There is a verse in the Taittiriya Upanisad that speaks a lot about the organization of the cosmos and the life standards of the different inhabitants of different planets:

“Take a noble young man, who is well versed in the Vedas, very intelligent, handsome, and strong. Let the world be full of wealth for him. That is the measure of human bliss.
If we multiply this limit of human bliss a hundred times, it equals the bliss of a manuṣya-gandharva. If we multiply the bliss of a manuṣya-gandharva one hundred times, it equals the pleasure of a deva-gandharva, and if we multiply that one hundred times, it equals the bliss of the ancestors living in Pitṛloka. If we go further and multiply this standard of bliss of the Pitṛs one hundred times, we come to the standard of bliss of a lower demigod born in Swargaloka.
If we multiply the bliss of the lower demigods by one hundred, we reach the standard of bliss of the sacrificial demigods, and one hundred times that is the bliss of principal demigods. If we again multiply this one hundred times, we reach the standard of bliss of Indra. Each one of these different standards of bliss is matched by a self-realized soul who has no material desires.” (TU 2.8)

What are the manuṣya-gandharvas? What are the sacrificial demigods?

Based on Prabhupada’s commentary on CC Antya 2.10, it seems that by “manuṣya-gandharva” this verse refers to these earthly Gandharvas who live in Bhārata-varṣa. Although very elevated if compared to ordinary human beings, these earthly Gandharvas have a much lower standard of living than the deva-gandharvas living in Swargaloka.

The Puranas describe our universe as being composed of 14 planetary systems, one of them being Bhu-Mandala, of which our planet is part. Bhu-Mandala is described as being composed of different islands, or dwipas. The first one is Jambudwipa, of which Bharata-varsa is part.

Bharata-varsa is in turn composed of the nine dwipas described in the purport. Some interpret the word “dwipa” as being literally an island, part of a gigantic flat structure, but Prabhupada concludes that “dwipa” is just a metaphor for planets floating in the ocean of space. As he mentions on CC Madhya 20.218: “The planets are called dvīpas. Outer space is like an ocean of air. Just as there are islands in the watery ocean, these planets in the ocean of space are called dvīpas, or islands in outer space.”

From this description, it appears that our planet is just one of these nine dwipas that compose Bharata-varsa, and Bharata-varsa is in turn just one of the divisions of Jambudwipa, the central island of the planetary system of Bhu-Mandala.

Apart from Jambudwipa, there are six other great islands, called Plakṣadvīpa, Śālmalīdvīpa, Kuśadvīpa, Krauñcadvīpa, Śākadvīpa, and Puṣkaradvīpa. Each of these islands is divided into seven regions, therefore it appears that each is also formed by several planets. In this way, the whole planetary system is formed by different planets spread around the cosmos. Souls who have the necessary qualifications are however capable of moving through these different planets and thus accessing the different parts of Jambudwipa and the other larger islands with ease, just like Pariksit Maharaja visited the different varsas of Jambudwipa and received tribute from the different kings there.

Most of the other varsas that compose Bhu-mandala are called earthly heavens because the inhabitants there have a much higher standard of living than we enjoy on our planet. It’s described that they live for 10,000 years and enjoy a standard of living similar to the inhabitants of Treta-yuga. It’s also described that when the inhabitants of the celestial planets fall from their positions, having exhausted their karma, they take birth in one of these varsas to enjoy their remaining piety before taking birth on Earth to generate a new set of karma.

Higher than Bhu-Mandala are the planetary systems of Bhuvarloka and Swargaloka, and still higher are Maharloka, Janaloka, Tapoloka, and Satyaloka.

Just like the relative standard of material happiness of the celestial Gandharvas is a hundred times superior to the earthly Gandarvas, inhabitants of Pitṛloka, enjoy a standard of living one hundred times better than them.

Pitṛloka is the court of Yamaraja, the planet of the ancestors. Although it is geographically situated at the bottom of the universe, it is a celestial planet, where the ancestors of pious families can live in great delight, remaining connected with their descendants. To be promoted to Pitrloka, one has to not only be pious but also produce pious descendants who will maintain the family traditions and offer oblations (pinda) to the ancestors every year.

The descendants can, in turn, later also join their ancestors in Pitrloka, and thus the family remains connected in the afterlife for as long as the next descendants remain faithful and continue to offer oblations to the ancestors every year, generation after generation. However, when the family tradition is broken, as it happens with most families in Kali-yuga, all the ancestors fall from Pitṛloka and receive their next bodies according to their karma. The family is thus permanently destroyed. Arjuna mentions this when he says that “An increase of unwanted population certainly causes hellish life both for the family and for those who destroy the family tradition. The ancestors of such corrupt families fall down because the performances for offering them food and water are entirely stopped.” (BG 1.41)

The karma-devās are persons who are elevated to the celestial planets by perfectly performing ritualistic activities from the Karma-Kanda section of the Vedas. Different from other demigods, who live for the whole duration of the reign of Manu (306.72 million years), the duration of life of these sacrificial devas is fixed according to the amount of their piety. As soon As their pious credits are exhausted, they fall from the celestial planets together with the rain and assume human bodies. From there, they may again perform fruitive activities for several lives until they can again be elevated to the celestial planets.

After them we have the principal demigods, who preside over the different celestial planets, and finally Indra, who is the leader of all demigods. The verse emphasizes however that just like all the previous standards of pleasure mentioned before, all these progressively higher standards of happiness are matched by a self-realized soul, who is free from material desires. This is indicated by the line śrotriyasya cākāma-hatasya, which is repeated after each new standard of happiness is described.

The logic is similar to when we say that the wealth of a street sweeper is matched by the king, as well as the wealth of an ordinary soldier and a minister. Whatever a sweeper, a solder, or a minister can pay, the king can also pay. It suggests that the king is more wealthy than all of them, but it doesn’t directly reveal the extent of the wealth of the king.