Author Topic: Gravitational Waves Have Been Detected At LIGO  (Read 148135 times)

Online meberbs

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #120 on: 02/24/2016 12:44 am »
...

New experimental results that are a surprise are much more useful to get us to understand things we didn't understand before.  The LIGO results aren't a surprise.  They're the opposite.  We turned over another rock and found exactly what we expected.  We'll keep turning over rocks, looking for surprises, and the LIGO hardware might yet help us find surprises under different rocks, but so far, no surprises, and no help toward new physics.
There are four natural forces in the Universe. Electromagnetic, Strong Nuclear, Weak Nuclear, and Gravitational.

Humans currently have a fairly decent mastery of the Electromagnetic force, some mastery of the strong and weak nuclear forces, though incomplete (commonplace power generating fusion reactors are still in development), and absolutely no control and limited knowledge of Gravitational.

Throughout our history we were not able to harness any of these without first gaining a more or less complete understanding of what they actually were, and how they worked in nature. To any extent, even limited use such as a nuclear weapon.

My point here was that the only shred of hope mankind will ever have of trying to master Gravity is to gain a total and full understanding of how it works in nature, and working backwards from there. That historically, is how we have gotten this far, up until now. This doesn't mean it is ultimately, or will ultimately be possible to actually gain any control over gravity under the processes by which this Universe operates, all it means is that you 100% can't without first understanding the natural force in its normal domain. THAT to me is why experiments and programs like this one, and this discovery, are so important. The more we know about the natural state the better equipped we become, if there is ever a chance of manipulating it.

This is an entirely inaccurate depiction of the state of science and history of scientific progress.

First, we understand gravity better than the strong or weak nuclear force. With the recent detection of gravitational waves, the last major prediction of general relativity is confirmed. Dark energy and dark matter could potentially be related to gravity, but the evidence is against that for dark matter, and we really don't know for dark energy. On the other hand, the weak and strong nuclear forces rely on our understanding of particle physics, which generally is incomplete (the standard model has 19 free parameters, not counting the fact that neutrinos shouldn't have mass but do, which adds at least 7 more.)

Using nuclear reactors is a horrible example of claiming that we have somehow understood nuclear forces, since the main challenge in fusion is slamming nuclei together hard enough to overcome the electromagnetic forces. The energy comes from binding with the strong nuclear force, but we don't need to understand the nuclear force to notice the energy released. Also, when we first invented fission bombs, we hadn't even begun to suspect the existence of quarks (first theorized in 1964), let alone the strong and weak nuclear forces.

Again for electromagnetism, the first telegraph was in 1844, but Maxwell published the first version of Maxwell's equations in 1861-1862.

While understanding gravity is useful, we don't necessarily need a full understanding of it to make use of it. (We already use gravitational assists for interplanetary missions, and GPS clocks need corrections for general relativity) Contrary to your claim, I don't know of a case where we didn't start using something before we fully understood it in any branch of science. The biggest openings we have left for truly new physics lie in particle physics, the union of General Relativity and quantum, and the few unexplained phenomena such as dark energy and dark matter.

Offline Nilof

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #121 on: 03/02/2016 09:28 pm »
Well, if we bring up the weak force, I'd argue we understand the electroweak force better than we understand gravity (indeed, this is the corner of the standard model where we can make 18 digit predictions). But the strong force, while we understand it's basic laws, is definitely very poorly understood even for very simple systems in the sense of solving it to make predictions.

In fact, we understand gravity incredibly well even at our current particle physics energy scales. Gravity is not incompatible with quantum mechanics in that sense, in fact gravity can be treated as a quantum force very effectively. The actual issue is that a direct interpretation of GR as a quantum force leads to ultraviolet divergences, i.e. there exists an energy scale (the Planck scale) far beyond our current accelerators at which the equations explicitly stop being applicable.

