CRONOLOGY OF THE UNIVERSE :-

The initional hot and dense state is called the PLANKepoch , a brief  period extending  from  time zero to one Planck time unite of approximately 10^-43 seconds. During the Plank epoch , all types of matter and all  types of energy were concentrated into a  dense state, where gravitational is believed to have been as strong as the oyher fundamental forces , and all the forces may have been unified. Since the Plank epoch ,the Universe has been expanding to its present form, possibly with a very brief  period of cosmic inflaction which caused the Universe to reach a much larger size in less than 10^-32 seconds.

HISTORY OF TIME & UNIVERSE:-

After the Plank epoch and inflaction came the quark , hadron , and lepton epochs. Togather ,these epochs encompassed less than 10 second of time following the Big Bang. The observed abundance of the elements can be explained by combing the overall expansion of space with nuclear and atomic physics. As the Universe  expands , the energy density of electromagnetic radiation decreases more quickly than dosethat  of matter because the energy of a photon decrease  with its wavelenth . as the Universe expanded and cooled , elementary particles associated stably in to ever larger combinations.