You may know this already, but just like a Lego car, you are made up of building blocks. Leiden physicist Johannes Diderik van der Waals discovered how these building blocks –molecules – are ‘glued’ together, thereby demonstrating why you exist.
Imagine a Lego car made from blocks without studs at the top or indentations at the bottom. Such a car would fall apart immediately, because it is the specific shape of Lego blocks that makes it possible for them to click together. Leiden physicist Johannes Diderik van der Waals discovered the molecular equivalent of these studs and indentations: a natural force that is known to this day in scientific circles as the ‘Van der Waals Force’.
Steam engines
Incidentally, Van der Waals did not make his discovery by focusing on the specific shape of these building blocks. He was studying an entirely different problem. In the 19th century, steam engines and cooling devices first made their appearance in research and industry. This led to the remarkable discovery that physicists did not fully grasp a fundamental natural process.
The process in question is that by which gases become liquid when cooled down. If you cool down water gas (water vapour), you get water. The reverse process (heating up creates gas) is easy to observe, for instance when boiling an egg.
However, in the steam and cooling engines it turned out that above a given temperature, a gas could no longer become liquid. This showed that physicists did not really understand how cooling and condensation work.
Dissertation
In his PhD dissertation at Leiden University Van der Waals demonstrated that the problem can be solved by introducing a new force of attraction between molecules: the Van der Waals Force. This force impacts the transition from gas to liquid because in order to turn into a gas, molecules have to overcome their mutual attraction. In a gas, the molecules float more or less ‘randomly’ in space.
With the new force introduced by Van der Waals, physicists were able to adjust their formulae so as to explain the strange behaviour observed in the steam and cooling engines. In addition, this force also proved to play a role in the fact that molecules are able to clump together into larger structures, such as stones, potatoes and even human bodies. This argument also applies on a larger scale. Without forces such as the Van der Waals Force, all matter in the Universe would consist of loose particles, or dust. This Leiden discovery thus contributed to our current understanding of the structure of all matter in the Universe.
Second Golden Age
Some science historians consider the publication of Van der Waals’ dissertation to be a turning point in Dutch science. They see his dissertation as the start of what they call the Second Golden Age of Dutch science. During this period, a series of fundamental discoveries were made in the Netherlands, which in turn led to the award of many Nobel Prizes.
A Nobel Prize was just as impressive a performance then as it is now, although the enormous personal veneration of Nobel Prize winners that is common today was unknown in the early twentieth century. In 1910 it was Van der Waals’ turn to receive his Nobel Prize. He was awarded this prize for his discovery of the Van der Waals Force and his explanation of the remarkable behaviour of gases and liquids.
Van der Waals’ legacy is still present in academic circles in Leiden today. Students in the lecture halls of the Faculty of Science buildings located at the Leiden Bio Science Park continue to learn about his theories that have withstood the test of time remarkably well.
