During one of my visits to CERN, the European research institute for particle physics in Geneva, I met Elmajid Nath-Kaci-Uvutmar, a Touareg from North Africa. As a boy, he fell seriously ill and was nursed back to health by the ‘White Fathers’ in a desert monastery. They renamed him Majid Boutemeur while he stayed there for his education until he was about 14 years old. He found work on a small boat, cleaning fish, until one day in Marseille he decided to stay in France to be trained in physics. I met him at CERN where he was working on the development of software for particle accelerators. I asked him: ‘You were fourteen when you decided to become a physicist. Suppose that you meet a thirteen- or fourteen-year-old boy or girl, asking you: please give me one good reason to go and study physics. What would you reply?’ He looked into my eyes and said:

Brilliant, the true grit of the scientist knowing that the primary product of research is failure. ‘The conditions of nature give us no alternative’, Huygens warned us. Even a ‘failed’ experiment or theory is useful when mapping new land. How awful would it be if I were to come home one evening and say to my wife and daughter: ‘Darlings, physics is finished.’ Fortunately, such a disaster will never happen. We should be so lucky.

That which we call ‘gravity’ is one of the consequences of the structure of space-time. Einstein asserted that the mass-energy-momentum of matter contributes to that structure. But how? What is the interaction? What mechanism is hidden in the = of the Einstein equation? Or, more plainly: how does the Sun tell space-time around it that it's supposed to be curved, and by how much?

The present generation of physicists hasn't found an answer yet, or even a formulation that is clearly a good starting point. Possibly younger folk must give it a go. I hope that they will not have the wrong image of advancement in the sciences. Contrary to street wisdom, great advances in physics are not revolutionary but stepwise.