Otto Frisch was closely involved with the discovery of the nuclear fission; he spent a Christmas in Sweden visiting Meitner who was reported to some strange result obtained by a former colleague Hahn. "Hahn discovered that when uranium was bombarded with neutrons one of the decay products was the much lighter element barium." Frische said that, "his reaction was that Hahn had made a mistake, but Meitner was more inclined to trust Hanhn's qualities as a good chemist. After some thought and calculations they could conclude that this must in fact be what was later called nuclear fission." After this discovery Frisch rushed back to Copenhagen to infrom Niels Bohr, but when Frisch had told him he missed the most important aspects because he was so excited about this discovery. After this Frisch continued to work on fission at Birmingham and looked more into chain reactions.