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Apollonius of Perga

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Apollonius of Perga was a monumental Greek geometer and astronomer.

Conic Sections
Conic Sections

He is most famous for his study of conic sections. These are two-dimensional shapes created by the intersection of a plane and a cone. Apollonius built upon the foundational work of Euclid and Archimedes. He brought the study of these shapes to a level of sophistication that lasted until the invention of analytic geometry. His specific definitions for the ellipse, parabola, and hyperbola remain the standard in mathematics today. Because of his massive influence, he is considered one of the greatest mathematicians of antiquity.

To understand his work, one must visualize the mechanism of a conic section.

Conic Sections
Conic Sections

A conical surface is generated by rotating a line segment around a bisector point. The endpoints of this segment trace circles in different planes. A single cone is one branch of this double conical surface. It consists of an apex, or vertex, a base, and an axis. A section occurs when an imaginary plane cuts through this cone. If the plane passes through the vertex, the resulting section is a triangle. If the plane is parallel to the base, the section is a circle.

Apollonius categorized the different types of sections based on the angle of the cut.

Conic Sections
Conic Sections

An ellipse is formed when the plane is inclined to the base. The angle of this plane must be greater than zero but less than the angle of the cone's side. A parabola occurs when the cutting plane is parallel to the side of the cone. A hyperbola is created when the plane is parallel to the axis. This type of cut intersects both cones in a double conical surface, resulting in two distinct branches.

Parabola connection with areas of a square and a rectangle
Parabola connection with areas of a square and a rectangle

He also developed a specialized method called the "application of areas" to describe these shapes.

Parabola connection with areas of a square and a rectangle
Parabola connection with areas of a square and a rectangle

This method was used to establish mathematical relationships without modern algebraic symbols. For a parabola, he asked if a rectangle formed by certain segments would equal the area of a specific square. If the rectangle matched the square, the shape was a parabola. If the rectangle was smaller, the shape was an ellipse. If the rectangle was larger, the shape was a hyperbola. He used terms like "deficit" and "surfeit" to describe these differences in area.

Very little is known about the personal life of Apollonius.

We can estimate his era through the writings of the 6th-century commentator Eutocius of Ascalon. Eutocius noted that Apollonius was from Perga in Pamphylia. He likely lived during the reign of Ptolemy III Euergetes, who ruled Egypt from 246 to 222 BC. This suggests Apollonius was born after 246 BC. While he was from Perga, evidence suggests he lived and studied in Alexandria. This city was a major center for Hellenistic culture and scientific research.

Apollonius was a prolific writer, yet much of his work has been lost.

Conica of Apollonius of Perga fol. 162b and 164a
Conica of Apollonius of Perga fol. 162b and 164a

His most important surviving work is titled *Conics*. This text is divided into eight books. Only the first four books survive as original Greek texts. Books five through seven are only known through an Arabic translation by Thābit ibn Qurra. The status of the eighth book is uncertain, though fragments exist. He also wrote on astronomy, proposing that planets move in eccentric orbits. This hypothesis was widely accepted until the Renaissance changed our understanding of the solar system.

His mathematical style was highly structured and influenced later teaching methods.

Conica of Apollonius of Perga fol. 162b and 164a
Conica of Apollonius of Perga fol. 162b and 164a

In *Conics*, he used a system of definitions and propositions to be proved. This arrangement is very similar to how modern geometry textbooks are organized today. His work connects geometry to the broader study of the heavens through his astronomical theories. Even today, his legacy is visible in the stars. A crater on the Moon is named the Apollonius crater to honor his contributions to science.

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🖼️ Images & Media (6)
File:Conic Sections.svg
Conic Sections.svg
File:Parabola connection with areas of a square and a rectangle.gif
Parabola connection with areas of a...
File:Пифагоровы штаны.png
Пифагоровы штаны.png
File:Cartesian-coordinate-system Oxy P.svg
Cartesian-coordinate-system Oxy P.svg
File:Conica of Apollonius of Perga fol. 162b and 164a.jpg
Conica of Apollonius of Perga fol. 162b...
File:Apollonius of Perga. Conicorum. Florence, Giuseppe Cocchini, 1661 01.jpg
Apollonius of Perga. Conicorum. Florence,...
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