I will also note that this is also the case, although in a different way, for quantum electrodynamics which has a Landau pole. This is a sign that it needs to be included into electroweak theory, and in this sense gravity can be said to be understood just as well as electromagnetism was before it was integrated into electroweak theory (at the level of fundamental laws, obviously GR is harder to find solutions for). Electroweak theory also has a landau pole, which means it has to be integrated into a GUT eventually, and so on.

There isn't a lack of theories that could fully describe quantum gravity either, string theory is a very natural and beautiful self-consistent candidate.

The actual issue is not really that we lack theoretical understanding, but rather that our current approximative description of the universe is so ridiculously accurate that we're struggling to build experiments that can actually falsify it and give us pointers on which possible candidate theory is the most accurate extension.
« Last Edit: 03/03/2016 11:12 am by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Stormbringer

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #122 on: 03/03/2016 02:19 am »
in the work of Zvi, Dixon and friends for which they won the Sakurai prize N=8 supergravity does not lead to ultraviolet divergences so far as has been calculated which may be as many as five loops so far.

http://www.preposterousuniverse.com/blog/2013/10/03/guest-post-lance-dixon-on-calculating-amplitudes/

Quote
Finally, let me mention N=8 supergravity. This theory was invented by Eugene Cremmer and Bernard Julia in the late 1970s, with other important contributions from Bernard deWit and Hermann Nicolai, Joel Scherk and others. When superstring theory had its 1984 revolution, N=8 supergravity was quickly pronounced dead — because string theory was manifestly free of all ultraviolet divergences, and how could any point-particle theory dare to make that claim? However, it never received a proper burial. At that time, it was generally thought that N=8 supergravity would diverge at three loops, but no-one could do a full calculation past one loop. With the unitarity method, we could get to two loops in 1998 (with Zvi, Dave Dunbar, Maxim Perelstein and Joel Rozowsky), to three loops in 2007 (with Zvi, David, John Joseph Carrasco, Henrik Johansson and Radu Roiban), and to four loops in 2009. We still have found no direct sign of a divergence in N=8 supergravity, although the conventional wisdom has retreated from a first divergence at three loops to a first one at seven or eight loops. Zvi, John Joseph, Henrik and Radu are pushing ahead to five loops, which will also give important indications about seven loops. A first divergence at even the seven loop order would be the smallest infinity known to man…
« Last Edit: 03/03/2016 02:28 am by Stormbringer »
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Offline Nilof

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #123 on: 03/03/2016 09:56 am »
in the work of Zvi, Dixon and friends for which they won the Sakurai prize N=8 supergravity does not lead to ultraviolet divergences so far as has been calculated which may be as many as five loops so far.

http://www.preposterousuniverse.com/blog/2013/10/03/guest-post-lance-dixon-on-calculating-amplitudes/

Quote
Finally, let me mention N=8 supergravity. This theory was invented by Eugene Cremmer and Bernard Julia in the late 1970s, with other important contributions from Bernard deWit and Hermann Nicolai, Joel Scherk and others. When superstring theory had its 1984 revolution, N=8 supergravity was quickly pronounced dead — because string theory was manifestly free of all ultraviolet divergences, and how could any point-particle theory dare to make that claim? However, it never received a proper burial. At that time, it was generally thought that N=8 supergravity would diverge at three loops, but no-one could do a full calculation past one loop. With the unitarity method, we could get to two loops in 1998 (with Zvi, Dave Dunbar, Maxim Perelstein and Joel Rozowsky), to three loops in 2007 (with Zvi, David, John Joseph Carrasco, Henrik Johansson and Radu Roiban), and to four loops in 2009. We still have found no direct sign of a divergence in N=8 supergravity, although the conventional wisdom has retreated from a first divergence at three loops to a first one at seven or eight loops. Zvi, John Joseph, Henrik and Radu are pushing ahead to five loops, which will also give important indications about seven loops. A first divergence at even the seven loop order would be the smallest infinity known to man…

Right, I was considering a mention of SUSY and how it makes everything so much simpler, but left it at a brief mention of string theory, which provably has no UV divergences and requires SUSY for fermions. SUSY is a very natural geometric idea which can in a way be viewed as just a stronger form of conservation of momentum (since the simplest form essentially boils down to introducing a pair of spinor charges whose anticommutator is the momentum, and positing that both charges are conserved, not just their anticommutator).

