If a nuclear reaction converts matter into energy, what converts energy into matter?

Question

If a nuclear reaction converts matter into energy, what converts energy into matter?

In: Physics

Answer 1

Nuclear reactions do that too. Different nuclei have different amounts of binding energy. For nuclei smaller than ^(56)Fe fusion produces energy and fission absorbs energy, making “more matter”.
For nuclei larger than that, fusion absorbs energy and fission produces it.

Photons can also turn into matter in [pair production](https://en.wikipedia.org/wiki/Pair_production).