LIGO gravitational wave announcement

Pixel42

Schrödinger's cat
Pixel42
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There have been rumours for weeks and mentions in at least one thread, but I think with a press conference just two days away it's time for its own thread.

Here's the Guardian's article:

https://www.theguardian.com/science...acetime-gravitational-wave-discovery-expected

A decades-long search for gravitational waves is expected to end in triumph this week when scientists declare they have discovered ripples in the fabric of spacetime, possibly created by the collision of two massive black holes travelling at close to the speed of light.

First predicted by Einstein, and generated by the most cataclysmic events in the cosmos, gravitational waves stretch and squeeze space and all within it as they spread out across the universe. Their discovery, if confirmed, is certain to earn a Nobel prize.

Scientists have hunted for signs of the waves for decades, but until now, their attempts have been frustrated by false signals and instruments that were not sensitive enough to detect the waves by the time they reached Earth.

That is expected to change on Thursday, when physicists in the US reveal their latest data from an experiment known as LIGO, or the Advanced Laser Interferometer Gravitational-Wave Observatory. The team have detectors in Washington and Louisiana that can spot passing gravitational waves via the minuscule changes in length they produce in two 4km-long pipes.

At a press conference in Washington, LIGO scientists are anticipated to reveal a clear, unambiguous gravitational wave signal. It may have come from two vast black holes, one 29 times more massive than the sun, the other 36 times more massive, spiralling around each other and finally crashing together to form a new black hole 62 times the mass of the sun. For all its heft, the new body may be no more than 200 miles wide.
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Well, I'm glad to see that on this island Earth, an advanced scientist finally constructed a working Interocitor Interferometer.
 
3point14 said:
Are there any potential, practical benefits from this?
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We usually discover this stuff first, and the practical benefits come later.

A few hundred years ago, people used amber to "prank" each other via static electricity. General Relativity was a cool thing, but most things that have since needed it weren't yet invented (like GPS).
 
DuvalHMFIC said:
We usually discover this stuff first, and the practical benefits come later.

A few hundred years ago, people used amber to "prank" each other via static electricity. General Relativity was a cool thing, but most things that have since needed it weren't yet invented (like GPS).
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Oh, don't get me wrong, this was not a prelude to rant against blue sky research.

GPS is my go-to for arguing in favour of such research (relativity and quantum theory both required.)

I was just curious.
 
There are many, many reasons gravity wave discovery will be awesome. First we get a GR test, then we get an astronomy tool---the rumor, in particular, corresponds to a type of binary black hole that's been predicted to arise only from the very earliest batch of stars in the Universe.

There is, however, an additional guilty pleasure I will take on top of that.

http://vixra.org/abs/1103.0048 said:
LIGO, LISA Destined to Detect Nothing

Authors: Stephen J. Crothers

It is claimed that the LIGO and LISA projects will detect Einstein's gravitational waves. The existence of these waves is entirely theoretical. Over the past forty years or so no Einstein gravitational waves have been detected. How long must the search go on, at great expense to the public purse, before the astrophysical scientists admit that their search is fruitless and a waste of vast sums of public money? The fact is, from day one, the search for these elusive waves has been destined to detect nothing. Here are some reasons why.
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Are these the same kind of stardust gravitational waves BICEP2 detected? If not, would there be any similar implications for inflationary cosmology?
 
constantine said:
Are these the same kind of stardust gravitational waves BICEP2 detected? If not, would there be any similar implications for inflationary cosmology?
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No. BICEP2 was looking for the imprint of primordial gravitational waves, which would have been sort of Big Bang leftovers whose wavelengths are a good fraction of the size of the Universe.

LIGO is looking for a burst of gravitational waves emitted, fairly nearby and fairly recently, by a pair of black holes or neutron stars merging. Shorter wavelengths (hundreds of kilometers), higher frequencies (kilohertz). It tells us about astronomy, not cosmology.
 
This could be useful in detecting supernovae before the light reaches us. Light has to pass through the interstellar/intergalactic media and so travels very slightly under the speed of light in an absolute vacuum. As far as we know, nothing impedes the progress of gravity waves.
 
BenBurch said:
This could be useful in detecting supernovae before the light reaches us. Light has to pass through the interstellar/intergalactic media and so travels very slightly under the speed of light in an absolute vacuum. As far as we know, nothing impedes the progress of gravity waves.
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Supernovae are much more nearly spherically symmetric than compact-object mergers, so they're comparatively weak gravitational wave sources; even far-future detector proposals (LIGO upgrades, DECIGO, LISA) could only be sensitive to supernova GW from within the Milky Way---and that means the events will be very rare, one or two per century. (LIGO can search for mergers from thousands of nearby galaxies.)

