Kṛṣṇa says that "This instruction, bhakti-yoga instruction of Bhagavad-gītā, was first given, imparted by Me, to the sun-god, Vivasvān." That is mentioned in the Bhagavad-gītā.
Now, it is a question of believe or not believe. That is a different thing. We believe. We take it. Because it is said by Kṛṣṇa, we take it, accept it. And we apply our reason also, not blindly take it, that if I see that in every planet, in our this planet there is a president . . . formerly, in this planet also, there was only one king, and he was ruling over all the planets. Gradually, people have divided their interests and become different nations. From Vedic history we can see . . . I understand, somebody was telling me that in Australia also there is some Śiva temple here.
(aside) Who was telling me that? Yes. He was telling me.
So the archaeological investigation has found so many relics, and in the Vedic literature we also find the mention of all the island, sapta-dvīpa, seven islands. Seven islands means Asia, Europe, North America, South America, Africa, Australia and Oceania. These are mentioned already in the Vedic literature. So it is not that the world was not known to Vedic culture. It was fully known. And one king—he was that Mahārāja Pṛthu—he was the only one ruler all over the world, and he was ruling over these seven islands—that is mentioned—although his residential quarter was in the Brahmāvarta, the piece of land between the rivers Yamunā and Ganges. That tract of land is still considered a very sanctified land. Practically all the Vedic culture is there still.