Nuclear fission

Nuclear fission is a powerful reaction where the center, or nucleus, of an atom splits into smaller pieces. This splitting releases a huge amount of energy, even more than what we get from burning fuels like coal or gas. It also gives off light energy called gamma photons and can create new forms of matter.

This process was first discovered in 1938 by scientists Otto Hahn and Fritz Strassmann, with help from physicists Lise Meitner and Otto Robert Frisch. They found that when certain big atoms split, they can also release tiny particles called neutrons. If these neutrons hit other atoms, they can cause a chain reaction, where many atoms split one after another.

We can use nuclear fission to make energy in power plants, where the reaction is controlled to produce heat and electricity. The same process, but uncontrolled, powers nuclear weapons, which release energy very quickly and with great force. However, using fission also creates materials that stay dangerous for a very long time, called nuclear waste, which we must handle carefully.

Physical overview

Nuclear fission is a process where the nucleus of an atom splits into two or more smaller nuclei. This splitting can happen on its own or be caused by a particle hitting the nucleus. When fission occurs, it releases a lot of energy. Most of this energy comes from the movement of the smaller nuclei created, with smaller amounts coming from other particles like neutrons and gamma rays.

Fission can sometimes happen without any outside help, as a type of natural process called spontaneous fission. It was first seen in 1940. When fission is caused by an outside particle, like a neutron, it forms a temporary compound system. This system can then break apart in different ways, usually into two main pieces, but sometimes into three pieces as well. One common way fission happens is when a neutron hits a uranium-235 nucleus, causing it to split into smaller nuclei and release more neutrons. These new neutrons can then cause more fission events, leading to a chain reaction.

The energy released in fission comes from the difference in mass between the original nucleus and the smaller pieces created. This mass difference turns into energy, according to Einstein’s famous equation. The binding energy of nuclei plays a big role in how much energy is released. Heavier nuclei, like those of uranium, have less binding energy per particle compared to the smaller nuclei they break into, which is why so much energy is released when they split.

History

Discovery of nuclear fission

The discovery of nuclear fission happened in 1938. Scientists were studying the tiny parts inside atoms, called nuclei, and how they could break apart. This work built on many years of studying radioactivity and the structure of atoms.

Four great scientists were key to this discovery: Otto Hahn and Fritz Strassmann, who did the experiments, and Lise Meitner and Otto Robert Frisch, who explained what was happening. They found that when uranium atoms were bombarded with neutrons, the nuclei could split into two smaller pieces. This process released a lot of energy and was named "nuclear fission" because it was similar to how living cells divide.

This discovery opened up new possibilities in science and would later lead to important developments, including new ways to produce energy and powerful tools for research.