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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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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 ...
58 views

### Should LIGO have been impacted by Lorentz contraction?

What bearing would or could Lorentz-Fitzgerald length contraction have on Ligo detections? Was this accounted for?
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 ...
129 views

### Does frequency of light change in the LIGO interferometer arms?

There are a number of questions on the internet and on this site asking about how the LIGO interferometer measurement works given that the gravitation wave stretches both the length of the ...
45 views

### LIGO test masses in free fall

I know that the LIGO test masses are considered to be in free fall. However, they are supported by pendula. I thought that free fall means the only acting force is gravity - doesn't the tension in the ...
59 views

### How Does LIGO’s Splitter Mirror Cause Two Different Frequencies When a GW is Present?

When a gravitational wave is present in LIGO, how does the splitter mirror work to send out a different frequency than the laser frequency on the arm perpendicular to the laser direction? What are ...
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 ...
5k views

### 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 ...
61 views

### 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 ...
78 views

### 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 ...
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 ...
43 views

### Is it possible (either in practice or in principle) to produce images with a LIGO-type gravitational “telescope”?

I was reading an article in the newspaper today that referred to LIGO (and gravity-wave measurements in general) as "a new type of telescope". That got me thinking -- as I understand it, LIGO uses ...
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 ...
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 ...
79 views

### 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 ...
27 views

### Non-Planar Ring Oscillator in LIGO

How does total internal reflection from non-planar surfaces in an NPRO help eliminating standing wave and why a planar structure can't give the same result? I understand that to produce optical diode ...
41 views

### How can gravitational waves from such a long distance affect the beam of light?

Even if it does affect it should affect all the surrounding object making it impossible to detect any change. It would be like keeping a man and a scale in a room, and if a gravitational wave is ...
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 ...
29 views

### Simplified analytical model of LIGO signal

What is a simplified analytical model of the LIGO signal? It looks like a chirped sinusoid, but somewhat asymmetric. Wikipedia shows some pictures of these signals, but the signal model is generated ...
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 ...
275 views

### 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 ...
139 views

### Why do numerical relativity papers show $\ddot{h}_\times$ instead of $h_\times$ for gravitational waves amplitude?

I am very confused about why numerical relativity papers, when talking about gravitational wave extraction, usually plot the real part of the fourth Weyl scalar, $\Psi_4$, instead of its double ...
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 ...
9k views

### Why does the LIGO observation disprove higher dimensions?

I recently read this article which claims that last year’s LIGO observation of gravitational waves is proof that, at least on massive scales, there cannot be more than three spatial dimensions. I ...
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 ...
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 ...
23 views

### 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 ...
75 views

### How do the LIGO team arrive at the number of round trips in the laser arm etalon?

The quoted number of laser beam round trips in the arm cavity for LIGO on the MIT site is 280 times. How did they arrive such a number? Since the laser frequency is stabilized to less than 1 Hz, the ...
392 views

### 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 ...
72 views

### 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? ...
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 ...
47 views

### Variability of the orbital inclination of a black hole merger?

How variable should we expect the orbital inclination of a typical black hole merger to be, relative to the galactic plane? The LIGO simulation seems to give the impression that the orbital ...
103 views

### 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 ...
118 views

### What causes the 20 second period in LIGO data?

I download LIGO data on GW150914 (gravitational waves) via the code in Mathematica ...
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 ...
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 ...
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 ...
44 views

### 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 ...
74 views

### What information can we know by LIGO's detection of gravitational waves?

LIGO's detection of gravitational waves can help estimate Hubble's constant in a new way. Another paper might be informative. Apart from that what information can we get from the observed ...
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?
79 views

### If light was 2 parts per trillion slower than gravitational waves, would we know this from Gauss' law? [duplicate]

In the recent neutron star merger. The gravitational waves started 100 seconds before the collision, which is when they reached a max and STOPPED. The mass quadrupole had stopped changing, which means ...
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?
299 views

### Implications of the LIGO detections on the 'Modified Gravity' Program

We all know that GR needs modification at the microscopic scale but there are some attempts to modify GR in the classical regime as well, known by the name of "Modified Gravity". As far as I ...
158 views

### Did LIGO detect gravitational waves from Big Bang Inflation?

I recently watched an installment of "Spaces Deepest Secrets" that examined the efforts of the BICEP2 team. (Strangely, it was titled "When Black Holes Collide.") The team was looking for ...
243 views

### Would it be scientifically useful to put a LIGO or VIRGO on the moon?

Or a couple of them on the moon? It seems to me that it's seismically pretty quiet there, with no trucks bouncing around on a nearby highway messing things up. Maybe four LIGOs at the vertices of a ...
144 views

### 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 ...
108 views

### Is the LIGO detector acceptance different for gravitational and for non-gravitational waves?

The famous signals recorded by the LIGO observatories are characterized as observations of passing gravitational waves, where at each observatory site: Test masses are hung by wires near the vertex ...
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 ...