In the beginning Hindus believed Ganga flowed in the heavens but she was held captive by the creator god brahma.  Then brahma decided to send the river ganga down to earth but there is one problem, the Ganga has got such mighty fools and if she comes on the earth the earth will drown.
so the god Shiva blocked Ganga’s for gathering her waters in the locks of his hair so she would just open one lock of his hair and the Ganga fluid.

One Hindu believers explain it as, “She’s the mother because she gives birth to everything this holy river came from the river in heaven that we call the Milky Way.  They say that Milky Way actually is a reflection that you see in those waters which are still beyond Sciences have dated the universe to about fourteen billion years. Best we can figure Hindus have it at what. Hindus do not believe in one creation. They say that these are cycles of creation  and the primordial creation could be something like eight point six billion years of or actually this whole creation myth is
very difficult to comprehend.”

He also said, “Because we say the gods like Brahma has created the universe but then they ask a question who created Brahma right and then there always a question them creation happened and then the gods habit they say that the sages when they were in their trance they got that revelation that how the creation happened but since it is in that level of consciousness you and me we commoners will not understand it so we believe that it’s beyond us.”