Wolfgang Ketterle came to the Massachusetts Institute of Technology (MIT) in 1990. He worked with a different alkali atom, sodium, and published his BEC results four months after Cornell and Wieman, but with a condensate containing some hundreds of times more atoms. In an interference experiment he showed that all the atoms really were linked in a single wave of matter. By first separating a condensate into two parts and then causing these to expand into each other, he could observe distinct interference patterns – rather like what happens when two stones are thrown into still water at the same time. The interference pattern would not have formed unless the matter waves were coherent.