At the beginning, the universe was
Very cold
Very hot
Denser
About quarks, it is true that
They cannot pulled apart
They are formed by electrons
They form protons and neutrons
When the first atoms did appear?
3 minutes after the Big Bang
Before the 20 minutes after the Big Bang
Atoms have ever existed
After recombination
Electrons joined to other particles
Universe was opaque
Photons were free from electrons
First stars did appear
400 thousands years after the Big Bang
400 million years after the Big Bang
400 years after the Big Bang