There is a delay between gravity waves, neutrinos, and light from a supernova, but it's not the interstellar medium---it's the star itself. At the time the GW-emitting part of the supernova is going on, there's still most of a star's worth of hydrogen around it, feeling the impact of various shocks and radiation pressure forces and deciding which way to go. After the GW event has passed, the system still takes a second or so to become transparent to neutrinos, and a few hours to release photons. After that, though, all three components travel through the ISM at speeds indistinguishable from c.
 
Useful background article on the BBC news website: http://www.bbc.co.uk/news/science-environment-35533241

If detection of these waves is now a reality, we are at the beginning of a new era in astronomy - especially once three detectors are online, allowing the source of the ripples to be triangulated.

Gravitational waves will join the myriad types of light, plus some particles like neutrinos, that scientists already use to probe the far reaches of the universe.

Crucially, because they travel straight through matter, nothing can obscure the source of these waves - there are no shadows. And they could offer an unparalleled "view" of objects that don't emit light, like black holes.

This is why gravitational astronomy has been described as listening to, rather than looking at, the cosmos.

Tuck Stebbins, from Nasa's Goddard Space Flight Center, told the AFP news agency that gravitational waves could even be a window - in fact, the only possible window - on the origin of the universe.

"These waves are streaming to you all the time and if you could see them, you could see back to the first one trillionth of a second of the Big Bang," he said.
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Now this is the sort of thread that makes this forum special for me, and why I always find myself coming back, despite everything.

Thanx for the E :D
 
Nice opening to the livestream: "Ladies and gentlemen, we have detected gravitational waves. We did it."
 
So far:

The signal was detected on September 14, 2015.
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It was “exactly” what Einstein’s theory predicted for two colliding black holes.
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The two black holes are indeed about 30 solar masses. They are about 1.3 billion light years away.
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This detection is proof that binary black hole systems can exist. Each black hole was about 150km in diameter. Each contained 30 solar masses and was accelerated at about half the speed of light. That is what collided. “It’s mindboggling,” says Reitze.
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Being 1.3 billion light years away means that these black holes collided 1.3 billion years ago. The gravitational waves have been travelling through space for 1.3 billion years. When they arrived at Earth on 12 Sept. 2015, they caused the LIGO machinery to move by 1/1000 of the width of a proton particle. LIGO detected it. Amazing.
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We are going to see things that we never knew existed, predicts Reitze, who goes on to call LIGO a ‘scientific moonshot’, likening it to the Apollo moon landings of the 1960s.
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https://www.theguardian.com/science...latest-physics-einstein-ligo-black-holes-live
 
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Positively brilliant. And they had never seen such an event before ....luck favours the prepared mind....in this case the prepared science community. :thumbsup:



The two detectors...Perhaps as significant as the CBR....maybe more.
 
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Bit more:

The tell-tale signal can be seen by just by eye rising above the noise of the detector. It was detected first in the LIGO Livingston detector. The clincher was that 7 milliseconds later the same signal was seen in the Hanford LIGO detector. The time delay was produced by the gravitational waves travelling in a particular direction
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The signals correspond very well indeed to a theoretical model produced by Einstein’s relativity. There is little to no ambiguity in this detection.
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The signal came from the Southern sky, in the rough direction of the Magellanic clouds, the satellite galaxies of the Milky Way. At 1.3 billion light years away, however, it is very far beyond the Magellanic clouds, deep in intergalactic space somewhere.
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“This is the first of many to come,” says González. We can now listen to the Universe.
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https://www.theguardian.com/science...latest-physics-einstein-ligo-black-holes-live
 
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I think the most staggering part is this (source is that in ohms post):
About 3 times the mass of the sun was converted into gravitational waves in a fraction of a second—with a peak power output about 50 times that of the whole visible universe.
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BREAKING NEWS:

"Minor earth tremor in Australia attributed to Stephen Crothers repeately banging head against wall, before removing said head with double-barrelled shotgun. More to follow."

Sorry, I might have made that up.
 
The BBC version.

And from it:

"Gravitational waves go through everything. They are hardly affected by what they pass through, and that means that they are perfect messengers," said Prof Bernard Schutz, from Cardiff University, UK.
"The information carried on the gravitational wave is exactly the same as when the system sent it out; and that is unusual in astronomy. We can't see light from whole regions of our own galaxy because of the dust that is in the way, and we can't see the early part of the Big Bang because the Universe was opaque to light earlier than a certain time.
"With gravitational waves, we do expect eventually to see the Big Bang itself," he told the BBC.
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jonesdave116 said:
BREAKING NEWS:

"Minor earth tremor in Australia attributed to Stephen Crothers repeately banging head against wall, before removing said head with double-barrelled shotgun. More to follow."

Sorry, I might have made that up.
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Actually, I imagine he is probably in a bar somewhere (or will be soon), searching for a way to spin this to make him look smokingly good and criticize the mainstream yet again. It's not often that hucksters admit they're wrong, after all.
 
I presume people all over the world are already planning "Super-LIGO"?
 
