Anew Einstein lives in America. His name is Edward Witten. He is one of the world's pre-eminent mathematical physicists, whose work has received almost every conceivable prize available in his discipline. Professor Witten, an American, is affiliated to the renowned Institute for Advanced Studies in New Jersey, where Einstein worked after he fled Germany. Several years ago, Prof Witten "temporarily" left the IAS to work for another robust institution: the California Institute of Technology. Caltech lured him to join as a visiting professor with enticements of a salary increase and the chance to start a large research group.

America's top universities compete with each other for the world's best researchers. They are willing to pay the "market value" for top scientists, in the same way that Europeans pay for top football players. But it is not just salary that is used in the battle for the best scientists; large research funds and promises of cutting-edge facilities are also strong incentives.