Eratosthenes of Cyrene

Hello! My name is Eratosthenes. I was born in a sunny city called Cyrene way back in 276 BCE. Even as a little boy, I loved asking questions. I wanted to know about the stars, the land, and the stories people told. I was so curious about everything. I read every scroll I could find and enjoyed learning so much that when I was old enough, I traveled all the way to Athens to study with the best teachers in the world.

In Athens, I studied everything. I learned about numbers, which is called mathematics. I also studied poetry and learned how to draw maps of the world, which is called geography. Because I was interested in so many different things, my friends gave me a nickname: 'Beta.' Beta is the second letter of the Greek alphabet. They were teasing me a little, saying I was the second-best at everything, but I didn't mind. I thought it was fun to be good at lots of different things instead of just one.

One day, around the year 245 BCE, something wonderful happened. The king of Egypt invited me to work at the most amazing place in the world: the Library of Alexandria. It was a giant, beautiful building filled with thousands and thousands of scrolls that held all sorts of knowledge. I was asked to be the head librarian. It was my job to take care of all the information and help other smart people who came from all over the world to study there.

While working at the library, I heard a fascinating story. In a city called Syene, which was south of Alexandria, on one special day each year, the sun shone directly down into a deep well, leaving no shadows at all. But on that very same day in Alexandria, I noticed that tall things, like sticks or poles, made a small shadow on the ground. This observation gave me a big idea. I realized that the Earth must be curved like a ball. Around 240 BCE, I used math and the length of the shadow in Alexandria to figure out how big the whole world was. It was the very first time anyone had measured the Earth.

I also created one of the first maps of the known world and invented a clever way to find special numbers called prime numbers. I lived a very long and happy life filled with questions and discoveries, living to be about 82 years old. People remember me today as the person who first measured our planet, and my ideas helped sailors and travelers understand the amazing world they lived in.