Wednesday, November 26, 2014

On Planck’s Law, Blackbodies and the Physics of Diversity

Dr. Jedidah Isler
Reproduced from the June 2014 Issue of STATUS: A Report on Women in Astronomy.  The article below is written by Dr. Jedidah Isler, Syracuse University, Department of Physics.

Diversity and inclusion are important, yet vexing, issues that we struggle with in every arena. Academia and, more specifically, astronomy are not exempt. Many interpretations of the experiences of diverse people have been offered, but unfortunately, many have fallen short in pivotal ways.

As an astrophysicist, I see the beauty and logic that physics allows us to impose on the cosmos, but also on a broader array of issues. Sociophysics, for example, “uses concepts from the physics of disordered matter to describe some aspects of social and political behavior.” [1] I would like, then, to describe a few diversity issues in terms of a physical concept that astronomers are familiar with, namely Planck’s Law. This analogy is not perfect, but it affords us a mechanism to address some of the complexity of diversity conversations and direct us towards more globally beneficial diversity practices.

Even before I begin, I acknowledge that I cannot address all aspects of diversity, which includes the full spectrum of ethnicity, class and sexual expression. I focus on the diverse experiences of women (broadly defined), but these principles can generally be extended to other dimensions of diversity. Still, I encourage expansion of our colloquial definitions of diversity, even as social psychologists grapple with characterizing our behavior surrounding it. My goal is not to establish who suffers most, but to suggest that different groups suffer differently and in profoundly complicated ways. Thus, this article is for all of us. It is an attempt to provide a familiar framework for this complex issue.

Perhaps the best place to begin this conversation is with blackbody radiation. Blackbodies are thermodynamic idealizations that are uniquely defined by their temperature. We describe the spectrum of blackbody radiation with Planck’s law, which predicts the intensity of radiation as a function of wavelength. Therefore, Planck’s law will immediately tell us the surface brightness of a blackbody at any wavelength. We can also determine its peak wavelength of emission, which is inversely proportional to the temperature, via Wien’s Law.

Armed with the temperature and these laws, one can determine which filter is best suited to observe the peak of blackbody radiation. Using the wrong filter for a blackbody of a given temperature is a sure-fire way to accumulate non- detections. For example, an object with T=5,000 K has its peak emission at 5,796 Â and is not likely to have detectable emission at 300 GeV with the Fermi Gamma-Ray Space Telescope. Planck’s Law tells us that there is non-zero emission from such a source at that energy, but it is far below instrument sensitivity limits. An exception is the Sun, which has had detections with Fermi/LAT of radiation associated with flares due to non-thermal processes. [2]

Social psychological research about diversity can offer us some interesting parallels with astrophysical observations. I suggest that the filter we use to observe a blackbody is analogous to our lived experiences and sensitivities. The farther removed the lived experiences of the observer from the peak wavelength of source emission, the more difficult it is to understand and accurately interpret or even perceive the ‘signal’ of another’s experience. Let’s now reinterpret the idea of a non-detection. We can clearly see that in a given situation, language like “that doesn’t really happen” or “it’s all in your head” is unproductive (and generally inaccurate). The nontrivial displacement between the filter and the peak source emission suggests lack of filter sensitivity, not necessarily lack of true signal.

