## ABSTRACT

The central assumption of Euclid’s geometry, is the existence of parallel straight lines which indeed accords with everyday experience. In the eighteenth century though, it was shown that this assumption could be altered, to produce two different but still logically consistent geometries. Following Riemann one can assume that every pair of straight lines cross.1 Alternatively, following Bolyai and Lobachevsky, one can assume that when extended far enough, straight lines will always move apart.