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On Vera Rubin: A life

Today’s blog shares insights into the life of Vera Rubin by astronomer, writer, and media consultant Dr. Jacqueline Mitton, PhD from the University of Cambridge, and co-author with her husband Simon Mitton of Vera Rubin: A Life published by Harvard University Press in 2021.


David: How did you develop an interest in Vera Rubin?


Jacqueline: When I was a graduate student in Cambridge (UK), doing a PhD in optical astronomy in the early 1970s, I was asked by a student society to give a talk on “Women in astronomy”. I guess they asked me because I was the sole female graduate student in optical astronomy at the University Observatories and only the second woman they had ever had as a research student. (The radio astronomy department had done a bit better.) I knew very little about women astronomers at the time but I prepared my talk, taking a historical perspective, and learning a great deal in the process. It was the start of a life-long passionate interest and the first of countless talks I’ve given on the same topic. Rubin had not started her large-scale project on the rotation of galaxies when I gave that first talk but I certainly knew how prominent a figure she had become when, shortly after her death in 2016, I heard that Princeton University Press was in search of someone to write a biography of her. It was a unique opportunity not to be missed.


David: Rubin’s discovery of flat rotation curves is often associated directly with the idea of dark matter. Would it not be more accurate to say that given what was observed, Rubin discovered that galaxies do not appear to obey Newton’s second law?


Jacqueline: You seem to be making reference to the hypothesis known as Modified Newtonian Dynamics (MOND), first put forward by the physicist Mordehai Milgrom in 1983. It is essentially one version of many hypotheses that postulate alternatives or modifications to general relativity, the gravitational theory accepted by the majority of physicists. However, MOND goes even further. If Newton’s 2nd law does not hold universally, then all kinds of forces, not just gravitational forces, are implicated.


MOND has its proponents, but also has many critics who cite where it falls down. One of the most serious criticism is that it does not eliminate the need to postulate dark matter in certain astrophysical situations but there are also many other problems with MOND that have not been resolved.


The evidence of Rubin’s observational data (and of others before and since) is that many spiral galaxies rotate in a manner that does not appear consistent with the apparent distribution of detectable matter if you set aside tinkering with well-established physical principles. As Rubin herself put it in a 1982 paper, the observations were “consistent with virtually nonluminous massive halos”. But you are right to point out that they do not prove the existence of dark matter. So it is not surprising that some people have had a go at seeing what a bit of tinkering with the physics might achieve. Nevertheless, even though the nature of dark matter remains elusive, the majority of astrophysicists favour the hypothesis of dark matter pervading the universe as the best theory currently available not just for the rotational behaviour of galaxies but also in other astrophysical situations, notably the anisotropy of the cosmic microwave background.


I’d like to return now to your question and the particular way you phrase it. I think it is possible to say of galaxies with flat rotation curves that they appear not to follow Newton’s second law of motion. But is it “more accurate”? More accurate than what? It’s equally valid to say that the galaxies behave as if surrounded by massive halos of something mysteriously elusive. It’s not accurate to suggest that the existence of dark matter follows from flat rotation curves as night follows day. However, it’s no more accurate to suggest that a deviation from Newton’s second law is the explanation. I would be happy to settle for saying that flat rotation curves belong to a whole slew of evidence that challenges our understanding of matter and energy in the universe that may be settled if the nature of dark matter can be elucidated.


David: One of Rubin’s teachers attributed insight and brilliance to males, while only hard work could distinguish a female scientist. There is a documentary circa 2006 where well known astronomers curb Rubin’s intellectual contribution by characterizing her velocity curves as being impactful due to their beauty, as images that “leapt to the eye”. On more than one occasion in my experience, male astronomers have asked “Isn’t she wonderful?” in reference to a female astronomer with ideas, which nobody would ever ask of a male counterpart. Are there pressures that work against women in science with ideas so that not only are women underrepresented but those with ideas in particular are even more underrepresented?


Jacqueline: First let’s be clear about how Rubin remembered the incident at school. In her own autobiographical memoir written in 2011 she says “The first day of class, he [the high school physics teacher] defined two kinds of discoveries: those that took insight and brilliance (here his examples all came from males) and discoveries that required hard work but not brilliance (his example was the discoveries of Marie Curie). I was often angry in class for his similar comments.” Rubin intuitively recognized that his remarks were pointedly sexist, prejudiced and ill-informed.


