158 | ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
possibility of a chain reaction that has excited the interest in uranium as a 
practical source of atomic energy * * *, It is perhaps sufficient to say that 
there is some evidence now that, if U* could be separated in quantity from the 
natural mixture of isotopes, a chain reaction could, indeed, be produced. But 
herein lies the catch, for there is no practical large-scale way in sight of Separating 
the isotopes of the heavy elements, and certainly it is doubtful if a way will be 
found. But I should not want to indicate that the uranium matter is a dis- 
appointment * * *,. Success in this direction may await the development 
of a new instrument or technique just as the airplane depended upon the gas 
engine. 
H. E. White % faced the future with more confidence. 
Should uranium atoms of atomic weight 235 be responsible for the observations 
just described, it seems reasonable to suspect that a small piece of uranium metal, 
composed entirely of these atoms alone, should act like a bomb and explode 
with far greater violence than any known explosive. Here then may be the 
source of energy that will make the rocket ship a reality. 
Distinctly disquieting is the note struck by a series of papers pub- 
lished in Nature and the Physical Review on the products of uranium 
fission produced by neutron bombardment by several Japanese work- 
ers at the Nuclear Research Laboratory in Tokyo. Using one of the 
largest cyclotrons in the world, on May 3, 1940, they were able to 
announce production of a radioactive element of atomic number 93. 
This is the element later named neptunium which, with plutonium 
of atomic number 94, played such an important part in the develop- 
ment of the atomic bomb. There can be no doubt that the Japanese 
were thoroughly alert to all the possibilities of the reaction. 
Can uranium fission help in the problem of stellar energy produc- 
tion? Already Saha? has suggested that the highly ionized atoms 
of iron, nickel, and calcium identified by Edlén as the source of the 
coronal lines have been produced through some process akin to ura- 
nium fission. Perhaps it is too early as yet to attempt to apply this 
new knowledge to specific astrophysical problems, but its eventual 
importance cannot be doubted. 
One of the most embarrassing questions which astronomers are 
frequently called upon to answer is, “What use is astronomy? Why 
bother to look at a star you can see only through a 100-inch telescope ?” 
The atomic bomb should provide an eternal answer to such queries. 
So-called “practical” men would certainly have found little to interest 
them in the experiments and theories which atomic physicists found 
so fascinating prior to about 1940. It is true that the cyclotron had 
valuable applications in therapeutics. But on the surface, much of 
the work would have seemed. as useless as the discovery of a white 
dwarf star or the identification of molecules in interstellar space. Yet 
18 Classical and Modern Physics, p. 615, 1940. 
16 Observatory, vol. 66, p. 18, 1945. 
