July 30, 2014

LIGO: A Quest for Gravity Waves.

LIGO, Livingston. (All Photos by Author).
LIGO, Livingston. (All Photos by Author).

We had to go there… last month’s NASA Tweetup at the Johnson Spaceflight Center saw us undertake the great American road trip from Astroguyz HQ north of Tampa, Florida, to Houston on the other side of the Gulf of Mexico and back. Ever the opportunists, we scoured the route for any astronomical pilgrimages of note. Then, like a bolt from the sky, a lone commenter drew our attention to a recent news piece we did on LIGO, the Laser Interferometer Gravitational-Wave ObservatoryA quick search of Google Earth made me realize that our projected “flight path” would take us right past the Livingston, Louisiana facility.  Anyway, the commenter had mentioned that LIGO has yet to detect gravity waves, so we decided to hit the road and find out for ourselves…

The author and staff with a replica of a LIGO focusing lens.

Author & staff with a LIGO lens.

Situated in backwoods Louisiana just outside of Baton Rouge, LIGO is a unique observatory in an improbable, un-astronomy-like location. No remote windswept mountains here, just two curious arms of concrete and steel trailing off into the wilderness. One of two such detectors in the country, it shares a 1,865 mile baseline with its sister facility in Hanford, Washington. The first of their kind in terms of Laser Interferometry, their mission is simple yet demanding; to search for gravity waves. First proposed by Albert Einstein in 1916, the capability to detect such waves given off by merging pulsars, supernovae or black holes has just emerged in the last decade. Earlier searches have been conducted by resonant mass bar detectors in the 1960’s. Three additional interferometric detectors have been established worldwide: Virgo outside of Pisa, Italy, one near Kamioka, Japan, and the GEO600 in Hanover, Germany. One additional detector in Australia has been proposed. LIGO is the brainchild of  Rainer Weiss and a joint project of Caltech and MIT, and is one of the largest NSF projects ever undertaken, an awesome project for the world of physics. The existence of gravity waves was proven in the 1970′s by examination of the Taylor-Hulse pulsar (PSR 1913+16), which was the recipient of the 1993 Nobel Prize in physics. Direct detection of gravity waves would no less than open a new window on the universe. It would also be prime Nobel material, as well as just  plain cool…

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Engineers work on Advanced LIGO.

We may have been the first visitor to plan their stay overnight in nearby Walker with the specific goal of visiting LIGO. Our contact with Science Education Center program leader William Katzman was outstanding; he and the rest of the LIGO staff were thrilled and enthusiastic. Postdoctoral Scholar Amber Stuver was our guide, and we were granted an almost unrestricted access and personalized tour of this cutting edge facility.

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LIGO control room.

Data for LIGO is painstakingly gathered by measuring minute changes in the interference pattern of laser beams reflected down the two 4 km long arms. (has anyone ever thought of a “LIGO 8K run?”) Accuracy is exacting; LIGO can detect changes as small as 1/1,000th of the diameter of a proton!  Needless to say, they also must account for interference from everything, from earthquakes worldwide to the local delivery truck at the door…

LIGO is also a unique place to see theoretical physics in action, and houses a first class museum with hands on physics displays, to boot. We were amazed to see grad students at the helm, expertly “manning the comm.” of such an advanced facility. It was a big shift from NASA’s button-down shirt and tie environment of Mission Control in Houston the day before… the atmosphere was more reminiscent of The Big Bang Theory. Seriously, Sheldon would’ve felt right at home… and it shows kids (and parents) that you can have a punk rock outlook and still be an astrophysicist.

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One of LIGO’s Fabry-Perot  arms as seen from the roof.

Why the multiple detectors? Well, the reason is two-fold. One is to rule out terrestrial interference; an Earth-bound source would not shake all detectors simultaneously. A second reason is that multiple detectors give us the ability to gauge the direction of the prospective incoming gravity wave with some accuracy against the celestial sphere. Remember, like neutrinos, gravity waves can travel right through the bulk of the planet, and therefore can approach the detectors from underneath, as well.

Besides searching to make the first direct detections of  gravity waves, LIGO is expected to reveal key properties of the elusive graviton, such as its theoretical zero rest mass and its spin rate, which is expected to be twice that of a photon. Binary pulsar collisions are predicted to occur once every 10 years or so; this source is a prime canidate for a first detection. LIGO recently completed a two year data run with a goal of collecting one year’s worth of cumulative data. The earthquakes in Chile and Haiti were felt and recorded by the detectors. LIGO also generates copious amounts of seismic data that is available online; they even show a sharp spike in activity when the daily rush hour occurs!

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Warning vibration sensitive measurements underway!

Rarer still, LIGO may detect the merger of two black holes. This would be a strict test for the Theory of General Relativity; a close binary pair of black holes should generate massive amounts of gravity waves. Other surreptitious discoveries might be in the offing, such as the detection of pulsars spawned by supernovae and star-quakes on the same… and like any emerging field of astronomy, who knows what else is waiting to be discovered… LIGO has even given us some lower constraints on the early universe, and may prove to show us the first observational evidence proving or disproving String Theory.

But not satisfied with this uber-creation, physicists are casting their eyes on even more exotic instruments. Advanced LIGO is an upgrade to the existing system that is expected to go online in 2014. This upgrade will increase LIGOs sensitivity ten-fold.  Further afield, plans are on the drawing board for a joint NASA ESA space mission known as LISA, or the Laser Interferometer Space Antenna. LISA calls for a constellation of three reflectors placed in an Earth trailing solar orbit at a 20° degree offset. LISA’s three 5 million kilometer arms would form a huge Michelson interferometer and probe the gravitational wave universe in unprecedented detail. LISA is very ambitious and is not, however, expected to launch until 2018 at the earliest.

If you find yourself  looking for something off-beat to do in the Baton Rouge area, do make an effort to get out to LIGO; an open house style “Science Saturday” is held every third Saturday of the month. They’re off of exit 22 north-bound, and signs make it an easy find.  And we’d like to send out our appreciation to the folks at LIGO: the staff was more than helpful in providing my wife and I a tour this unique and little known piece of cutting edge science!

Einstein@Home Screenshot!

Screenshot of Einstein at Home!

NOTE: And don’t forget: YOU can participate in the search for gravity waves the Astroguyz way; by running the http://www.einsteinathome.org/screensaver!

Comments

  1. Jacob Slutsky says:

    Hi, I would like to use the image of the LIGO sign on this page in a talk. For some reason, I couldn’t find your contact email listed anywhere.

Trackbacks

  1. [...] are the use of liquid metal (mercury in a precisely rotated dish!) telescopes, and of course, the Laser Interferometry Gravitational wave Observatory, a “telescope” used to hunt for gravity [...]

  2. [...] of this space will recall our past visit to the LIGO facility based in Livingston, Louisiana as well as frequent news posts reported in this space such as the constraints that the sensitivity [...]

  3. [...] pulsar and/or black hole mergers. Cosmology is really coming on to its own, as new instruments like LIGO and Ice Cube may soon give us complimentary views on the sky in both gravity waves and neutrino [...]

  4. [...] Laser Interferometer Gravitational wave Observatory (LIGO) is a pair of detectors based in Livingston, Louisiana and Hanford, Washington that hunts for [...]

  5. [...] written about the Laser Interferometer Gravitational Wave Observatory (LIGO) before. LIGO consists of a pair of [...]

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