Rafael, age 11 from Melbourne, asked what a nuclear bomb actually does. Well, a nuclear bomb is like any other bomb in that it causes an explosion by releasing a massive amount of energy all at once. However, nuclear bombs work differently than other bombs.

Atoms are tiny particles that make up everything around us, including ourselves. Nuclear bombs work by changing the cores of atoms, called nuclei, to turn them into different types of atoms. This process releases a lot of heat energy, which quickly turns into a powerful wave of pressure, resulting in an explosion.

Atoms consist of even smaller particles called protons, neutrons, and electrons. The nucleus is the central core of an atom made up of protons and neutrons, surrounded by a cloud of electrons. Chemical reactions occur when electrons are rearranged, while nuclear reactions occur when protons and neutrons inside the nucleus are rearranged.

There are two types of nuclear bombs. In fission bombs, the nuclei of atoms with many protons and neutrons, such as uranium, are split apart. In fusion bombs, two small nuclei, like the cores of hydrogen atoms, are fused together. However, fission bombs are simpler and more common.

Some nuclei require very little energy to split apart, such as those in certain types of uranium or plutonium atoms. These nuclei can undergo fission even without external energy. When a nucleus undergoes fission, it splits into two smaller nuclei and releases a few neutrons.

To create an explosion, a certain amount of uranium must be brought together in one place. For example, a fission bomb typically uses a purified sphere of uranium weighing about 52kg. Additionally, specific types of uranium with a specific number of neutrons are required.

When a nucleus undergoes fission and releases neutrons, these neutrons can hit other nuclei, causing them to undergo fission as well and release more neutrons. This chain reaction continues, resulting in a massive explosion.

An unexploded fission bomb usually consists of separate pieces of uranium or plutonium that are too small to start a chain reaction on their own. A chemical explosive is used to bring these pieces together, triggering the chain reaction and causing the bomb to detonate.

After a nuclear explosion, the two smaller nuclei left over are radioactive, which can be very harmful to human health if there are enough of them in one place. This leftover radioactive material is called “fallout.” The fallout, along with the immense size of the explosion itself, is what makes nuclear bombs more dangerous than other bombs.

Nuclear bombs have only been used twice in history, both during World War II by the United States against Japan. Efforts are being made worldwide to ensure that nuclear weapons are never used again.