Theodorus of Cyrene facts for kids
Theodorus of Cyrene (Greek: Θεόδωρος ὁ Κυρηναῖος) was an ancient Greek mathematician. He lived a very long time ago, around the 5th century BC. We know about him mostly from the writings of Plato, another famous Greek thinker. In one of Plato's books, called the Theaetetus, Theodorus talks about a cool math idea. Today, we call this idea the Spiral of Theodorus.
About Theodorus's Life
We don't know a lot about Theodorus's life. Most of what we know comes from Plato's books. Theodorus was born in a place called Cyrene. This was a Greek city in North Africa. He taught math in both Cyrene and Athens, a big city in Greece.
In Plato's book Theaetetus, Theodorus says he is quite old. This helps us guess that he was active in the middle of the 400s BC. He also mentioned that he studied with Protagoras, who was a famous teacher of public speaking. After that, Theodorus focused on geometry, which is the study of shapes and spaces.
Theodorus's Math Work
Theodorus is famous for one main math idea. It's about numbers that are "irrational." An irrational number is a number that cannot be written as a simple fraction. For example, the square root of 2 is an irrational number.
In Plato's book, Theodorus's student, Theaetetus, explains Theodorus's discovery. Theodorus showed that the square roots of numbers like 3, 5, 6, and so on, up to 17, are irrational. This means you cannot measure them perfectly with a simple unit.
The exact way Theodorus proved this is not known today. He might have used a method that looked at whether numbers were even or odd. He stopped at the number 17. The square root of 2 was probably already known to be irrational.
The Spiral of Theodorus
The most famous thing connected to Theodorus is the Spiral of Theodorus. It's a cool drawing made of many right triangles. Each triangle is added to the last one. The sides of these triangles create lengths that are the square roots of numbers like 2, 3, 4, and so on, up to 17.
If you keep adding more triangles, the spiral will start to overlap itself. A mathematician named Philip J. Davis later made this spiral into a smooth, continuous curve. He wrote a book about spirals, including Theodorus's, and how they appear in math and nature.
Theodorus's student, Theaetetus, later developed a more general idea about irrational numbers. This helped people understand these special numbers even better.
See also
In Spanish: Teodoro de Cirene para niños
- Chronology of ancient Greek mathematicians
- List of speakers in Plato's dialogues
- Quadratic irrational
- Wilbur Knorr
