Modern enterprisers (the astronauts who travel in space) may take information from Śrīmad-Bhāgavatam that in space there are fourteen divisions of planetary systems. The situation is calculated from the earthly planetary system, which is called Bhūrloka. Above Bhūrloka is Bhuvarloka, and the topmost planetary system is called Satyaloka. These are the upper seven lokas, or planetary systems. And similarly there are seven lower planetary systems, known as Atala, Vitala, Sutala, Talātala, Mahātala, Rasātala and Pātāla lokas. All these planetary systems are scattered over the complete universe, which occupies an area of two billion times two billion square miles. The modern astronauts can travel only a few thousand miles away from the earth, and therefore their attempt to travel in the sky is something like child’s play on the shore of an expansive ocean. The moon is situated in the third status of the upper planetary system, and in the Fifth Canto of Śrīmad-Bhāgavatam we shall be able to know the distant situation of the various planets scattered over the vast material sky. There are innumerable universes beyond the one in which we are put, and all these material universes cover only an insignificant portion of the spiritual sky, which is described above as sanātana Brahmaloka. The Supreme Lord very kindly invites the intelligent human beings to return home, back to Godhead, in the following verse of the Bhagavad-gītā (8.16) :

ābrahma-bhuvanāl lokāḥ punar āvartino ’rjuna mām upetya tu kaunteya punar janma na vidyate

Beginning from Satyaloka, the topmost planet of the universe, situated just below the eternal Brahmaloka, as described above, all the planets are material. And one’s situation in any of the many material planets is still subject to the laws of material nature, namely birth, death, old age and disease. But one can get complete liberation from all the above-mentioned material pangs when one enters into the eternal Brahmaloka sanātana atmosphere, the kingdom of God. Therefore liberation, as contemplated by the speculative philosophers and the mystics, is possible only when one becomes a devotee of the Lord. Anyone who is not a devotee cannot enter into the kingdom of God. Only by attainment of a service attitude in the transcendental position can one enter into the kingdom of Godhead. Therefore the speculative philosophers, as well as the mystics, must first of all be attracted to the devotional cult before they can factually attain liberation.