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Questions tagged [ligo]

The Laser Interferometer Gravitational-Wave Observatory (short LIGO) is a large interferometer used for the detection of gravitational waves. Use this tag for questions about this specific installation; for questions more generally about the properties of gravitational waves or gravitation, use [gravitational-waves] and/or [general-relativity]

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153 views

Distortion of interference pattern at LIGO

Does the vibration due to the earthquakes distort the interference pattern of LIGO's interferometer?
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266 views

Is there high ring-down frequencies in LIGO's recent discovery?

This question is from Physics overflow: question in physicsoverflow. I am reading LIGO's new discovery of gravitational waves by black hole merger. During the merger, two phases are not hard to ...
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1answer
359 views

How did the scientists know two black holes collided 1.3 billion years ago?

I saw a TEDx talk the previous day about the LIGO experiment and in that video he said they are waiting for the day Jan 1st 2017 for the Ripple in Gravity caused by two black holes colliding each ...
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1answer
95 views

Gravitational waves detection

I am aware that the everything with mass produces gravitational waves and the only reason why we don't detect them is because they are incredibly small. If gravitational waves act like every other ...
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1answer
106 views

Is there any issue/concern for a slight wavelength shift of the laser light in the LIGO experiments? [duplicate]

A friend and I were having a discussion about the LIGO experiments and were wondering if there is any issue with the laser light undergoing a wavelength shift as a result of the gravitational wave? ...
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1answer
57 views

Does LIGO accounts for Sagnac effect?

After reading Sagnac effect one thing immediately come to my mind is LIGO, I only read that the team building LIGO have already considered the curvation of Earth surface but what about Earth's ...
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1answer
88 views

How does one derive theoretically the shot-noise limited sensitivity of LIGO?

It is said that LIGO can measure 1/1000 the width of a proton. How does one derive, using the design parameters of LIGO(arm length, laser power, etc.), its sensitivity?
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Pease explain why does the phase bw two sidebands in PDH method changes from pi (when laser is at perfect resonance with cavity) due to dithering?

since, this signal is compared with the original modulating signal and the net phase shift gives the error signal which is fed to the servo for control. Hence, knowledge of phase deviation due to ...
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45 views

Is LIGO designed as a bandpass instrument?

This question intended for those that may have personally worked on LIGO and are knowledgeable about its detailed systems architecture. I understand that LIGO basically uses a Michelson-Morley type ...
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215 views

LIGO detection statistic, SNR formula

According to B. P. Abbott paper published in Physical Review Letters, "Observation of Gravitational Waves from a Binary Black Hole Merger" http://journals.aps.org/prl/abstract/10.1103/PhysRevLett....
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Why are the arms of the LIGO interferometer so long? [duplicate]

The LIGO experiment consists of two interferometers, where each one of them has two 4 km long arms. Within these, light is further trapped via Fabry-Pérot cavities to achieve a total path length of ...
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2answers
155 views

What actually is the event that we think we have detected with gravitational waves? [duplicate]

This answer shows the "event" that is creating excitement. It looks to the untrained eye like a single "blip" on a detector. It appears to last less than a second. It is, later in the answer, ...
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71 views

Is the signal detected by LIGO a result of the merging of the horizons or the singularities?

Regarding gravity waves, some YouTube videos show simulations of the gravity waves detected by LIGO in August of 2017. Is the "chirp" the result of the merger of the event horizon or the merger of ...
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1answer
260 views

Why is there blindspot for LIGO interferometer?

I am thinking maybe when the gravitational wave hits the 2 mirrors at the same time but the two mirrors are very far apart, so what could be the cause for the blindspot?
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1answer
290 views

Why did we take so long to directly detect gravitational waves?

According to this article, http://www.sciencemag.org/news/2016/02/gravitational-waves-einsteins-ripples-spacetime-spotted-first-time, the search for gravitational waves was beset by continual ...
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2answers
63 views

Data for speed of gravitional wave

By the distance of the two LIGO detectors and the time delay for the same gravitational wave(GW) event, the speed of GW can be determined. guys, do you know where can I find related data?
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91 views

What can and can't gravitational waves affect?

Owing to the relative weakness of gravity, I would have assumed that the gravitational waves detected by LIGO couldn't expand / contract the nuclei of atoms (governed by the strong interaction) or ...
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1answer
48 views

Why does an interferometer with mirrors even work? [duplicate]

My understanding is being thwarted by something basic I am missing. One starts with a light beam that is split into two perpendicular paths. There are two light paths that travel some distance. The ...
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1answer
207 views

What is the probability that gravitation wave detections were coincidental errors? [duplicate]

The reported discovery of gravitational waves has been put in question by the scientific community: https://www.quantamagazine.org/strange-noise-in-gravitational-wave-data-sparks-debate-20170630/ In ...
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1answer
108 views

Why does the magnitude of the Gravitational wave reach maximum peak upon merger?

We all know that objects which are accelerating in space-time produce Gravitational waves. My question is why is there a burst of GW upon two black holes merging. Also, does that mean that let's say ...
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1answer
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Where does the rate of mergers per halo in the “Did LIGO detect dark matter?” paper come from?

It was recently proposed that dark matter (DM) could be made of primordial black holes (PBHs) of $\sim 30 M_{\odot}$, like the first ones detected by LIGO. This idea was written in "Did LIGO detect ...
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1answer
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Determining the direction of origin for gravitational waves

For LIGO's first gravitational wave detection, GW150914, the signal first reached Livingston, LA and then about 7 ms later reached Hanford, WA. Based on the sequence it was stated that black-hole ...
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1answer
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LIGO detection: What do we know about the black hole system?

