Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

All Questions

0
votes
1answer
33 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 ...
1
vote
1answer
38 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 ...
38
votes
5answers
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 ...
0
votes
1answer
75 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 ...
1
vote
1answer
39 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 ...
1
vote
1answer
51 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 ...
0
votes
1answer
73 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 ...
0
votes
1answer
40 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 ...
1
vote
0answers
42 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 ...
2
votes
1answer
46 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 ...
5
votes
1answer
221 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 ...
5
votes
1answer
133 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 ...
90
votes
3answers
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 ...
1
vote
0answers
48 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 ...
1
vote
2answers
70 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 ...
1
vote
0answers
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 ...
-1
votes
1answer
335 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 ...
4
votes
1answer
69 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? ...
0
votes
3answers
205 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 ...
3
votes
1answer
102 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 ...
4
votes
1answer
110 views

What causes the 20 second period in LIGO data?

I download LIGO data on GW150914 (gravitational waves) via the code in Mathematica ...
0
votes
1answer
58 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 ...
3
votes
1answer
78 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 ...
3
votes
1answer
137 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 ...
0
votes
1answer
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 ...
0
votes
1answer
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 ...
-1
votes
1answer
77 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 ...
1
vote
1answer
250 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?
9
votes
1answer
297 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 ...
2
votes
1answer
151 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 ...
7
votes
2answers
227 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 ...
7
votes
1answer
137 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 ...
0
votes
2answers
106 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 ...
1
vote
1answer
204 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 ...
1
vote
1answer
645 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?
1
vote
1answer
106 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 ...
4
votes
3answers
166 views

Will gravitational wave detectors be able to locate black hole collisions in time to view them?

Can a single LIGO identify the general direction of a black hole collision? Could multiple observatories be able to accurately pinpoint the direction from them so that telescopes could quickly point ...
2
votes
1answer
79 views

Easy to grasp physical description of LIGO sensitivity?

Every now and then friends ask for an overview explanation of detection results from LIGO. I know/understand just enough to be useful to them. One of the examples I use (I think it originated in a ...
0
votes
1answer
166 views

What's the relationship between classical gravitational waves and gravitons? [duplicate]

LIGO have detected gravitational waves, why we are still far away from detecting gravitations? how to understand the statement below? A classical wave may be considered to be a coherent ...
1
vote
1answer
282 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 ...
4
votes
2answers
156 views

Dark matter and LIGO

In addition to the functioning LIGO detectors (two in USA and one in Italy), I am aware there are some gravitation wave detectors under construction. More detectors should provide more statistical ...
1
vote
1answer
46 views

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 ...
10
votes
1answer
164 views

What LIGO should detect that it has not yet?

What would the lack of detection of such phenomena tell us about the Universe? What should be the most frequent signals detected, theoretically speaking? I'm a lay person in the area, so you might ...
10
votes
1answer
179 views

How does the orientations of the two black holes' spins show up in LIGO data? (GW170104)

Today's Phys. Rev Letter GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2 shows the analysis of the third confirmed detection of a black hole merger by the LIGO ...
31
votes
5answers
2k views

What will we learn from further LIGO events?

LIGO announced a third gravitational wave detection today. The news outlets didn't comment on significant differences between this one and previous detections. Did this third event teach us anything ...
3
votes
2answers
126 views

Hypothetical - If a gravitational wave was somehow produced on Earth, could its origin be triangulated?

Suppose object X is hidden somewhere on Earth and can, somehow, produce "weak" gravitational waves, that do not cause anything perceivable by people, but can be detected by all gravitational wave ...
2
votes
1answer
91 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 ...
5
votes
2answers
171 views

Colliding black holes

If objects approaching the event horizon of a black hole appear to slow down to outside observers, how was LIGO abel to "see" black holes collide? Wouldn't their collision appear to stop as their ...
0
votes
1answer
95 views

As a gravitational wave passes by a region, do the space-time dimensions undulate and move in a wavelike fashion?

As a gravitational wave passes by a region, do the space-time dimensions undulate and move in a wavelike fashion? Does LIGO measure the movement of the space-time dimensions as a gravitational wave ...
7
votes
1answer
214 views

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 ...