Sundials for Your Home and Garden
A sundial is a device that can be used to measure time. The sundial is able to indicate time by using the path of the sun as it moves across the sky.
As the sun moves, it shines on a pole known as a gnomon, and the gnomon casts a shadow. Throughout the day, the shadow cast on the dial plate of the sundial passes markings indicating the time of day. Noon is the point in the day when the sun casts its shortest shadow on a sundial. Sunrise and sunset are when the sun casts its longest shadows.
* The sundial is not only the world's oldest time measurement tool but also one of the oldest scientific tools known to man.
* The sun's apparent path across the sky is different in different parts of the world. Each sundial must be made specifically for the part of the world where it is located.
* The sundial was the most widely used time measurement device until the 19th century.
Who Invented the Sundial?
Researchers are unsure exactly when the first sundial was conceived but believe it occurred sometime around 3500 B.C. at the hands of the ancient Egyptians. Scientists have located sundials from Egypt that were built in the 13th century B.C. that are still intact. Placing a stock, or gnomon, into the ground, the Egyptians calculated time by measuring the length of the shadow the gnomon would cast. Both the ancient Egyptian and Babylonian civilizations used the concept of using shadows to measure time. Obelisks constructed by both civilizations not only allowed for the measurement of time throughout the day but also allowed them to track seasons by determining the shortest and longest days of the year.
* The Samrat Yantra, the largest sundial in the world, is located in Jaipur, India, and stands 88 feet tall. This massive sundial is nearly 300 years old and measures time in 2-second increments.
* "Gnomon" is an ancient Greek word meaning "indicator."
The Greeks were able to use their advanced knowledge of geometry to improve on the design of the sundial. Developing their own dials based on the Babylonian models, the Greeks were able to build sundials that were marked to measure time throughout the year. Theodosius of Bithynia was even believed to have created a sundial that could be used anywhere on Earth. Early sundials were also used in Rome and China.
* History of Sundials: This page explains the history of sundials, from ancient Egypt to the European Renaissance.
* When Time Began: The History and Science of Sundials: Here, you will be able to learn more on the history of sundials.
How Are Sundials Made?
There are several different types of sundial, but the two most common types are vertical and horizontal dials. Vertical dials have a dial plate that stands vertically, with the gnomon tilted to account for the tilt in the Earth's axis. These dials are read similarly to a wall clock. Horizontal sundials are the type most commonly seen in gardens. They feature a face that lies horizontal. The gnomon is generally in the center of the face, casting a shadow around the plate through the day.
* Sundials: Encyclopedia Britannica has a useful entry about sundials.
* The Sundial: This page from NASA explains in detail exactly what a sundial is.
How Do Sundials Work?
Different sundials work in different ways. Equatorial sundials, for instance, have a fixed dial plate that is parallel to the equator. Analemmatic sundials do not use lines to indicate different hours of the day, but rather a series of points along an ellipse where the vertical gnomon will cast a shadow throughout the day.
In order for a sundial to work properly, the gnomon must be tilted in line with the Earth's axis. If the planet's tilted axis is not accounted for, the accuracy of the sundial will be affected. The angle of the gnomon in relation to the dial plate is the same as the latitude of its location. For example, the latitude for New York City is 40.71 degrees north, so sundials in New York City need to be raised at an angle 40.71 degrees from the dial plate. This makes the hypotenuse, or long side, of the gnomon parallel with Earth's axis.
* The History of Sundials: How Stuff Works gives a brief history of sundials, then explains how they function.
* Analemmatic Sundials: How to Build One and Why They Work: Here, you can find information on the analemmatic sundial and learn how to build your own.
* How Do Sundials Work? The British Sundial Society provides more information on how sundials function.
* Making an Equatorial Sundial Activity: This document from Museums Victoria explains an equatorial sundial and how to make one.
Additional Information About Sundials
* How to Measure Time With a Sundial: Find in-depth information about how measuring time with a sundial works from the American Mathematical Society.
* Making a Horizontal Sundial: The University of Montana provides this step-by-step guide to making a horizontal sundial for people of all skill levels.
* How to Make a Sundial the Simple Way: Sky & Telescope provides an explanation for creating your own sundial at home.
* The Garden Sundial: Not Just an Ornament: The New York Times details the use of sundials in gardens.
* The Ultimate Garden Accessory: This Telegraph article explains the benefits of having a garden sundial.
* Mosaic Sunclocks: See examples of sunclocks, including sundials, and how they can also be works of art.
* Collecting Antique Clocks: A 400-Year-Old Sundial: An author details his experience with collecting antique timepieces, including sundials.
* Sundials of London: Explore many examples of sundials located around the city of London.
* Sundials, Time and Again: This Washington Post article details the resurgence of garden sundials.
* Sundials: This article provides an in-depth history of sundials from a mathematical perspective.