I would to know how much we can infer from the LIGO detection on the black hole system. I understand that at least the following can be verified: Spins Inclination Initial masses Final masses ...
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1answer
274 views

LIGO discovery: if the space “time” metric is changed, how is it measured? [duplicate]

Regarding the wonderful 2016 news about gravitational waves. Travel time in one arm of the LIGO is ~ 30μs. A gravitational wave affects the arm for some few hundred of these laps. Then for example ...
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1answer
41 views

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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Could the LIGO design be also used to detect space - time distorsions (curvature) caused by a small gold sphere?

Suppose  you put  a gold sphere inside the LIGO interferometer, not in the path of the laser beams, but sufficiently close to  (in the vicinity of) one of the laser beams. Would the space  - time ...
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1answer
40 views

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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1answer
53 views

How would the gravitational strain waveform look like for a planet in orbit with a star?

So far I've read and seen about various type of waveforms for different sources of Gravitational waves such as black holes, neutron stars etc. So the waveforms would be for Compact Binary Coalescence ...
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1answer
66 views

How to generate numerical relative waveforms representing gravitational wave strain for different masses?

I have read in many sources that Numerical relativity produces a general solution for the waveforms which are to be expected by LIGO data to identify the different masses which are observed . Can ...
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1answer
115 views

Will the Sun's fast (but subluminal) removal cause gravitational waves?

Reading this question How fast does gravity propagate?, I'm curious over the consequences of the sun being removed. As should be clear, we cannot just remove the sun as it violates energy ...
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1answer
139 views

LIGO: Importance of photons

In LIGO, a photon beam travels in two perpendicular direction and time taken by each beam is noted. Non zero time difference is a signature of GWs here. What if I use electron beam travelling at ...
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1answer
54 views

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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1answer
66 views

black hole chirp physics

I have read that the chirp frequency in the first LIGO data is related to the period of the orbit of merging black holes. I have also read that that the frequency is related to time-dependent ...
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1answer
701 views

How to know the distance of the black hole merger? [duplicate]

I have a question about the detection of the gravitational waves by LIGO. When there is no electromagnetic wave coming from the black holes, then how do they know in which distance it is?
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1answer
144 views

Gravitational Waves and LIGO [closed]

Last month, we as a species did something remarkable. We detected the presence of gravitational waves. While we all are celebrating and excited about the newest discovery of mankind. I could use ...
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2answers
475 views

Could discovered gravitational waves in fact be an aether wind? [duplicate]

Proving the existence of gravitational waves might revolutionise cosmology, but the method used by LIGO is quite similar to the famous Michelson-Morely interferometer built more than a hundred years ...
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31 views

Can we measure the amount by which LIGO black hole mergers warp space itself, relative to the mass of the merger?

In our day and age we can calculate the mass and maximum volume of a black hole. With LIGO we can also now calculate by how much is space warped, relative to the distance to a black hole merger, such ...
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43 views

Bound on large extra dimensions using gravitational waves

Are there proposed observations using gravitational waves which put a bound on the size of large extra dimensions (say in the context of ADD model)? The claim in the ADD paper is that you cannot ...
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32 views

Concept of timelike coordinate in Brinkmann form of Plane gravitational wave

I have been studying about the gravitational wave memory effect from these papers: 1: https://arxiv.org/pdf/1705.01378.pdf 2: https://arxiv.org/abs/1003.3486v1 Now, it is evident that ...
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50 views

Slowdown of gravitational waves measurement

As far as I can understand, the gravitational waves also slow down on interaction with matter similar to light rays. I am trying to understand if we can measure this? Suppose we put two detectors on ...
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How are black hole masses calculated from gravitational waves? [duplicate]

I would like to know what data is used from gravitational wave detections to calculate black hole masses and how. Also, what else can you deduce from gravitational wave detections? What was the exact ...
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285 views

Power inside resonating cavity

In LIGO they use 20W laser source, but then the light gets into Fabry-Perot cavity and this light's power inside it is 100kW [1]. How is that possible? It seems to me that in order to gather so much ...
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99 views

Formula to calculate the ringdown frequency of two black holes given their mass?

Is there a simple formula to approximately calculate the ringdown frequency of two black holes given that we know their masses?
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274 views

How to convert a wave from Amplitude time to Amplitude Frequency domain? Regarding Gravitational waves strain data

I have read that on applying FFT on gravitational wave strain we can bring Amplitude time domain to Amplitude-frequency domain. But when I apply this conversion on the data I had I get this curve I'...
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0answers
41 views

How to extract the masses from LIGO strain data? [duplicate]

I am a Computer science student working on LIGO data. I have seen this well describing link How were the solar masses and distance of the GW150914 merger event calculated from the signal? On how to ...
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1answer
60 views

Can LIGO detectors be used to detect other bodies such as planets etc other than binary black hole systems?

I am new to LIGO and I have a question which puzzles me, Is it possible to detect other bodies or planets from the existing LIGO s6 data which were publicly released. I wanted to know if this strain ...
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2answers
87 views

Does LIGO insulate against radio waves?

I haven't actually been able to find any information about this, I know LIGO insulates against certain types of EM radiation but I was wondering about radio waves in particular. Can anyone help?
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Would placing 2 LIGO type detectors at antipodal points increase their sensitivity?

I am guessing the answer to this question is no, or we would have already done it. My question is based on my (almost complete, sorry) ignorance of whether the mass of the earth would absorb ...
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36 views

What would the effects of the GW150914 gravity wave burst be on observers much closer that 1.3B LY? [duplicate]

The effects of the GW150914 gravity wave burst were barely observable with state of the art instruments, i.e. LIGO. What would the effects of GW150914 gravity wave burst be on observers much closer ...
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3answers
206 views

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 ...