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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Once LIGO confirms a gravitational wave signal, can data from less sensitive detectors give more insight?
Only detectors above a certain sensitivity can measure with a high enough signal to noise ratio (SNR) to successfully pick out gravitational waves using matched filtering.
However, once we have ...
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What is the point of the reaction mass in the LIGO mirror suspension system?
I learned from the LIGO official website that the LIGO mirror suspension system consists of a "main chain" and a "reaction chain", and there are small electric motors gently pushing the masses on the ...
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A question about gravity [duplicate]
Some time ago I encouraged by 11 year old son to watch Cosmos: A Spacetime Odyssey with Neil DeGrasse Tyson, and subsequently Cosmos: A personal Voyage with Carl Sagan, as well as other astronomy ...
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Does an object creates gravitational waves when only accelerating in one direction?
I know from reading about the gravitational waves detected by Ligo, that when an object has angular acceleration, it produces gravitational waves.
I'm wondering if an object creates gravitational ...
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In the B mode power spectrum, what is the relationship between the multipole number and the wavelength of the seed gravitational waves?
One of the key datasets of the recent BICEP2 results is the B mode power spectrum shown below. The existence of these B modes implies the existence of gravitational waves prior to inflation.
My ...
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Do two photons traveling in opposite directions emit gravitational waves?
Do two photons traveling in opposite directions emit gravitational waves? If so, does it mean that any volume filled with photon gas will eventually degrade into graviton gas?
In other words, if flat ...
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Gravitational waves in other dimensions
I know this question is purely speculative, as we don't know if more dimensions do exist and also we do not know if gravity is indeed stronger in other dimensions (if they were to exist). But, one of ...
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How do inflationary models predict the generation of gravitational waves during the inflationary period?
Recent results from the BICEP2 experiment have produced a lot of talk about the primordial gravitational waves produced during the inflationary period.
I would like to have some explanation about how ...
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What is the status of gravitational wave searches? [closed]
What is the status of gravitational wave searches such as LIGO?
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Binary black hole merger viewed from inside the event horizon
How did the metric evolve inside the event horizons of the black holes whose merger caused the GW150914 signal?
In principle the Schwarzschild metric of a non-rotating black hole is known inside the ...
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What do we mean when we say gravitational waves are non-linear and do not superpose like EM waves?
I have read this question:
Now it's not actually true that general relativity obeys a law of superposition, but it is an extremely good approximation for a small-amplitude gravitational wave passing ...
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What is the wavelength of gravitational waves?
What is the wavelength of gravitational waves? I have looked for an answer but so far not identified one.
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Is it possible to produce gravitational waves in a very small space using some gas? If so, how?
From what I know, gravitational waves are produced when accelerated massive bodies move through space-time and create ripples in the gravitational fields throughout the space-time. This is significant ...
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Is there absolute proof for gravitational waves?
As you probably know gravitational waves seem to have been proven unless you've been living under a rock for the past day. The experiment involves the reflecting off mirrors and waves of light and it ...
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What theoretical predictions took the longest to be experimentally confirmed? [closed]
Looking forward to Einstein's general relativity centennial in 2015, I was thinking about how cool it would be if LIGO detects gravitational waves in 1916 (centennial of Einstein's "weak field" paper) ...
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Damhsa Theory: Can gravitational waves really affect the long term climatic evolution of Earth?
As a glaciologist I'm often involved in topics related to the long-term climatic evolution of Earth, and to the factors that can trigger or end ice ages.
Recently, I came across the paper "Applying ...
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Can LIGO be explained in terms of gravitons?
If electromagnetic waves from a star are so faint, all that can be detected are single photons on a photographic plate.
For the LIGO experiment, the gravitational waves were so weak, I would have ...
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Why gravitational waves are not produced by objects moving at constant velocity?
Gravitational wave is produced by change in gravitational field, source. If something is moving away from me at constant speed, its gravitational field will vary. But why only accelerating bodies ...
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Theoretical solution to binary black hole merger based on Hawking and Ellis
Following Hawking and Ellis, Chapter 9, Fig. 60, Pg. 322, the following figure is meant to illustrate the contrast between apparent horizons and event horizons in the case of a binary black hole ...
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How well can we localize gravitational wave sources?
A recent question cited a story about the recent gravitational wave detection saying that we can use the gravitational wave sensing to find supernova earlier in their process of collapse:
[with the ...
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Do gravitational waves impart linear momentum to objects? (e.g. Quasar 3C 186)
The Washington Post article This black hole is being pushed around its galaxy by gravitational waves also includes an excellent NASA Goddard video description (also in YouTube) of the proposed ...
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Does rotation always slow down in general relativity?
Suppose I have a rotating object in empty space. Will it lose angular momentum due to interactions with spacetime?
The most obvious case if if the object has a quadrupole moment. Then the quadrupole ...
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Bondi news in BMS supertranslation
What does "news" mean in "Bondi news"? Is it information? What about memory in gravitational memory, is it information as well?
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Would dark matter absorb gravitational waves?
Would the vast and seemingly diffuse clouds of dark matter floating around our galaxy (and most others) absorb gravitational waves? Is this perhaps why we haven't detected any yet?
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LIGO only measures of diagonal components of metric tensor?
In a paper from Paik et al. 2016, they state (Section 3) that, a terrestrial gravitational wave (GW) detector measures only one off-diagonal component of the metric tensor.
Can anyone further expand ...
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Simple quadrupole field not yet in Lorenz gauge?
I'm having trouble reproducing some of the results regarding gravitational waves in the Wald's General Relativity.
