Gravitational Waves - a highly anticipated 'Update' tomorrow

[ack]

Rumors have been flying high ever since the tweet below surfaced, and lots of people anticipate an announcement that gravitational waves (as predicted by Einstein) have been observed, from two black hole merging into each other. The announcement is scheduled for tomorrow, and this could be big, but my sense is it will be carefully worded that there are strong indications and that more observation is required. Rumors started appearing as early as September 25 2015, just a short while after LIGO got a major upgrade...

http://news.discovery.com/space/more-gravitational-wave-rumors-colliding-black-holes-160208.htm
https://www.washingtonpost.com/news...ke-a-big-announcement-on-gravitational-waves/
http://www.bbc.com/news/science-environment-35533241

 

[ack]

Announcement of the press conference http://www.ligo.org/news/media-advisory.php

 

[Joe Whip]

This would be fantastic news!

 

[amirm]

Most exciting! For those of you are not into astrophysics, gravitational waves are exactly that: waves that propagate as gravitational forces. As they pass objects they cause them to oscillate (due to space time curvature changing around them). If we can successfully detect them we will be able to observe phenomena very closer to the birth of the universe. We can't do that with current detection methods involving electromagnetic fields because at the birth of the universe, it was too opaque for them to propagate.

The trick up to now has been to detect the wave at its very low levels. If we have accomplished that based on this observation, it will be a big deal.

 

[RayDunzl]

"LIGO's detectors are searching for gravitational waves emanating from the depths of space. Gravitational waves are the evanescent vibrations of space-time generated by some of the most violent explosions and events occurring in the Universe; events like supernovae (exploding stars) and the collision and merger of black holes and neutron stars (the remnants of massive stars after their thermonuclear deaths).

These events are so cataclysmic that when they occur, they cause the very fabric of space itself to vibrate like a drum. The waves of rippling space-time emanate in every direction, traveling at the speed of light, physically distorting everything in their paths. But the farther they travel from their source, the smaller and smaller the ripples become until, by the time they reach the Earth, the spatial distortion caused by the waves is on the order of a billionth the diameter of an atom! This unimaginably small movement is what LIGO’s detectors are designed to sense."

Maybe we can get them to settle some audio questions after hours.

https://www.ligo.caltech.edu/news/ligo20150918

 

[amirm]

Wow. And I thought my ears were sensitive.....

 

[853guy]

"LIGO's detectors are searching for gravitational waves emanating from the depths of space. Gravitational waves are the evanescent vibrations of space-time generated by some of the most violent explosions and events occurring in the Universe; events like supernovae (exploding stars) and the collision and merger of black holes and neutron stars (the remnants of massive stars after their thermonuclear deaths).

These events are so cataclysmic that when they occur, they cause the very fabric of space itself to vibrate like a drum. The waves of rippling space-time emanate in every direction, traveling at the speed of light, physically distorting everything in their paths. But the farther they travel from their source, the smaller and smaller the ripples become until, by the time they reach the Earth, the spatial distortion caused by the waves is on the order of a billionth the diameter of an atom! This unimaginably small movement is what LIGO’s detectors are designed to sense."

Maybe we can get them to settle some audio questions after hours.

https://www.ligo.caltech.edu/news/ligo20150918

Well, it's certainly a lot easier to save $30K for an Audio Precision and make the same measurements we've always been making, than it is to build two dedicated $620 million facilities in the hope we might find something new.

It's exciting news though. Looking forward to what the report has to say.

 

[ack]

The claim is that:

Gravitational waves HAVE indeed been detected.

Two colliding black holes produced the gravitational waves.

The signal was detected on September 12, 2015.

It was “exactly” what Einstein’s theory predicted for two colliding black holes.

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.

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.

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.

The signals correspond very well indeed to a theoretical model produced by Einstein’s relativity. There is little to no ambiguity in this detection.

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.

“This is the first of many to come,” says González. We can now listen to the Universe.

 

[Al M.]

Wow.

 

[Steve Williams]

Truly fascinating stuff

 

[Steve Williams]

watch the press conference live NOW

 

[amirm]

Fantastic development. Just as much for science of measurement and for understanding of our universe. What great news to wake up to. Thanks Ack.

 

[853guy]

Cool!

Albert Einstein I salute you.