Sadly we don't yet have experimental evidence for SUSY, and it is not at all obvious that we will obtain it within our lifetimes. However its simplicity and the fact that it makes so many things simpler means that it is imho overwhelmingly likely that we will find it at some point.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline RonM

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #124 on: 03/03/2016 02:00 pm »
There isn't a lack of theories that could fully describe quantum gravity either, string theory is a very natural and beautiful self-consistent candidate.

The actual issue is not really that we lack theoretical understanding, but rather that our current approximative description of the universe is so ridiculously accurate that we're struggling to build experiments that can actually falsify it and give us pointers on which possible candidate theory is the most accurate extension.

Right, I was considering a mention of SUSY and how it makes everything so much simpler, but left it at a brief mention of string theory, which provably has no UV divergences and requires SUSY for fermions. SUSY is a very natural geometric idea which can in a way be viewed as just a stronger form of conservation of momentum (since the simplest form essentially boils down to introducing a pair of spinor charges whose anticommutator is the momentum, and positing that both charges are conserved, not just their anticommutator).

Sadly we don't yet have experimental evidence for SUSY, and it is not at all obvious that we will obtain it within our lifetimes. However its simplicity and the fact that it makes so many things simpler means that it is imho overwhelmingly likely that we will find it at some point.

A good summation of the state of modern physics.

Unfortunately, no matter how natural and beautifully self-consistent the math, a theory that doesn't make predictions that can be tested is more philosophy than theory. Of course, as you mentioned the problem is our current theories are too accurate. We need to find some flaws in current theory to point the way.

Perhaps continued observations by LIGO will spot a small deviation from theory. If not, we'll have to keep trying.

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #125 on: 05/03/2016 08:20 pm »
PRIZE IN FUNDAMENTAL PHYSICS AWARDED FOR DETECTION OF GRAVITATIONAL WAVES 100 YEARS AFTER ALBERT EINSTEIN PREDICTED THEIR EXISTENCE

Selection Committee of previous Breakthrough Prize winners recognizes contributors to experiment recording waves from two black holes colliding over a billion light years away

$3 million prize shared between LIGO founders Ronald W. P. Drever, Kip S. Thorne and Rainer Weiss and 1012 contributors to the discovery

https://breakthroughprize.org/News/32

Offline sghill

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #126 on: 05/03/2016 08:21 pm »
PRIZE IN FUNDAMENTAL PHYSICS AWARDED FOR DETECTION OF GRAVITATIONAL WAVES 100 YEARS AFTER ALBERT EINSTEIN PREDICTED THEIR EXISTENCE

Selection Committee of previous Breakthrough Prize winners recognizes contributors to experiment recording waves from two black holes colliding over a billion light years away

$3 million prize shared between LIGO founders Ronald W. P. Drever, Kip S. Thorne and Rainer Weiss and 1012 contributors to the discovery

https://breakthroughprize.org/News/32

Mazel Tov!!!

I couldn't agree more with the award for this discovery!
« Last Edit: 05/03/2016 08:22 pm by sghill »
Bring the thunder!

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #127 on: 05/03/2016 08:35 pm »
I don't think it works out to much each.

Offline sghill

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #128 on: 05/03/2016 08:47 pm »
I don't think it works out to much each.

I meant the award, not the cash.  Though I guess they can all take their families to Disney with $3k.
Bring the thunder!

Offline 1

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #129 on: 05/03/2016 09:01 pm »
From the quoted article:

Quote
The Special Breakthrough Prize can be conferred at any time in recognition of an extraordinary scientific achievement. The $3 million award will be shared between two groups of laureates: the three founders of the Laser Interferometer Gravitational-Wave Observatory (LIGO), who will each equally share $1 million; and 1012 contributors to the experiment, who will each equally share $2 million.

