What Is A Sun Dial

Photo by Ana y Paco Sancho

The definition of a Sun Dial is simple, it measures time according to the position of the sun.

Standard sun dials cast a shadow on to a flat surface marked with each hour of the day. When the sun changes position, the shadow covers up more of the dial. Although that is the most widely seen sun dial, you can have a sun dial designed for any surface that can cast a predictable shadow.

Sun dials have been dated as far back as 3500BC, where they were said to be used by the Ancient Egyptians. The Romans hold the record for having the biggest sun dial built. Around 100BC it is said the first universal sun dial was built by a mathematician.

When thinking about how a sun dial is designed you have to know a few things first. The most common sun dial is a disk mounted on a bar. With this method the bar must be parallel with the earth’s axis. The disk has to be marked so that one you can tell the time from one end of the bar as the Earth rotates. During winter months one half of the disk will be hard to read because of the shading, and during the summer months the opposite half of the disk is usually hard to read.

As with all things new technology has taken over sun dials. Now there are many different styles of designs including the following.

• Ring Sun Dials

• Precision Sun Dials

• Reflection Sun Dials

• Analog Calculating Sun Dials

• Optical Sundials

• Digital Sun Dials

Let’s take a little time here to talk about digital sun dials, since this is what we are probably most familiar with. There are two basic types of digital sun dials.

The first one is an optical fibre sun dial the way it works is sunlight enters through a slit in the device and as the sun advances the light moves. The light shines on sockets causing digits to come up on the display screen, revealing the time.

The second of the two digital sun dials are fractal dials. These are a lot more complex, but the basis of constructions comes from fractal geometry. Hence the name fractal sun dial.

I feel since sun dials have been such a widely used tool for so long, that it’s important for you to understand what they can do. Although you may think it isn’t very practical to know right now, you may very well need to use it someday.

A lot of research is done with the use of modern sun dials, these modern sun dials are created by some of the world’s smartest people. If you want to see the worlds largest sun dial still built you can go to India. It is called the Samrat Yantra and the stone structure stands a massive 27 metres high. They have said it can tell time with a margin of a fraction of a second. I would love to see this in person someday, but it will have to wait for now.