Introduction by Prof. Dr. J.T. Devreese

“Nature uses only the longest threads to weave her patterns, so each small piece of her fabric reveals the organization of the entire tapestry” (Richard Feynman, 1964)

The attractive and brain teasing experimental kit presented by Wim Peeters, Joris Dirckx and Dirk Van Dyck, made me think of the physics lessons at secondary school.

Our physics teacher, who also taught mathematics and chemistry, was so overloaded with teaching and other tasks, that he needed to set up his experiments during the lessons, he had no choice. He always started gathering all necessary equipment out of different glass cupboards, standing along the walls of the class. The beakers, the pots, glass tubes, rubber tubes, clips, flasks, …or a battery, copper or iron conductors with some specific diameter, light bulbs, a current meter, a voltage meter, capacitors ,… were taken out while the teacher commented al these tools and asked all kinds of questions like: “What do we measure with this instrument?”. The secret we were about to reveal became clear as the set up of the experiment progressed, in continuous interaction between teacher and pupils – sometimes slowly, sometimes all of a sudden.. It was like a thriller. Many times the plot, the solution, the answer followed only as “The End” of the lesson.
Unforgettable was the experiment on the propagation of the pressure in liquids and gasses for which our teacher had a complex set up in mind. U-shaped tubes, glass vessels, pistons, pressure meters, plastic grains, coloured liquids and more of this was put together step by step. During the interactive process of setting up all these apparatus we were given a introductory explanations with the views of Archimedes, Stevin, Pascal and Gay-Lussac on this experiment. After building up the suspense the whole preparatory process culminated in the sentence: “ When I open up this cock, the level of the liquid in this arm of the U-shaped tube will rise.” So the stopcock was opened with due solemnity and the level of the liquid…lowered! The reaction of our teacher was a unique lesson in the essence of the scientific method. He asked: “Where did I make a mistake in my thinking?”. A teacher’s question which in other lessons would have been unthinkable. We felt that only a carefully controlled experiment can remain undisputed. During the remaining part of the lesson we interactively searched for a solution of our dilemma. On the play ground, soon every pupil of the whole school was talking about nothing but our physics experiment.
During these interactive physics sessions, we were immersed in the creative interaction between inductive and deductive reasoning that constitutes the scientific method,
Our curiosity and fascination was sparked off directly by numerous physical phenomena demonstrated during the classes. For example the memorable experiment with this lead bell, that produced a dull and unattractive sound. But, after our teacher immersed the lead bell in liquid nitrogen for about a minute, we suddenly could hear a clear and bright sound. We were all highly surprised and wanted to know how this could happen, how it was possible, what the explanation was. The demonstration of the absorption lines of hydrogen-, helium- and other gases , and the confrontation with the absorption spectrum of the sun, was another unforgettable Erlebness. We all were extremely fascinated when our teacher explained Kepler’s laws and how they lead to the universal law of gravity. We drew planetary trajectories on the play ground, indicated areas and wrote down all necessary formulas. We all fell under the spell of Kepler. For us, seventeen year old schoolboys, Kepler was “The Lord of the (elliptic) Rings”.

It is remarkable that the same theme ( the fascination for physics phenomena and their sometimes counter -intuitive explanations) which was so prominent in my own early physics education, is also the Leitmotiv of the experimental kit of Peeters-Dirckx-Van Dyck. The initiators of this experimental kit were well inspired when they coupled this fascination, this “wondering” to Simon Stevin’s devise “Wonder en is gheen wonder” (“Wonder, yet no wonder”). Stevin incorporated this adagium in his vignette, that contains the “clootcrans”( a wreath of spheres) which is the cornerstone of his derivation leading to the general law of the composition of forces. He used this vignette as a mark on his inventions and as a seal. Stevin means with this devise that natural phenomena, which initially surprise us and seem impossible, after scientific analyses no longer should wonder us. “Wonder, and is no wonder” can be supplemented , as suggested by Stevin’s son Hendrick, with “ and no wonder is wonder”. “Wonder is no wonder” points to the fascination for the appealing character of natural phenomena to which student, teacher and researcher are attracted.

