The first idea of atomic bomb proposed by E. Fermi and, especially, L. Szilard, who was the real writer of Einstein's letter to President F D Roosevelt in 1939, was shown to be based on a fast neutron chain reaction in normal uranium which was later proved to be inert for fast neutrons At that time such an idea was also proposed independently by L. Peierls in Britain, but he soon abandoned it because of its great critical mass estimated theoretically by himself.
The large scale enrichment of uranium was at first pursuited to produce a thermal nuclear chain reaction (the nuclear reactor) effectively. This stream was thus independent of that for the construction of the bomb at the early stage Those two streams above were, however, joined together in 1940 by O. Frisch and Peierls in their memorandum on a super bomb, which first showed the technological principle of atomic bomb based on the fast neutron chain reaction in pure uranium 235 In contrast to these two streams in the U.S. were kept divisitive by compartmentalization of information adopted by V.Bush, the chairman of NDRC.
The idea of the Frisch-Peierls memorandum is studied in detail in comparison with the MAUD reports, the British official reports, completed in the summer of 1941. It is shown that the influence of the British research on the atomic bomb was the most important factor for the full start of the development of the bomb in the U.S. in the autumn of 1941. The problem on independence between NAS report of November 6,1941 and the MAUD reports is discussed.
A plan of plutonium bomb was existed separately from a plan of uranium bomb at the beginning of the development of atomic bombs. The following is the transition of significance of the plan of plutonium bomb.
In December 1940, the plan of plutonium bomb was posed in England and U.S.A. independently.
In December 1941, the plan of plutonium bomb was not stated clearly, but it was interested in whether the fission chain reaction using uranium is feasible or not. Because, such reactions will produce the "94" (plutonium) which is material of plutonium bomb.
In June 1942, the plan of plutonium bomb was stated clearly, and also it caused Army and Industries to be concerned in the development of atomic bomb in earnest.
In December 1942, the chain reaction was proved. So the plan of plutonium bomb was changed from which to be for ending the war to which to be concerned with the atomic power policy of the post war.
The juvenile magazine Shonen'en was the first to put in articles on science and technology in Japan. As it was well received, many magazines just like Shonen'en were published one after another.
Shigeaki Nakagawa was one of famous journalists who wrote the articles on science in these juvenile magazines.
He learned German from R. Lehmann who was a teacher of Ogakusha in Kyoto. He learned physical sciences through the learning of German When he was a teacher of Kyoto Normal School, he wrote many science textbooks on referring to F Schoedler's Das Buch der Natur. Then he resigned his post as a teacher, and he was engaged on a staff of the education magazine He published a magazine Shonen'en with Teisaburo Yamagata in 1888.
Articles which he wrote in juvenile magazines incorporated a variety of ideas designed to arouse interest in science and technology. His articles had a great influence on the popularization of science to the youth.
Enlightenment of science to the youth became gradually performed by specialists of science The main medium of science to the youth changed from the juvenile magazine to the book. So he ceased to play the role of popularizer of science to the youth.
A Babylonian capacity unit "silà" was also used as a unit of "thickness" of a log. Neugebauer and Sachs almost clarified the meaning of the silà through a study of YBC 4669, 8600, that is, "x silà of a log" means a capacity of a circular cylinder whose height is 6 šu-si But the contents of VAT 8522 Vs.I which treats the thickness of a log remains obscure despite their efforts.
I find a clue to the solution to the calculation in VAT 8522 Vs.I in the expression of relation
1 silà=(6 šu-si)³=(0;l ninda)³
and the number 1;20 which is hidden in line (6a) of the text. Neugebauer suggested that 1;20 was a "normalizing constant" and I regard this as a proportional constant between the area of a square and the area of its inscribed circle in case of a certain equivalent transformation of a prism into a circular cylinder The process of the calculation made by a Babylonian scribe in a roundabout way is as follows.
In the first place he takes the cubic roots of 1,4 silà and 8 silà, and gets 4 dal,2 dal respectively (unit; 6 šu-si). Namely he transforms each circular cylinder into a cube retaining the same volume. Consequently "dal" is a side of the cube and not a diameter here. Next after taking the average of the dais, an assumed circular cylinder which is inscribed in the averaged cube is introduced and the area its base is calculated by a usual formula. This "whole area" is multiplied by 6,40 ( = 5,0 * 1;20) to get the true volume. At this point Babylonian "normalization of a log" has been completed. The last calculation, which is omitted in the text is, in my judgement, as follows. By dividing the volume by the area of the base of the normalized log, the length of the log is obtained, and then by multiplying it by 9/10 the length of the log which should be cut down is obtained.