In plain words
It went on gathering what its daily life needed. Humanity also went on discovering certain secrets. More than that, it also came to recognise that there was a great deal it did not know. Humanity also understood that what we have learned is little, and what we have still to learn is much. A human being cannot make the earth. A human being cannot create water. When branch rubs against branch, fire arises, but a man cannot place fire in a branch and keep it there. That is a task beyond a human being. There is fire in the branch, yet that fire keeps the branch safe and does not burn it. No human being can do such a thing. So, in this way, the human being came to recognise, to some extent, that some kind of power lies hidden within, unseen by our eyes, unheard by our ears, unfelt by our mind. He came to worship it, thinking it might be a power beyond the human. For any power, direct proof is essential. They also went on enquiring what could be the right witness to this direct proof for us. They came to believe that the sun itself is this direct proof for us. If there were no sun, there would be no light. Not light alone: every kind of creation would come to a standstill. In this world, if any tree is to grow, if any crop is to ripen, if any living thing is to grow, hydrogen is essential for all of them. The chief energies of this sun are hydrogen and helium. If this hydrogen and helium were both gone, there would be no world at all. So they believe that the sun itself is the direct proof for us. In the principle of the sun they went on discovering certain secrets of many kinds.
Little by little they came to believe in the sun as the chief deity of the Gāyatrī mantra. Dhiyo yo naḥ pracodayāt. As the sun shines, so the human intellect too must shine without measure. They went on offering prayers that the light of the sun might enter our intellect. So the sun itself is the basis of direct proof. On the basis of the sun, they went on chanting the Gāyatrī mantra, and came to believe that Gāyatrī is the Mother of the Vedas. They also believed that this Gāyatrī belongs not merely to one time, one land or one person, but to the three times, bhūr bhuvas suvaḥ. Tat savitur vareṇyaṃ bhargo devasya dhīmahi dhiyo yo naḥ pracodayāt. What wipes out darkness is light. Without light, darkness will never leave us. The sun that wipes out this darkness took the chief place in this form of Gāyatrī.