Marietta Blau in the history of cosmic rays

Carlson replies: Ruth Lewin Sime correctly points out the important contributions to the nuclear emulsion technique by Marietta Blau, which are unfortunately often forgotten. Blau, together with Hertha Wambacher, observed cosmic-ray-induced “stars” in 1937. In my article, I pointed out that many results of fundamental importance were indeed obtained using nuclear emulsions, in particular the discovery of the pion that earned Cecil Powell the 1950 Nobel Prize in Physics.

In 1950 Blau and Wambacher were nominated for the Nobel Prize in Physics for the method of exposing sets of emulsion plates at high altitude and for observing cosmic-ray-induced stars. ¹ Among the other 28 nominees that year was Cecil Powell, who received 16 nominations.

Contrary to what Sime says, the names of Blau and Wambacher are not absent from the “Nobel texts.” In its 1950 recommendation to the Royal Swedish Academy of Sciences, the Nobel Committee for Physics included as an enclosure a nine-page detailed and accurate account, written by committee member Axel Lindh, ² on the work by Blau and Wambacher. Lindh wrote that without any doubt Blau and Wambacher were the first to use plates of emulsions to study cosmic rays and the first to use the technique to observe cosmic-ray-induced stars, a phenomenon earlier observed in cloud chambers. Lindh noted that Wambacher, in a 1938 paper, ³ wrote that E. G. Steinke was the one who had proposed using emulsions to study cosmic-ray stars. In his conclusion, Lindh acknowledged the pioneering work by Blau and Wambacher but noted that it was not of sufficient significance for a Nobel Prize.

The committee report ⁴ discussing the nomination of Blau and Wambacher states that among the notable descriptions of progress made using the emulsion technique are a 1925 article in which Blau says that protons also can be observed and one by Blau and Wambacher in 1937 reporting cosmic-ray-induced stars. The report ends with the proposal to award the 1950 Nobel Prize in Physics to Powell.