Deliberately or not, every author is of course present in every book he or she writes - even in a scientific text. - Abraham Pais

Today we live in the midst of upheaval and crisis. We do not know where we are going, nor even where we ought to be going. Awareness is spreading that our future cannot be a straight extension of the past or the present … The century now approaching its end has been one of indiscriminate violence, it has been perhaps the most murderous one in Western history of which we have record. Yet I would think that what will strike people most when, hundreds of years from now, they will look back on our days is that this was the age when the exploration of space began, the microchip was invented, revolutions in transport and communication virtually annihilated time and distance, transforming the world into a "global village," and relativity theory, quantum mechanics, and the structure of the atom were discovered, in brief that this has been the century of science and technology.

Once I even took the train to Utrecht, forty miles from Amsterdam, with my yellow star, this star which I still have. Why did I go? I just wanted to visit some friends. I was a little bit crazy, a little bit insane

Special relativity killed the classical dream of using the energy-momentum-velocity relations of a particle as a means of probing the dynamic origins of its mass. The relations are purely kinematic. The classical picture of a particle as a finite little sphere is also gone for good. Quantum field theory has taught us that particles nevertheless have structure, arising from quantum fluctuations. Recently, unified field theories have taught us that the mass of the electron is certainly not purely electromagnetic in nature. But we still do not know what causes the electron to weigh.