Those who know the duration of the [Cosmic] day and night understand that a day and a night of Brahma each last for a thousand Yugas (total of 8,640,000,000 years).
All the manifested entities come forth from the unmanifest at the coming of the day of Brahma, at the coming of the night they are dissolved into that alone which is known as the Unmanifest. (Gita 7:17‐18)
All beings, O Arjuna, are absorbed into My Nature (Prakrti) at the end of a cycle of time (311,040,000,000,000 years). Again I send them forth at the beginning of a new cycle. (Gita 9:7)
The Sacred Scriptures teach us that the scheme of creation or rather “projection” of the Universe is not a linear process as is taught by the Abrahamic coalition, but cyclic; as is every dynamic process in the cosmos that we can observe; such as time itself, the seasons, the life cycles of plants, animals and humans. The orbits of the planets and even those of the atoms are all cyclic.
The dynamic sequence of the Universe consists of :
(a) coming into being — expansion from a single point (bindu),
(b) existence and
(c) dissolution/transformation — contraction back into the point from where it originated (the Big Crunch!).
Everything in the universe is under the sway of these three forces which are eternally at work. There is a metaphysical principle that, the microcosm corresponds exactly to the macrocosm — Isvara projects the universe from within Himself as the spider projects its web. He enters into it, sustains and preserves the Universe and then dissolves it into His own Being. Then according to His will, He again projects the Universe, and so on for all eternity.
Isvara is the efficient cause as well as the material cause of the universe. He projects the universe from within Himself and then enters into it — through His power of omnipresence. He pervades the entire cosmos from within and without. Nothing can be created from nothing, so Isvara
Himself is the material substance from which the physical universe arises, it exists in Isvara and is withdrawn back into Isvara at the end of the Creation cycle. The process of Emmanation/Projection is followed by a period of withdrawal and then re‐projection. The Hindu theory of cosmology is one of a Unified Field, in which matter, the Godhead and the individual Selves (jivas) are all modification of the one Being — Brahman.
The purpose of the manifestation of the Universe is essentially a mystery. Isvara has no external compulsion or inner necessity to project because He is full and complete in Himself. Seeing that Isvara is complete in Himself and Absolute, there is nothing which He needs to accomplish and certainly no desires which He needs to fulfil from somewhere or something outside of His own Being. So the Hindu sages have taught that the purpose of the Universal Projection is Sport (Lila). A spontaneous outburst of energy aimed at Self‐expression. When one engages in a game with oneself, there is nothing to achieve or any competitiveness— it is an end in itself.