Gardening & Landscaping Information

Can Your Sundial Really Tell The Time?


"I am a sundial, and I make a botch
Of what is done far better by a watch"

So wrote Hilaire Belloc, but is this really fair? Sundials are the earliest known form of time-keeping having been used for some five thousand years. The Greek historian Herodotus stated that sundials were first used by the Chaldeans and Sumerians in Babylonia which was part of the modern Iraq. They used vertical rods on their buildings and noted the position of the shadow to record the passing of the hours. The concept was developed by the Greeks and Romans who constructed various different shapes of dial to enable them to tell the time and the season of the year. Usually these were bowl-shaped dials with vertical or horizontal gnomons (shadow-casters) and hour lines marked in the hollow of the bowl. Over the years more elaborate designs were produced until the advent of accurate clocks when the function of the sundial became more decorative than as a reliable means of telling the time.

The question is often asked "Can a sundial really tell the correct time?" to which you will receive the Alice in Wonderland reply that it depends upon what you mean by "the correct time". Our clocks and watches work on the basis of there being exactly twenty-four hours between one day and the next but, because of the eliptical nature of the earth's orbit around the sun, the time shown on the sundial will vary according to the seasons. In February by the clock the sun is almost fifteen minutes slow, whereas during the spring and summer months it gains and loses between four and six minutes in two cycles. At the other extreme in November the sundial appears to be some seventeen minutes fast. In fact the sundial is accurate on only four days of the year, about April 15, June 14, September 2 and December 25. Some sundials include a table showing the deviation from "clock time" according to the date.

The time indicated by the sun will also vary with the location of the dial. The sun travels across the sky at the rate of fifteen degrees per hour so every degree of longditude represents a difference of four minutes from the standard meridian for the region. The angle of the gnomon also depends on the situation, so to set up your sundial correctly you need to know both the latitude and longditude of its location. For the United States and the United Kingdom this site can provide the information. The gnomon should be set at the angle in degrees which is equal to the latitude of your location. The sundial can then be fixed with the gnomon pointing to the Pole Star. There are various ways of achieving this, the easiest of which, is to use a compass adjusted for the magnetic variation. Further details are beyond the scope of this article, but for those interested look at this site.

If you have read this far you will have discovered that there is a great deal more to the sundial than a mere item of garden decoration. If this has piqued your interest in the subject, then you are not alone. There are Sundial Societies in countries around the world. The North American Sundial Society has details of its objects and activities on its website.

A number of sundial trails have been established. A good example is the Thames Sundial Trail in London, England. This site lists a number of other trails in countries all over the world but only two in the United States. However the North American Sundial Society has a complete list on its website.

Two rather different designs are shown here. The first, which is commonly referred to as a Human Sundial, uses the person's shadow to indicate the time. By standing in the appropriate box for the date the shadow will show the correct time. The second is a Digital Sundial which sounds like a contradiction in terms but in reality is just a rather clever design.

Many sundials have a motto inscribed on the face. Often these are rather serious in tone and of the "Tempus fugit" variety but you also find some written in a lighter vein. Here are a few of my favourites:

The shadow of my finger cast
Divides the future from the past

The clock the time may wrongly tell,
I never if the sun shines well

I stand amid the summer flowers
To tell the passage of the hours

And finally again from Hilaire Belloc:

I am a sundial, turned the wrong way round.
I cost my foolish mistress fifty pounds!

Hugh Harris-Evans is the owner of The Garden Supplies Advisor where you will find further articles, gardening tips and product reviews.


MORE RESOURCES:

Expo shows off Snohomish County's outdoor recreation
The Seattle Times
... Department sponsors the expo and will be on hand with information on county programs and facilities, along with vendors and recreation groups with displays and demonstrations on camping, fishing, landscaping, gardening, climbing and boating.



Myers Park home to nation's largest Earth-Kind research program
Celina Record
The Earth-Kind Environmental Stewardship Program is an American Society for Horticultural Science (ASHS)-recognized educational program focused on protecting the environment and conserving natural resources through research-based landscaping, gardening ...

and more »


Oman Daily Observer

Largest sewage treatment plant
Oman Daily Observer
The quality of treated water produced at Al Ansab STP is so good that it can be used for various purposes such as irrigation, beautification, landscaping, gardening, cleaning, toilet flushing and other industrial requirements.

and more »


North Shore Times

Better Homes and Gardens' presenter Jason Hodges to create Australian Garden ...
North Shore Times
Mr Hodges started his landscaping gardening maintenance business, Greenart Gardens 20 years ago with a ute from his parents' Willoughby home. “I find the north shore to be one of the most appreciative communities in Australia for general space and ...

and more »


Home and Garden Show
Bayshore Broadcasting News Centre
The 29th annual Port Elgin Rotary Home and Garden Show has about 80 vendors at the Plex and takes place from 10 AM to 4 PM today (SAT) and tomorrow (SUN). Both shows feature landscaping, gardening and home renovation businesses.


Google News

home | site map    LINKS |       Visit Internet Clipart for great graphics
© 2011