What is a Sundial?
A sundial is essentially a clock. But more specifically it is a clock that uses the position of the sun to indicate the time. Typically a gnomon casts a shadow upon a plane or surface. On this surface are found markings that indicate the time by the position of the shadow. There are several types of sundials. Each type serves the same purpose: to tell time by the position of the sun. But the method used to extract the data from each sundial is different. The scope of this hand out is not to instruct you in the different types of sundials, or how to use them, but to teach you how to use one type in particular. This type is known as the horizontal sundial. These are, in my opinion, the simplest to setup, and use. To find out about the other types of sundials that are known, I would direct you to one of the books that I have included in the section called Suggested Reading. Any of these books will tell you much more about sundials and their various forms than this hand out. If you are eve
A sundial is the most primitive form of a clock. The simplest sundial consists of a stick set in the ground, which casts a shadow indicating the time of day. In mankind’s early history, the most basic division of time was night and day. Beyond that, it was obvious that the sun rose over one horizon, and set in the other. It’s a sure bet that the shadows cast while the sun made its trip across the sky, did not escape the notice of primitive humans. Morning shadows were long, gradually becoming shortened to disappear at noon, then lengthening again in the opposite direction, trailing the sunset. Shadow casting would have been a natural tool for telling time. No one can be sure when the first sundial appeared, but we do know that as early as 3500 B.C. Egyptians were building sundials that not only kept time but indicated the longest and shortest day of the year. Sundials are generally made with a bottom circular disk that represents the face of a clock, upon which are segmented lines indi
Sundials measure time of day based on the relative position of the sun in the sky. How do sundials work? The sun appears to move across the sky because earth spins on its axis. Sundials mark the time of day based on the apparent postion of the sun in the sky. Because earth’s axis is tilted, and thanks to Standard and Daylight Saving time, creating an accurate sundial becomes a little complicated. Sundials have a stick or rod of some type (called a gnomon) that creates a shadow which falls on numbers representing the time of day. If the gnomon is vertical, the time will not remain accurate throughout the year because earth’s axis is tilted and the earth moves around the sun. This causes the North Pole to tilt away from the sun during winter and towards the sun in summer, altering the location of sunrises and sunsets on the horizons as well as the height of the sun in the sky at noon. To compenstate for this variable, the gnomon must be parallel to earth’s axis. This can be accomplished
