In the higher planetary systems, there are not only different types of human beings, but also animals like lions and elephants. There are trees, and the land is made of emeralds. Such is the creation of the Supreme Personality of Godhead. Śrīla Bhaktivinoda Ṭhākura has sung in this regard, keśava! tuyā jagata vicitra: “My Lord Keśava, Your creation is colorful and full of varieties.” Geologists, botanists and other so-called scientists speculate about other planetary systems, but being unable to estimate the varieties on other planets, they falsely imagine that all planets but this one are vacant, uninhabited, and full of dust. Although they cannot even estimate the varieties existing throughout the universe, they are very proud of their knowledge, and they are accepted as learned by persons of a similar caliber. As described in Śrīmad-Bhāgavatam (2.3.19), śva-vid-varāhoṣṭra-kharaiḥ saṁstutaḥ puruṣaḥ paśuḥ: materialistic leaders are praised by dogs, hogs, camels and asses, and they themselves are also big animals. One should not be satisfied with the knowledge imparted by a big animal. Rather, one must take knowledge from a perfect person like Śukadeva Gosvāmī. Mahājano yena gataḥ sa panthāḥ: our duty is to follow the instructions of the mahājanas. There are twelve mahājanas, and Śukadeva Gosvāmī is one of them.

svayambhūr nāradaḥ śambhuḥ
 kumāraḥ kapilo manuḥ
prahlādo janako bhīṣmo
 balir vaiyāsakir vayam

(Bhāg. 6.3.20)

Vaiyāsaki is Śukadeva Gosvāmī. Whatever he says we consider to be factual. That is perfect knowledge.