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Hertz's Ideas on Mechanics

Rarely, if ever, was the human spirit under a closer critical scrutiny than in the following masterpiece of the great scientist of the 19th and 20th centuries, Henri Poincare. The work itself is seldom cited. Yet, the reader can find in it all the objections that can be raised against the main scientific inventions of the human spirit. They are still valid today, exactly as they were more than a century ago, or three centuries ago, for that matter. It is, first and foremost, advisable to pay close attention to the definition of central forces as given by Poincare. Like all of the classics of science, he understood them with a string attached: their magnitude should depend only on the distance between points. Einstein himself used the definition of central forces in that connotation when he judged the whole system of the classical mechanics and introduced the general relativity. However, the very first definition of the central forces, as it appears in Newton's Principia, doesn't ask anything of the kind. What can we say, but repeat with Nietzsche: the first reaction is usually the right one! It is also advisable to pay attention to the critique of the concept of energy: it stands even today as it was then, in this work of Poincare. Yet, in spite of the overwhelming cases against energy, the theoretical physics doesn't seem to stop speculating upon the kinds of energy that might exist in the world. Finally, it is worth paying attention to the criticism of the way in which Hertz assigns matter through a hypothesis: it seems like the hypothesis of missing mass of today. It is our conviction that this masterpiece is not quite known to the English speaking readers. This is why we undertook here the burden of its translation. We hope to give it another chance, in order to have, at least nowadays, more than a century from its first publication, the impact it deserves on the human spirit.