Phases of the universe
i -Before 10E-43 second -Plank era- the gravitational force was as strong as the other three quantum forces, all of which were unified. The universe existed in a phase of "Nothingness" or empty higher-dimensional space.
ii- At10E-43 second -GUT era- the symmetry broke down creating a rapidly expanding bubble. At the stage the four forces split apart. Gravity was the first to break free releasing a shock wave through the universe.
iii- At 10E-34 second -end of inflation- the temperature dropped to 10E22 degrees and the last three forces split apart too. The inflationary period ended, the universe coasting to a Friedman expansion. The universe was a hot plasma of free quarks, gluons and laptons.
iv- At 3 minutes -nuclei form- the temperature was low enough for hydrogen to fuse into helium (75% hydrogen, 25% helium) with trace of lithium.
v- At 380,000 years -atoms re born- the temperature dropped to around 3,000 degrees Kelvin allowing atom to form. Photons could then travel freely. This is the radiation measured by the satellites COBE and WMAP.
vi- At one billion years -stars condensed- the temperature dropped to 18 degree Kelvin. Quasars, galaxies and galactic clusters were formed as a by-product of the small quantum ripples created in the big bang fireball. Elements up to iron were formed in the stars while exploding stars ejected higher elements into the universe.
vii- At 6.5 billion years -de Sitter expansion- the Friedman expansion drew to its end to be followed by the de Sitter expansion driven by an unknown anti-gravity force.
viii- At 13.7 billion years -today- the temperature of the background radiation has dropped to 2.7 degrees Kelvin and the universe is still accelerating.

Stages of the universe
The universe can be described as having 5 stages:
- Stage 1: Primordial era, between 10E-50 and 10E5 seconds. During this period the universe expanded rapidly and cooled. During this period the four forces that were initially unified broke apart into the four separated forces existing today (gravity, electromagnetism, strong and weak nuclear forces). At first the universe was opaque and the sky white as the light was absorbed soon after it was created. But, 380,000 years after the big bang, the universe was cool enough for the atoms to form and the sky became black. The microwave background radiation dates from that time. Finally hydrogen fused into helium but life was impossible.
- Stage 2: Stellar ferrous era, between 10E6 and 10E14 seconds. The hydrogen gas was compressed during this period forming the stars in which hydrogen fused into helium making the stars emit light. We live in this period after the conditions wee met to make life possible.
- Stage 3: Degenerate era, between 10E15 and 10E39 seconds. The hydrogen in the stars is exhausted and the fusion process stops leaving dead unchaining stars (dwarf stars, neutron stars, and black holes) in the sky. The universe gradually falls into darkness, the temperature falls, and the planets orbiting these stars will freeze. This will be the case o the earth -if it is still intact- whose surface will be frozen and intelligent life will disappear unless it has found new hospitable territory somewhere else (such as orbiting small red dwarf stars that will live longer than giant stars).
- Stage 4: Black holes era, between 10E40 and 10E100 seconds. The only source of energy will be the slow evaporation of black holes (according to Stephen Hawking and J. Berkeinstein, black holes radiate a small amount of energy called evaporation) that cannot be found experimentally because it is too small. Black holes, weighting as much a galactic cluster, can emit energy for various length of time, up to 10E117 seconds. At the end of their lie, black holes explode. In theory intelligent life could survive in the shadow of this evaporation.
- Stage 5: dark era, after 10E101 seconds. All heat sources will be exhausted and the universe temperature will be 0 degree Kelvin when the atoms come to a halt. Absolutely no life can exist anymore.