Why did the roman make advancements in practical technology during the pax romana?

Answer 1

Much of the technology had been developed before the Pax Romana. The three elements of the Roman architectural revolution (Roman concrete, the arch and the vault), the hypcaust (the system of underfloor heating), the arched bridges, the aqueducts and the stone-paved roads were developed before the Pax Romana. The ballista (a crossbow-like catapult), the groma (a surveying instrument) and the siege machines of the Greeks had already been adopted. What happened during the Pax Romana was that there was large scale construction of infrastructure (roads, bridges, aqueducts, ports and dams) and public buildings using new technologies which had already been developed, rather than further technological innovation. The use of these technologies was pushed further with the construction of ambitious projects, such as the Colosseum, the Pantheon and the bridge over the River Danube), New and more efficient types of ballistas were also developed.