Ether, the sky, we cannot see, we cannot touch, we cannot smell—but we can hear the sound. As soon as there is sound, that, we know that there is ether, or sky. The sound vibration. . . As we have got experience of this material sound and therefore the material sky, similarly, there is spiritual sound and there is spiritual sky. Without sky, there is no sound. So there is spiritual sky. We get information from śāstra: paravyoma. Vyoma is called sky, and there is another sky. This is material sky, what we have experience. There is spiritual sky. And about that spiritual realization, as this creation begins from the sky—ether, then air, then fire, and then water, then land—kṣitir āp tejo marud vyoma—similarly, the spiritual world also begins from the spiritual sky. After this sky ends, there the spiritual sky begins.
That is stated in the Śrīmad-Bhagavad-gītā, paras tasmāt tu bhāvaḥ anyaḥ (BG 8.20): "There is another bhāva," means nature, "that is sanātana nature, eternal nature." This nature, this sky, is temporary. It has got a duration of life, maybe millions and trillions of years, but it is not permanent. It is emanating from the Supreme Lord's breathing period. Yasyaika-niśvasita-kālam athāvalambya jīvanti loma-vilajā jagad-aṇḍa-nāthāḥ (Bs. 5.48). So after this sky, there is another sky, and the sound produced from that sky is oṁkāra and Hare Kṛṣṇa mantra. This is the sound vibration from the spiritual sky. Therefore it is effective immediately. Just like you contact thousands of miles away—somebody is speaking, and you can contact by the sound vibration you catch up with your machine, radio machine—similarly, the sound vibration from the spiritual sky you can also receive. That is Hare Kṛṣṇa mantra.
Therefore Narottama dāsa Ṭhākura has described this Hare Kṛṣṇa mantra, "not of this material sky." Golokera prema-dhana, hari-nāma-saṅkīrtana. Hari-nāma-saṅkīrtana, this is not a material sound. And in the Vedānta it is stated, śabdād anāvṛtti. By chanting the spiritual sound. . . The impersonalists, they chant oṁkāra: praṇavaḥ sarva-vedeṣu. (BG 7.8) All Vedic mantras are preceded by the spiritual oṁkāra. That oṁkāra. . . Kṛṣṇa says, akṣarāṇām oṁkāro 'smi. Vedeṣu, praṇavaḥ sarva-vedeṣu, A, U, M, these are described in the Bhagavad-gītā. So either you vibrate oṁkāra or Hare Kṛṣṇa mantra, they belong to the spiritual world. This sound does not belong to this material. Material sound, if you chant once, twice, thrice, you will feel disgusted. But spiritual sound, if you chant twenty-four hours, you will never feel disgusted, but you will feel more and more spiritual bliss. That is the difference. Actually, you see these boys and girls and others, they are chanting Hare Kṛṣṇa practically from early in the morning, five o'clock, till ten o'clock daily, but nobody is feeling any disgust. They like to chant. That is the difference between material sound and spiritual sound.
So we can enter into the spiritual world, the spiritual sky. The spiritual sky is there, sanātana. That is eternal, sanātana. Everything eternal there. In the material world they are, everything, temporary, asat. And everything in the spiritual world, that is called sat. Oṁ tat sat. That is spiritual world. So the Vedic injunction is asato mā sad gama: "Try to transcend from this asat, material world, to go to the spiritual world, sat." Oṁ tat sat. That is actually our business. In the human form of life this is only business: "How to transfer me to the spiritual world." Sanātana. Because I am sanātana. Jīva-bhūtaḥ sanātanaḥ (BG 15.7). Jīva is sanātana, eternal. Na hanyate hanyamāne śarīre (BG 2.20). The jīva is never destroyed after the destruction or annihilation of this body. He is eternal. Nityaḥ śāśvato 'yaṁ na hanyate hanyamāne śarīre. So this is our business, that "I am eternal. As Kṛṣṇa, God, is sac-cid-ānanda-vigraha (Bs. 5.1), and I am part and parcel of sac-cid-ānanda-vigraha, so as Kṛṣṇa is eternal, so I am also eternal." The Vedic mantra says that nityo nityānām. Kṛṣṇa is nitya, eternal, and we are plural number, nityānām. Cetanaś cetanānām (Kaṭha Upaniṣad 2.2.13). Sat cit. . . So as Kṛṣṇa is sac-cid-ānanda-vigraha, so we are also sac-cid-ānanda-vigraha. The difference is: Kṛṣṇa is the maintainer, Viṣṇu is the maintainer, and we are maintained. We are not maintainer.
There are millions and trillions of living entities, not only in this universe. There are millions and trillions of universes, and there are millions and trillions of planets. Yasya prabhā prabhavato jagad-aṇḍa-koṭi-koṭiṣv aśeṣa-vasudhādi-vibhūti-bhinnam (Bs. 5.40). Koṭiṣu, there are innumerable universes, and as you see, experience, within this universe, within this ball-like sky. . . In the evening. . . in the night, at least, we can see so many twinkling stars. Similarly, there are innumerable universes. And there are innumerable. . . In each and every universe there are innumerable these planets. This is called material world. You cannot estimate how many universes are there and how many planets are there. But this is only one-fourth manifestation of God's creation. All these universes taken together, ekāṁśena sthito jagat (BG 10.42)—this is only one-fourth manifestation. Therefore the Vaikuṇṭha, spiritual world, is called tripāda-vibhūti, three fourth. This is one fourth. So just imagine. We cannot have any estimation even the one-fourth manifestation of the one-fourth energy of God, and what to speak of the three-fourth energy manifestation, opulence, everything. In the spiritual world the number of living entities are far greater than the number of living entities here in this material world.