THE imagination plays an important but often unacknowledged role in scientific research.
The nature of the scientific method is hypothesis followed by experiment.
In the hypothesis, you put forward your best theory, based on a logical synthesis of known facts, about the nature of some aspect of physical reality. You then design an experiment which, when carried out, will either support your hypothesis or cause you to reject it. Imagination plays a role mainly in the design of the hypothesis, a role vividly illustrated by the life of the famous German chemist August Kekul.
In 1850 Kekul, a young student of architecture, appeared as a witness before a grand jury that was investigating the circumstances of the death of Countess Gorlitz. Her charred body had been found several weeks earlier in an undamaged room. It was widely believed that her death was due to spontaneous combustion caused by excessive drinking.
Another witness called before the grand jury was a chemist, Justus von Liebig. Von Liebig convincingly demonstrated that the toxic effects of alcohol ingestion would kill a person long before tissue alcohol levels could rise to a sufficiently high level to cause the body to become flammable. Kekul was so impressed by this evidence that he gave up his architecture studies and became a student of chemistry under the guidance of von Liebig. He went on to have a very distinguished career in chemistry.
THE grand jury investigation in 1850 ended in the conviction of a servant, a man called Stauff, for the murder of the Countess.
Stauff had been caught selling stolen goods belonging to his employer, in particular a ring designed in the form of an alchemical talisman. The design was of two intertwined snakes biting their own tails. This design became embedded in Kekul's imagination and played an important part in his later career.
Kekul is probably best known for solving the structure of the benzene molecule. He had deduced from experiments that the molecule is composed of six atoms of carbon and six of hydrogen. However, there are many different ways in which these atoms could be joined together to form the molecule and Kekul found it very difficult to figure out the correct arrangement.
He wrestled with his, problem for a long time until eventually one evening while dozing at the fireside he had an illuminating dream. A vision of atoms appeared in his dream. These carbon and hydrogen atoms danced about and occasionally joined up in a long snake like fashion. Then, suddenly: "One of the serpents caught its own tail and the ring thus formed whirled exasperatingly before my eyes. I awoke as by lightning and spent the rest of the night working out the logical consequences of the hypothesis."
Kekul had hit on it. He proposed that the benzene molecule is a hexagonal ring of carbon atoms from which hydrogen atoms dangle like charms from a bracelet. At first other chemists were sceptical about this ring shaped formula, but, as it became apparent that the architectural arrangement of the atoms in the molecule neatly explained the known properties of benzene the formula quickly became generally accepted.
The universal acceptance of the rind structure over the past 150 years is rather surprising when one considers that no one on earth had ever seen a benzene molecule until, in June 1988, the first picture of one, photographed in a scanning tunnelling electron microscope, was published.
Kekul was quite adept at dozing off and reawakening with solutions to important problems. Earlier in his chemistry career, before the benzene episode, he had a very similar experience when working out the structure of the methane (marsh gas) molecule. He knew that the molecule contained a single atom of carbon and four atoms of hydrogen. But how were the atoms joined together to form the molecule of methane?
THEY had to be joined together in such a way as to explain the chemical properties of methane. When working on this problem, Kekul was staying in London, and late one evening was returning home alone by omnibus. As usual he took a seat on the roof. It was a warm balmy evening and the streets were fairly empty.
Kekul fell into a light doze. He had a dream in which carbon and hydrogen atoms danced around and took up various configurations. One configuration, which solved his problem, was in the form of a cross with carbon at the centre and four hydrogen atoms spreading from it in a cross shape. He awoke with this image, the basic structure of the methane molecule, in his mind.
While the general case of the importance of the imagination holds, Kekul's trick of solving his problems while dozing and dreaming seems to have been peculiar to himself. I have often nodded off after sitting for a protracted period mulling over some scientific puzzle or other. The net effect of this exercise for me is to awaken a short time later with a dry mouth and in a somewhat ratty humour.
In 1981 at the IBM research laboratory in Zurich, Gerd Binning and Heinrich Rohrer developed the scanning tunnelling electron microscope (STM).
In 1986, Binning and Rohrer shared the Nobel Prize in physics with Ernst Ruska, who played a major part in inventing the original form of the electron microscope in the 1930s. The STM is specialised for the examination of surfaces. It is exquisitely sensitive to surface detail and can readily image molecules and atoms.
The microscope works by bringing the tip of a very fine metal needle to within 40 billionths of an inch of the surface to be examined. A small voltage is applied between the needle and the surface and the needle is scanned over the surface.
An electric current passes between the surface and the tip of the needle and the size of the current increases and decreases as the gap between the tip of the needle and the surface decreases and increases. Monitoring the changing current as the needle passes over the surface gives a measure of surface undulations.
The resolution of the system is good enough to allow individual atoms to be "seen". Measurements of the undulating current are fed into a computer, where the information is processed to produce an image of the surface. In 1988 the STM was used to examine an array of benzene molecules - laid out on a metal strip. The outline of the molecule seen in the STM resembles a doughnut. It took almost 150 years for technology to advance sufficiently to image for the first time what Kekul had seen in his imagination.