Another point we can unearth here is that members of various groups must endeavor to understand their similarities and respect their differences. We can relate this to another fundamental principle of blackbodies: Planck curves for distinct temperatures never intersect. In a similar way, even for apparently single-identity groups, such as White women, individual experiences are not identical and do not overlap, like a group of blackbody sources with similar temperatures. A single filter may not be able to distinguish between these slightly different signals.
Figure 1. Blackbody curves in wavelength units, to within a constant factor.
From top to bottom, T = 6000, 5900, 5800, and 5700 K.
(Illustration by Nancy Morrison)
A second way to interpret this lack of overlap among different temperature blackbodies is to consider Planck’s Law across the entire spectrum as shown, for example, in Figure 1. The behavior of surface brightness with respect to temperature is significantly different at shorter wavelengths (where the surface brightness at a given wavelength is approximately proportional to a high power of the temperature) than at longer wavelengths (Rayleigh-Jeans limit, where the surface brightness is only linear with temperature). For example, White women experience privileges that women of color do not, afforded them by being a part of the dominant race in the United States. When considering the oft-discussed pay wage gap between women and men, it is instructive to note that Black and Latina women also experience a pay gap with respect to White women. [3]  Thus, the situation is disconcerting for women in general, but becomes even more dire as we consider the effects of race and gender. We come face to face with the fact that one can not escape racialized gender. In addition, the use of ‘women’ in terms of gender diversity without a qualifying statement of race reifies White women as the normative example of the female gender in America. [4, 5]

On the other hand, persons with intersectional identities (e.g. Black women, Latina women, and those of mixed heritage) may not be sufficiently well-represented by a single parameter. Simply stated, a Black woman is neither just Black or just a woman. She is Black + woman, [5, 6] and the concerns, prejudices, stereotypes, disadvantages and advantages she faces are unique. Further, she will encounter disproportionately more prejudice and discrimination than would a member of a single identifying group [7]. In the framework we are constructing, multiple identity groups are analogous to multi-temperature blackbodies, like accretion disks, [8] which require more parameters to characterize fully. While the spectral energy distribution of a multi-temperature blackbody has a different shape from that of a classical blackbody, the overarching necessity of adjusting the filter used for best evaluation remains germane. In fact, the need for multiple filters is underscored, as the broadband behavior of the curve may not be known a priori.

Women of color accrue some advantages due to their relative invisibility with respect to race and gender. Studies have shown that Black women are allowed to show more aggressive behavior in the workplace without repercussions than Black men or White women, due to their intersectionality. [9] However, the same study also showed that this leeway did not extend to situations when Black women made mistakes. In those cases, they were more heavily sanctioned than either of the other groups considered. Therefore, while each group has parameter spaces within which they can operate with relative advantage, none of these advantages are absolute.

So how do we address the biases that arise from the interconnectedness of race and gender in our research groups? As professional scientists, we are accustomed to referring to the experts, so we look to the extant research on diversity. The problem is that the relevant literature has largely ignored intersectionality. “[Empirical social psychology] research into the intersections of diversity did not arise until 2008 with Robert Livingston,” says Erin Thomas, Gender Diversity Coordinator of STEM Initiatives at Argonne National Labs and Ph.D. in Psychology. She continues, “until that point, race and gender studies were characterized mostly by Black men and White women.” [10]

Black women were the first group to be considered intersectional, but now many psychologists are expanding their investigations to other women of color, and are also considering class and sexual expression. For example, the new book by Joan C. Williams and Rachel Dempsey, What Works for Women at Work, [11] identifies similarities and differences between the work experience of White women and women of color. Williams also has an NSF-supported initiative called the Gender Bias Learning Project, where she has developed a Gender Bias Bingo [12] and worked extensively on the subject of ‘double jeopardy’ [13] at the University of California, Hastings Center for Work Life Law.

Diversity is a complex subject. There is no panacea that we can sprinkle around the telescope to achieve an unbiased interaction with people whose life experiences are different from ours. As participants in a diverse world, we must do our part on many fronts. We must continue to push for scientific honesty, integrity and inclusion in the investigation of diversity as a research topic, as well as insist on responsive implementation of best practices unearthed from that research. Given the history of oppression and silencing of ‘others’ in this country, there is no reason to assume that the problem will fix itself. Moreover, the evidence suggests [14] that our scientific community has suffered due to loss of talent, uneven playing fields, and hostile work spaces. We have an individual responsibility to constantly assess our filters, and evaluate the resultant detections or non-detections thereof, to determine whether our perception sensitivity is high enough to make an informed statement on a given matter.

