Thursday, February 11, 2016

gift of nature

Watched the webcast from the National Science Foundation regarding the detecting of gravity waves from the USA-based LIGO detectors.

On 14 Sept 2015, even before the official science run had begun, the Laser Interferometer Gravitational-wave Observatories detected a strong signal. And it was exactly what Einstein had predicted.

The event was from a binary black hole merger 1.3 billion years ago. The black holes were about 30 solar masses each. Like a stone dropped in a smooth lake, ripples went out.

The 4 kilometer long interferometer at LIGO can accurately detect very tiny shifts in gravity, on the order of 1/1000th the diameter of subatomic particles.

David Teitze, the LIGO lab executive director started the press conference. He acknowledged the funding from NSF. He noted that in the future the detectors may be able to detect 100 or 500 stellar mass black holes as the sensitivity is increased.

Gabriela González, research scientist at Louisiana State University and spokesperson for the LIGO Scientific Collaboration, described the two detectors, called Hanford and Livingston. She talked about the brief signal, less than a 1/10th of a second, being first observed in Livingston. The space-time "strain" or deformation was very minute, on a scale of of 10-21. Then, 7 milliseconds later, the signal appeared in Hanford detector! A "gift of nature."

They have been able to infer extraordinary detail from the signal detections:
  • the black holes were 29 and 36 solar masses
  • the resulting single black hole had 62 solar masses
  • there 3 solar masses were emitted in energy
  • the distance was 1.3 billion light-years
  • the frequency of the event is in the range of human hearing (slowed down it sounds like a chirp)
  • they localised the signal to the southern sky in the direction of the Magellanic clouds
Gabby spoke of more instruments. The GEO600 was a pathfinder system. The VIRGO in Europe will be online later this year. The KAGRA in Japan is due in 2018 or 2019. And still more are planned.

Rainer "Ray" Weiss, a LIGO co-founder, discussed some history and the detector design. He was key in considering how to eliminate noise from detection. He is thrilled to see Einstein's field equations validated.

He spoke briefly of the LISA Pathfinder in space now and that he hopes to see increased collaboration between ESA and NASA.

Kip Thorne, another LIGO co-founder, spoke as well. He made the analog to watching a glass-smooth ocean and that they happened to be present to see a storm. The merger-collision took 20 ms and produced 50 times the power of all stars in the Universe.

He emphasised the LIGO system is still at only 1/3rd of its rated capacity and they are anticipating more detections this year. Regardless, this event gives us a much deeper understanding of highly warped space-time. This also places limits on the theoretical graviton mass.

Ronald Drever, the Scottish experimental physicist and third co-founder was ill and could not attend.

Dr France Córdova of the NSF recognised contributions by the UK, Germany, and Australia. The results were made possible by a world-wide village.

Caught a question by our own Ivan Semeniuk. He noted that these were fairly large black holes. He was curious what this meant for the future. Gabby emphasised these were stellar mass black holes, relatively small, compared to others, compared to super-massive systems in the cores of galaxies. A fascinating aspect is that these objects could not be seen in electromagnetic range; now they are "visible." That's it right there. LIGO opened a window.

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