This morning’s *Observer* column.

So, here we were in this small room. On the table, lying open on a cushion, was Isaac Newton's copy of the first edition of his Principia Mathematica or, to give it its full title, PhilosophiĆ¦ Naturalis Principia Mathematica, the book in which he sets out his laws of motion (the basis of classical mechanics), as well as the law of universal gravitation, his derivation of Kepler's laws of planetary motion and much else besides. It was the keystone of the scientific revolution and was written at Trinity College, just down the road.

On closer inspection, it became clear that the book had been in the wars. It had at some stage, for example, been rescued from a fire. Some of the pages were singed round the edges, but the miracle of its survival paled into insignificance as one turned the pages, because Newton had clearly been dissatisfied with the first edition of his magnum opus. On page after page he had written corrections and added entire paragraphs in his immaculate, tiny handwriting.

What we were looking at was not the creation of this amazing work but, in a way, its recreation…