So the main three don't quite get the lions share, so to speak, but they do get the largest individual slices by far. I think this is a good split. It recognizing both the importance and sheer magnitude of the vision of the three founders, but also the huge amount of work and contributions done by the other 1012. Congrats to all involved.
« Last Edit: 05/03/2016 09:02 pm by 1 »

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #130 on: 05/04/2016 06:26 am »
Just a shame the Nobel prize cannot be subdivided so.

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #131 on: 05/05/2016 05:14 pm »
Colliding Black Holes May Sing Different Gravitational Songs

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This simple cosmic song may not be the only music these gravitational-wave emitters are capable of producing. At the American Physical Society April Meeting, held April 16 to 19 in Salt Lake City, Niels Warburton, a postdoctoral fellow at the MIT Kavli Institute, discussed simulations showing what kind of gravitational-wave "song" should be produced by collisions involving black holes that spin faster and are significantly larger than those that have been detected by LIGO.

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The two black holes that LIGO observed merged together and produced a "chirp" — that is, the frequency of the signal rose steadily, then was cut off abruptly when the two objects combined. But Warburton and his colleagues showed that fast-spinning black holes create a signal that reaches a peak frequency, and then starts to lower in frequency, before fading out.

"Instead of chirping, you get this kind of singing sound from the black hole," Warburton said. "It'll rise, it won't get cut off, it'll sing, and then it's quiet at the end."

"[It's] a completely different gravitational-wave signature … than what was detected [by LIGO]," he said. If a gravitational-wave detector picked up a signal that looked like the one the researchers' model describes, "you would know you were looking at a gargantuan system, something that is rotating extremely close to the maximum," he said.

This runs contrary to what scientists expected from a merger involving a very fast-spinning black hole, according to Jolyon Bloomfield, a lecturer at MIT, who presented research at the same press conference.

"It was certainly very unexpected to see something that didn't chirp," Bloomfield said, when asked during the press conference what he thought of the results. "Every template that we've seen so far … has had this beautiful, chirping feature, and we just assumed that [if we] make [the spin of the black hole] bigger … it chirps bigger. But this is quite interesting work that says no, the chirp actually goes away. Something else is happening here."

http://www.space.com/32723-colliding-black-holes-sing-different-songs.html
« Last Edit: 05/05/2016 05:14 pm by Star One »

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #132 on: 05/06/2016 05:13 pm »
Was gravitational wave signal from a gravastar, not black holes?

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“Our signal is consistent with both the formation of a black hole and a horizonless object – we just can’t tell,” says B. S. Sathyaprakash of Cardiff University, UK, who is part of the LIGO team. But if we can detect larger black holes merging, or a pair that is closer to us, it should settle the matter, he says. “That’s when we can conclusively say if the late-time signal is consistent with the merged object being a black hole or some other exotic object.”

Ultimately, the black hole explanation is likely to win out, but it is worth double-checking, says Pani. “As scientists, we try to play the devil’s advocate and not believe in paradigms without observational evidence.”

https://www.newscientist.com/article/mg23030724-100-was-gravitational-wave-signal-from-a-gravastar-not-black-holes/

Offline Rodal

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #133 on: 06/16/2016 02:20 pm »
LIGO and VIRGO announced a second observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes.

This event was much smaller than the first detection: The first event involved black holes that were 29 and 36 times as massive as the sun, while this new collision, which took place 1.4 billion years ago, brought together black holes of 8 and 14 solar masses.  While the first detection “jumped out” from the data, the researchers say, the second one was only noticed thanks to the analysis of specially developed software.

The detection of smaller black holes makes some LIGO researchers hope that they’ll soon detect the interactions of ultra-dense neutron stars, which are even less massive and very poorly understood.

