Apollonius of Perga

Apollonius of Perga

(Ancient Greek: Ἀπολλώνιος ὁ Περγαῖος Apollṓnios ho Pergaîos; c. 240 BC – c. 190 BC) was an ancient Greek geometer and astronomer. He is famous for his work on conic sections.

Apollonius built on the ideas of earlier thinkers like Euclid and Archimedes. He defined the shapes we now call ellipse, parabola, and hyperbola. These definitions are still used today and were important before the development of analytic geometry.

Apollonius also studied astronomy. Although much of his work on stars did not survive, later writers like Pappus of Alexandria talked about his ideas. One of his theories was about how planets move in eccentric orbits. People believed this until the Middle Ages.

Today, a feature on the Moon called the Apollonius crater reminds us of his important work. Together with Euclid and Archimedes, Apollonius is regarded as one of the greatest mathematicians of antiquity.

Life

We know very little about the life of Apollonius. He was an important ancient Greek mathematician who lived around 240–190 BC. He was born in Perga, a city in Pamphylia. He likely spent most of his time working and studying in Alexandria, in Egypt.

Apollonius wrote letters to his friends. He asked them to review his books about conic sections. Conic sections include shapes like ellipses, parabolas, and hyperbolas. One of his friends, Eudemus, helped him check his work. Apollonius sent his books to another important person named Attalus. Attalus loved collecting books and supported artists and scholars.

Writings

Apollonius wrote many books about geometry. Only one of his books, called Conics, still exists today. This book has eight parts. We only have the first four parts in the original Greek language. Parts five through seven are available in an Arabic translation. We do not know much about the eighth part.

Conics is about shapes known as conic sections. These shapes include ellipses, parabolas, and hyperbolas. These shapes are formed by cutting a cone with a flat surface. For example, if you cut the cone at an angle, you get an ellipse. If you cut it parallel to a side, you get a parabola. And if you cut it parallel to the cone’s axis, you get a hyperbola. Apollonius was the first person to define these shapes in the way we still use today.

Attributed ideas

Apollonius made many contributions to geometry and astronomy. He is known for describing how two different ways of tracking planet movements are related. One way uses a circle called an "eccentric," and the other uses circles called a "deferent and epicycles." This idea was later explained by the astronomer Ptolemy in his work called the Almagest.

Apollonius also helped connect geometry with algebra, even before algebra was fully developed. Ancient Greek mathematicians used pictures to solve problems that we might now solve with numbers and equations. For example, instead of saying a square’s area is its side length times itself, they would draw the square and measure its sides with lines. Apollonius used similar geometric methods to study special curves called conic sections, like ellipses, parabolas, and hyperbolas. His work laid important groundwork for later advances in mathematics.

Legacy

Apollonius' work, called the Conics, had a big impact on geometry. People studied it from ancient times all the way to today. In the 4th century, Serenus of Antinoöpolis wrote about parts of the Conics. In the 6th century, Eutocius of Ascalon also wrote about it.

In the 9th century, the Banū Mūsā translated the Conics into Arabic. The first printed version in Latin came out in 1566. In 1626, Jacobus Golius found more books of the Conics in Arabic. This helped scholars understand the full work better. New ways to study geometry developed, but Apollonius' ideas stayed important. Translations of his work into English started in the late 19th century. Notable versions were by Thomas Heath in 1896, Ivor Thomas in 1941, and R. Catesby Taliaferro in 1952. These were part of the Encyclopædia Britannica's Great Books of the Western World series. Ancient Greek mathematics and analytic geometry kept building on his work.