So this Bhagavad-gītā, science of Bhagavad-gītā, is not a new presentation. Just from this verse we can understand that it was instructed to the sun-god. Sun-god, apart from what is the duration of age of sun-god, but from the Manu, because the next statement is vivasvān manave prāha . . . Vivasvān. The sun-god's name is Vivasvān.
Just like your the chief executive head is called the president, similarly, there is a chief executive head also in the sun planet, president. And the present president's name is . . . just like your present president's name is Mr. Nixon, similarly, the present predominating deity in the sun planet is known as Vivasvān.
So everything is in detail. This is called Vedic literature.