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Questions tagged [gravitational-waves]

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How does LIGO detect Gravitational Waves if they bend both space and time?

Please note that this is not an inquiry into the mechanisms of technology that LIGO uses to detect gravitational waves. Also, I am not a flat-earther. I was watching physicists vs. flat-earthers ...
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Pendulum usage in gravitational wave detectors

I've read that pendulums are (or were) used to calibrate the distance between the mirrors in a gravitational wave detector. In principle pendulums are supposed to be moving in just one plane no matter ...
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Has anyone ever tried to derive gravitoelectromagnetic waves equation?

Has anyone ever tried to derive gravitoelectromagnetic waves equation? As we know, there is Maxwell-like equation in gravity. Has anyone here ever formulated gravito electromagnetic waves equation ...
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Could LIGO detect two simultaneous gravitational waves?

Hypothetically if two (or more) gravitational waves were passing through the LIGO detector at the same instant, can the LIGO team deduce from the data that there were two simultaneous waves passing? ...
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What does it mean by $h_{\mu\nu}$ having “gauge symmetry”?

$$\partial^\rho \partial_\rho h_{\mu\nu} - \partial_\mu \partial^\rho h_{\rho\nu} - \partial_\nu \partial^\rho h_{\rho\mu} + \partial_\mu \partial_\nu {h^\rho}_\rho = 0$$ Here $h_{\mu\nu}$ is a ...
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How is the approximate gravitational wave stress energy momentum tensor not 0?

In Section 35.7 of Misner, Thorne, and Wheeler, p. 955, an "effective" stress energy momentum tensor for gravitational waves is defined: $$T^{\text{GW}}_{\mu \nu} = \frac{1}{32 \pi} \left< \bar{h}...
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Gravitational waves and Possible distortions in time?

Straight off, i know similar questions have been asked at How close would you have to be to the merger of two black holes, for the effects of gravitational waves to be detected without instruments? ...
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Gravitational wave equations? [closed]

I am looking for a set of equations, one to calculate GW amplitude in watts and one to calculate frequency... I believe I have located the correct frequency equation yet I cannot find a source for ...
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Red-shifting due to emitting gravitational waves

Light waves exert their own gravitational pull and must be emitting gravitational waves, losing energy in the process. Does this mean that light becomes red-shifted as it travels even without the ...
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Proper time elapsed along a worldline

The question is about the following metric describing the gravitational wave propagating along the $z$ direction: $$ds^2=-dt^2+(1+h(t,z))dx^2+(1-h(t,z))dy^2+dz^2$$ where $$h(t,z)=H\cos{k}(t-z).$$ $...
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Effective stress-energy tensor for a gravitational wave, compared to static semi-Newtonian case

There is a calculation that I had been thinking for a long time of working out to my own satisfaction, both because of its intrinsic importance and because it seemed like it would be fun. This was to ...
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107 views

Is Gravity Cumulative

This is to tie in with a previous question >The Sun's Orbit - Is it What We Think? Are gravitational waves cumulative? and if so how does this affect our galaxy and other astronomical bodies? Now ...
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Why gravitational waves are not part of thermal phenomena?

Electromagnetic waves are part of thermal phenomena in the form of thermal radiations. But why gravitational waves do not show up as a thermal phenomenon, for example, why gravitational waves do not (...
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Do gravitational waves diminish over time/distance?

Just wondered how they compare to sound waves, naturally they travel at the speed of light, but I was wondering if they diminish over time like sounds waves. Cheers.
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Do you create gravitational waves by clapping your hands?

I was thinking that given that GW's can be created by the merger of both black holes and neutron stars I don't see why any two colliding objects wouldn't also be able to create gravitational waves, ...
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Is it possible that the LIGO results are anomalies? [duplicate]

Since it was reported recently that the supermassive black holes at the centres of galaxies may in fact be as many as 20,000 smaller black holes I wondered if, if these black holes collide with one ...
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Visualising Gravitational waves

I'm studying General relativity, and I want to clarify the qualitative nature of how gravitational waves propagate. Simple is best, so I want to imagine a single binary black hole system orbiting in ...
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About the “Spindown problem”

I am studying General Relativity, following the lessons too, and some days ago the professor mentioned, in a very "fancy and quick" way a thing called "the spindown problems". For what I understood, ...
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Do stars amplify or refract gravitational waves?

I am curious if stars (or other massive bodies) amplify or refract gravitational waves in a manner similar to the following. Amplification In the case of amplification, do massive bodies affect ...
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Why are both LIGO detectors nearly co-aligned? [duplicate]

A lot of the papers I've been reading say that's the case, so we needed VIRGO to analyze the polarization of the GWs, but not a single one of them explains the reasoning behind this decision. Why ...
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How do the LIGO facilities know that their gravitational waves have not been distorted by other events and other waves?

Several black hole collisions have been detected. How do they determine if the gravitational waves have been strengthened or weakened by interaction with other event waves?
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What causes the 20 second period in LIGO data?

I download LIGO data on GW150914 (gravitational waves) via the code in Mathematica ...
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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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Gravitational Potential Energy irony

While calculating potential energy of an object with respect to Earth which equals work done to bring it from infinity to that point. The gravitational force and displacement are in same direction, ...
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How much uncertainty has the relic graviton background?

In the paper [1], it is mentioned that inflation predicts that a relic graviton background is about 0.9 K (cf. cosmic neutrino background, 1.945 K, and cosmic microwave background, 2.73 K). How much ...
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Is a seismic gravity perturbation a gravitational wave?

