A boy’s wonder led to a world-renowned career in science

For years, people have been asking me, “Why did you become a research scientist? Where does your passion for science come from?” Whenever I speak to high school or university students, they always ask me that. But that wasn’t always the case. Twenty years ago, audiences listening to my lectures were more interested in my work than in my motivations. Perhaps the respect that comes with age is the reason. I don’t shy away from that question – I try to answer honestly and accurately because it’s an interesting question in general. Why do people become research scientists? What did science represent 60 years ago for a young man starting out on this adventure?

Reminiscing about my childhood and adolescence in front of young people who live in a very different world is both nostalgic and stimulating. The discussion that often ensues shows me that the curiosity of youth has persisted throughout the years. Our knowledge about the universe and life has grown considerably, and we now have immensely more powerful ways to educate ourselves and gather information about the world. But the enthusiasm I see in the eyes of my young audiences, that I hear in their questions, is not very different from my own when I was their age. It’s just that the world they are growing up in is more complex, more difficult to understand, than the one I was lucky enough to live in.

During the post-World War II economic boom of my youth, there was a feeling of hope that the world was progressing toward an increasingly advanced and enlightened civilization, despite the shocks of the Cold War and European decolonization. Young people attracted to research careers found it easier to pursue their passion than they do today. Confidence in the human body of knowledge had not yet been undermined by the poison of post-truth that is currently attacking the foundational principles of science. André Malraux declared that the 21st century would undoubtedly be religious, but we didn’t really believe this. I never could have imagined that I would be living today in such an irrational world, where creationism is thriving and more than a few believe that the Earth is flat or that vaccines are dangerous.

The students I speak to don’t believe this nonsense, of course, but they are select audiences who are willing to listen and who share the values of the scientific method. It is vitally important that these values don’t remain the exclusive preserve of an educated elite surrounded by skeptical masses easily swayed by lies. Our society needs science more than ever, so it’s essential for us to talk about curiosity in general and scientific curiosity in particular, as well as those things that encourage it. This is my message to those who come to listen.

I speak to these audiences about how the body of knowledge has expanded over time, a story that has always fascinated me, and about the advances I have witnessed over 50 years. My purpose is to show them the beauty of scientific work and the strength of its values. In speaking to you about science, I feel compelled to remind you that scientific truth is a subtle, ever-evolving concept. This fumbling for truth, fraught with periods of doubt and misgiving, can also yield splendid moments of exaltation and triumph.

But let’s return to the initial question: why did I become a researcher? For as long as I can remember, I have always been attracted to numbers and loved taking measurements. I remember counting the tiles on the bathroom wall and the cobblestones in the schoolyard as a very young child. I would measure the length of the diagonal of a square or rectangle, and compare it to the sides. I was doing trigonometry without knowing it. The concept of classifying objects using precise measurements led me to create a table of metals ranked by density, from light aluminum to heavy uranium. There was no internet or Google back then, so I collected all this data from the Little Illustrated Larousse dictionary. I was also passionate about geometry, and would draw circles with a compass and ellipses by holding a string with two nails, which I stretched with a pencil.

When I was 11 or 12, I became fascinated by the number pi. I remember seeing it written on a wall at the Palais de la Découverte science museum in Paris, its numbers arranged in a long spiral. It fascinated me that pi went on ad infinitum, without any detectable pattern or repetition. How were we able to determine this sequence of numbers with infinite precision, while the measurements from my clumsily traced circles only told me that pi (the ratio between the circumference and the diameter of a circle) was some number greater than three?

The mystery of pi deepened. The Palais de la Découverte had an interactive experiment that intrigued me. It consisted of tossing a needle on the floor and counting the number of times it spanned two floorboards. The exhibit had a poster that explained the experiment. If the needle has a length equal to the thickness of one floorboard, the probability of the needle spanning two floorboards was equal to 2 over pi, or about 64%. Each person who tossed the needle by pressing a button added to the statistics, which were displayed on a counter. The value of pi, obtained after tens of thousands of needle tosses, was thereby calculated to two or three decimal places. I was intrigued that the value of pi could be determined by such an experiment, and I began to understand the concept of probability and its relation to mathematics. I would sometimes repeat the experiment at home with a handful of pencils, which I would throw on the parquet floor in my room. It was not until much later that I became convinced that the value of pi and the properties of the circle did indeed play a role in calculating the probability of a pencil spanning two squares of parquet flooring.

The Palais de la Découverte’s planetarium immediately interested me in astronomy. I remember its star-speckled dome traversed by zigzagging planets, and the silhouettes of Parisian monuments at its base. The rising sun made the stars fade away, while triumphant music accompanied the new dawn, dazzling the spectators as their eyes slowly adjusted to the light.

Serge Haroche is a physicist who won the 2012 Nobel Prize in Physics for his research on the interaction between light and matter. This excerpt is from his book, La Lumière révélée: De la lunette de Galilée à l’étrangeté quantique (OJ.SCIENCES, 2020).