It quickly turned out that uranium fission gave off something like ten times as much nuclear energy per nucleus than did any other nuclear reaction known at the time.
Even so, the quantity of energy released by uranium fission was only a tiny fraction of the energy that went into the preparation of the neutrons used to bring about the fission, if each neutron that struck a uranium atom brought about a single fission of that 1 atom.
Under those conditions, Rutherford’s suspicion that mankind would never be able to tap nuclear energy probably still remained true. (He had been dead for 2 years at the time of the discovery of fission.)
However, those were not the conditions.
The Nuclear Chain Reaction
Earlier in this history, we discussed chain reactions involving chemical energy. A small bit of energy can ignite a chemical reaction that would produce more than enough energy to ignite a neighboring section of the system, which would in turn produce still more—and so on, and so on. In this way the flame of a single match could start a fire in a leaf that would burn down an entire forest, and the energy given off by the burning forest would be enormously higher than the initial energy of the match flame.
Might there not be such a thing as a “nuclear chain reaction”? Could one initiate a nuclear reaction that would produce something that would initiate more of the same that would produce something that would initiate still more of the same and so on?
In that case, a nuclear reaction, once started, would continue of its own accord, and in return for the trifling investment that would serve to start it—a single neutron, perhaps—a vast amount of breakdowns would result with the delivery of a vast amount of energy. Even if it were necessary to expend quite a bit of energy to produce the 1 neutron that would start the chain reaction, one would end with an enormous profit.
What’s more, since the nuclear reaction would spread from nucleus to nucleus with millionths-of-a-second intervals, there would be, in a very brief time, so many nuclei breaking down that there would be a vast explosion. The explosion was sure to be millions of times as powerful as ordinary chemical explosions involving the same quantity of exploding material, since the latter used only the electromagnetic interaction, while the former used the much stronger nuclear interaction.
The first to think seriously of such a nuclear chain reaction was the Hungarian physicist Leo Szilard (1898-1964). He was working in Germany in 1933 when Adolf Hitler came to power and, since he was Jewish, he felt it would be wise to leave Germany. He went to Great Britain and there, in 1934, he considered certain new types of nuclear reactions that had been discovered.