Ptolemy was an Alexandrian mathematician, geographer, astrologer, author, and astronomer who lived roughly around AD 90. His exact birth and death dates are unknown.

Claudius Ptolemaeus had Greek and Roman citizenship, although he was born in lived most of his life in Egypt.

Even though some theorists have written about family life most of it is not believed to be true. Therefore, we do not know much about his life except the great things he did.

Ptolemy’s main contribution is his ‘geocentric theory’, which explains how the Earth is the centre of the universe. His theory was accepted, until the 17th century.

His most famous book the Almagest (astronomy) gives us a great look at his geocentric theory, and his view of the brightness of the stars and their behaviours.

This book is the only book that has survived from the ancient world and even though the information may not all be accepted today, is considered a very valuable book.

The Almagest has 13 volumes in total, and Ptolemy filled it with various theories, calculations, diagrams, and formulas that showed his understanding of the planets.

He also invented the Handy Tables a set of astronomical calculations that help show the position of the sun, moon, planets, and even the eclipses of the sun and moon.

He also invented the branch of mathematics known as Trigonometry, which is the study of the sides and angles of the triangles and how they relate to each other.

His work in geography is written in detail in his book The Geographia. He drew maps from the Canary Islands right up to China and from the Arctic to the East Indies.

This map is believed to be the entire kingdom that belonged to Rome during the Roman Empire.

He borrowed from other geographers and scientists to put his book together, but the sections, which he did on his own are, not believed to be very exact.

Even so, this book laid the foundation for many other theorists who followed in Ptolemy’s footsteps to make more accurate versions of maps of lands and provinces.

In the Geographia, Ptolemy gave clear instructions on how to create maps, lists of various places depending on their surface shape and features (topographical maps).

His work in astrology is as important. He has been referred to as a genius in this area and included all his astrological knowledge into four books called the Tetrabiblos.

Tetrabiblos means Four Books, which refers to the four books that he wrote which were so important and respected it was almost similar to that of the Bible.

This book gives details on the ancient practices of horoscope astrology (the study of the specific position of the heavens and stars at a particular moment in time and the effects the moving planets have on the entire system, in relation to man).

Ptolemy did not believe that the study of astrology was the same as that of science. He believed that it was not 100% true and that a lot of it can be guesswork.

He outlined all these beliefs in his Tetrabiblos too, showing that while astrology is something that can be used in life, it should not be relied on entirely.

Ptolemy also contributed to the study of music, by writing the Harmonics a book on music theory, and the mathematics of music.

This great man even studied the properties of light, colour, and the reflection of the rays of light. These studies are included in his book The Optics.

This book is very important because it gives us a peek into the history of the study of light before technology changed things.

In honour of all these great things that he gave to the world, many items and characters are named after him.

There are two craters, one on the Moon, the other on Mars, which are named Ptolemaeus.

The asteroid 4001 Ptolemaeus is also named after Ptolemy.

Books and movies have characters named after him, and an English TV presenter, Sir Patrick Moore has even named his Ptolemy.

This great man lived until he was about 85 or 90 years, and died around the year 165 in Alexandria, Egypt, his birthplace.