 

[amirm]

A bit about Hanford LIGO observatory which is in our neck of the woods: http://www.nsf.gov/news/news_images.jsp?cntn_id=137628&org=NSF

"At each observatory, the 2 1/2-mile long L-shaped LIGO interferometer uses laser light split into two beams that travel back and forth down the arms. The beams are used to monitor the distance between mirrors precisely positioned at the ends of the arms. According to Einstein's theory, the distance between the mirrors will change when a gravitational wave passed by the detector."

Pretty clever use of length/distance to magnify movement. Trick I am sure is to isolate all the natural sources of vibration and noise.

 

[DaveC]

A bit about Hanford LIGO observatory which is in our neck of the woods: http://www.nsf.gov/news/news_images.jsp?cntn_id=137628&org=NSF

"At each observatory, the 2 1/2-mile long L-shaped LIGO interferometer uses laser light split into two beams that travel back and forth down the arms. The beams are used to monitor the distance between mirrors precisely positioned at the ends of the arms. According to Einstein's theory, the distance between the mirrors will change when a gravitational wave passed by the detector."

Pretty clever use of length/distance to magnify movement. Trick I am sure is to isolate all the natural sources of vibration and noise.

I wonder what isolation devices they use?

 

[spazmatron]

What gets me with these types of experiments and discoveries is that all the while this is going on we still have naked tribes in the rain forest.. Throwing spears and running free through the woods.

Then of course everything in between.

 

[ack]

The race is on who's going to report it first in detail. So the NYTimes appear to be the ones - watch the video

http://www.nytimes.com/2016/02/12/science/ligo-gravitational-waves-black-holes-einstein.html

 

[amirm]

I wonder what isolation devices they use?

The Internet has answer for everything . It says they use both passive and active isolation mechanisms: https://www.ligo.caltech.edu/LA/page/vibration-isolation

"Vibration Isolation
For an instrument that needs to remain as still as possible, it is ironic that LIGO is so sensitive that it can feel the smallest vibrations from near and far. LIGO is essentially a giant seismometer capable of sensing vibrations from traffic on nearby roads, weather patterns on the other side of the continent, staff biking alongside detector arms, ocean waves crashing on shores thousands of miles away, and of course nearly every significant earthquake on the planet. Since gravitational waves will make themselves known through vibrations in LIGO's mirrors, the only way to make gravitational wave detection possible is to isolate LIGO's components from environmental vibrations to unprecedented levels. The change in distance between LIGO's mirrors (test masses) when a gravitational wave passes will be on the order of 10-19 m. To achieve this level of sensitivity, LIGO was constructed with multiple levels of active and passive vibration isolation systems. Many of LIGO's larger infrastructure systems that provide some additional levels of isolation are discussed in previous sections. But LIGO's most sensitive components (its optics) required even more complex and highly specialized mechanisms for isolating them from even the smallest imaginable vibrations.

Outside of its pre-stabilized laser, LIGO's vibration isolation systems are comprised of two basic elements: Optics Suspensions and Seismic Isolation.

Optics Suspensions (Passive Isolation)

LIGO's mirrors must be so well shielded from vibration that the random motion of the atoms within the mirrors and their housings can be detected. To achieve this level of shielding, each of LIGO's 40 kg test masses is suspended within a 360 kg quadruple pendulum system (or 'quad'). This system of multiple pendulums significantly reduces motion at the level of the test masses where it really counts. Suspensions make use of both passive and active vibration isolation components.

[...]

Seismic Isolation (Active Isolation)

The first line of defense against vibration is LIGO's "active" damping system. In contrast to Initial LIGO's instrument, where optics were located on top of seismic isolation platforms, the Advanced LIGO instrument suspensions are mounted below in- and out-of-vacuum active vibration/seismic isolation systems, giving them the quietest possible environment for operation.

Internal seismic isolation platforms (ISIs) employ position- and vibration-sensors tuned to different frequencies of environmental vibrations, along with permanent-magnet actuators that work together to counteract ground movements keeping the instrument virtually motion-free. This level of isolation can reduce the magnitude of vibrations introduced to the suspensions (at the point of their attachment to the ISI) to a level of at most 2x10-13 m. The suspensions do the rest, reducing this noise level nearly six more orders-of-magnitude to achieve LIGO's desired detection sensitivity of 10-19 m."

Wonder what our turntables would sound like when designed this way!!!

 

[ack]

The press conference, may want to jump to 5:00

 

[amirm]

Halfway through watching it. It is incredibly exciting and awe inspiring. And remarkable connection to what we do in discovering waveforms from billion+ year past that is in audible band!