Zhang Heng

Hello. My name is Zhang Heng, and I want to tell you my story. I was born a very long time ago, in the year 78, in a part of China called Nanyang. When I was a boy, I didn't have video games or television to watch. Instead, I loved to look up at the giant night sky. It was my favorite thing to do. I would watch the moon glow and count the twinkling stars, and I always wondered how they all moved and what secrets they held up there.

I wanted to understand the stars so much that I decided to build something special to help me. Around the year 125, I invented a globe called an armillary sphere. It was not just any globe. Mine was powered by flowing water, which made it turn slowly, just like the real sky does every night. It was like having my very own little planetarium where I could watch the stars dance whenever I wanted. This machine helped me map out the stars and learn their patterns.

Besides looking up at the sky, I also wanted to understand the earth beneath my feet. Sometimes, the ground would shake, which we call an earthquake. It was very scary for people because no one ever knew when or where an earthquake would happen. So, in the year 132, I built my most famous invention: the world's first seismoscope. It was a big, beautiful bronze jar with eight dragon heads on the outside. Each dragon held a small ball in its mouth. Below the dragons were eight toads with their mouths wide open. When the earth rumbled, even if it was very far away, a special part inside the jar would move and make one dragon drop its ball into a toad's mouth below. The direction the ball fell told us which way the earthquake had come from. People were amazed that we could know something about an earthquake from so far away.

I was also a painter, a poet, and I worked for the emperor, helping him understand the world. I lived to be 61 years old, and I spent my whole life being curious and asking questions. Today, people remember me as a great scientist and inventor from ancient China. My ideas helped people understand that we can use science to learn about the beautiful sky above our heads and the powerful ground beneath our feet.