Claudius Ptolemy Lesson for Kids: Facts, Biography & History

Instructor: David Wilson

David has taught college history and holds an MA in history.

One of the most famous astronomers and geographers in history, Claudius Ptolemy, created an idea for the organization of the universe that would be used for over 1,000 years. Learn about Ptolemy's legacy and life in this lesson.


When was the last time that you got a good look at all the stars in the sky? When you look up at the night sky, you might feel pretty small. Now imagine looking up at it without telescopes or any of the instruments we use to study the universe. How could you be sure what part the Earth plays in the giant picture?

Nearly 2,000 years ago, a famous astronomer (someone who studies the stars and planets) named Claudius Ptolemy came up with the idea for a universe based around Earth. While it's no longer the model astronomers use today, it influenced science for the next thousand years.

Drawing of Ptolemy
Image of Ptolemy

Life of Ptolemy

While the writings that Ptolemy produced about astronomy and geography have survived through the centuries, we know almost nothing about the man himself. What we do know is that he lived in the Egyptian city of Alexandria about 2,000 years ago and was a citizen of ancient Rome. His first name, Claudius, reveals that his family had been given citizenship by someone by that name, possibly the Roman emperor Claudius.

He had a teacher named Theon, who is mostly famous for being unskilled as an astronomer. But Ptolemy still thrived as an astronomer, because he had access to the great library of Alexandria, which was rich with information on the subject.

Famous Works

Ptolemy wrote a number of books during his life. The Mathematical Compilation (or Syntaxis Mathematica in Greek) is by far the most important work by Ptolemy, where he lays out the math behind his understanding of the universe. Ptolemy describes a geocentric model of the solar system, meaning that Earth lies at the center, not the sun. While we know today that this is incorrect, Ptolemy uses convincing arguments to demonstrate that the Earth is at the center and does not move, with all other objects -- the sun, other stars, planets, and moons -- moving in a giant circle around Earth, which is called an orbit.

Geocentric model developed by Ptolemy
geocentric model

The Mathematical Compilation laid out the organization of the solar system. Earth sat at the center, and going outwards was the moon, Mercury, Venus, the sun, Mars, Jupiter, and finally Saturn. You'll notice there are some missing planets. Back before the invention of telescopes, people had no idea that planets like Uranus and Neptune existed, as they were too far away to see with just your eyes.

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