"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.
Science is one of a handful of things that defines us as a very special species. It is amazing how far we have been able to get and how accurate our predictions are. I think understanding how the universe was born is very important. It really gives us a perspective on many things.
