Copts, the Christian descendants of ancient Egyptians, celebrate today as the day the Nile rises with the tears of Isis. It's a great example of the linkage between religion and ancient science, as ritual codified and helped retain knowledge - in this case the vital calendrical information about the river's flow across the farmland, brining the vital rich soils that sustained Egypt for millennia.

Of course the gift of the Nile has been reposessed by the Aswan High Dam, though the conventional wisdom about the disaster of that project neglects the several floods and droughts that have been mitigated by its presence.