In section 4.4 of gravitational radiation, eq.4.4.49 shows the far-field generated ...
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Do gravitational waves cause time dilatation?
The effect of gravitational waves in transverse traceless gauge on matter is represented by the expansion and contraction of a ring of test particles in the direction of polarization of the wave.
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Derivation of Teukolsky equation
I have been trying to derive the Teukolsky equation via the Newman-Penrose formalism. I have derived the following formula (see Eq. (2.14) in Teukolsky's paper)
\begin{equation}
(*)
\left[(\Delta +3\...
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Newtonian Gravitational Waves
I was thinking about the classical equations for gravity. I got stuck on two equations:
$$\vec{\nabla}.\vec{g}= 0$$
and
$$\vec{\nabla} \times \vec{g}= 0$$
The first equation is Gauss law of ...
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How does the propagation of gravity work for photons?
As explained in the answers to this post, photons apparently exert a gravitational pull on other objects. It has also been explained on this site, that gravity propagates at the speed of light.
I'm ...
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Are there more unconfirmed GR predictions?
News says that we have finally observed "gravitational waves", one of GR's predictions. I've read about some other predictions of GR like how gravity affects the flow of time, gravitational lensing ...
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Do gravitational waves travel always in a straight line (along a geodesic) like EM waves?
There are a lot of questions and answers on this site about light traveling in straight lines in vacuum (following a geodesic). And there are a lot about both EM and gravitational waves traveling at ...
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Energy-Momentum Tensor of a Gravitational Wave
In radiation gauge ($\gamma=0$), the Einstein field equation in vacuum for a perturbation $\gamma_{\mu\nu}:=g_{\mu\nu}-\eta_{\mu\nu}$ is given by $$ \boxed{ \partial^\alpha\partial_\alpha \gamma_{\mu\...
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How do gravitational waves propagate?
How do gravitational waves work like water waves? Spacetime isn't supposed to be a surface, it is solid, so how do gravitational waves propagate through it like transverse waves on the surface of ...
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Is my interpretation of how a gravitational wave is formed correct?
I'm sure many here are familiar with the following image showing the 2D representation of how the fabric of spacetime is warped by the presence of mass:-
Can this fabric be interpreted as an ...
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Does the existence of "gravitational waves" (assuming they exist) imply that time exists as a 4th dimension in the universe? [closed]
I'm new to thinking about special and general relativity and I have no formal training as a physicist. However, I've been doing a bit of thinking about spacetime recently. I was wondering if "...
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Transfer of energy from gravity back to other "more familiar" forms of energy?
In this question I've mentioned an account of the recently reported 2nd observation of gravitational waves, LIGO and Virgo Collaborations, Phys. Rev. Lett. 116, 241103, 15 June 2016, where 1 of the ...
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Could future experiments on "Gravitational Casimir Effect" confirm the existence of gravitons?
From Casimir effect, we know that when two plates are placed very close to each other in vacuum, they attract each other because the quantum fluctuations that press on the two plates' outer surfaces ...
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Do gravitational waves have an effect on gravitational forces between two object?
I'm pretty new to the subject of gravitational waves. Do gravitational waves have an effect on gravitational forces between two objects? If so, how?
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Redshift of merging black holes
How did they found that the gravitational waves where emitted at redshift $z=0.09$?
I understand the measurement of redshift for an electromagnetic wave where we have measured in a lab various ...
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Gravitational waves as dark energy?
Is the energy carried by gravitational radiation a viable candidate for $\Lambda$ / dark energy?
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Applications of the Linearized Einstein Field Equations (EFE)
Look up linearized Einstein field equations anywhere and the first thing you'll see will be a discussion of gravitational waves. Using the linearized EFE's is pretty handy when studying gravitational ...
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Do rotating bodies emit gravitational waves?
Suppose we have a cylinder of mass $m$, radius $R$ and height $h$ in rotation with speed $\omega$ around its symmetry axis with no friction (ideal situation).
I'd expect this cylinder to emit ...
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Andromeda & Milky Way Merger: Gravitational Waves
When the Andromeda galaxy and Milky Way merge in the future, the super-massive black holes at their respective galactic centers will likely eventually merge. Similarly to the gravitational waves ...
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What are the differential equations that model a self-propagating gravitational wave in space-time?
Light is a self-propagating wave, but it's very complicated.
Imagine, if you will, a wave in space-time that by assumption was self-propagating like light, except that it was a gravitational wave.
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Would two objects orbiting each other emit gravitational waves on every direction or only on their plane of rotation?
Imagine a system where two massive objects are orbiting each other, something like a binary black hole or neutron star system. Such a system should emit gravitational waves. I'm curious on the ...
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Does the ringdown phase of a black hole merger ever stop?
When binary black holes merge they emit gravitational waves in three stages, the inspiral in which the two black holes shed angular momentum through gravitational waves at a rate that becomes ...
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Is it true that speed of gravity was confirmed in 2017?
I was reading a Wikipedia article on speed of gravity, https://en.wikipedia.org/wiki/Speed_of_gravity .
The following quote is taken from the mentioned article.
In the relativistic sense, the "...
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Difference between gravitational wave detectors
There are a lot of different gravitational wave detectors and they all have their own wave period and frequency they operate at. This picture shows that
The last three (pulsar timing, space ...
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As of 2021 in how many binary systems has the period decrease due to gravitational waves been measured?
I am searching for data for the period decrease of binary systems due to gravitational waves. I am aware of three systems in which it was possible to measure this period decrease:
The Hulse-Taylor ...
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