As an astrophysical community, we can sharpen our discernment of different lived experiences. First, in connection with the need for attention to our own sensitivities, I highlight the written testimony AAS submitted at the National Research Council’s Women of Color in Academia Conference. [15] This work addressed barriers and recommendations for improvement at the departmental, institutional, and organizational level. (Full disclosure: I was a co-author of this work.) Second, we can incorporate evidence-based diversity trainings into the curriculum for graduate schools, into research grants, and at our very own AAS. As the world and our field are becoming increasingly diverse, significant gains in research, insight and innovation can be realized by making our discipline more welcoming to all, by recognizing and appreciating the filters and peak wavelengths of all who wish to participate.

I would like to thank Erin Thomas, Ph.D. for her help identifying relevant research studies and Joan Williams, Esq. for sharing her research with me before her book became available. In addition, many thanks are owed to Nancy Morrison and Joan Schmelz for their patience and keen eye in editing this work.

[1] S. Galam 2012, Sociophysics: A Physicist's Modeling of Psycho-political Phenomena (Springer), book/978-1-4614-2031-6

[2] program/mon/NOmodei.pdf

[3] R. Dozier 2010, “The declining relative status of black women workers, 1980-2002,” Social Forces, 88, 4, 1833–1857, http://

[4] P. T. Reid and L. Comas-Diaz 1990, “Gender and ethnicity: Perspectives on dual status,” Sex Roles, 22, 397–408, http://

[5] K. L. Johnson, J. B. Freeman, and K. Pauker 2012, “Race is gendered: How covarying phenotypes and stereotypes bias sex categorization,” Journal of personality and social psychology, 102, 1, 116,

[6] A. K. Sesko and M. Biernat 2010, “Prototypes of race and gender: The invisibility of Black women,” Journal of Experimental Social Psychology, 46, 2, 356-360, science/article/pii/S0022103109002698

[7] V. Purdie-Vaughns and R. P. Eibach 2008, “Intersectional Invisibility: The Distinctive Advantages and Disadvantages of Multiple Subordinate-Group Identities,” Sex Roles, 59, 377-391,

[8] L. X. Li, E. R. Zimmerman, R. Narayan, and J. E. McClintock 2005, “Multitemperature blackbody spectrum of a thin accretion disk around a Kerr black hole: model computations and comparison with observations,” The Astrophysical Journal Supplement Series, 157, 335,

[9] Rosette, A.S., and Livingston, R.W. 2012, “Failure is not an option for Black women: Effects of organizational performance on leaders with single versus dual-subordinate identities,” Journal of Experimental Social Psychology, 48, 5, 1162–1167,

[10] Thomas, E. 2013, personal communication

[11] J. C. Williams and R. Dempsey 2014, What Works for Women at Work: Four Patterns Working Women Need to Know (New York University Press, forward by Anne-Marie Slaughter)


[13] F. Beal 1969, Double Jeopardy: To Be Black and Female,

[14] National Research Council 2009, Gender Differences at Critical Transitions in the Careers of Science, Engineering, and Mathematics Faculty (The National Academies Press, Washington, D.C.), p. 255

[15] D. Norman et al. 2012, “Women of Color in Astronomy and Astrophysics,” The National Academies, wocconference/files/2012/03/6.3.-American-Astronomical- Society.pdf


Anonymous said...

Social scientists were studying and explaining "intersectionality" well before 2008 (the term was coined by Kimberle Crenshaw, a Black woman, critical race theorist, and UCLA Law professor in 1989), and folks have been pointing out and studying demographic groups in the U.S. besides "Black men and white women" since the 19th century. You can find more information about pre-2008 sociological and other scholarly and non-academic work around intersectionality here: Intersectionality

audra said...

What a great idea. I especially like the filter analogy. Thank you for taking the time to write this.

Anonymous said...

A wonderful article; thank you. I was pondering just yesterday the issues that people face who are in the not-well-studied area of intersectionality. For your example Black + woman, I was thinking the prejudices and disadvantages are not simply additive, but compound quickly.