And what can we learn by this process? Lord Kṛṣṇa describes the spiritual and material worlds as follows in the Bhagavad-gītā (8.17-20):
By human calculation, a thousand ages taken together form the duration of Brahmā's one day. And such also is the duration of his night. At the beginning of Brahmā's day, all living entities become manifest from the unmanifest state, and thereafter, when the night falls, they are merged into the unmanifest again. Again and again, when Brahmā's day arrives, all living entities come into being, and with the arrival of Brahmā's night they are helplessly annihilated. Yet there is another unmanifest nature, which is eternal and is transcendental to this manifested and unmanifested matter. It is supreme and is never annihilated. When all in this world is annihilated, that part remains as it is."
People become awestruck when they learn that the life span on Brahmaloka is many millions of years. One has to undergo severe austerities and renunciation, accepting the sannyāsa order of life, in order to reach Brahmaloka. However, we must consider one essential fact: even Lord Brahmā, the presiding deity of that planet, is not immortal.