Q. What are the three Planetary systems and how do they work ?
A. There are three planetary systems, triloki: the higher planetary system, the middle planetary system, and the lower planetary system.
Bhagavad gita 14.18 :
Those situated in the mode of goodness gradually go upward to the higher planets; those in the mode of passion live on the earthly planets; and those in the abominable mode of ignorance go down to the hellish worlds,there is an upper planetary system, consisting of the heavenly planets, where everyone is highly elevated. According to the degree of development of the mode of goodness, the living entity can be transferred to various planets in this system.
The mode of passion is mixed. It is in the middle, between the modes of goodness and ignorance. A person is not always pure, but even if he should be purely in the mode of passion, he will simply remain on this earth(MIDDLE PLANETARY SYSTEM) as a king or a rich man. But because there are mixtures, one can also go down. People on this earth, in the mode of passion or ignorance, cannot forcibly approach the higher planets by machine. In the mode of passion, there is also the chance of becoming mad in the next life.
The lowest quality, the mode of ignorance, is described here as abominable. The result of developing ignorance is very, very risky. It is the lowest quality in material nature. Beneath the human level there are eight million species of life—birds, beasts, reptiles, trees, etc.—and according to the development of the mode of ignorance, people are brought down to these abominable conditions. Or they will go to hellish planets (LOWER PLANETARY SYSTEMS)
There is an opportunity for men in the modes of ignorance and passion to be elevated to the mode of goodness and also beyond the three modes, and that system is called Krishna consciousness. But one who does not take advantage of this opportunity will certainly continue in the lower modes.