Stars, Peripheral Scientists, and Equations: The Case of M. N. Saha


Peripheral actors rarely make an appearance in the general story of scientific practice, and their work in science is usually viewed as somewhat derivative of the practices of the main community. Contrary to this received model, here I argue that the peripheral contexts of science can be quite important and reveal novel conduits to creative scientific thinking. Not only can such contexts offer us a new window into how contributory expertise in science could be born amid difficult circumstances, they also allow us to see how new scientific communities could be founded during such encounters. Using case studies of M. N. Saha and other physicists in early twentieth-century India, I argue that such modest practices begin when peripheral protagonists seek to initiate new trading zones with the established centers of science. The resulting exchanges can give rise to new breakthroughs and conceptual changes in scientific practice. Such peripheral breakthroughs can be studied cognitively, giving us newer models of scientific practice as well as creating a new kind of self-image for such scientists.

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  1. 1.

    If p M , p N ,… are the pressures of the reacting substances, R is the gas constant, C p the specific heat at constant pressure, and C is Nernst’s chemical constant, then \( \log K = \log \frac{{p_{M}^{Vm} p_{N}^{Vn} \ldots }}{{p_{A}^{vA} p_{B}^{vB} \ldots }} = - \frac{U}{4.57T} + \frac{{\sum vC_{p} }}{R}\log T + \sum_{v} C. \) Applied to calcium atoms, then \( \sum_{v} {\text{C}}_{p} = {\text{C}}_{p} ({\text{C}}_{a}^{ + } ) + ({\text{C}}_{p} )_{c} - {\text{C}}_{p} ({\text{C}}_{a} ), \) with ionization here serving here as chemical decomposition. Then we can take C p (C a = C p (C + a ) and (C p ) c  = 5/2 R. Since the chemical constant C has the same value for both Ca and Ca+, Saha calculated the value of the electron molecular weight as 5.5 × 10−5 and thus arrived at the value of Σ v C = −6.5.

  2. 2.

    Putting those same ideas in the language of partition functions and electron number density, we can write down the same relationship in a slightly different form:

    $$ \frac{{N_{II} }}{{N_{I} }} = \frac{{2Z_{II} }}{{n_{e} Z_{I} }}\left( {\frac{{2\pi m_{e} kT}}{{h^{2} }}} \right)^{3/2} e^{ - \chi /kT} , $$

    where N I and N II are the ratios of neutral and ionized atoms, Z I and Z II are the partition functions, N e is the density of free electrons, and X is the energy needed to ionize an atom from its ground state.


  1. 1

    Fred Hoyle, Of Men and Galaxies (Seattle: University of Washington Press, 1964), 12.

  2. 2

    See Sharon Traweek, Beamtimes and Lifetimes: The World of High-Energy Physicists (Harvard University Press, 1992) and Karin Knorr-Cetina, Epistemic Cultures (Cambridge, MA: Harvard University Press, 1999).

  3. 3

    See Philip Kitcher, The Advancement of Science (Oxford: Oxford University Press, 1993), 58–59.

  4. 4

    There might, of course, be other closely similar forms of practices.

  5. 5

    Following Kuhn, here I take progress to be simply the capacity for puzzle solving.

  6. 6

    The notion of a trading zone with multiple stages of cooperation is borrowed from Michael Gorman, “Levels of Expertise and Trading Zones: Combining Cognitive and Social Approaches to Technology Studies” in Michael Gorman, David Gooding, Alexandra Kincannon, eds., Scientific and Technological Thinking (New York: Lawrence Erlbaum Associates, 2005), 287–302. This, in itself, is an extension of Peter Galison’s 1997 version of the same idea. Peter Galison, Image and Logic: A Material Culture of Microphysics (Chicago: University of Chicago Press, 1997).

  7. 7

    The concept of contributory expertise has been borrowed from Harry Collins and Robert Evans, Rethinking Expertise (Chicago: The University of Chicago Press, 2007).

  8. 8

    The twin notions of mavericks (and followers) have been borrowed from Michael Weisberg and Ryan Muldoon, “Epistemic Landscapes and the Division of Cognitive Labor,” Philosophy of Science 76 (2009), 225–252. Briefly, mavericks and followers are two different cognitive styles in science—mavericks lead in a practice, and followers (of course) follow. Here, I argue that, contrary to popular belief, mavericks can often come from the peripheral communities.

  9. 9

    This was the very first translation of Einstein’s relativity papers into English, only four years after they first appeared in German.

  10. 10

    To my knowledge, the best account of Saha’s contribution in astrophysics can be found in Jytirmoy Gupta, ed., M. N. Saha in Historical Perspective (Calcutta: Thema, 1994). Santimoy Chatterer’s article on Saha is also a very good source for Saha’s overall career, but does not dwell much on his early contributions in astrophysics: Santimoy Chatterjee, “Saha—The Scientist and the Institution Builder,” Indian Journal of the History of Science 29 (1994), 99–110.

  11. 11, accessed December 16, 2014. Within any given letter, the sequence can run from 0 to 9 range, indicating temperature.

  12. 12

    Spectroscopic data on the elements can be obtained by putting samples of known gases into discharge tubes, exposing those tubes to electric arcs or to Bunsen burner flame, and finally recording the resultant spectra. A flash spectrum is obtained by using a spectroscope with a diffraction grating and exposing it to the light of the sun or other similar stars. The term flash spectrum refers to the brief window of time during which such spectra must be recorded. The recorded spectra can be continuous or might show patterns of various emission (bright) or absorption (dark) lines, which then call for further explanation.

  13. 13

    Norman Lockyer presents the problem of the enhanced lines in his book Contributions to Solar Physics (London: Macmillan and Co., 1873).