Stevin is an excellent anchor figure for this experimental kit because he was one of the first to describe and apply the modern scientific method. In an essay dated 1608, titled “Vant Menghen van Spiegheling en Daet” ( “On the combination of theory and practice”) Stevin states that theory (“spiegheling”) and praxis / experiment (“daet”) should go hand in hand with each other. In his work on hydrostatics and statics we incessantly see the symbiosis between axiomatic theory and observation. The modern scientific method was developed from the 16e century on, through the works of Copernicus, Stevin, Gilbert, Kepler and Galileo and reached maturity in the works of Newton and Huygens.

Stevin discovered the hydrostatic paradox (1586) , which he derived theoretically and which he illustrated with experiments. He also was the first to calculate the force exerted by a liquid on a vertical or inclined wall of a vessel and he discovered the principle of the hydraulic press. The insight that pressure applied to an enclosed incompressible static fluid is transmitted undiminished to all the parts of the fluid, was later formulated by Pascal and the upward force acting on a mass in a liquid is the legendary discovery of Archimedes. Some of the basic experiments in the experimental kit (“Picking up a needle”, “The strange beaker”, “The turning cylinder”, “equilibrium of a vessel”) illustrate the laws of hydrostatics, pointing to the evolution Archimedes – Stevin – Pascal – Huygens. Apart from the intrinsically beautiful natural phenomena which are offered by the experimental kit –think of the surprising effects related to the hydrostatic paradox of Stevin- is it important to recall that hydrostatics and mechanics, historically can be considered as the first fields in which the scientific method proved its value. Also in the field of mechanics the experimental kit holds several intriguing experiments :” Lifting the bottle with sand”, “unwilling bottle”, “Chain sliding from the table”,” Car on an inclined plane”, “The wobbling wheel”.

The field of hydrostatics also illustrates some sociologic aspects of science: a physics law not always bears the name of its discoverer. Stevin’s hydrostatic paradox e.g.
(thoroughly described and proved in 1586) is often named after Pascal…, who was born in 1623. Several classical hydrostatics experiments, associated with Pascal, in reality already were invented and described in 1586. In the book ‘Wonder en is gheen wonder -de geniale wereld van Simon Stevin- ”, a survey is given of the contributions to hydrostatics of Archimedes, Stevin, Pascal, Huygens and others.

The association of this experimental kit with Stevin is also significant for another reason: Stevin displays a wealth of didactic talent, whereas the experimental kit is full of instructive firework. The notions “visible language” and ‘visual didactics” apply to the expositions by Stevin. New information can only be comprehend and absorbed in the mind of the pupil, if it can be connected with other information already present in their experience. This didactical principle is implemented in a wonderful way in the present experimental kit by the choice of the experiments, which are straightforward and directly visible, mostly surprising, sometimes mind teasing and then subtle again. The mirror quartet, the “Turning water”, the “Shadow ring” are nice examples of easy to demonstrate natural phenomena which at the same time ask for subtle explanation.

With this initiative and the realisation of their experimental kit Peeters-Dirckx-Van Dyck follow – with their own original angle of incidence - the tradition set by scientists such as Faraday (with his wonderful “Christmas Lectures”) and the Flemish-Dutch physicist Minnaert (with his unsurpassed three volumes “De Natuurkunde van ‘t Vrije Veld” - “Physics in the open air”.) to fascinate students and public with “daily life”-, yet surprising phenomena and experiments which they can observe and perform themselves, and for which a nice, subtle explanation can be found, step by step.

The experimental kit of Peeters-Dirckx-Van Dyck will lead both teacher and student in a research adventure, where they can explore every step, every element of the set up, every step towards the explanation –experimental/theoretical – of a fascinating natural phenomenon for themselves. I wish teachers and pupils many “Aha”-moments on this search.

I congratulate my colleagues physicists, Wim Peeters, Joris Dirckx and Dirk Van Dyck with this splendid initiative!

Jos Devreese
Professor of Theoretical Physics, em.
Universiteit Antwerpen en Technische Universiteit Eindhoven.

References:
- M. Minnaert, De Natuurkunde van 't Vrije Veld 1, 2 en 3, fifth edition (W.J. Thieme & Cie, Zutphen, 1974) ( in Dutch)
- Jozef T. Devreese and Guido Vanden Berghe, Wonder en is gheen wonder. – De geniale wereld van Simon Stevin.
Davidsfonds Leuven, (2003). ISBN 90 – 5826 –174-3 (only in Dutch) An English version will soon be available.
- The Faraday Christmas Lectures. See for example:
- http://www.gutenberg.org/etext/14474