On a recent visit to Ireland, I was privileged to hold and examine at my leisure, what I consider to be a priceless scientific document. Hand-written and semi-legible in places, with crossings-out and notes scribbled in margins, it was, nevertheless, a revelation. I discovered it in the Visitors’ Centre of the University College of Maynooth.
Fifteen miles west of Dublin, Maynooth has, throughout a history reaching back to pre-Norman times, played a major part in Irish life and politics. The college, that dominates the western end of the main street, and much of the surrounding countryside, is one of the reasons for this. Prior to its incorporation as a constituent college of the University of Ireland in 1966, and the subsequent admission of lay students, Maynooth was principally concerned with the training and ordination of Catholic priests. For a time, it was the largest ecclesiastic college in the world, larger even than its equivalent in Rome.
From its inception in 1795, the college has consistently championed the cause of scientific research, the fruits of which can be seen in the fascinating exhibits that adorn its museum. Many of these exhibits are the inventions of Natural History Professor Nicholas Callan (1799 – 1864), and include very early electric cells and some of the world’s first induction coils.
A student of Callan, and later himself a professor at the college, was Gerard Molloy, who went on to become an authority on radio and communications. One of Molloy’s demonstrators during some of his lectures was radio pioneer, Guglielmo Marconi, whose mother was Irish. The Molloy Prize is still awarded annually to the top student in Experimental Physics.
The document to which I referred was an exercise book containing the notes for a series of lectures about electricity given by Gerard Molloy in 1874. Among discussions of Callan’s inventions, and the then relatively recent discoveries of Michael Faraday, is a description of the electrolysis of sodium sulphate solution. This gives an account of the formation of the anode and cathode products, together with a theoretical discussion of the mechanism of the reaction. As a piece of scientific logic, it is beautiful in its simplicity and impossible to fault. In the light of modern theory, however, it is completely wrong.
According to Molloy, the sodium, being electropositive, is attracted to the negative electrode, where it reacts with water to form sodium hydroxide and atoms of hydrogen. The sulphate, on the other hand, is attracted to the positive electrode, and ‘as it cannot exist by itself’, also reacts with water, this time to give sulphuric acid and atoms of oxygen. No reference is made, anywhere, to the concepts of ions, or even electrically charged particles. The word ‘electron’ is not used.
The theory, nevertheless, does exactly what a good theory should do. It accounts for the observations recorded in a scientific experiment. Within its parameters, it gives a model that shows how hydrogen and oxygen might be formed at the electrodes, and why the solution becomes more concentrated in sodium sulphate as the electrolysis proceeds. It gives possible reasons for the changes in acidity and alkalinity around the different electrodes. Like any good theory, it shows the capability of being used to predict, accurately, the results of further electrolyses. It is capable of being verified experimentally.
It also illustrates something of the nature of theory that is not always grasped by students of science in our schools, or even conveyed to them by their teachers. I suspect that perhaps a number of science graduates remain unaware of this nature. In addition, this lack of understanding deprives the non-scientist of full involvement in decision-making wherever science is concerned.
Within the context of its time, Molloy’s theory was a good one. The word ‘electron’ was adopted by Johnstone Stoney in 1881, seven years after Molloy’s lecture. It referred, however, to a quantity of electricity rather than a particle. The negative nature of cathode rays evolved only slowly toward a belief in their particle nature, culminating in J.J. Thomson’s measurement of their charge to mass ratio in 1897. Realisation of the electron nature of beta-rays from radioactive decay came later still. The theory of ionic bonding, on which our modern description of electrolysis in based, was not developed until 1916.
From our perspective at the start of the 21st Century, it is easy to feel superior to the scientists of an earlier era. On reflection, we should realise that even the most compelling and cherished theories of today will probably end up in the dustbin of scientific history, along with those of yesterday.
One of the science teachers I had at school said that the path of scientific progress is paved with dead theories. He may have been quoting someone else, but his sentiments were no less valid for that.
Dalton’s atomic theory, in its day, was a major breakthrough, handing 19th Century science over to the dominance of Chemistry. Before that, the phlogiston theory governed the discoveries of alchemy and laid the foundations on which that Chemistry was to be built. The 20th Century has seen unprecedented advances on the twin backs of relativity and quantum theories. This does not mean that we have even approached the end of the story.
What we need to emphasise to our students is that no scientific theory can ever be regarded as true. Neither can it be said to explain phenomena. A theory is nothing more than a working model, the conclusions of which happen to coincide with experimental observations. Its only validity is in the fact that it is the best model for its time, and can be used to make predictions about what is not known. When its predictions fail, then the theory must at best be modified, at worst, abandoned altogether.
The non-scientific public seems to have acquired a belief that Science deals with certainties. The result is that the scientific community comes in for severe criticism when it gets something wrong. If we, as teachers, were to emphasise the very tentative nature of theory, then perhaps we might enhance in our pupils, if only slightly, their capacity to make informed decisions whenever science touches their future lives.
As a by-product, some of these future adults may see otherwise dry museum exhibits, such as Gerard Molloy’s lecture notes, transformed into the enthralling document I found them to be.