Ancient Roman Engineering

                       Analogy between an invisibility cloak and ancient Gallo-Roman theaters.

Stephane Brûlé et al.

                                           

It is interesting to see how nature guides the path of our structures and makes me wonder what forces shaped ancient buildings.

"Co-author Stephane Brûlé, a civil engineer at a Lyon-based company called Menard, demonstrated the possibility of this kind of large-scale acoustic and seismic cloaking a few years ago with colleagues from the Fresnel Institute in Marseille. The researchers drilled a periodic array of boreholes into topsoil and discovered that sound waves reflected most of their energy back toward the source when they encountered the first two rows of holes. Brûlé noticed a similar foundational structure while on holiday in Autun (a town in central France), thanks to an aerial photograph of the semicircular structure of a Gallo-Roman theater buried under a field.

When Brûlé superimposed a more detailed archaeological photograph of the theater's structure over an image of one of the invisibility cloaking metamaterials he and his Fresnel colleagues had made in the lab, the ancient theater's pillars lined up almost perfectly with the microscopic elements in the metamaterial. He discovered similar overlap with images of the foundational structure of the Roman Colosseum and other, fully enclosed amphitheaters from the same era.

Roman engineers may not have done this deliberately; they could have just been lucky, according to Brûlé. Or they might have noticed over the centuries that certain structures were more resistant to earthquake damage than others and modified their designs accordingly. "Rigorously, we cannot say more for the moment," he told Physics World."

https://arstechnica.com/science/2019/05/study-says-ancient-romans-may-have-built-invisibility-cloaks-into-structures/