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Questions tagged [gravitational-waves]

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Is the gravitational waves velocity also $c$, regardless the adopted inertial frame, and the source movement conditions? [duplicate]

The second postulate of STR was made exclusively for light (electromagnetic waves)? If gravitational waves also travel at velocity $c$, then are they obliged to fulfill this second postulate? Any ...
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Gravitational $N$-body mergers?

Beyond binary systems and its mergers, have numerical relativity groups computed an approximation to $N$-body GW signals/waveforms or is that a hard unsolved task?
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Why aren't gravitons spin 1?

Expressing the metric as $g_{\mu \nu} = \eta_{\mu \nu} + h_{\mu \nu}$, assuming $h_{mu \nu} \ll 1$ we can write the Einstein Hilbert action to leading order in $h_{\mu \nu}$ and quantize the ...
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Is a body in passing gravitational wave still in free fall?

I have a simple apparatus: a box and inside it a test particle (small bullet). If the device is in inertial motion or affected only but (static) gravitational field of another massive body (in free ...
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Could the persistent effects of gravitational waves solve the black hole information paradox?

I am not bothered that much by the fact that two observers describe the same phenomenon differently. Something similar , in principle ,  happens with simultaneity in special relativity,  and special ...
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Could two atomic clocks really be used to detect gravitational waves from a distant source? If so, how?

Three articles report on the recent paper in Phys Rev. D: Flanagan, Éanna É. et al. 2019 Persistent gravitational wave observables: General framework (also ArXiv): Phys.org: Gravitational waves leave ...
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Could gravitational waves be the cause of inflation? [closed]

Ok, crazy idea time. Context: https://www.livescience.com/65441-gravitational-wave-memory.html Quick lay summary: Apparently gravitational waves alter the structure of the space they pass through. ...
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How to convert from a tensor GW perturbation to a scalar one?

Typically the gravitational wave (GW) strain is calculated (e.g. by the Quadrupole formula) as some tensor object $h^{ij} (t)$. However, I often read of the strain as some scalar time series, i.e. $h(...
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For a given chirp mass, how to decide between different binary systems?

Suppose we observe a gravitational wave with chirp mass $M$. How to decide between the different possibilities of BH mergers, NS-BH, WD-NS, WD-NS mergers? Can it be done with ONLY gravitational wave ...
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What does it mean to hear the gravitational waves?

In last few years, I watched a lot of YouTube videos claiming that gravitational waves can be and has been heard. They also play a short audio signal. How do experiments such as LIGO replicate the ...
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How do LIGO and Virgo know that a gravitational wave has its origin in a neutron star or a black hole?

It is being said that gravitational-wave detectors are now able to distinguish neutron star waves from those originating from black holes. Two Questions: How do LIGO and Virgo know that a ...
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In general relativity, is there a difference between matter-energy and spacetime?

This is the third time I try to formulate a question in a proper format so as to understand what is going on with gravitational waves at a physical level. I am told that a spacetime oscillation and/...
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From a gravitational wave detector perspective, what is the difference between a gravitational wave and a phonon?

I already asked a question but it seemed that it was not precise enough. My problem is that I cannot see how gravitational waves have anything to do with spacetime. An EM wave or a phonon can put ...
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Does charging and discharging a capacitor create very small gravitational waves?

If I understand it correctly, curvature in a region of spacetime is due to concentration of energy and momentum in that region. If I further understand things (I don't) a gravitational wave is a ...
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1answer
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Direct observation of Gravitational Waves via increased resolution

First, congrats to the event horizon team for the first photograph of a black hole. Not to downplay the significance of the photo, but it is a bit blurry. Still, it got me thinking. One might expect ...
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Is it possible to use the principle of EHT to build a virtual gravitational wave detector to detect very long wavelength gravitational waves?

The press conference of the EHT is fascinating. While there are some features such as the asymmetry in the ring that is to be followed up by the team, I was actually wondering, whether it is possible ...
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How much more precise would LIGO have to be?

The planets and a spinning black hole both drag their local frames and thus generate gravitational waves The amplitude should be proportional to the size of the celestial body, while the frequency of ...
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Can expanding space stretch the wavelength of GWs? [duplicate]

I have read this question: Redshifting of Light and the expansion of the universe Now analogously, we could talk about GWs traveling in the empty voids of space, where the expansion of space is ...
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When space expands where do the energy of the gravitational wave dissipate to? [duplicate]

I think it is safe to say that gravitational wave do not dissipate unless it met matter along the way imparting some of it's energy to cause some distortion or when it's frequency is stretched even ...
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1answer
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How can the big bang be “observed”?

The Big Bang Observer is a proposed spacecraft to study gravitational waves. Especially the one that are thought to originate from the Big Bang. Question. How can we observe waves that has an origin ...
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Are GWs made of gravitons (are gravitons the quanta of GWs) or not?

I have read this question: What is the difference between gravitons and gravitational waves? I have read this on wikipedia: However, if gravitons are the quanta of gravitational waves, then ...
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Why gravitational wave stretches on $x$-axis would necessarily compress on the $y$-axis?

I read gravitational wave is a traverse wave, usually produced by inspiraling neutron stars or black holes, and laser interferometer such as LIGO is commonly used to detect them, since the setup of ...
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Polarization states of a massive graviton

How could I reconcile the fact that there are 6 polarization states for a gravitational wave (3 transverse and 3 with longitudinal components) with the fact that the spin-2 graviton should allow a ...
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Non-test-particle dynamics from inside a black hole horizon

It seems to me that most arguments in favor of impossibility of communication from beyond black hole horizon region are based on "test-particle" scenario, where the falling object is (very) light with ...
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Multi-Frequency gravitational wave sources

A star can emit light with different frequency at a time. Is it possible for a gravitational wave source to emit gravitational waves of more than one frequency at a time?
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Visual simulation of gravitational lensing

Is there a way to generate an accurate visual computer simulation of gravitational lensing?
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If I were to shake a black hole, does it grow bigger?

