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SCIENCE: a way of knowing

"Babies and young children think, observe, and reason. They consider evidence, draw conclusions, do experiments, solve problems, and search for the truth" [1]. Like anyone else, I was a scientist at birth. I have since continued to cultivate my natural curiosity and desire to explore. Thus, while I am frequently in search of answers, their lure magically disappears as soon as they have been found. Answers are satisfying when they are the bridge to further questions. Luckily they often are.

Cultivating one's curiosity is not always easy. School, as one can read in many of the learning stories available on the LDI Web site (see the Learning Stories Research project) as well as in the biographies and autobiographies of a good many scientists (in the framework of LDI's "The Scientific Mind" [TSM] project I get to read quite a number of them), is often a factor that must be overcome, rather than what it also could be: a facilitator. Elements in the environment - the presence of a friend, sibling, or other close or not so close relative; finding the right book; the visit to a science museum; or participation in an environment where kids can get involved in explorations and experiments - may be crucial.

In my case, important factors were the presence, at an hour's walking distance from my childhood home, of a flee market, open on Saturday afternoons, where, out of whatever little money I had been able to accumulate, I could buy used radio parts. More strongly appealing to my imagination, and at much closer distance from home, was a well-stocked retailer of new electronic components. Everything imaginable was there on display behind large windows. Evening after evening I stood there, staring at the objects of my desire behind the thick glass. The store issued a free catalogue every year. I never failed to pick one up when the new edition was out. It was a great stimulus for "doing science in the mind" with those things I couldn't buy. The experience must perhaps have conditioned me to opt later, while studying physics at the Delft University of Technology (DUT), to do my degree work in theoretical physics. DUT being a technological university, the overall orientation in physics envisions application, rather than the theory behind it. So, the theoretical specialization was only available after one had proved to be a good experimentalist. Thanks to that requirement I got a thorough grounding in both theory and experiment. In retrospect, I think it may have helped me

I had the privilege of being admitted to the Theoretical Physics Group headed by Professor Ralph Kronig. He personally supervised my research. Initially I was the only theoretical physics student in the whole group, which Kronig had given new life after he had served for several years as Rector Magnificus (Vice-Chancellor). When I graduated we had grown into a group of four. Even today's Theoretical Physics Group at Delft is still very small. There is a distinct advantage in being part of a small learning community. My work with Kronig focused on second order effects in the interaction between electromagnetic radiation and matter. Some of it is reflected in a joint publication (Kronig & Visser, 1966).

"Kronig is an eminent physicist and a gentleman," writes Abraham Pais in his biography of another great physicist of the past century, Niels Bohr. (Pais, 1993, p. 244). He refers to one of the bizarre stories in the history of science regarding the discovery of a key scientific concept (the electron spin) and the subsequent awkwardness regarding the attribution of credit for it. Kronig, fresh out of Columbia University and visiting Europe, had the original idea. He was discouraged by Pauli from publishing it. A few months later, two young Dutch physicists, Uhlenbeck and Goudsmit, who worked with Ehrenfest in Leiden, had the same idea and published it. Dirac's view on what happened is of interest:

Ehrenfest liked the idea very much. He suggested to Uhlenbeck and Goudsmit that they should go and talk it over with Hendrik Lorentz, who lived close by in Haarlem. They did go and talk it over with Lorentz. Lorentz said, "No, it's quite impossible for the electron to have a spin. I have thought of that myself, and if the electron did have a spin, the speed of the surface of the electron would be greater than the velocity of light. So, it's quite impossible." Uhlenbeck and Goudsmit went back to Ehrenfest and said they would like to withdraw the paper that they had given to him. Ehrenfest said, "No, it's too late; I have already sent it in for publication."

That is how the idea of electron spin got publicized to the world. We really owe it to Ehrenfest's impetuosity and to his not allowing the younger people to be put off by the older ones.


Excerpt from a letter, dated March 25, 1926, by L.H. Thomas to Samuel Goudsmit reproduced from Goudsmit's account of "The discovery of the electron spin." (Available on the Website of the Instituut-Lorentz. The letter was reproduced from a transparency used by Goudsmit during his 1971 lecture on the above topic. The original is presumably in the Goudsmit archive kept by the AIP Center for History of Physics.)

There are, of course, interesting lessons to be drawn from such experience, for both young and old, particularly as regards the intergenerational dimension of how people learn and grow together and how they impact - positively and negatively - on each other's learning. Peer review - informal in this case and certainly not blind - is another issue that comes to mind. I have always found Kronig's gentlemanlike behavior - as referred to by Pais - in this context exemplary and believe that setting examples in relevant matters is a key pedagogical issue. I owe much to Kronig in this regard. For further reading about this fascinating story, see also Sin-itiro Tomonaga's (1997) "The Story of Spin" and the Website of the "Instituut-Lorentz." The latter source also features a link to Goudsmit's version of the story, which focuses, among other aspects, on the importance of the cumulatively constructive process of building knowledge. A letter by Uhlenbeck and Goudsmit to Nature on "Spinning Electrons and the Structure of Spectra", published in Volume 117, pp. 264-265 (February 20, 1926), is equally of interest. So is, for readers who master the Dutch language, Kronig's obituary by Kokkedee. The latter noted the awkwardness that never a Nobel Prize was awarded for what everyone agrees was one of the key ideas in the physics of the first half of the twentieth century. Putting all the different accounts together, one gets a good feel of the complexity and profoundly human nature of doing science.

My continued and current interest in science is particularly motivated by my belief that the mindset of a good scientist - i.e., a scientist who contributes to creating new insights in the perspective of building a better world - is an attribute of the mind that should not only be developed in members of the scientific community but that can also tremendously benefit members of the human species in general, whatever their role in life. This has led me to the idea that contributing to the growth of the scientific mind is an important aspect of the development of human learning.


[1] Gopnik, A., Meltzoff, A. N. & Kuhl, P. K. (1999). The scientist in the crib: Minds, brains and how children learn. New York: William Marrow and Company, Inc.

Dirac, P. M. (1983). Origin of Quantum Field Theory. In L. M. Brown & L. Hoddeson (Eds.), The birth of particle physics. New York: Cambridge University Press. I found the quote on September 1, 2001, at

Kronig, R. & Visser, J. (1966). A rigorous solution of Dirac’s equation. In Proceedings of
the Royal Netherlands Academy, 69B
, 332-335.

Pais, A. (1991). Niels Bohr's times in physics, philosophy and polity. Oxford, UK: Oxford University Press.

Tomonaga, S. (1997). The Story of Spin. Chicago: University of Chicago Press.

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