As the modern astronauts who go to the moon or other heavenly planets by force of jet propulsion have to come down again after exhausting their fuel, so also do those who are elevated to the heavenly planets by force of yajnas and pious activities
SB Canto 4
My Lord, the transcendental bliss derived from meditating upon Your lotus feet or hearing about Your glories from pure devotees is so unlimited that it is far beyond the stage of brahmānanda, wherein one thinks himself merged in the impersonal Brahman as one with the Supreme. Since brahmānanda is also defeated by the transcendental bliss derived from devotional service, then what to speak of the temporary blissfulness of elevating oneself to the heavenly planets, which is ended by the separating sword of time? Although one may be elevated to the heavenly planets, he falls down in due course of time.
The transcendental bliss derived from devotional service, primarily from śravaṇaṁ kīrtanam (SB 7.5.23), hearing and chanting, cannot be compared to the happiness derived by karmīs by elevating themselves to the heavenly planets or by jñānīs or yogīs, who enjoy oneness with the supreme impersonal Brahman. Yogīs generally meditate upon the transcendental form of Viṣṇu, but devotees not only meditate upon Him but actually engage in the direct service of the Lord. In the previous verse we find the phrase bhavāpyaya, which refers to birth and death. The Lord can give relief from the chain of birth and death. It is a misunderstanding to think, as do the monists, that when one gets relief from the process of birth and death he merges into the Supreme Brahman. Here it is clearly said that the transcendental bliss derived from śravaṇaṁ kīrtanam by pure devotees cannot be compared to brahmānanda, or the impersonal conception of transcendental bliss derived by merging into the Absolute.
The position of karmīs is still more degraded. Their aim is to elevate themselves to the higher planetary systems. It is said, yānti deva-vratā devān: persons who worship the demigods are elevated to the heavenly planets (BG 9.25). But elsewhere in Bhagavad-gītā (9.21) we find, kṣīṇe puṇye martya-lokaṁ viśanti: those who are elevated to the higher planetary systems must come down again as soon as the results of their pious activities are exhausted. They are like the modern astronauts who go to the moon; as soon as their fuel is used up, they are obliged to come back down to this earth. As the modern astronauts who go to the moon or other heavenly planets by force of jet propulsion have to come down again after exhausting their fuel, so also do those who are elevated to the heavenly planets by force of yajñas and pious activities. Antakāsi-lulitāt: by the sword of time one is cut from his exalted position within this material world, and he comes down again. Dhruva Mahārāja appreciated that the results of devotional service are far more valuable than merging into the Absolute or being elevated to the heavenly planets. The words patatāṁ vimānāt are very significant. Vimāna means "airplane." Those who are elevated to the heavenly planets are like airplanes, which drop when they run out of fuel.