A brief overview of how the Universe began according to OCR A-level Physics.

1) At the start of the Universe, it was very hot/ extremely dense/ singularity.
2) All forces were unified (my thoughts: gravitational, electromagnetic, strong nuclear and weak nuclear). (my thoughts: Force is a component of energy as energy in the form of work is force applied to a particular direction/ distance like a person pushing a heavy object to a location).
3) Expansion led to cooling. (my thoughts: As the further particles go, the less they collide so their kinetic energy decreases and the pressure they exert decreases so temperature decreases).
4) Quarks/ leptons soup form (my thoughts: I don’t know why, perhaps the Scientists at Large Hadron Collider may discover how this came about).
5) More matter than anti-matter (my thoughts: possibly because of quarks and leptons combining into protons, neutrons and electrons).
6) Quarks combine to form hadrons/ protons/ neutrons.
7) Imbalance of neutrons and protons creates primordial Helium.
8) Atoms are formed (my thoughts: as Helium nuclei fuse to heavier nuclei).
9) Gravitational force is responsible for formation of stars/ galaxies.
10) Temperature becomes 2.7 K/ 3 K or the universe is saturated with cosmic microwave background radiation (my thoughts: as that leftover energy is not being used or converted into matter so it stays as background radiation).