Light is a benefit for mankind; this is why the nations of this world – or their diplomats – decided to celebrate it for an entire year. Light was the first thing to be created by God, as we are told in the Book of Genesis, and we all remember how Haydn in his oratorio Die Schöpfung prepares us for the solemn moment when, after a mysterious pianissimo, the full orchestra and the entire choir rejoice after having reached this word of the text, ‘Licht’, C major and fortissimo. God was still alone then and Light the first demonstration of His power. The universe did not yet exist; only two days later, according to the Biblical report, the sun and the moon were created. We have to imagine that those who rejoice in the event are angels, not human beings. When, however, in their stead man, ‘le maître de la nature’ as he was called by Descartes, made an attempt at demonstrating his power in the same way, recently, only 70 years ago, there was not so much to rejoice in. I still remember when, in 1945 after the war had come to an end in Europe, a light ‘brighter than a thousand suns’ (‘heller als tausend Sonnen’ to quote the title of Robert Jungk's famous book of 1956) was produced in East Asia, above the town of Hiroshima, light as force de frappe to use the French expression, surpassing in its efficiency everything we had experienced before, with thousands of victims. Afterwards, the crime could only be justified as a test; in contrast to God, man can never be sure of his exploits right away. As a matter of fact, there was a second ‘test’ shortly afterwards (Nagasaki), and there would have been a third one, on Tokyo, if the Tenno had not been so wise to give in. When man is left alone with his creativity, he is incalculable (‘quand il veut faire l'ange il fait la bête’, as said Pascal), and only researchers of the forgotten past applied their tests to themselves (Madame Curie, for instance). When we produce too much light, the benefit cannot be taken for granted, and certainly we don't see the stars any more.