Milestone-Proposal talk:1972 - Rainer Weiss's Invention of the Gravitational Wave Antenna Used in the Large Interferometric Gravitational Observatory (LIGO)

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Comments on Milestone Proposal -- Jbart64 (talk) 20:17, 4 September 2019 (UTC)

I am the Milestone Advocate for this proposal. I have worked closely with the proposer and other supporters, and my comments are already incorporated into the final proposal. I fully support this proposal.

This Milestone focusses on the 1972 initial conception of the design for the LIGO gravitational wave antenna. The efforts to construct prototype antennas spanned multiple decades and occurred in multiple locations, leading up to the construction of world-class observatories that are sensitive enough to detect gravity waves from astronomical phenomena. Hence, three plaque sites are proposed. The goal is to dedicate the plaques at the three operational observatories to commemorate the fifth anniversary of the detection of gravitational waves.

Rainer Weiss’ original copyrighted design for a Laser Gravitational Wave "antenna" is described in his 1972 report entitled "Electromagnetically Coupled Broadband Gravitational Antenna," Quarterly Progress Report, Research Laboratory of Electronics, MIT. 105: 54, which is available at https://www.ligo.caltech.edu/system/media_files/binaries/385/original/Rais_IFO.jpg?1506978796. This paper is notable since Weiss described in great detail the design and promise of using laser interferometry to detect gravitational waves. The paper laid out in 22 pages the blueprint for the Laser Interferometer Gravitational-Wave Observatory, which Weiss called an antenna at that time.

The Milestone proposal includes several supporting source documentation items, although many more are available. The successful implementation of this achievement resulted in the Nobel Prize in Physics being awarded to Weiss and two others (Barry Barish and Kip Thorne of Caltech), who worked to further develop and implement the initial concept. Quoting the Caltech announcement about their Nobel Prize award: “Today, no one disputes the fact that LIGO owes its very existence to Rainer Weiss.” (see https://www.ligo.caltech.edu/news/ligo20171003) Yet, the Milestone proposal comports with Milestone rules and focusses on the initial date of the achievement rather than the person. It thus recognizes the origins of the overall gravitational wave antenna concept, while quietly implying the successful work and contributions of the many thousands of people who enabled its successful development and implementation.

Therefore, while this Milestone is intended to be installed only five years after LIGO’s historic detection of gravity waves, it acknowledges nearly 50 years of work from conception (1972), through design, planning, testing and prototyping, as well as decades of research and engineering, invention and innovation, advances in computing, lasers, and optics, and especially the contributions of Barish, Thorne, and Weiss.

Since becoming operational through December 2018, LIGO has detected 11 gravitational waves: 10 from binary black hole mergers, plus the first detection of a collision of two neutron stars in August 2017 which simultaneously produced optical signals detectable by conventional telescopes. All 11 events were observed in data from the first and second observing runs of Advanced LIGO. (see https://arxiv.org/abs/1811.12907) The Virgo observatory joined the search and, on 14 August 2017, jointly detected with LIGO a binary black hole merger, followed by a binary neutron star merger three days later.

The LIGO and Virgo facilities are now working together in detecting gravity wave candidates. Because gravity waves propagate at the speed of light (which was only recently verified using these antennas), the waves arrive at each antenna at different times. By resolving these timing differences, it is possible to localize from which general direction these signals originated, and to alert other observatories where to conduct a search for that specific event. Since beginning its third observing run through 31 July 2019, the LIGO/Virgo collaboration has detected 18 binary black hole merger candidates and 4 binary neutron star merger candidates. (https://www.ligo.caltech.edu/news/ligo20190812)

Dave Bart Milestone Advocate