GSU Stonemasons · Pattern A · Physics Sandbox

The Arch That Stands

Build a Roman arch stone by stone. Place the keystone last — and feel the moment compression takes over and the structure becomes self-supporting. Then load it and see what happens to a pile vs. an arch.

The secret the Romans discovered: compression, not adhesion

A pile of stones falls. An arch stands — and the heavier you load it, the tighter the joints squeeze together. The arch converts every downward load into outward thrust, which the abutments absorb. No mortar required for the Romans' biggest arches — gravity itself was the adhesive.

The keystone is last, not first. All voussoir stones lean on each other through a wooden centering frame. The keystone drops into the crown, the centering is removed, and the arch becomes a self-supporting compression ring.

Choose: build an arch or a pile — then drop a load and compare

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Structure

Stones Placed

Waiting

Status

Keystone Set

🥉 Bronze — Arch built

🥈 Silver — Pile collapsed

🥇 Gold — Arch survived load

✦ Platinum — Both tested

Ask GENO: "What is a voussoir and why is it wedge-shaped?" or "How did Romans build arches without modern tools?" — GENO AI Tutor available 24/7, answers in 32 languages.