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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15
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2answers
2k views

LIGO flawed by the identical expansion of laser wavelength and arms in presence of a gravitational wave?

LIGO, Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming to directly detect gravitational waves. The device measures the phase shift laser beams. If I ...
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How were the solar masses and distance of the GW150914 merger event calculated from the signal?

The GW150914 signal was observed, giving us the frequency and amplitude of the event. Because LIGO has two detectors a rough source location could be derived. But how do these three factors allow for ...
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5answers
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Are the LIGO observations proof of a black hole merger, and what happened to the black holes?

Recent reports claim that the gravitational waves detected by LIGO match up with the signal expected from two black holes merging as predicted by general relativity. Additionally, the masses of both ...
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9answers
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Why is the detection of gravitational waves so significant?

LIGO has announced the detection of gravitational waves on 11 Feb, 2016. I was wondering why the detection of gravitational waves was so significant? I know it is another confirmation of general ...
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Is there a good chance that gravitational waves will be detected in the next years?

Is there a good chance that gravitational waves will be detected in the next years? Theoretical estimates on the size of the effect and the sensitivity of the newest detectors should permit a ...
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1answer
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How is it that distortions in space can be measured as distances? [duplicate]

Imagine yourself and anything you're able to perceive to be drawn onto a rubber band. Any means of determining distances would be affected by the stretching/contracting of the rubber band. The ...
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3answers
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Transfer of energy from gravity back to other “more familiar” forms of energy?

In this question I've mentioned an account of the recently reported 2nd observation of gravitational waves, LIGO and Virgo Collaborations, Phys. Rev. Lett. 116, 241103, 15 June 2016, where 1 of the ...
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3answers
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How strong were the gravitational waves that LIGO detected at the source?

Congrats to the LIGO team on the announcement of their discovery of gravitational waves! The articles I've read say that the distortion we see here is much smaller than a proton. What about at the ...
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How would we estimate, ahead of time, “the chances” of LIGO spotting black holes colliding in the period that it has been operating? [duplicate]

Can anyone summarize calculations that have been done about the theoretical probability of a detectable black hole collision happening in the observable universe within the time that LIGO has been ...
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1answer
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What was the rate of Black Hole - Black Hole mergers expected to be detected by LIGO prior to GW150914?

My question is a more detailed version of the one found here, which elicited some good information but the question was never really answered. From table 4 in a 2010 paper we see the estimated rate ...
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1answer
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What makes us think we can actually detect gravitational waves?

This refers to the discussion about gravitational waves for the YouTube video LIGO Gravitational Wave Observatory. I have two questions: When the gravitational wave passes through the space where ...
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1answer
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How does LIGO remove the effects of environmental noise?

Since LIGO is dealing with readings at nanometers, events such as vehicles driving nearby, and constant (but extremely minor) tremors of the earth can cause movement with the mirrors at nanometers. ...
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What is black hole spin?

First of, congrats to the people at LIGO. In this article, the BBC notes that the latest LIGO results show that a new black hole was formed with a spin of $0.2$ (dimensionless number). What exactly ...
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How did LIGO detect the source location of the black holes mentioned to be the cause of today's announcement?

Today LIGO announced discovery of Gravitational waves. What method was used to determine the source location of the waves?
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Could (old) LIGO have detected GW150914?

The merging black hole binary system GW150914 was detected in only 16 days of aLIGO data at a signal level that appears to be well above the detection threshold at around 5 sigma. There are no further ...
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Meaning of $5.1\sigma$ significance with regards to GW150914

I couldn't find any publication by LIGO that explains how we should interpret this value. The closest I have found is the following quote: This means that a noise event mimicking GW150914 would be ...
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4answers
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Isn't LIGO basically measuring the luminiferous aether?

I am bit confused about this one. I am not very acknowledgeable about gravitational waves and LIGO. But if it is basically a Michelson interferometer and can detect shifts in vacuum, doesn't this ...
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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 ...
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1answer
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How did LIGO scientists determine the source of the gravitational waves they detected? [duplicate]

I read the newspaper today and I found that LIGO had detected gravitational waves. This is from their official website: For the first time, scientists have observed ripples in the fabric of ...
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1answer
426 views

Is there a “CGBR”?

