CERN's first Dutch computer

An electron travels alone in its subatomic world until, suddenly, a photon appears in the distance. Both particles, following their inexorable trajectory in space and time, meet, interact, and collide; like someone hitting two balls against each other, changing their direction and speed and moving away from each other again.

What I have just described so literally is one of the most elementary physical processes we know, the Compton scattering, in which an electron and a photon interact following the laws of Quantum Electrodynamics, enunciated by Feynman and others in the first half of the twentieth century and that we represent simply with a diagram like the one we see below.

This process is one of those responsible for the fact that when an electrically charged particle, such as the electron, is accelerated, it emits electromagnetic radiation (photons), a key phenomenon that must be well known if one considers building an accelerator in which particles such as our beloved electrons circulate and collide because a bad compensation of this effect could cause all the energy imbued in the particle beam to be re-emitted by phenomena of this type instead of serving to accelerate the particles, turning the accelerator into a machine that emits radiation (something that is not bad in itself, since there are medical techniques based on this effect, but that is detrimental if what is wanted is to accelerate the beam).

For all this, we can imagine that the physicists of the European Center for Nuclear Research (CERN) were very interested, after its creation in 1954, in knowing these physical effects and their consequences. To this end, in the theoretical division located in building 4 of the newly created campus, several dozen theoretical physicists were striving to predict these elusive quantum phenomena, arriving at formulas like this one:

However, the road did not end there. Perhaps it did for us theoretical physicists, who pride ourselves on being able to navigate through a tide of complicated calculations and integrals to arrive at expressions like the one above, containing a few fundamental constants, but not for those interested in experiment. If these effects were to be considered for the construction of real machines, someone had to put numbers into those formulas. Someone had to substitute e for 1.60217657 × 10-19 coulombs and c for 299792458 m/s and then do the necessary multiplications and divisions to get the final number.

Today this is trivial. One has but to open one's favorite calculus program or navigate to Wolfram Alpha on one's computer, enter the combination sought and, in a matter of milliseconds, get an answer. But before the wonderful computers we have today, and even before pocket calculators existed, the only machine available to perform these tedious calculations was one within everyone's reach: the human brain.

Before electronic computers existed, the best computing resource was human computers. And at CERN there was the best: Willem Klein.

The child who calculated

In the words of Klein himself, the Dutch son of a Jewish doctor who in the last years of his life earned the nickname “human computer”, his first contact with mental arithmetic was when, at the age of ten, he discovered the decomposition of numbers into prime factors.

Although it may sound like a Saturday afternoon movie cliché, this profound insight into the structure of numbers amazed the very young Klein, and from then on he began to develop his mental arithmetic skills while children his own age were engaged in more childlike activities. While his friends played soccer, Klein was able to factor numbers up to 20000. And he didn't stop there. He became interested in other experiments in mental arithmetic, and at the age of 14, after discovering the logarithm tables, he began to memorize them methodically. And he took it seriously. Such was his fascination with this mathematical operation that, by the time of his death, he had become only the second known man (along with the German mathematician Ruckle) to memorize the first 150 logarithm tables.

This fondness for mathematics, together with an interest in show business and show business, began to cause headaches for his strict father, who tried to get his son to follow in his footsteps in the health profession instead of devoting himself to doing demonstrations more typical of carnies than of a distinguished physician, as he had already begun to do among his neighbors. It was not until the death of his father in 1937 and the subsequent destructuring of Europe due to World War II that young Willem finally abandoned his medical studies and spent several years touring the old continent with his mental calculus tricks alongside a guitarist and an accordion player.

Of course, the newly divided Europe was not the right place for such a banal show as the one Klein performed and the Dutchman soon grew tired of his skills not arousing the expected interest, so he abandoned his attempts to achieve fame through mental calculation and began teaching grammar in schools in Belgium and Holland. Klein's life would have become just another ordinary one if it were not for the fact that the 20th century was the century of science.

The human calculator

The 1940s were the years of economic recovery, of the new world division that would initiate the Cold War and, on a scientific level, were the advent of a deeper understanding of the structure of matter that would lead, over the next twenty years, to an unparalleled scientific revolution.

One of the consequences of this “new science” was that increasingly, numerical calculations and approximations were necessary to obtain numbers that could be compared with experiments. Richard Feynman's famous anecdote about how groups of women with simple mechanical calculators acted as human parts of a computer during the Manhattan Project is a good example of the growing need for computation that science was beginning to require. It is not surprising, then, that the Amsterdam Institute of Mathematics, to which rumors had reached it about a young expert in mental calculation, ended up hiring Klein as a human calculator, a position in which the Dutchman merely performed the mental and arithmetic calculations that other men, more concerned with more formal aspects of mathematics, would take hours or days to do.

However, Klein's career would not end there and, with his fame as the best human calculator in Europe growing, in 1958 he would become part of the Theoretical Division housed in building number 4 of the newly created CERN, corridors that have housed the likes of John Bell, Raymond Stora or, nowadays, John Ellis. There, the not-so-young Willem became the go-to resource for the increasingly complicated numbers that particle physicists needed to crunch, earning him the nickname “human computer” in his own right.

Of course, Klein's talent began to prove obsolete in the following decades due to the development of modern computing. Nevertheless, his incredible ability would not be forgotten, and in the summer of 1976, in a show in front of 600 scientists and clearly influenced by the show business hobby he had carried since his youth, Klein entered the Guinness Book of Records by mentally calculating the 73rd root of a 507-digit number in just 2 minutes and 43 seconds. A spectacular feat that gives almost everyone a headache just by imagining it.

Unfortunately, this would not be the last time that the Dutch genius of mental calculation would make the front pages of the newspapers, because in 1986, this genius of numbers was found stabbed to death in his home and, to this day, the identity of his murderer has not been found out.

However, despite this tragic end, the figure of Willem Klein deserves to be remembered not only in those places where he left his indelible mark in the form of a calculator but also by all of us who, having worked in science, appreciate perspective and want to honor those great men who, in more difficult times, advanced knowledge for the common good of our society.