The soul, unaffected by the nature of the body, has its own nature called adhyatam(spirituality). The whole perishable world is called adhibhoot(something that exists; being); the conscious/soul in perishable things is Adhidaiva(something that bears;bearer of the being). The nature of the soul is spirituality or the conscious element living in the body. Karma(work) for the soul is in the form of universe creation and for the being, is in the form of Yagya.(selfless work aiding in steady sustainable working of the universe)

At the time of departure(prior to death), being in a practiced yogic meditative state(mind concentrated on the soul) with devotion, keeping the air intake between the two eyebrows well(where the soul/conscious is said to be situated in the being), the one who remembers the immeasurable energy which is the basis of universe, he attains the same state as freely propagating electromagnetic wave ,that is, the soul does not bind to any other being and is liberated as a free energy form in the universe.

Sat, Treta, Dwapar, Kali yugas constitute Mahayuga.(4 yugas(period of time) make up 1 mega cycle in time). 1000 Mahayugas make up one day of energy, 1000 Mahayugas make up one night of energy. At the beginning of the day, the physical world(perceivable by senses) is created from the unmanifest (upper nature of energy; electromagnetic energy wave which is not perceivable by senses), when the night sets in, the manifest substances merge into the same unmanifest(all the physical world disintegrates into electromagnetic wave radiation).
1 Mahayuga = 432000 years
Kalpa, 1 energy day = 1 energy night = 4 billion 32 crore years

Other than the upper nature of the energy soul is the eternal unmanifest (which is not bound to any being, remains unaffected in all energy interactions, hence eternally free in the universe); that unmanifest is often called the highest attainable state.

----