For a few years now, I have often been asked the following question: “Why did you become a researcher?
Where does his passion for science come from?
When I speak to high school or college students, there is never a time when they don't ask me, something that didn't happen when I was younger.
In my lectures twenty years ago, my listeners were more interested in my research than in my motives.
The age and the honors that have accompanied it are the cause of these recent interpellations.
I do not shy away from them, but I try to answer with the greatest honesty and precision that I am capable of, because the question, beyond what I am concerned about, is interesting.
Why do we become researchers?
What did science represent 60 years ago for a young man who was embarking on this adventure?
Remembering the years of my childhood and adolescence before an audience of young people who live in a very different world from that time is a somewhat nostalgic exercise, but also stimulating.
Frequently, the debate that arises shows me that, despite the time that has passed, the curiosity of youth remains the same.
Our fundamental knowledge about the universe and life has increased considerably, the means we have to educate ourselves and gather information about the world are immensely more powerful today, but the enthusiasm that I detect in the eyes of the young people who listen to me and in his questions is not very different from the one that motivated me when I was his age.
It's just that the world they grow up in is more complex, more difficult to understand, than the one I was lucky enough to live in.
During the period of the Glorious Thirty of my youth, despite the Cold War and the ups and downs of decolonization, hope reigned that the world was heading towards a future of progress and increasingly advanced and enlightened civilization.
Young people who were attracted to research found the paths that allowed them to exercise their passion more easily than now.
Confidence in knowledge had not yet been undermined by the post-truth poison that today attacks the very principles of science.
Malraux had announced that the 21st century would undoubtedly be religious, but we did not quite believe it and I could never have imagined that today I would live in such an irrational world,
Of course, the students who question me don't believe in this nonsense, but they are select audiences, willing to listen to me and share the values of the scientific method.
It is crucial that these values are not exclusive to an educated minority in the face of a mass that doubts or is influenced by lies.
Our society needs science more than ever, and talking about curiosity in general and scientific curiosity in particular, as well as what fosters it, is an essential issue.
This is the message I try to convey to those who come to listen to me.
I tell them about the advances towards knowledge whose history has fascinated me and those that I have witnessed for more than half a century.
With this, I hope to show you the beauty of scientific work and the strength of its values.
When I talk to you about science, I am compelled to remember what scientific truth is, a subtle and evolving notion.
It is this groping search for the truth, which goes through periods of doubt and suspicion, but also of splendid moments of exaltation and triumph.
But let's go back to the initial question: why did I become a researcher?
For as long as I can remember, I've always been drawn to numbers and passionate about making measurements.
I remember, as a very young child, counting the tiles on the bathroom wall and the cobblestones in the schoolyard.
He measured the length of the diagonal of a square or a rectangle and compared it with those of its sides.
He was doing trigonometry without knowing it.
The idea of classifying objects based on precise measurements also led me to fill in a table with the list of metals, ordered from lowest to highest density, from light aluminum to heavy uranium.
At that time there was no internet or Google, and I got all this data from an illustrated Little Larousse.
From my earliest childhood, I have always loved to measure, classify and compare.
Geometry also fascinated me.
Immediately I began to draw circles with a compass and ellipses holding a string with two nails, which I tightened with the help of a pencil.
From the age of 11 or 12, I was fascinated by the number pi.
I remember seeing it written on one of the walls of the Palais de la Découverte, which I visited frequently, where its decimals formed a long spiral.
That this sequence went on to infinity, with no regularity or repetition to be detected in it, fascinated me.
How were we able to determine this succession of figures with infinite precision, while my measurements, obtained from the figures that I so clumsily drew, only told me that pi, the ratio between the circumference and the diameter of a circle, was something greater than 3?
The mystery of this number went even further.
At the Palais de la Découverte there was an interactive experiment that intrigued me.
It consisted of throwing a needle to the ground and counting the number of times it fell between two strips.
The explanatory poster that accompanied it indicated that, if the needle had a length equal to the thickness of the strips, the probability of this happening was equal to 2 over pi, around 64%.
And successive visitors, by pressing a button, made a launch whose result was added to the statistics, which were displayed on a counter.
The value of pi, obtained after several tens of thousands of tosses, gave the number to two or three exact decimal places.
I was intrigued that that could be determined by an experiment like this,
and I began to conceive of the notion of probability and to glimpse its relation to mathematics.
Returning home, I sometimes repeated the experiment with a handful of pencils, which I threw on the parquet in my room.
It was not until much later that I was able to convince myself by reasoning that the value of pi and the properties of the circle did indeed play a role in calculating the probability of the pencils hitting two sticks at the same time.
The planetarium of the Palais de la Découverte immediately attracted me to astronomy.
I remember the starry vault crossed by the ballet of the zigzag planets and the sunrises cutting out the silhouette of the Parisian monuments that had been represented at the base of the dome of the planetarium.
The star made the stars go out while triumphant music accompanied the new dawn and the spectators left dazzled, trying to get used little by little to the light of day.
Serge Haroche (Casablanca, 1944) is a physicist and winner of the 2012 Nobel Prize in Physics for his research on the interaction between light and matter.
This excerpt is a preview of his book 'The revealed light.
From Galileo's telescope to quantum strangeness', from the editorial Debate.
It will be published on the 13th.
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