Powerful enough earthquakes generate gravity perturbations that propagate at $c$ and can be detected by sensitive enough seismographers. See, e.g., this news in Nature: In the latest paper, Vallée ...
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If two black hole mergers happen close enough would there be any interesting effects due to their waves constructive and destructively interfering?

If two pairs of black holes were to merge at the same time in the same plane within close proximity (small odds) what effects could be observed due to their waves constructively and destructively ...
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What causes primordial gravitational wave in the early universe?

Is it collision between primordial black holes or perhaps big bang itself, I read that if we can observe very first polarized light e.g. CMBR etc then inflation theory is proven. So my question is ...
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What are the Maxwell's equations for gravitational waves?

Maxwell's four equations can be used to describe the propagation of electromagnetic waves. What is the equivalent for gravitational waves - if that question makes sense?
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Classical mechanics gravitational waves

Would there be gravitational waves even if general relativity was wrong? For example imagine there was a theory of gravity that was consistent with special relativity. How different could ...
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Hulse-Taylor binary data gap in the nineties

I was wondering what is the reason there are no data points in the famous Hulse-Taylor plot of the period decay in the 1990s. Does anyone know why no one collected data during this period?
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Why is the Ricci scalar non-zero in this case?

The Einstein equations can be written as (1): $$R_{ab}-\frac{1}{2}Rg_{ab} = -8\pi GT_{ab}$$ or by contracting the above equation with the metric tensor and resubstituting: (2) $$R_{ab}=8\pi G(\frac{1}...
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Could a powerful gravitational wave cause electrons to emit light?

I imagine electrons being accelerated by passing gravitational waves, say from a nearby kilonova, so I would expect the electrons to emit light. Am I right?
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What is the experimental evidence for the gravitational field having positive energy density?

Recent direct observation of gravitational perturbations attributed to merging black holes and merging neutron stars has reliably confirmed the existence of gravitational waves. The observed fact that ...
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Redshift z=40 and gravitational waves

Why z=40 is the critical value of the redshift (more or less) to decide find out primordial gravitational waves around it? I have read that is related to the following issue: black hole mergers ...
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1answer
59 views

Attributing Gravitational waves to a source

At a given time, there would be n number of binary neutron stars or Black Holes or even Super Novae, all of which would be leaving a gravitational wave imprint ..So how do LIGO scientists know which ...
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Lowest 'Order' of Radiation

I've noticed an interesting phenomenon (admittedly from only two data points). In electromagnetism, $A^\mu$ obeys Maxwell's equations: $$ \square A^{\mu} = j^\mu . $$ where I've chosen $\mu_0 = \...
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2answers
468 views

Do gravitational waves carry energy?

We now know that gravitational waves are real. Do they carry energy? I mean thy are waves and every wave carries energy. If they carry energy, how do they do it? Is there any equation to describe ...
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How to use Ashtekar's variables in classical gravitational physics?

I have often heard of Ashtekar's variables in General Relativity, because of the naturalness with which they would allow a canonical formulation of gravity, useful for a hypothetical quantum gravity ...
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How does a neutron star collision turn mass into gravitational waves?

I heard on the TED Radio hour that in the neutron star collision that LIGO recently detected, some of the mass of the neutron stars was turned into energy in the form of gravitational waves. How does ...
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1answer
80 views

Determine expansion rate of universe from gravitational waves LIGO?

I heard on the TED Radio Hour that the LIGO team was able to make an independent measurement of the Hubble constant and the increasing expansion rate of the universe when they detected the ...
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How to show that the polarization tensor of the gravitational plane wave in vacuum is transverse

This is Ta-Pei Cheng's book p.254. I am trying to understand (13.28). The Lorentz gauge condition (13.18) is like below. How can I use the (13.18) condition to show (13.28)? I am trying to calculate ...
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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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Gravitational waves & cosmological redshift

Are gravitational waves streched by the expansion of the universe in the same way as EM radiation is? In that case how does one differentiate between a gravitational wave from a given event (say ...
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Stochastic versus primordial gravitational waves

I have read differences terms but I doubt if they are exactly the same in Cosmology: Primordial gravitational waves (and their background). Stochastic gravitational waves (and their background). ...
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Gravitational waves' path and interaction with black holes

As a gravitational wave propagates away from its source, how does its path get affected if a black hole is in its way? I was trying to picture it visually and here was my 'before' (with the line being ...
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1answer
141 views

Could LIGO have detected R'lyeh if it existed?

In Possible Bubbles of Spacetime Curvature in the South Pacific, that R'lyeh might be exist within a bubble of spacetime. (It appears to be a joke paper since some of the references are fictional, but ...
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1answer
162 views

Observation of Hawking radiation

Is it conceivable that Hawking radiation could be observed using e.g. gravitational waves or imprints in the CMB?
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Gravitational waves detector orientation

For a wave of the form, say, $$ ds^2 = -dt^2 + [1 - A\sin(\omega(t-z))]dx^2 + [1 + A\sin(\omega(t-z))]dy^2 + dz^2$$ how should one orient the detector (that works by monitoring the distance between ...
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Difference in Gravitational Waveforms for different objects?

This is an extension of one of my older questions: How would the gravitational strain waveform look like for a planet in orbit with a star? Let's say at some distance D there are two objects which ...