As it is confirmed in the Bhagavad-gītā, full knowledge means knowing Kṛṣṇa to be the Supreme Personality of Godhead. In the Vedas and the Bhagavad-gītā it is also stated that in the brahmajyoti, or spiritual sky, there is no need of sunlight, moonlight or electricity. All the planets there are self-illuminating, and all of them are eternally situated. There is no question of creation and annihilation in the brahmajyoti, or spiritual sky. The Bhagavad-gītā also confirms that beyond the material sky there is another, eternal, spiritual sky, where everything is eternally existing. Direct knowledge of the spiritual sky can be had only by great sages and saintly persons who have already surpassed the influence of the three material modes of nature by engaging in devotional service, or Kṛṣṇa consciousness. Unless one is constantly situated on that transcendental platform, it is not possible to understand the spiritual nature.
Therefore it is recommended that one should take to bhakti-yoga and keep himself engaged twenty-four hours a day in Kṛṣṇa consciousness, which places one beyond the reach of the modes of material nature. One in Kṛṣṇa consciousness can easily understand the nature of the spiritual sky and Vaikuṇṭhaloka. The inhabitants of Vṛndāvana, being always engaged in Kṛṣṇa consciousness, could therefore very easily understand the transcendental nature of the Vaikuṇṭhalokas.
Thus Kṛṣṇa led all the cowherd men, headed by Nanda Mahārāja, to the lake where Akrūra would later be shown the Vaikuṇṭha planetary system. They took their bath immediately and saw the real nature of the Vaikuṇṭhalokas. After seeing the spiritual sky and the Vaikuṇṭhalokas, all the men, headed by Nanda Mahārāja, felt wonderfully blissful, and upon coming out of the lake, they saw Kṛṣṇa, who was being worshiped with excellent prayers.