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Fifty Years of Paradigm Shifting

February 25, 2013

Following the dictum attributed to Mark Twain, that you shouldn't let your schooling interfere with your education, I read a lot of extracurricular items while in graduate school. As all students know, even their chosen profession is not as exciting as they had once thought, so they look elsewhere for enlightenment.

Thomas Kuhn's, The Structure of Scientific Revolutions, Second Edition

One book I thoroughly enjoyed was
Thomas Kuhn's, "The Structure of Scientific Revolutions," published in 1962, when I was still in high school.[1] I read the book nearly a decade after it's publication, but its observations about the scientific method still had the ring of truth. At the very least, it added the word, "paradigm," to my vocabulary.

(The cover of my second edition of Kuhn's book. Barely readable is the price, $2.45, which is even less than the price of most eBooks, today.)

The main point of Kuhn's book is that there are two types of science. One science, "normal" science, is what I and most of my colleagues did daily in our laboratories. The things we did were "by the book," and the few surprises were from lack of experimental control or a misunderstanding of which page of the "the book" we were on.

Kuhn's other type of science was "revolutionary" science. Unlike normal science, revolutionary science challenges the wording in "the book," and leads to a different way of thinking about nature. A few examples would be the heliocentric solar system, quantum theory, and relativity. The idea of paradigm enters when we consider the interaction between normal and revolutionary science.

Normal science works within a paradigm, defined as the collection of truths shared by a particular group of scientists. I would often glance at the periodic table on my laboratory wall for guidance, and the many chemical notions embedded in that table are a paradigm. If someone were to tell me about some work on an element between hydrogen and helium, I wouldn't believe him.

The problem with paradigms, as Kuhn pointed out, is that ideas outside the paradigm (such as the element with an atomic number between one and two, above) are rejected by the normal scientists without their giving them much thought. Thus, scientific papers demonstrating results outside the paradigm are rejected by journal referees. One example is Dan Shechtman's quasicrystals.

As I reported in a previous article (The 2011 Nobel Prize in Chemistry, October 7, 2011), it took two years for Shechtman to get his paper on quasicrystals accepted for publication. The reason for rejection was obvious to those working in the current crystallographic paradigm. The icosahedral point group symmetry discovered by Shechtman wasn't possible. Crystallography forbids 5-fold symmetry, since a lattice like that is not uniform under translation.

Eventually, more examples of quasicrystals appeared, including some that were dismissed by their discoverers as being "wrong" when they discovered them, and buried in some drawer without publication. Finally, in 1992, the International Union of Crystallography changed its definition of a crystal from "a regularly ordered, repeating three-dimensional pattern" to a solid with a "discrete diffraction diagram."[3] Shechtman was awarded the 2011 Nobel Prize in Chemistry.

What happened in the quasicrystal case, as in other scientific revolutions, is that the essential paradigm in a scientific field was changed. As if there weren't enough "shifts" in physics already (Doppler shift, Lamb shift, phase shift, redshift, etc.), Kuhn promoted this idea of a paradigm shift. Kuhn argued that when little inconsistencies start to pile up in a paradigm, scientists become more aware that things are not quite right. Finally, someone comes along with a new paradigm that sets things straight.

Some of the Old Guard will have a hard time adjusting to the new paradigm, but the logic of science prevails, and everyone shifts to the new paradigm. The old paradigm, say phlogiston, is now considered wrong, and everyone buys into the new paradigm, caloric theory, which is then superseded by the next paradigm, the mechanical theory of heat. Paradigm shifting often takes a lot of time.

Benjamin Thompson Count Rumford

Benjamin Thompson,
Count Rumford

Thompson, who saw the heat generated while boring cannon, did some careful measurements. He published his results as "An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction."

Thompson's experiments demonstrated the mechanical equivalent of heat.

(Via Wikimedia Commons))

Kuhn wrote that there's resistance to paradigm shift because paradigms are incommensurate; that is, they can't be directly compared, since they talk about different things. You can't go in a straight line of reasoning from Newtonian mechanics to relativity.

Although scientists can see the truth about paradigms, they are usually resistant to the notion of incommensurability. In their minds, the old paradigm was dumped because it was wrong, and the new paradigm was accepted because it was right. They carry their own idea of a valid comparison, usually relating to agreement with experiment, in their mind.

Kuhn has a rightful place in twentieth century history of science, alongside George Sarton, Gerald Holton and Karl Popper. My article presented a thumbnail sketch of Kuhn's ideas from a scientist's viewpoint. Matthew C. Rees has a recent article in The New Atlantis that looks at Kuhn from a philosophical standpoint.[4]


  1. Thomas S. Kuhn, "The Structure of Scientific Revolutions: 50th Anniversary Edition," University Of Chicago Press (Fourth Edition edition, April 30, 2012), ISBN-13: 978-0226458120, 264 pages (via Amazon).
  2. D. Shechtman, I. Blech, D. Gratias and J.W. Cahn, "Metallic phase with long range orientational order and no translation symmetry,", Physical Review Letters, vol. 53, no. 20 (November 12, 1984), pp. 1951-1953.
  3. Kenneth Chan, "Israeli Scientist Wins Nobel Prize for Chemistry," The New York Times, October 5, 2011.
  4. Matthew C. Rees, "The Structure of Scientific Revolutions at Fifty," The New Atlantis, no. 37 (Fall 2012), pp. 71-86.

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