All the material planets-upper, lower and intermediate, including the sun, moon and Venus-are scattered throughout the universe. These planets exist only during the lifetime of Brahmā. Some lower planets, however, are vanquished after the end of one day of Brahmā and are again created during the next day of Brahmā. On the upper planets, time is calculated differently. One of our years is equal to only twenty-four hours, or one day and night, on many of the upper planets. The four ages of earth (Satya, Tretā, Dvāpara and Kali) last only twelve thousand years according to the time scale of the upper planets. Such a length of time multiplied by one thousand constitutes one day of Brahmā, and one night of Brahmā is the same. Such days and nights accumulate into months and years, and Brahmā lives for one hundred such years. At the end of Brahmā's life, the complete universal manifestation is vanquished.
Those living beings who reside on higher planets like the sun and the moon, as well as those on Martyaloka, this earth planet, and also those who live on lower planets-all are merged into the waters of devastation during the night of Brahmā. During this time no living beings or species remain manifest, although spiritually they continue to exist. This unmanifested stage is called avyakta. Again, when the entire universe is vanquished at the end of Brahmā's lifetime, there is another avyakta state. But beyond these two unmanifested states is another unmanifested state, the spiritual atmosphere, or nature. There are a great number of spiritual planets in this atmosphere, and these planets exist eternally, even when all the planets within this material universe are vanquished at the end of Brahmā's life. There are many material universes, each under the jurisdiction of a Brahmā, and this cosmic manifestation within the jurisdiction of the various Brahmās is but a display of one fourth of the energy of the Lord (ekapād-vibhūti). This is the inferior energy. Beyond the jurisdiction of Brahmā is the spiritual nature, which is called tripād-vibhūti, three fourths of the Lord's energy. This is the superior energy, or parā-prakṛti.
The predominating Supreme Person residing within the spiritual nature is Lord Śrī Kṛṣṇa. As confirmed in the Bhagavad-gītā (8.22), He can be approached only by unalloyed devotional service and not by the processes of jñāna (philosophy), yoga (mysticism) or karma (fruitive work). The karmīs, or fruitive workers, can elevate themselves to the Svargaloka planets, which include the sun and the moon. Jñānīs and yogīs can attain still higher planets, such as Maharloka, Tapoloka and Brahmaloka, and when they become still more qualified through devotional service they can enter into the spiritual nature, either the illuminating cosmic atmosphere of the spiritual sky (Brahman) or the Vaikuṇṭha planets, according to their qualification. It is certain, however, that no one can enter into the spiritual Vaikuṇṭha planets without being trained in devotional service.
On the material planets, everyone from Brahmā down to the ant is trying to lord it over material nature, and this is the material disease. As long as this material disease continues, the living entity has to undergo the process of bodily change. Whether he takes the form of a man, demigod or animal, he ultimately has to endure an unmanifested condition during the two devastations—the devastation during the night of Brahmā and the devastation at the end of Brahmā's life. If we want to put an end to this process of repeated birth and death, as well as the concomitant factors of old age and disease, we must try to enter the spiritual planets, where we can live eternally in the association of Lord Kṛṣṇa or His plenary expansions, His Nārāyaṇa forms. Lord Kṛṣṇa or His plenary expansions dominate every one of these innumerable planets, a fact confirmed in the śruti mantras: eko vaśī sarva-gaḥ kṛṣṇa īḍyaḥ/ eko 'pi san bahudhā yo 'vabhāti. (Gopāla-tāpanī Upaniṣad 1.21)