Eratosthenes of Cyrene

Hello! My name is Eratosthenes. I was born a very, very long time ago, in the year 276 BC. I loved to learn new things and read all day long. My favorite place in the whole world was the library. It was a very big and special place called the Great Library of Alexandria, and I was in charge of it! It had so many scrolls, which were like old-fashioned books. There were more scrolls than you could ever count, all filled with wonderful ideas and stories. I was so happy to be surrounded by so many things to learn.

I loved to study everything about the world. I looked up at the shiny stars in the night sky. I looked at maps to see all the different places people lived. And I really loved numbers because they helped me count and measure things. One day, I heard something very interesting. Someone told me that far away in a city called Syene, there was a deep well. On one special day of the year, at noon, the bright sun would shine right down to the very bottom of the well. That meant there were no shadows at all! This made me think. I went outside in my city, Alexandria, at the exact same time. I looked at a tall stick, and I saw that it made a shadow on the ground! Why was there a shadow in my city but no shadow in Syene? This gave me a big, brilliant idea.

That little shadow was a very important clue. It told me that the Earth was not flat like a piece of paper, but round like a big ball! I used my love for numbers to do some very clever counting. I measured the shadow in my city and used that little measurement to figure out how big the whole world was. It was like solving a giant, wonderful puzzle. And guess what? I did it! I was the very first person to measure the size of our Earth. That is the discovery people remember me for the most.

I lived a long and happy life full of learning and discovery. I lived to be 82 years old. Even today, a long, long time after I looked at those shadows, people still remember me. They remember me as the person who first measured our big, round Earth. I am so glad my big idea helped everyone understand our amazing planet a little bit better.