Imagine I were to shake a black hole rigorously, does it grow bigger? I think it will simply radiate all the kinetic energy gained from the shaking as gravitational wave right? In the normal case, if ...
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Where do gravitational waves draw the energy from?

Imagine binary neutron stars inspiral, they generate gravitational wave which carries energy away and causing the pair to become ever closer. Since all wave must carry energy I wonder where do ...
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Would inspiraling binary wormholes produce gravitation wave?

Mathematically I am wonder would two binary wormholes radiate intense energy as gravitational wave as they get closer and closer together, I like to know what happens to the mass (or negative mass) ...
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Radiation Pressure Noise in Gravitational Wave Detection

I am trying to work out where equation 9 comes from in Martynov et al. (2016), who discuss the radiation pressure noise in the LIGO detector. $$L(f) = \frac{2}{cM\pi^2 f^2} \left(h \nu G_{-} P_{\rm ...
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Do gravitational waves violate the information paradox? [duplicate]

I know when black holes collide, the remnant black hole has a lower mass than the sum of the original two masses. This is due to energy loss via gravitational wave emission. Does this violate the ...
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1answer
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What comes out of binary black holes at end of inspiral?

When 2 blackholes are orbiting each other so close that they lose more energy in form of gravitational wave, this process is inspiral and is unstoppable until it explodes. This is an extremely violent ...
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Does dark matter need a second force to collect in ordinary matter?

Some experiments search for dark matter interactions at the center of bodies like the Sun and Earth, assuming that if there is some interaction with ordinary matter that allows dark matter to lose ...
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Is there any way gravitons can be found in gravitational waves? [duplicate]

I've been thinking for the past week about this thing, maybe due to my poor understanding of GR... So, if we try to measure the speed of a gravitational wave (I don't know if it's possible yet), and ...
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Why do external observers see LIGO results if an object falling into a black hole never reaches the event horizon? [duplicate]

If I throw a clock towards a black hole, its time slows down, it is redshifted, and according to many theories it never reaches the event horizon from my point of view. How is it then, that a star can ...
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Now when we can measure gravitational field, how does the principle of equivalence hold true?

LIGO measured gravitational field waves. The whole thought experiment of Einstein, leading to ‘principle of equivalence’, assumes that there is no way to know inside the rocket that whether its ...
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Do gravitational waves affect the flow rate of time?

Since LIGO has been able to detect the presence of gravitational waves, this implies that there is a density wave traveling through space with a high potential front and a low potential back side. ...
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Electric quadrupole radiation and supernova core collapse

I have a question when I'm learning the electric quadrupole radiation in E&M. In the radiation zone, the vector potential $\vec{A}(\vec{r},t)$ generated by the current distribution $\vec{J}(\vec{r}...
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Gravitational waves and chirp waveform

When two neutron stars collide emitting gravitational waves, what exactly does the chirp waveform represent and how is it used to infer the distance to the source?
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Could gravitational waves give an illusion of an expanding universe? [closed]

‪Could the effect of “expanding” gravity (gravitational waves spreading at the speed of light) as it travels through space (and therefore becomes less local) red-shift all EM waves and thus give us ...
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Speed of gravitational wave in strong gravity

I have a question about gravitational waves which I can't really find an answer to. My current understanding is that one assumes there is some frame in which the metric has the form $g_{\mu\nu} = \...
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Two black holes merging in our Milky way: GW signal strength?

Gravitational waves detected recently by LIGO interferometers were generated at very large distances, e.g. 440 MegaParsec for GW151226. Would Joseph Weber be able to detect such event with his ...
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Are there any time-periodic solutions to Einstein's equations apart from black holes?

Are there any solutions to Einstein's equations which are periodic in time? A black hole only has mass, charge and angular momentum according to the no-hair theorem. (Although this might just mean in ...
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Gravitational waves interference lensing

Is it possible to detect gravitational waves interference pattern in space, using a telescopes alone or a telescope coupled by gravitational lensing?
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Can the vibrations from the Earth affect gravitational wave detectors?

I was very interested in gravitational wave detectors and how they work exactly. From what I know they set up two lasers with mirrors set up to cancel each other out. Then if movement is detected from ...
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On what timescale does gravitational wave emission circularise an orbit?

Gravitational waves remove both energy and angular momentum from a binary orbit. Both rates are enhanced in non-circular (eccentric) orbits and I presume that (like tidal friction) the net effect will ...
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Significance of the LIGO experiment with respect to length contraction

it might be best to first detail my (admittedly limited) understanding of the LIGO experiment. a beam of light is split along two 4Km evacuated pipes then reflected back where their interference ...
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Could a black hole and a white hole cause gravitational waves, if orbiting one another?

I have been puzzled by an idea that I came across while reading about white holes. But I've only just started learning about white holes, so my knowledge is severely limited. It seems I also can't ...
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Two black holes colliding (classical mechanics)

I had this question come up in my exam where two identical black holes are in orbit around each other. There is a loss of energy via gravitational waves : $$\frac{d E}{d t} = kr^4\omega^6$$ where $k$ ...
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Energy of an event for a human observer at a distance of 1 astronomical unit to physically feel the gravitational waves using inverse square law?

I'm asking this question to satisfy my curiosity about how much energy (in joules) it would take for a human astronaut to feel a gravitational wave from a distance of 1 astronomical unit (AU) from two ...