Very Important Slokam, study well, with concentration....
Srimad Bhagavad-Gita :
Chapter-8 .( Akshara-brahma-yogam )
Slokam-18. ( When Brahma's day is manifest, this multitude of living entities comes into being, and at the arrival of Brahma's night they are all annihilated.)
avyaktat vyaktayah sarvah prabhavantyaharagame,
ratryagame praliyante tatraiavyaktasamjnake.
aharagame = when brahma's day begins;
avyaktat = from the avyaktam ( unmanifest );
sarvah vyaktayah prabhavanty = all living entities ( sarva-characaram-s ), come into being;
ratryagame = when brahma's night begins;
avyaktasamjnake = of the name avyaktam ( unmanifest );
tatra eva = in itself ( in the avyaktam itself );
praliyante = annihilated ( layanam into it / united).
Thus Lord Krishna previously described that created beings from the highest material planet Maharloka of Brahma down to the lower heavenly planets called Mahat are all subjected to rebirth in the material existence.
Now He explains that the creation and dissolution of all the material worlds like Earth, the galaxy, our solar system, all the universes up through the heavenly planets to the topmost planet of Maharloka are all created and absorbed back into the avyakta or the unmanifest which is regulated by Brahma's day and night each comprised of 4 billion 320 million years.
All sentient beings in physical existence were created by Brahma from his subtle body.
This subtle body is one of the transformations of prakriti or the material substratum pervading physical existence.
This the unmanifest is from Brahma and is within material existence although super subtle and from which emanates countless myriad of unlimited beings accompanied by their respective bodies and minds and senses with which to enjoy their respective activities and pleasures.
This happens at the dawning of Brahmas day when he awakes.
At the closing of Brahma's day and the beginning of his night all beings who emanated from his subtle body are withdrawn again into his subtle body to repose in dormancy until his awakening again after 4 billion 320 million years.
What subsequently is the process?
Lord Krishna is answering.
From the unmanifest form of the effect is the cause.
Therefore from the unmanifest which is the cause, all created beings, moving or stationary come into existence.
When is this?
At the commencement of Brahma's day every 4 billion 320 million years and at the end of Brahma's day all created beings are merged back into the unmanifest for 4 billion 320 million years.
This verse clarifies that the knowers of day and night also know the cycle of the unmanifest and the manifest and what happens to all created beings.
The less intelligent jivas try to remain within this material world and are accordingly elevated and degraded in the various planetary systems.
During the daytime of Brahma they exhibit their activities, and at the coming of Brahma's night they are annihilated.
In the day they receive various bodies for material activities, and at night these bodies perish.
The jivas (individual souls) remain compact in the body of Vishnu and again and again are manifest at the arrival of Brahma's day.
When Brahma's life is finally finished, they are all annihilated and remain unmanifest for millions and millions of years.
Finally, when Brahma is born again in another millennium, they are again manifest.
In this way the jivas are captivated by the material world.
To be continued ...