MikeG said:
I presume people all over the world are already planning "Super-LIGO"?
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According to Kip Thorne:
Thorne says that we expect to see more signals from similar sources within the next year. Tweeks and improvements will advance LIGO’s sensitivity by about three times. He promises, “A huge richness of gravitational wave signals in LIGO.”
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Hmmm, according to the Guardian blog/ tweety thing:
The 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?

According to New Scientist, who have done some sleuthing in publicly available observatory logs, LIGO may be investigating another two signals, detected in December 2015.

Let’s wait and see.
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I think the news is most exciting. I'm so very glad it has happened while I'm alive! I'll be watching and listening for
many years I hope.
 
Paper available here: http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102

Up sum from the Guardian:

On 14 September 2015 at 9:50 GMT, the two detectors of the newly upgraded Laser Interferometer Gravitational Wave Observatory (LIGO) detected a signal.

It was unambiguously a gravitational wave signal because it matched the predictions from Einstein’s general theory of relativity almost precisely.

A gravitational wave is a ripple in the invisible fabric of the universe, called the spacetime continuum. The particular ripple moved the LIGO detectors by about one thousandth the width of a proton (the tiny particle found at the heart of a hydrogen atom).

It was generated by two black holes that collided 1.3 billion light years away. The masses of the individual black holes were large, at around 36 and 29 times the mass of the Sun each. They were just 150km across each, and collided at half the speed of light.

The merger formed a single black hole of 62 solar masses. The missing three solar masses of matter were transformed into the energy that powered the gravitational waves detected by LIGO.

This transforms the way in which we can observe the Universe, and is expected to lead to the discovery of unanticipated celestial objects.
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https://www.theguardian.com/science...latest-physics-einstein-ligo-black-holes-live
 
BenBurch said:
This could be useful in detecting supernovae before the light reaches us. Light has to pass through the interstellar/intergalactic media and so travels very slightly under the speed of light in an absolute vacuum. As far as we know, nothing impedes the progress of gravity waves.
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If nothing impedes the progress, how is it detected? How does it affect mass? Are they detecting the ether moving?

I'm trying to imagine something that affects mass but is not affected by mass.
 
Space is warped and the interferometer picks up the "bend" as the wave passed...You need to look at the youtube videos.
I think you need some catch up on your gravity/space/time/mass and energy concepts.

Here is a good pre-discovery article
http://scienceblogs.com/startswithabang/2010/08/25/what-is-the-speed-of-gravity/

It's related to gravitational lensing

2006-0523-lens-full.jpg

Quintuple quasar gravitational lens. Image credit: Hubble
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he background quasar is the brilliant core of a galaxy. It is powered by a black hole, which is devouring gas and dust and creating a gusher of light in the process. When the quasar’s light passes through the gravity field of the galaxy cluster that lies between us and the quasar, the light is bent by the space-warping gravity field in such a way that five separate images of the object are produced surrounding the cluster’s center. The fifth quasar image is embedded to the right of the core of the central galaxy in the cluster. The cluster also creates a cobweb of images of other distant galaxies gravitationally lensed into arcs.
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http://www.universetoday.com/8200/hubbles-best-gravitational-lens/

Space is bent by the mass of the galaxy in front of the quasar so the light "curves".

In this case....the "ripples" from the gravitational collapse move out like the ripples on a pond...it was predicted but up until now we had no way to detect them..huge scientific breakthrough. On a scale with the discovery of the residual background radiation from the big bang.

If the earth suddenly disappeared with a pop....it would produce a gravity wave.

That's what happened here on a much larger scale.....an enormous amount of mass was converted into energy in a tiny fraction of a second....energy equivalent to 50 times the output of all the stars in the universe.....that's the scale of this event. :boggled:

That caused the gravity wave.

The back story ....cool read
http://www.sciencemag.org/news/2016/02/here-s-first-person-spot-those-gravitational-waves
 
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Skeptic Ginger said:
If nothing impedes the progress, how is it detected? How does it affect mass? Are they detecting the ether moving?

I'm trying to imagine something that affects mass but is not affected by mass.
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By using light.

A more sensitive class of detector uses laser interferometry to measure gravitational-wave induced motion between separated 'free' masses. [...] Each observatory has two light storage arms that are 4 kilometers in length. These are at 90 degree angles to each other, with the light passing through 1 m diameter vacuum tubes running the entire 4 kilometers. A passing gravitational wave will slightly stretch one arm as it shortens the other.
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Even with such long arms, the strongest gravitational waves will only change the distance between the ends of the arms by at most roughly 10−18 meters.
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https://en.wikipedia.org/wiki/Gravitational_wave#Ground-based_interferometers

ETA: This might be better: How does LIGO look for gravitational waves?.

Each detector looks like a giant “L” stamped on the landscape – two four-kilometre arms at right angles to one another.

Inside each arm is a tunnel carrying a laser beam.

The laser bounces up and down each arm of the detector before recombining at a detector.

Any expansion of one of the arms relative to the other will shift a mirror slightly, changing the pattern revealed on the detector.
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