yaddoe said:
I claim that it is an assumption to say that all matter popped into existence in the big bang
If you don't know how matters can be form, then I would suggest that you do some reading.
I would suggest that you start some encyclopedias, which will at least start small, rather than beginning with astrophysics textbooks. The textbook would explain in more in-depth detail, but you might not understand it all.
Start with Wikipedia Big Bang, since it is readily available. If you want to explore further about the Big Bang cosmology you can look up the References and find other books, journals, etc.
To put it simply, the Big Bang only describe or explain the evolution of the universe as we know it - that is when the universe began to expand from the singularity, which in turn, to form matter, and then matters (mostly hydrogen atoms) into stars, and then planets, etc.
To expand from my brief outline above, we would look at the singularity.
The singularity, as far as we can tell, was too hot and too dense for MATTERS to form. This mean that the singularity is ever more denser than any black hole, and more hotter than any star. It is only when the universe began to expand from the singularity (about 13.7 billion of years ago) that the universe began to rapidly cool down for energy to convert to subatomic particles.
And subatomic particles began to form into atomic particles (electrons, protons, neutrons). The (atomic) particles are the building block of matter, and the 1st matters to form were hydrogen atoms.
When there were enough clouds of hydrogen were formed in the young, and ever-expanding universe, large clouds of hydrogen were pulled together by gravity, making them more massive, that eventually form the 1st new stars between 200 and 400 millions years after the initial expansion (Big Bang). Stars don't just appear out of nowhere.
Stars are formed from hydrogen and gravity. The energy from the stars, like light and heat, come from the fusion of hydrogen atoms to form into helium atoms, from which nuclear scientists would call it
thermonuclear fusion.
These young 1st stars began forming heavier elements, and by the time these 1st stars began dying and exploding as supernova, more heavier matters were created to form other new stars as well as planets. Our Sun (as well as the rest of our Solar System) was actually formed from gigantic molecular cloud (or nebula, about 4.6 billion years ago), and the (molecular) cloud (or nebula) itself was most likely created from the supernova of older stars.
Anyway, matters don't just pop out of nothing. For you think that, clearly showed that you don't understand the Big Bang model.