The gross materialists do not believe in the existence of God or the demigods. Nor do they believe that different planets are dominated by different … - A. C. Bhaktivedanta Swami Prabhupada

We understand in the sun planet also there are varieties of living entities, but their bodies are made of fire. As our body is made of earth, similarly, their bodies are made of fire. There are five elements in the material nature: earth, water, fire, air, and ether. So in different planets, there are different atmospheres and different bodies also. Don't think that each and every planet of the same quality. No. Same quality in the sense because these five elements are present there. Without these five elements, no material thing exists. So somewhere the fire is prominent. Somewhere the air is prominent. Somewhere water is prominent. Somewhere earth is prominent. So in this planet, or in some other earthly planet, earth is predominant. Similarly, there are other planets also. So don't think that other planets are vacant. No.

Modern scientists and so-called scholars think that there are no living entities on planets other than this one. Recently they have said that they have gone to the Moon but did not find any living entities there. But Srimad-Bhagavatam and the other Vedic literatures do not agree with this foolish conception.

Shudras does not require any training. Shudra means no training. Ordinary worker class. Otherwise other three, especially two, namely the Brahmins and Kshatriyas, they require very magnificent training.