In 132 AD, China built a machine that could detect earthquakes hundreds of miles away: How Zhang Heng created the world's first earthquake detection device?

In 132 AD, China built a machine that could detect earthquakes hundreds of miles away through a device created by Chinese scientist Zhang Heng. The machine is known as the first seismograph in history. It used a pendulum, metal dragons, and frogs to detect ground vibrations. The invention helped the Han court learn about earthquakes taking place far from the capital and marked an important step in the history of earthquake detection.