History of the Sundial

The sundial or sun clock is considered to be the oldest known device for the measurement of time and one of the most ancient scientific instruments. It allows us to see our world in four dimensions – length, width, height and time.

The operation of a sundial is based on the knowledge that the shadow of an object will move from one side of the object to the other as the sun "moves" across the sky during the day.

Historians are unsure who invented the sundial or exactly when it was invented. It may have appeared in the Middle East or North Africa perhaps invented by the Sumerians around 5000 to 6000 years ago. Sundials are found in many ancient civilizations, such as Babylonian, Greek, Egyptian and Roman. They are also common in the Far East countries of China and Japan.

An early type of sundial called an obelisk – a tall four-sided monument - was built by Babylonians and Egyptians around 2500 BC. Obelisks were placed in many locations in their cities.

The oldest known sundial—a smaller version of the obelisk--dates to ancient Egypt from about 1500 BC. Time-keeping was so important to the Egyptians that they even made portable versions of the sundial. "Shadow clocks" were developed further by Chinese, Greek and Roman cultures.

An Egyptian sundial dating from around 800 BC is the earliest preserved sundial we now have. It was made of a straight base of green schist with a crosspiece on one end. The crosspiece was placed at the east end of the base in the morning and the west end in the afternoon. The shadow of the crosspiece on the base showed six time divisions.

Greek-style sundials were probably invented by the Chaldean priest and author Berosus who lived around 340 BC. His sundial consisted of a block with a half-circle bowl cut into it. The shadow of a small bead at the center of the bowl moves around in a circle divided into twelve equal parts. This type of sundial was popular with the Arabians and Romans.

Around 290 BC a sundial was captured from the Samnites and set up in Rome. Another sundial was brought to Rome from Catanian by Valerius Messala in 261 BC.

By 250 BC the Greeks such as Apollonius and Ptolemy used their knowledge of geometry to construct sundials known as the hemicyclium and the analemma, respectively. Around 100 BC the Tower of the Winds was constructed in Athens, containing sundials facing the eight cardinal compass points. In 1200 AD, Ab û al-Hasan wrote a treatise to introduce the concept of equal hours.

The years between 1500 and 1800 AD are considered the "great age" of sundials. Oronce Fine constructed a sundial made of ivory in 1524. Two Italian astronomers, Giovanni Padovani and Giuseppe Biancani, published treatises on how to construct a perfect sundial.

Stonehenge monument, constructed about 400 years ago, is a type of sundial, which traces the sun’s movements for the entire year. In 1728 an astronomical observatory known as Jantar Mantar was built in Jaipur, India.

The sundial was used to check the time on mechanical clocks until late in the 1800s when mechanical clocks became inexpensive and accurate enough to replace sundials as the timepiece of choice.