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The Scottish Connection

The search for gravitational waves has taken decades to produce its first results ...…

The Scottish Connection

The Scottish connection

The search for gravitational waves has taken decades to produce its first results, involving hundreds of scientists from countries all over the world. There are currently four people with PhDs from the University of Glasgow working in LIGO at the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT) and Professor Norna Robertson is one of that select group who has worked on the project in both Scotland and the US – not just bridging the Atlantic but also generations of researchers.

Q: How long have you been doing research into gravitational waves, and how long have you been part of LIGO at Caltech? Who have been the major influences on your career?

A: I started doing research into gravitational-wave detection as a PhD student in 1977 in Glasgow. Apart from two years as a post-doc in infrared astronomy, I have worked in the field of gravitational waves throughout my career. I joined LIGO at Caltech ten years ago, in 2007.

My PhD supervisors were Ron Drever and Jim Hough. However, Ron started his visits to Caltech (spending six months a year there) just a few days after I started my PhD, so de facto Jim was my supervisor – and a major influence in my career. Also, both my parents were scientists at the University of Glasgow (though neither were physicists) and they were definitely strong role models for me.

Q: Why is the search for gravitational waves so important? Why does it matter? What excites you most about it?

A: I guess one of the things which has excited me most about working in this field was the fundamental nature of what we were trying to achieve – verifying one of Einstein’s predictions, and opening a new field of  astronomy. And I enjoyed the challenge of making such incredibly sensitive measurements, where we were pushing the bounds of physics and technology in every aspect of our work.

Q: What do you think the project will lead to in future – ten years from now and 100 years from now?

A: In the next ten years, I look forward to seeing what new astronomy comes out of our detections. We will certainly see more black hole binary mergers and learn about their likely evolution, but we should also be detecting other sources, including some we haven’t yet conceived of. Just think what a field day that will provide for our theorists! In the 15-to-20- year timescale, the Space-based LISA project, working at much lower frequencies, should complement the work of ground- based detectors by detecting different sources and giving us new insights into the Cosmos. As for 100 years from now – who knows?

Q: Can you describe the role of the suspension systems in LIGO? How important are the suspension systems? Would LIGO have succeeded without the current design/with a different design?

A: Each suspension system, nicknamed the quad, consists of four cascaded stages of pendulums whose bottom mass is the test mass – the mirror whose motions we monitor when looking for gravitational waves. The quad provides more than a factor of a million isolation for the mirror from residual seismic noise, and is designed to minimise another fundamental source of noise – thermal vibrations in the suspension itself. Thermal noise reduction is achieved using very delicate, ultra-low- noise, silica fibres to support the silica mirror, and hence the lowest stage of the assembly is described as a monolithic silica suspension. The original LIGO suspensions consisted of a single stage pendulum, with the mirror hanging on steel wires. With that suspension we could not have achieved the noise performance that was needed to make our first detection.

Q: What are you most proud of in your own work – your own contribution to LIGO?

A: It is has been a long, long road since I started as a young research student 40 years ago. There have been  many challenges, and not just the formidable scientific and technological ones. Support for our work has ebbed and flowed over the years, but we kept going. Perhaps perseverance is one of my biggest contributions to the field!

Q: You headed a large team as both manager and scientific researcher. How did you combine these roles? Which role do you prefer?

A: I did manage a large team when I headed the Suspensions team for the Advanced LIGO project. In that position I was responsible for overseeing the design, fabrication, assembly and installation of the multistage suspensions supporting all the major optics in both Advanced LIGO detectors, including the quads described above. The work involved coordinating and managing a team of approximately 40 scientists, engineers and technicians from eight institutions within the USA and the UK. Given the UK involvement and the eight-hour time difference, this led to many early morning telecons, and a lot of travel! During that time I did not do much research, but I enjoyed the challenge of keeping the team working together, and felt a great sense of satisfaction when the final suspension was installed into the detector. It is fair to say I have enjoyed both aspects of my work over the years.

Q: How would you describe your experience as part of such an international team?

A: I enjoy the international aspects of my work. My job has taken me to countries all round the world, for meetings and conferences and collaborative work, and generally I enjoy travel. I have always felt welcome in the USA (a Scottish accent is a definite plus!).

Q: How did you feel when you first learned that LIGO had detected gravitational waves? When did you hear the news and how long before you were sure it was not another “false injection?”

A: Given my long connection with Glasgow, perhaps it was fitting that I heard about the detection when I was there on one of my visits. I can’t recall the moment when I realised this was the real thing – it built up gradually as I heard about all the checks which were being done to verify that these were indeed real signals. The most exciting day for me was the day of the announcement, and there were tears in my eyes as our LIGO Director told the world what we had achieved. It was then that the enormity of it all hit me, and I realised that what I had been working towards for more than 35 years had finally come to fruition. And I am lucky that I got to share all of this with my husband, who also works for LIGO.

Q: What advice would you like to give to young people thinking about a career in physics or astronomy/astrophysics?

A: Follow your interests and don’t be put off by what others may say.

Q: Was being female any barrier to your success as a scientist? How has this situation changed over the last 30 years?

A: I have never felt being a woman was a barrier. It has sometimes been a bit daunting – like the first time I walked into the physics lab as a first-year student and realised I was the only woman there. That was not easy, especially having come from an all-girls school. The situation has certainly changed for the better over the last 30 years. When I was appointed to a Lectureship at Glasgow, I was the only woman on the academic staff in physics. In fact as far as I was aware, at that time I was the only female physics lecturer in any of the Scottish universities. Networking with female colleagues in other science and engineering departments helped me, and the setting up of the Women in Physics group of the Institute of Physics was a great step forward. I think it was through that group that I first met our current RSE President, Dame Jocelyn Bell Burnell – a great role model for us all! Fast forwarding to the present time, we now have several female professors in Physics and Astronomy at Glasgow. I also see an increasing number of young women in the LIGO Scientific Collaboration starting out on their careers. There is still work to be done in this area, but progress has definitely been made.



Professor Norna Robertson, a Fellow of the RSE, the Institute of Physics and the American Physical Society, is a lead scientist at the California Institute of Technology (Caltech), working in the LIGO project. She also spends a few weeks every year working at the University of Glasgow, where she is a Professor of Experimental Physics. She gained her PhD at Glasgow in 1981, focusing on “experiments relating to the detection of gravitational radiation and to the suppression of seismic noise in sensitive measurements.” After a post-doc position at Imperial College in infrared astronomy, she returned to gravitational-waves research in 1983 as a Lecturer at Glasgow, where she was appointed Professor in 1999. In 2003, she moved to the USA to work at Stanford University, and in 2007 she moved to Caltech to head the Suspensions team for the Advanced LIGO project. Currently, she works on suspension-related research for possible improvements and upgrades for Advanced LIGO.




"The Scottish Connection". Science Scotland (Issue Twenty)
Printed from on 31/03/20 01:47:20 PM

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