The Chinese Brass Equatorial Sundial, also known as the equatorial ring sundial or armillary sundial, is a sophisticated timekeeping instrument used to determine the time based on the position of the sun in the sky. It is a variation of the traditional sundial and has been used in ancient China and other civilizations for centuries.
The equatorial sundial consists of a brass ring or hoop, which represents the celestial equator, and an adjustable armillary sphere that represents the celestial meridian. The sphere is oriented so that its axis aligns with the Earth's rotational axis, which is why it is called an "equatorial" sundial. The sphere has various rings and circles that are calibrated to celestial coordinates, allowing the sundial to be adjusted according to the observer's latitude and the date.
To use the equatorial sundial, it needs to be aligned with the North Star or the celestial pole for accurate timekeeping. As the Earth rotates, the sun casts a shadow on the brass ring, indicating the time of day. The position of the shadow corresponds to the position of the sun in the sky, and by reading the calibrated circles on the armillary sphere, one can determine the local solar time.
Chinese brass equatorial sundials were not only functional timekeeping devices but also works of art, showcasing intricate craftsmanship and often adorned with ornate engravings or inscriptions. They were utilized in important locations like palaces, temples, and observatories to mark the passage of time and coordinate various activities.
UNESCO 24 Solar Terms- YouTube
The Twenty-Four Solar Terms- UNESCO article
In ancient China, the sun's annual circular motion was divided into 24 segments called "Solar Terms." These terms originated in the Yellow River region and were developed based on observations of seasonal changes, astronomy, and natural phenomena. Gradually, this system spread throughout the country, encompassing cycles from the Beginning of Spring to the Greater Cold. Passed down through generations, the Solar Terms served as a practical guide for agricultural practices and daily routines, particularly for farmers.
They were later integrated into the Gregorian calendar and widely embraced by various communities and ethnic groups in China. Many rituals, festivities, nursery rhymes, ballads, and proverbs are associated with the Solar Terms, enhancing its status as an intangible cultural heritage and contributing to the community's cultural identity. Knowledge of the Solar Terms is transmitted through both formal and informal educational methods.
The Jantar Mantar Astronomical Observation Site- UNESCO
Equatorial sundials are found in various cultures around the world, each with its own unique design and historical significance. While not all cultures have equatorial sundials, some of the civilizations known to have developed and used similar equatorial timekeeping instruments.
One of the interesting sundials is found in India, namely, the Jantar Mantar in Jaipur. It is an astronomical observation site built in the early 18th century, and contains approximately twenty main fixed instruments, representing remarkable examples of masonry-built instruments with distinct features. This observatory serves as a testament to the astronomical knowledge and cosmological concepts prevalent in the court of a scholarly prince during the Mughal period.
The Jantar Mantar is the most important and well-preserved collection of fixed monumental instruments in India from the first half of the 18th century. Some of these instruments are the largest ever constructed in their respective categories. Intended for observing astronomical positions with the naked eye, they embody a fusion of architectural and instrumental innovations. The observatory follows the tradition of Ptolemaic positional astronomy, which was shared among various civilizations and played a role in completing the astronomical tables of Zij, marking the apex of this tradition.
Commissioned by Prince Jai Singh II, the Jantar Mantar served as a meeting point for diverse scientific cultures and gave rise to social practices associated with cosmology. It also represented royal authority through its urban design, timekeeping capabilities, and astrological predictions. This observatory serves as a representation of the amalgamation of political, scientific, and religious purposes.
How to Read a Sundial- YouTube
Make Your Own Sundial- YouTube
The first video shows a guide on how to read a sundial.
The second video shows how to make a sundial. Although the video uses wood, this can be done with more accessible materials such as paper.
