On 8 April 1911 something peculiar happened in the physics laboratory of Leiden physicist Heike Kamerlingh Onnes. In an experiment involving liquid helium, Kamerlingh Onnes observed how an electrical current suddenly encountered no resistance from the wire it ran through. This proved to be the first step towards one of the greatest physics discoveries in modern history.
At the time, Kamerlingh Onnes’ laboratory was already known as one of the most exciting places in the world in the field of experimental physics. After all it was in this lab that Kamerlingh Onnes had already set a world record three years earlier. He became the first person to confirm a remarkable prediction regarding the behaviour of gases. This prediction was based on the work of theoretical physicist Johannes Diderik van der Waals, who was born and later obtained his PhD in Leiden. He was awarded the Nobel Prize in Physics for his work in 1910.
Van der Waals predicted that the substances we know as gases can become liquid when compressed at a specific, very low temperature. Kamerlingh Onnes, who was primarily a man of action, wanted to find out whether this was true. It turned out that it was: in 1908, he succeeded in cooling down the light noble gas Helium sufficiently to make it liquid. This required a temperature of minus 273 degrees Celsius, which made the location of the experiment – the Kamerlingh Onnes Laboratory – for a while the coldest place on earth.
For Kamerlingh Onnes, this breakthrough formed the prelude to an accidental discovery that led to him also being awarded the Nobel Prize in Physics in 1913. This discovery took place on 8 April 1911. That was when Kamerlingh Onnes observed superconductivity, the bizarre phenomenon by which the electrical resistance of some materials suddenly disappears at specific, usually extremely low, temperatures.
This discovery not only led to exceptional new fundamental knowledge that shook the very foundations of physics, it also resulted in a number of useful applications. Since superconductivity makes it theoretically possible to let a current flow indefinitely, it also makes it possible to construct so-called superconducting magnets. A flowing current, as physicists know, always creates a magnetic field. By using superconductivity, in which the current just keeps flowing, you can therefore build very strong magnets. The only disadvantage is that you have to cool these magnets down to extremely low temperatures.
Nonetheless, superconducting magnets proved to be very important. They are used for instance in MRI scanners in hospitals. The many scans that these devices make of the human body day in, day out would not have been possible without this one accidental discovery by Kamerlingh Onnes.
Superconducting magnets also found their way into hover trains and the Large Hadron Collider, the 27-kilometre high particle accelerator of the European particle physics institute CERN that in 2013 allowed physicists to discover the long-sought Higgs particle. This was the most important physics breakthrough of the past decade and it would not have been possible without the pioneering work of Kamerlingh Onnes.
It therefore comes as no surprise that Heike Kamerlingh Onnes still enjoys a high measure of respect both in the Leiden academic world and far beyond. The Kamerlingh Onnes Building, once his laboratory, is still owned by Leiden University and is now home to the Law Faculty. Moreover, a new Kamerlingh Onnes Laboratory was erected at the Bio Science Park in Leiden in the 1990s, where a new generation of Leiden physicists, following in the footsteps of their predecessors, continue to conduct fundamental research, including research at extremely low temperatures.
