The early universe must have been extremely hot and dense, full of particles and radiation, and photons converted into particle-antiparticle pairs and vice versa. Four known forces in the universe: strong force, electromagnetism, weak force, gravity at high temperatures, the forces unify into electroweak force and gut force, and maybe a super force. Planck era before planck time (~10-43 second), no theory of quantum gravity. Gut era from planck time to end of gut force. Electroweak era from end of gut force to end of electroweak force. Particle era amounts of matter and antimatter nearly equal (roughly 1 extra proton for every 109 proton-antiproton pairs) Era of nucleosynthesis when matter annihilates remaining antimatter at 0. 001 second, and nuclei begin to fuse. Era of nuclei helium nuclei form at age ~3 minutes, and the universe became too cool to blast helium apart. Era of atoms atoms form at age ~380,000 years, and background radiation was released.