187 The Big Bang in Eras

To look at the development of the Universe through the Big Bang, astronomers have divided the development into steps or eras . These eras are our best scientific match to the data we currently have; they seem scientifically sensible. New data is being used to revise and heighten our understanding of these eras.

An illustration showing the development of the Universe. A representation of the evolution of the universe over 13.77 billion years. The far left depicts the earliest moment we can now probe, when a period of 'inflation' produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted about 375,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe.
Public Domain | Image courtesy of NASA.

The generally accepted Big Bang Eras include:

  1. Planck
  2. Grand Unification Theory (GUT)
  3. Electroweak
  4. Particle
  5. Nucleosynthesis
  6. Nuclei
  7. Atoms
  8. Galaxies

A summary of the Big Bang events occurred in this order:

  1. Big Bang beginning – a bright and hot event →
  2. Planck Era ; initial energy →
  3. Elementary Particles – photons create particles and antiparticles →
  4. Inflation of the Universe →
  5. Four Forces become distinct (strong, weak, electromagnetic, and gravity) →
  6. Protons, Neutrons, Electrons, and Neutrinos formed →
  7. Hydrogen ions fusion into helium ions 
  8. Stable, Neutral Atoms formed →
  9. Protoclouds formed →
  10. Stars, stellar systems, galaxies formed →
  11. Life, Humans; today


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