“The comparison of Krishna to the sun is very appropriate. As soon as the sun sets, darkness automatically appears. But the darkness experienced by the common man does not affect the sun itself either at the time of sunrise or of sunset. Lord Krishna’s appearance and disappearance are exactly like that of the sun. He appears and disappears in innumerable universes, and as long as He is present in a particular universe there is all transcendental light in that universe, but the universe from which He passes away is put into darkness. His pastimes, however, are everlasting. The Lord is always present in some universe, just as the sun is present in either the eastern or the western hemisphere. The sun is always present either in India or in America, but when the sun is present in India, the American land is in darkness, and when the sun is present in America, the Indian hemisphere is in darkness.
As the sun appears in the morning and gradually rises to the meridian and then again sets in one hemisphere while simultaneously rising in the other, so Lord Krishna’s disappearance in one universe and the beginning of His different pastimes in another take place simultaneously. As soon as one pastime is finished here, it is manifested in another universe. And thus His nitya-lila, or eternal pastimes, are going on without ending. As the sunrise takes place once in twenty-four hours, similarly the pastimes of Lord Kṛṣṇa take place in a universe once in the daytime of Brahma, the account of which is given in the Bhagavad-gita as 4,300,000,000 solar years. But wherever the Lord is present, all His different pastimes as described in the revealed scriptures take place at regular intervals.
As at sunset the snakes become powerful, thieves are encouraged, ghosts become active, the lotus becomes disfigured and the cakravaki laments, so with the disappearance of Lord Krishna, the atheists feel enlivened, and the devotees become sorry.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Third Canto, Chapter 02 – Text 07