The Physics Of Ancient Roman Architecture

The Physics Of Ancient Roman Architecture
The Pantheon in Rome, built around 120 CE

The Pantheon, which technically is the “Basilica di Santa Maria ad Martyres,” having been consecrated as a Christian church in the 600′s, was originally built as a temple to all the Roman gods back in the reign of Augustus, but destroyed in one of ancient Rome’s many devastating fires. It was rebuilt around 120 CE, completed in the reign of Hadrian (who decided to confuse future archaeologists by re-using the original massive portico with its inscription crediting the building to Marcus Agrippa), and has remained remarkably intact for nearly 1900 years.

The signature feature of the Pantheon is its giant dome, 43 meters across and 43 meters high, with an 8-meter open “oculus” in the center. The dome is made of concrete, then a relatively new material perfected by the Romans, and to this day is the largest un-reinforced concrete dome in the world.

The dome is a truly awe-inspiring sight, and like most tourists who visit the place, I immediately wondered “How in the world did they make that?” As I’m a great big geek with access to an academic library, this wondering has gone on a good bit longer than most, and led to reading journal articles about computer simulations of the Pantheon’s dome (many thanks to fellow Forbes blogger Sarah Bond for pointing me to that), and to checking out multiple books on Roman architecture and construction techniques. I’ll probably have more to say about that in another post, but for the moment I want to talk about a little basic physics.

You probably won’t be surprised to learn that there’s a great deal of science involved in the construction of something as colossal as the Pantheon, but in the general reductionist spirit of physics, we can break it down to a really simple balance of two forces: gravity pulling the components of the roof down, and forces from the concrete and bricks of the structure trying to keep it up. […]