The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences.  All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.


http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.241103

https://www.washingtonpost.com/news/speaking-of-science/wp/2016/06/15/ligo-scientists-announce-their-second-detection-of-gravitational-waves/

https://www.facebook.com/apsphysics/videos/10154335027472952/
« Last Edit: 06/16/2016 02:36 pm by Rodal »

Offline philw1776

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #134 on: 06/16/2016 07:44 pm »
These lower mass BHs & collision/mergers should be more common.  Hopefully lots of detections to come when they start up again this fall with increased sensitivity.
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Offline Eusa

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #135 on: 06/16/2016 08:34 pm »
Is the vibration after the merging meaningful?

Offline Stormbringer

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #136 on: 06/24/2016 04:39 pm »
sensitivity for these sorts of instrument may be about to take another quantum leap:

http://nextbigfuture.com/2016/06/russian-physicists-create-high.html

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June 23, 2016

Russian physicists create a high-precision 'quantum ruler'

Physicists from the Russian Quantum Center (RQC), MIPT, the Lebedev Physical Institute, and L'Institut d'Optique (Palaiseau, France) have devised a method for creating a special quantum entangled state. This state enables producing a high-precision ruler capable of measuring large distances to an accuracy of billionths of a metre. The results of the study have been published in Nature Communications.

When antigravity is outlawed only outlaws will have antigravity.

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #137 on: 06/29/2016 08:29 pm »
Event Horizon ringing damped by unstable space-time

Probing the event horizon of a black hole is not so easy.

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Now that gravitational waves have been detected, theoreticians have been furiously speculating about what we might learn from our gravitational wave observatories. Now that we have a couple of observed black hole collisions under our belt, it is time to consider what we might study. There's some speculation that, depending on the sort of physics at play, the event horizon of a black hole might be studied through gravitational waves.

For this to work, the gravitational wave signal has to change depending on what type of black holes are merging. A recent paper in Physical Review Letters indicates that, unfortunately, reality will probably not cooperate.

http://arstechnica.com/science/2016/06/event-horizon-ringing-damped-by-unstable-space-time/

Offline KelvinZero

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #138 on: 07/01/2016 11:42 pm »
People ask if this could revolutionise space flight. What if it discovered something like this in our vicinity? Something we hadn't been able to see before precisely because it wasn't shooting vast amounts of dangerous radiation our way?

http://www.centauri-dreams.org/?p=25605
The "Dyson Slingshot"
Two neutron stars, each with a diameter of 20 kilometers and a mass of one solar mass — and a combined orbital period of 0.005 seconds — would provide a departure velocity of 0.27 c

This was taken from my "dark matter planet/oberth effect" thread, but this example requires neither dark matter or oberth effect, is just more powerful and less hypothetical, and someone has apparently already done the math. It might be more interesting to discuss in terms of detection. Could we have missed an object like this and could gravity waves give us a way to detect it?



Offline bolun

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #139 on: 07/17/2016 08:08 pm »
Criticism for NASA.

Rainer Weiss laments NASA’s decision to pull of the space-based gravitational wave observatory LISA, and praises Europe’s determination to ‘go it alone’ with the eLISA mission and LISA Pathfinder. But he hopes for a new collaboration.

@DrStuClark Gravitational Waves sound like Radiohead's Planet Telex intro, from album The Bends. #spooky

https://mobile.twitter.com/ClickConsultLtd/status/697819704732291072?ref_src=twsrc%5Etfw

final question of the webcast press conference is whether LIGO has seen other signals. Gonzalez answers very carefully placing the emphasis back on the signal announced today. As she finishes one of her fellow panellists quips ‘that didn’t even sound rehearsed’.

Hmmm. What should we make of that?

http://english.nssc.cas.cn/ns/headline/201605/t20160518_163197.html

The 12th China-ESA Space Science Bilateral Meeting Opens in Shanghai

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In addition, both parties introduced the respective gravitational wave detection plans and agreed that there is a cooperation possibility in this area.

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