Ptolemy

When relaxing in the garden, considering the simple sundial can lead one's mind to wander. Where did it come from? Who thought it up? Has it always been the same? And while each of these seemingly simple questions does have an answer, the majority of those answers are anything but simple.

One of the keys to understanding the history of the humble sundial lies in knowing your – often ancient – history. And, the story of Ptolemy and his contribution to your favourite piece of garden décor is no exception.

About Ptolemy

There is very little biographical information available about the man we know today as Ptolemy – we know he was probably Greek, most likely lived in Egypt and was born Claudius Ptolemaeus, in the mid-80s AD. He was a mathematician, a geographer, an astronomer and astrologer who made a series of key observations and studies that he documented from Alexandria in Roman Egypt.

Those observations had a tremendous impact on later studies done by Islamic and European scientists centuries later. Ptolemy documented his work in a series of books: The Almagest, The Geography and The Tetrabiblos. It is the first of these that holds a particularly special place in the modern world as it is the only astronomical treatise that survives intact to this day.

Perhaps the key contribution Ptolemy made in The Almagest, also known as The Syntaxis, is the inclusion of the Handy Tables that include all the information you need to work out the position of the sun, moon and planets at any given time. The tables allow you to compute the rising and setting of particular stars, and even lunar and solar eclipses.

The Significance of Ptolemy's Work

Ptolemy took the work of scores of scholars from all walks of life and amalgamated it into one workable theory of the solar system. Ptolemy’s system is based on everything revolving around the earth, and includes just five planets, along with the sun and moon. Until Copernicus storms onto the astronomical scene in the middle of the 16th century, Ptolemy’s theory goes largely unchallenged.

In The Amalgest, he describes a complex instrument comprised of seven graduated rings that interlock to represent the basic orbitals of the known planets. The genius of Ptolemy's design is the fact that the rings are intended to swivel on an axis relative to their orbit – essentially giving the user a three-dimensional map of the heavens that could be adjusted to ascertain the position of a particular celestial object at a given time.

While it's easy for some to disregard Ptolemy because of his geocentric notions on the solar system, his place in the hallowed halls of astronomical achievement cannot be denied. The Handy Tables, for example, were accurate enough to benefit countless generations of calendar makers, time keepers, navigators and astronomers. And ultimately, his observations were amazingly accurate given the technology available at the time – the position of the planets within his system, for example, are great for observing such things with the naked eye.