"Chain reactions" at that time were a known phenomenon in chemistry, but the analogous process in nuclear physics, using neutrons, had been foreseen as early as 1933 by Szilárd, although Szilárd at that time had no idea with what materials the process might be initiated.
"Kædereaktion" var på den tid et kendt fænomen i kemi, men den tilsvarende proces i kernefysik, som bruger neutroner, var blevet forudsagt så tidligt som i 1933 af Szilárd, selv om han på det tidspunkt ikke havde nogen ide om med hvilke materialer processen kunne startes.