1938 Nuclear Fission ~ Realization of the Splitting of Uranium Nucleus

In 1934, Hahn and Strassman, continuing the work by Enrice Fermi, bombarded uranium with slow moving neutrons. They found that the uranium nucleus split up into smaller daughter nuclei, having a different atomic makeup from the parent and released large quantity of radiation. He thought he might have created a [synthetic element], heavier than uranium since no one at that time thought that it was possible to split the uranium nucleus and release the tremendous energy that bind the uranium nucleus.

But four years later (1938), Hahn and Strassmann identified that one of the daughter nuclei was actually barium which had an atomic number of 56, just a little more than half of the atomic number of uranium (92).

During her famous walk in the snow with her nephew Otto Frisch, Lise Meitner postulated that a nucleus might divide into two smaller "drops" like water. It might first elongate slowly, forming a narrow neck and then finally separate.

Simulating Nuclear Fission We can carry out a simple investigation of the fission by using water drops. Smear 5ml of cooking oil on a flat surface. Put a small drop of water on the surface and shake it vigorously. Observe if the water drop distorts or break up. If the drop splits into two, are the two parts of the same size? Are there any small droplets found?

The problem was that after the separation, the two drops would be driven apart at high speed by their mutual electric repulsion. Where could that energy come from to drive them apart?
Fortunately, Lise Meitner realized that the mass of the fission products was less than the total mass before fission took place. According to Einstein's formula ( E = mc² ), the mass lost must has been converted into energy. It was the source of energy for the fission!

Once the explanation came out, physicists and chemists in universities all over the U.S. began testing the premise and proved that it was true. The splitting of uranium nucleus was finally realized.

Bohr: Oh what idiots we all have been! Oh but this is wonderful! This is just as it must be!

Diagram showing splitting of nucleus

The mass of the fission products is less than the total mass before fusion takes place. The mass lost has been converted into vast amount of energy. Therefore, this process can be used to provide nuclear energy. Since the first nuclear reactor was built by Enrice Fermi in 1942, many nuclear power stations were opened around the world.


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