The recent discovery by the LIGO made me wonder about this. We know that there exists a CMBR, Cosmic Microwave Background Radiation, a blanket of electromagnetic energy covering the universe, made by ...
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1answer
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Orientation of the LIGO Arms

The orientation of the interferometer arms at both sites are approximately Northeast-Southwest and Nortwest-Southeast, though I assume that, on account of the Earth's curvature, no pair of arms is ...
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1answer
583 views

Gravitational waves detection, any news? [duplicate]

Is the detection of gravitational waves a reality with nowadays technology? Are there recent news?
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Why does LIGO have an arm length of few kilometers? Is the distance dependent on Gravitational Wave wavelength?

Antennas for capturing radio waves need to have $\frac{\lambda}{2}$ length for optimum reception of signal. Does it imply LIGO arm length is $\frac{\lambda}{2}$ of Gravitational Wave it is trying to ...
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1answer
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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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10answers
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How does Zumberge's 1981 gravitational measurements relate to gravitational waves?

Gravitational waves were discovered 35 years ago without fanfare in 1981/2 by Zumberge, R L Rinker and J E Faller, then completely ignored. See: "A Portable Apparatus for Absolute Measurements of ...
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G4v Gravitational Wave vs General Relativity vs LIGO Observation

CalTech emeritus professor Carver Mead produced an alternative prediction, to General Relativity, for gravitation wave observation which he published last year in anticipation of LIGO observations. ...
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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 ...
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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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How are the 4 km arms of LIGO measured so accurately?

The arms of the LIGO interferometer are 4 km long. Now, LIGO functions by measuring phase difference between two beams of light coming (as in a Michelson interferometer) to a sensitivity of $10^{-18}\:...
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Gravity vs Gravitational Waves

I thought I had a reasonable understanding of relativity, the speed of light speed limit, and how this stuff related to gravity. Then I read through all the answers/comments for this question: How ...
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How do the LASERs in LIGO realize that space has expanded as a gravitational wave passes by?

I read an article on LIGO, and I heard it mentioned that it is a nontrivial argument to say that the effect can be measured by interferometry. What happens to space as the wave passes? Does the light ...
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1answer
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How many galaxies could be the source of the recent LIGO detection?

The recent LIGO detection is pretty exciting, and a lot of people are asking whether there is a chance of optical detection of the black hole pair that created the signal. From a cursory reading of ...
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1answer
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Frequency and amplitude for the three gravitational wave events at LIGO

I was reading LIGO/VIRGO's article Binary Black Hole Mergers in the First Advanced LIGO Observing Run, and have two questions concerning the frequencies and the amplitudes of the three gravitational ...
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1answer
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LIGO event - energies involved?

So, we have two Black Holes merging shortly after LIGO turns on after the upgrade. Some questions: a) How lucky was it to see this event? What are the expected rate of occurrence? b) Was this event ...
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1answer
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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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What is the uncertainty in the one solar mass radiated away as pure energy? (Gravitational waves)

edit: Thanks to the comment below - I learned that the PLR is available to read http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.241103. In it, ref. 5 links to this preprint dated June15, 2016: ...
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1answer
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Is the GW150914 signal consistent with a superluminal gravitational wave burst?

I've been following the news about the detection of gravitational waves with interest and had a question for those with a physics background. I've gathered that the preferred explanation for GW150914 (...
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1answer
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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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Does the mass lost by merging black holes depend on how they merged?

We've all heard the news about the detection by gravitational waves of two black holes, one 29 solar masses and the other 36 solar masses, spiraling into each other to create a single black hole of 62 ...
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1answer
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Did LIGO detect dark matter?

Which is the title of this preprint They claim that: We consider the possibility that the black-hole (BH) binary detected by LIGO may be a signature of dark matter. Interestingly enough, there ...
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Can we make any implications about the internal structure of black holes from the 'chirp' that LIGO observed?

Are there any implications about a black hole's internal structure we can make based on the chirp issued? For example that a black hole does in fact contain or does not contain a singularity rather ...
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2answers
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Does shortening the path length of an excited etalon do work? What about LIGO?

Start with a high-Q etalon excited on-resonance with a laser for a time long enough that it has built up an essentially stable standing wave. There is a constant outwards-directed force on each mirror,...
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2answers
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Black holes are obvious answer to dark matter, why is that wrong? [duplicate]

Primordial Black Holes as dark matter candidate. I think this is interesting and new, in that there is a window of PBH masses (link from Count Iblis) And the first GW event from Ligo is right in that ...
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1answer
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How they can estimate when the black holes collided in the recent LIGO discovery? [duplicate]

How they can estimate when the black holes collided in the recent LIGO discovery? If LIGO can detect ripples in the gravitational waves, how they can figure out how old those waves are? Surely ...
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1answer
661 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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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 ...