Foundations of geometry possible exception of the parallel postulate) that any theorem proved from them was deemed true in an absolute, often metaphysical, sense. Today, however, many other geometries which are not Euclidean are known, the first ones having been discovered in the early 19th century. Euclid's "Elements" is a mathematical and geometric treatise consisting of 13 books written by the ancient Greek mathematician Euclid in Alexandria c. 300 BC. It is a collection of definitions, postulates (axioms), propositions (theorems and constructions), and mathematical proofs of the propositions. The thirteen books cover Euclidean geometry and the ancient Greek version of elementary number theory.
Lighthouse of Alexandria this mole, and the Ras el-Tin promontory represents all that is left of the island of Pharos, the site of the lighthouse at its eastern point having been weathered away by the sea. The lighthouse was constructed in the 3rd century BC. After Alexander the Great died, the first Ptolemy (Ptolemy I Soter) announced himself king in 305 BC, and commissioned its construction shortly thereafter. The building was finished during the reign of his son, the second Ptolemy (Ptolemy II Philadelphus). It took twelve years to complete, at a total cost of 800 talents, and served as a prototype for