latter ...
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0answers
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Distance through gravitational wave
I was wondering:
Do gravitational waves stretch the distance between objects?
So lets say you have an object A at the position a, and an object B at the position b. The distance between them is C. A ...
2
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1answer
86 views
Do dipolar gravitational waves exist?
There seems to be some controversy (see A, B) on this topic, so I'm posting a new question for discussion and clarification.
By definition, one cannot accelerate the center of mass of a closed system (...