  14. 14

    “[T]he lines in question are not due to radiation from the normal atom of the element, but from an ionized atom, i.e., one which has lost an electron.” M. N. Saha, “Ionization in the Solar Chromosphere,” Philosophical Magazine 40(472) (1920), 38–44.

  15. 15

    Ibid. Saha here refers to John Eggert, “Über den Dissoziationszustand der Fixsterngase,” Physikalische Zeitschrift 20 (1919), 570–574.

  16. 16

    The quantity considered is 1 gram-atom.

  17. 17

    To detach an electron from the atomic system one needs to add to each atom an amount of energy equivalent to that acquired by an electron falling through a potential difference V (measured in volts), and is governed by the quantum relation: \( \frac{eV}{300} \) = hν0.

  18. 18

    The lines arise from the upward or downward transitions between two orbitals of different azimuthal quantum numbers. The “sharp” lines show the p → s transitions, the “principal” lines show the s → p transitions, the “diffuse” lines are from d → p transitions, and the “faint” lines from f → d transitions. Of course, the names sharp, principal, diffuse, fundamental, etc. are only conventional, referring to the early days of spectroscopic work. Thus, they do not describe anything at all about the appearances of those lines.

  19. 19

    See M. N. Saha, “On A Physical Theory of Stellar Spectra,” Proceedings of the Royal Society of London A 99 (1921), 135–153.

  20. 20

    D. S. Kothari, one of Saha’s students at Allahabad University, puts the matter as follows: “The theory of thermal ionization introduced a new epoch in astrophysics by providing, for the first time, on the basis of simple thermodynamic considerations and elementary concepts of the quantum theory, a straightforward interpretation of the different classes of stellar spectra in terms of the physical conditions (temperature and to a lesser extent pressure) prevailing in the stellar atmosphere.” See D. S. Kothari, “Meghnad Saha: A Biographical Resume” in Gupta, Saha in Historical Perspective (ref. 10), 29–46.

  21. 21

    M. N. Saha, “On Radiation-Pressure and the Quantum Theory,” Astrophysical Journal, 50 (1919), 220–226.

  22. 22

    Abraham Pais on S. N. Bose, and G. H. Hardy on Ramanujan can be cited as examples of this genre of assessment, despite the very high praise that they accord to such scientists. See Abraham Pais, Subtle is the Lord: The Science and the Life of Albert Einstein (Oxford: Oxford University Press, 2005), 425–428, and G. H. Hardy, Ramanujan: Twelve Lectures on Subjects Suggested by His Life and Work (Cambridge: Chelsea Publishing, 1940).

  23. 23

    The notion of moral imagination has been borrowed from Michael Gorman. See Michael Gorman, “Heuristics, Moral Imagination, and the Future of Technology,” Behavioral and Brain Sciences 28(4) (2005), 551–551. Briefly speaking, moral imagination consists in the ability to visualize (and act upon) new possibilities in a situation and disengage oneself from a set of current mental models that determine or dictate a present situation. A peripheral scientist actively engaged in developing a (new) scientific research program must disengage herself from the current models of herself and her society and try to envision such things in an entirely new way.

  24. 24

    For different versions of Darwin’s theory of natural selection that were developed in the Argentinean context, see Alex Levine and Adriana Novoa, From Man to Ape: Darwinism in Argentina, 1870–1920 (Chicago: University of Chicago Press, 2010). Such different versions can also be taken as different varieties of peripheral creativity.

  25. 25

    Subbaiah Arunachalam,“Science on the Periphery Enriches Mainstream Science, but at What Cost?: The Case of Ethnobotany,” Knowledge and Policy 8(2) (1995), 68–84.

  26. 26

    George Basalla, “The Spread of Western Science,” Science 56 (1967), 611–612.

  27. 27

    Kyle Whyte and Robert Crease, “Trust, Expertise, and the Philosophy of Science,” Synthese 177 (2010), 411–425.

  28. 28

    G. J. Posner, K. A. Strike, P. W. Hewson, and W. A Gertzog, “Accommodation of a Scientific Conception: Towards a Theory of Conceptual Change,” Science Education 66 (1982), 211–227.

  29. 29

    Perhaps Posner should have labeled this as revision, not accommodation.

  30. 30

    See, accessed December 20, 2014.

  31. 31

    A similar process can perhaps also be seen in Michael Faraday, who developed a thinking-aloud protocol, perhaps thanks to his own self-educated background in the sciences. See: Ryan Tweney, “Discovering Discovery: How Faraday Found the First Metallic Colloid,” Perspectives on Science 14 (2006), 97–121.

  32. 32

    Eventually, this work was considered to be a professional contribution. The last person to join this group, Cecilia Payne, received a PhD in astronomy in 1925, thereby transforming herself from an amateur to a full-fledged professional member of the scientific community. Interestingly, Payne’s PhD work consisted of applying Saha’s theory to measure the absorption lines in the stars’ spectra, showing that the wide range of stellar patterns arise from the different ionization states of their atoms and not because they are made of different elements.

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I would like to thank the two referees of this journal who read an earlier version of this paper and asked me some important questions about the outcomes of a trade between a peripheral community and its more central counterparts. An earlier version of this paper was read at the 2014 History of Science Society Meeting at Chicago, and I thank my session participants for their requests for clarifications on the different stages of trade in peripheral science.

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Correspondence to Deepanwita Dasgupta.

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Deepanwita Dasgupta is a philosopher of science in the Department of Philosophy, East Tennessee State University.

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Dasgupta, D. Stars, Peripheral Scientists, and Equations: The Case of M. N. Saha. Phys. Perspect. 17, 83–106 (2015).

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  • M. N. Saha
  • trading zones
  • ionization
  • Saha equation
  • peripheral science