By James Riordon

The LIGO (Laser Interferometer Gravitational-Wave Observatory) laboratories in Livingston, Louisiana and Hanford, Washington were declared APS Historic Sites in a ceremony on June 20 at the Livingston LIGO Science Education Center. APS President Roger Falcone and APS Historic Sites Committee Chair Paul Halpern presented the labs with identical plaques, each bearing the citation shown in the figure.

LIGO Executive Director David Reitze noted that the LIGO historic site designation is unusual, considering that most other APS Historic Sites recognize events that took place decades ago. “When I first received word … that we had won this award,” said Reitze, “I was initially quite surprised because, I thought to myself, well we made these discoveries three years ago. ... But then I thought about it a little bit more. And I realized that, no, this was exactly the right thing to do because even though LIGO burst onto the scene … in 2015, this is something that’s been going on for a long, long time.”

Reitze pointed out that the National Science Foundation (NSF) began providing funding to Rainer Weiss to develop prototypes for LIGO over forty years ago. Weiss shared the 2017 Nobel Prize in Physics with Kip Thorne and Barry Barish. Construction of the LIGO sites began in 1995, and after running with the initial design parameters from 2002 to 2005, the observatories were upgraded to current sensitivities during the Advanced LIGO (ALIGO) construction phase that began in 2010.

The ALIGO upgrade was completed in 2015, and, said Reitze, “Literally, almost the day we turned on our detectors we detected the first gravitational waves from these colliding black holes.”

LIGO plaque

The LIGO facilities in Washington and Louisiana have been designated APS Historic Sites and will each receive a plaque honoring its contributions to direct detection of gravitational waves.

The LIGO labs are the 41st entry into the APS Historic Site ledger, which was signed by Roger Falcone on behalf of APS and David Reitze on behalf of LIGO. It is the first entry to be accompanied by dual plaques, in recognition of the joint contribution of the LIGO labs, located over 3,000 kilometers apart. Each plaque includes inscribed depictions of the gravitational wave signals as detected at the respective laboratories.

Michael Landry, Observatory Head of the LIGO Hanford laboratory, noted with a laugh that the Livingston facility is listed first on the plaques, and Hanford is second, rather than conventional alphabetical order. “I think that order is a nod to the order in which the signals were received,” said Landry. “I find it a little ironic that it took 1.3 billion years for that signal to get here, and yet when it was detected by the sites it was separated by 6.9 milliseconds.” The difference in arrival time gives Livingston a one part in 10¹⁹ priority as the first site to detect gravitational waves.

In gratitude for the NSF’s decades of support for gravitational wave research, Rainer Weiss presented NSF Director France Córdova with a photograph of Vannevar Bush at work cutting aluminum on a milling machine. Bush, explained Weiss, advised Franklin Roosevelt on scientific matters, and was crucial to founding the NSF. Weiss said that in the book Science, the Endless Frontier, Bush noted reasons that government should support science. As he handed the photograph to Córdova, Weiss said, “You’ve done very well.”

The APS Historic Site plaques will be mounted on rock native to the respective LIGO observatory locations outside the front entrances to the observatories’ visitor buildings.

The author is APS Head of Public Relations.

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