Warm up. The sun is 4.6 billion years old – how can it continue to produce so much heat and light?. Nuclear reactions. Create new atoms – different elements Fission – splitting or decay Fusion – merging, combines. H fusion.
(The series of changes matter goes through in a star’s formation, life & death.)
First random, spread out matter
Then a supernova explosion starts things moving/compressing
Gravity will keep pulling things together, generating heat & light