To understand the birth and evolution of the universe, it’s essential to talk about particles. They’re the building blocks of everything - dust, gas, stars, planets, galaxies, and all objects and living things in the universe.
Less than a trillionth of a second after the Big Bang, the energy transformed into tiny particles and radiation. These particles formed a very dense and hot ‘soup’ of quarks, gluons, electrons, neutrinos and other particles - these are the tiniest known building blocks of everything in the universe.
There are six different types of quarks (up, down, charm, strange, top, and bottom). These all have different characteristics. The two lightest types of quarks, up and down, combined to form protons and neutrons.
During the next stage of the universe’s development, protons and neutrons fused to form the lightest atomic nuclei - the stuff at the very centre of an atom.
The fusion process stops about 15 minutes after the Big Bang. The universe is now filled with a very hot, opaque particle soup of protons, helium nuclei, and electrons. Over the next hundreds of thousands of years, the universe expands and cools down, but its composition stays unchanged.