So how to get the knowledge of the sun? By receiving through the ear. That's all. Simply you have to receive the knowledge from the authority. It is not that practically you are experimenting by going to the sun, that it is so great and so long, so broad. That is not possible. You have to receive such knowledge through authority. That's all.
So even for material understanding which is beyond our sense perception we have to receive knowledge from authority. Similarly, we cannot understand what is God. But from the authoritative sources we can understand that God is so great. Just like in the Brahma-saṁhitā it is stated that yasyaika-niśvasita-kālam athāvalambya jīvanti loma-vilajā jagad-aṇḍa-nāthāḥ (Bs. 5.48)—that you see this universe, and in each universe there is a predominating demigod which is called Brahmā, or jagad-aṇḍa-nātha, the master of the universe. That master of the universe is living, only taking the duration of breathing of Mahā-Viṣṇu. Just like you are breathing, inhaling and exhaling. So when Mahā-Viṣṇu exhales, innumerable universes come out. And when He inhales, all these universes go into His body. So just imagine how great He is, how big He is. That is not conceivable with our limited sense. But if we believe, then you get the perfect knowledge.