The Propylaea, a gateway like no other

When Dr. Elliot taught the archaeology of the Athenian Acropolis at UBC in the late 50's, he told us that some architrave blocks on the Propylaea were hollowed out. Well, so what? If you walk through the Propylaea onto the Acropolis hill, you will go under the stone beams that are supported by large columns. The beams are load bearing. So far, so what? I cannot confirm this hollowing out in my literature search of the architrave blocks, but Dr Elliot became the head of the American School of Archaeology in Athens later in his career. I rely on him. It is hard to tell much , if you are standing under the beams now, as the temple has undergone many changes. The Propylaea had the first ,or as was believed at that time, the first, known load bearing beam where the architect understood that, weight for weight, a hollow beam is stronger than a solid beam. Thats what! If you understand that, with a load in the center of a beam, there is distraction force on the bottom surface of the beam and compression force on the top surface of the beam, then in the centre of the beam there must be no force, and therefore no need for material. Picture the 60 odd slaves, trying to haul up, with rudimentary winches, a solid block, vis-a- vis a hollow block, and you get the idea. Of course our long bones are hollow for the same reasons. If they were solid we would all weigh 600 pounds. The surgical implants for fractures are hollow as well. We build with I- beams these days, which are functionally analagous. The Propylaea may be the lamp that led the way. The architect in the 5th century BC was a genius.