We have to be careful to avoid falling into the same trap. What is the definition of “brilliance”? And what is it that matters when it comes to the pursuit of science? Is sitting in an office thinking any more worthy of admiration and more intellectually demanding than planning and executing arduous experimental or observational work? All science involves having ideas because it is about answering questions. Progress in science is multi-faceted and mostly happens in a messy sort of way, involving many different contributors over time. It’s not a series of linear steps nor is it done in isolation.


I have not seen the 2006 documentary you cite, but you appear to be dismissing the description of results as “beautiful” or “eye-catching” as derogatory or sexist. I would argue that nothing could be farther from the truth. “Beautiful” as used by scientists to describe results – whether they are a set of equations or a distinctive visual representation of something – is an expression of how powerful and influential they are.


Turning to Rubin’s own work, we need to understand that she was no theorist. She was a consummate observer and as such she was brimming with ideas about when, where, what, how and with what purpose she was going to observe. It was the observing itself that motivated her. Her ambition was to produce observational data of the highest possible quality, and present her results so they were easy to understand and convincing. She had the skill, the drive and the access to state-of-the art technology enabling her to do so. Her spiral galaxy observing programs were devised with the idea of looking for connections between their structural appearance and their internal dynamics. That is why she worked systematically on different types of spirals in Hubble’s classification scheme, tackling Sc (open), Sb (intermediate) and Sa (tightly wound) in turn.


Rubin had little interest in interpreting her rotation curves. She saw that as the job of others. In her papers, she is at first reluctant to make the link with dark matter, but is virtually driven to it in later papers by the impact of the theoretical work by Jeremiah Ostriker, James Peebles and Amos Yahil in the mid-1970s on the stability of rotating galaxies was having. Her flat rotation curves were seized on by others as observational support for the massive galactic haloes apparently needed according to the theoretical modelling to prevent spiral galaxies from disintegrating.


Sandra Faber, one of the most distinguished of American astronomers today, was mentored and inspired by Rubin at the start of her career. When Rubin died, her tribute was thoughtfully and carefully worded. Rubin’s work was particularly influential for three reasons, she said: the clarity of her papers, including beautiful illustrations; then the succession of papers that enlarged the sample and showed how common flat rotation curves were. Not least, Rubin’s presentations at numerous astronomical conferences, were clear, direct and ultimately compelling.


So on the question as you put it, I don’t think “having ideas” or perceived intellectual brilliance is a particular issue. Arguably, experimental and observational science presents more difficulties for women balancing their careers and family life than being a theorist. There have been and continue to be many pressures that inhibit women from following through successful careers , and not only in science.


David: In your experience has it gotten better for women in astronomy?


Jacqueline: Yes, of course things are much better than they were when Rubin and Margaret Burbidge were the leading pioneers fighting for change in the 1960s and 70s. Wendy Freedman, who went on to be the director of the Carnegie Observatories wrote a moving personal letter to Vera in 1986. “Thanks for speaking out” she said. “I often get the feeling that if things are any easier for women like me, it’s because women like you have taken the time and energy to help make it so.” Rubin had some wonderful catch-phrases, like “There is no problem in science that can be solved by a man that cannot be solved by a woman” and “Half of all brains are in women”. There’s no doubt that Rubin and Burbidge were particularly influential in stimulating changes in attitudes and the creation of opportunities for women to participate on equal terms with men, and they inspired successive generations of both men and women to continue what they started. Of course, misogynists will always be with us and women are not the only societal group underrepresented in astronomy.


David: Did Vera Rubin ever paint an astronomical scene?


Jacqueline: I don’t know what Rubin may have painted when she was at school but judging by her account of being interviewed for admission to Swarthmore College as an undergraduate, she almost certainly did not do so as an adult.


Readers of this blog who are not familiar with the background to the question are owed an explanation. Rubin said the following about the woman from Swarthmore who interviewed her, and the impact of the incident. “She never took my astronomy interests seriously… I was also interested in painting... I had done a fair amount of painting, and I must have told her it was among my hobbies. And she asked me if I had ever considered a career in which I painted pictures of astronomical scenes. And that line became a joke in our family for twenty years. And it probably still is among our kids. If you want to say something funny you say, have you ever considered a career in which you paint astronomical scenes?” [Interview by David DeVorkin September 21 1995. Oral Histories, Niels Bohr Library and Archives, American Institute of Physics.]


That sounds fairly definitive to me!


David: Thank you Professor!

 

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