What's the difference between fission and fusion?

Fission is the splitting of a heavy nucleus into two lighter ones, while fusion is the combining of two light nuclei to form a heavier one.

Fission and fusion are two different types of nuclear reactions that release energy due to the presence of high-powered atomic bonds between particles found within a nucleus. In fission, an atom is split into two or more smaller, lighter atoms. It's a process that often involves the nucleus of an isotope such as uranium-235 or plutonium-239. When these isotopes absorb a neutron, they undergo a nuclear reaction, resulting in two or more smaller nuclei, along with a few spare neutrons and a large release of energy. This is the process used in nuclear power plants and atomic bombs.

Fusion, on the other hand, is a process where two light atomic nuclei combine to form a heavier nucleus. This process is accompanied by the release or absorption of energy depending on the masses of the nuclei involved. Fusion power is the power generated by nuclear fusion processes. In contrast with nuclear fission, this form of power production is still not commercially viable, although it is a long-term goal of scientific research due to its potential for virtually unlimited, clean energy. Fusion is the process that powers the sun and other stars, as hydrogen atoms fuse together to form helium.

In terms of energy production, fusion is generally more efficient than fission. This is because a fusion reaction releases roughly three to four times more energy than a fission reaction. However, achieving the conditions necessary for nuclear fusion is quite challenging, requiring extremely high temperatures and pressure. This is why, despite its potential, fusion power is not yet a practical power source.

In summary, while both fission and fusion are nuclear reactions that can release large amounts of energy, they are fundamentally different processes. Fission involves the splitting of a heavy nucleus and is currently used in nuclear power plants, while fusion involves combining light nuclei and is the process that powers stars.