Querido Isaac, querido Albert

Reconstructing the past is a complex and slippery task, no matter which aspect of that past interests us. Historians rely primarily on published written sources, but there is another type of source: correspondences. Dear Isaac, dear Albert -a nod to Isaac Newton and Albert Einstein- reproduces, explaining the context in which they were written, an extensive set of letters from some of the best scientists in history. It is impossible to give an idea of the variety of topics that the letters that appear in this book deal with, both in their human and personal dimension, as well as in the scientific and institutional one, a book that has no parallel in any other published to date and that in more than one sense constitutes an alternative (partial) history of science. Among the many episodes covered are, for example, the letters covering the process by which Edmund Halley convinced, and endured, the ever-reluctant Isaac Newton to write his immortal 1687 book, Philosophiae Naturalis Principia Mathematica; the dramatic letter that Lavoisier wrote on the eve of being a victim of the guillotine; the information that Benjamin Franklin gave to the president of the English Royal Society of the aerostatic ascents that he witnessed in Paris; Charles Darwin's reaction when he received the news that Alfred Russel Wallace had arrived at the same theory of the evolution of species as him; the one Galois wrote to Auguste Chevalier the night before the duel that ended his life, summarizing his innovative mathematical ideas; those that Albert Einstein wrote to his then girlfriend, Mileva Maric, and others to various correspondents that show the influence that philosophy exerted in arriving at the theory of special relativity; the letter in which Max Planck explained to Robert Williams Wood the intellectual sacrifice he had to make to introduce light quanta; or one in which Francis Crick explained to his son the discovery of the structure of DNA.