As stated in the Bhagavad-gītā, there are three divisions of the material spheres, namely the ūrdhva-loka (topmost planets), madhya-loka (midway planets) and adho-loka (downward planets). Beyond the ūrdhva-loka planets, that is to say above the Brahmaloka, are the material coverings of the universes, and above that is the spiritual sky, which is unlimited in expansion, containing unlimited self-illuminated Vaikuṇṭha planets inhabited by God Himself along with His associates, who are all eternally liberated living entities. Śrī Nārada Muni could enter all these planets in both the material and spiritual spheres without restriction, as much as the almighty Lord is free to move personally in any part of His creation. In the material world the living beings are influenced by the three material modes of nature, namely goodness, passion and ignorance. But Śrī Nārada Muni is transcendental to all these material modes, and thus he can travel everywhere unrestricted. He is a liberated spaceman. The causeless mercy of Lord Viṣṇu is unparalleled, and such mercy is perceived by the devotees only by the grace of the Lord. Therefore, the devotees never fall down, but the materialists, i.e., the fruitive workers and the speculative philosophers, do fall down, being forced by their respective modes of nature. The ṛṣis, as above mentioned, cannot enter into the transcendental world like Nārada. This fact is disclosed in the Narasiṁha Purāṇa. Ṛṣis like Marīci are authorities in fruitive work, and ṛṣis like Sanaka and Sanātana are authorities in philosophical speculations. But Śrī Nārada Muni is the prime authority for transcendental devotional service of the Lord. All the great authorities in the devotional service of the Lord follow in the footsteps of Nārada Muni in the order of the Nārada-bhakti-sūtra, and therefore all the devotees of the Lord are unhesitatingly qualified to enter into the kingdom of God, Vaikuṇṭha.