In response Roosevelt created a government committee to coordinate and provide modest funding for early uranium research. It wasn't until March 1940, John R. Dunning and his colleagues at Columbia University had demonstrated conclusively that uranium-235 was the isotope that fissioned with slow neutrons, not the more abundant uranium-238 as Fermi had guessed. This finding was important, because it meant that a chain reaction using uranium-235 was possible, but only if the isotope could be separated from the uranium-238 and concentrated into a critical mass. Considering that uranium-235 and uranium-238 are chemically identical, they could not be separated by chemical means since their masses differ by less than one percent, separation by physical means would be extremely difficult and expensive. Many scientists thought the best idea for isotope separation was to use the high-speed
In response Roosevelt created a government committee to coordinate and provide modest funding for early uranium research. It wasn't until March 1940, John R. Dunning and his colleagues at Columbia University had demonstrated conclusively that uranium-235 was the isotope that fissioned with slow neutrons, not the more abundant uranium-238 as Fermi had guessed. This finding was important, because it meant that a chain reaction using uranium-235 was possible, but only if the isotope could be separated from the uranium-238 and concentrated into a critical mass. Considering that uranium-235 and uranium-238 are chemically identical, they could not be separated by chemical means since their masses differ by less than one percent, separation by physical means would be extremely difficult and expensive. Many scientists thought the best idea for isotope separation was to use the high-speed