Question: Can you explain nuclear fusion and nuclear fission please?

Simon Holyoake answered on 18 Jun 2013:

In simple terms, nuclear fusion is when the nucleus of atoms are joined or fused together (normally from a very high speed collision) this results in a release of large quantities of energy (in the form of photons created from some of the mass in the nucleus) as well as creating heavier elements (elements with larger nucleii and higher atomic mass)

Nuclear fission is the opposite, it is typically when very large atomic nucleii are split into smaller pieces, this normally happens when a free neutron is absorbed by a large nucleus, the extra neutron ‘tips the balance’ and the nucleus splits into lighter elements, releasing more neutrons which go on to split other nucleii, and in the process release photons (in the form of gamma radiation)