BG Chap 8 - Nature of all material planets

The inhabitants of Svarga, earth and the lower planets meet destruction in each day of Brahmā. The planets above Svarga are not destroyed at the end of Brahmā’s day. Those on Brahmaloka may continue to live until the end of Brahmā’s one hundred years. At the commencement of Brahmā’s day, when Brahmā awakens from sleeping state, all bodies, senses, objects of enjoyment, and places of enjoyment become manifest. At the commencement of Brahmā’s night, when it is time to sleep, they disappear within Brahmā, caused by his sleep. The word avyakta, used to refer to the beings becoming unmanifest, does not refer to pradhāna, since this is a description of the daily creation and destruction, during which time the elements like ether remain intact. Thus avyakta here refers to the sleeping state of Brahmā. Merging into pradhāna takes place only at the end of Brahmā’s life. In this way all living beings disappear at the coming of Brahmā’s night and reappear at the approach of his day under the control of karma. When Brahmā’s life is finished, they remain unmanifest within the body of Viṣṇu till the next creation takes place.