Home And Garden Articles

The Sundial - Garden Ornament or Exotic Timepiece?

Most of us regard a sundial as an attractive ornament for a park or garden. Their effectiveness as time keepers is highly variable

That's unfortunate, because it is not at all difficult to ensure that your garden sundial will be an accurate timepiece, provided, of course that the sun is shining.

But that will be covered in another article. For now, let's see what a sundial is, and what it is capable of.

Sundial History

We forget in this modern age that accurate, affordable watches and clocks have been around for much less than 200 years.

Before then, sundials were one of the few ways to tell the time with reasonable accuracy.

Shadow clocks dated at 1500BC are known from Egypt, but the first dials appear to have been Babylonian. The Greeks adapted the idea, the Romans developed it further, and by about 100BC had perfected the horizontal sundial (and placed it in their gardens).

Even in ancient days some people had schedules to keep, and both agriculture and religion required knowledge of the seasons and the movement of the sun to determine planting and the timing of ceremonies.

The sundial was an important means of providing that information, and considerable advances in mathematics, geometry and astronomy were made while it was perfected. The knowledge gained forms part of the foundations of modern science.

Types of Sundial

There are four reasonably common types of sundial.

They all have two things in common. Each consists of a raised structure, called the gnomon (silent "g") which casts a shadow onto a plate called the dial. The dial is divided into hourly or shorter time divisions and may also show other information.The part of the gnomon whose shadow indicates the time on the dial is called the style.

The most abundant form is the horizontal sundial, happily sitting on its pedestal or column and adding beauty and interest to the home garden.

Related is the equatorial sundial, with its dial oriented at the same angle as the latitude. It works slightly differently, and is easier to use when properly calibrated.

Thirdly, there is the vertical sundial, ideally located on a wall facing due south in the northern hemisphere, and north in the southern hemisphere. The principle is much the same, but the sundial only occupies a semicircular area. Vertical sundials displayed the time to the public, and were used to correct unreliable public clocks.

And the most elegant of all, the portable sundial. George Washington had one - at that time pocket watches were most unreliable. Modern examples can be a work of art. They combine a compass with an adjustable dial. The dial is tilted to correspond to local latitude, and the compass defines north. Pretty neat!

Sundial Accuracy

A properly designed and installed sundial can be a very accurate means of telling the time, down to intervals of less than a minute.

I won't go into the mathematics, but on a sundial 16 inches (40cm) in diameter, the shadow of the gnomon will move about 1/30th of an inch, or just under 1mm, in a minute. This may be small, it's enough for our eyes to see.

Two Major Problems

Apart from the frequent absence of sunlight (Problem 1), all sundials show time by calibrating outwards from the position of the sun at noon. If you live east or west of me, your noon is different to mine.

Although the earth moves around the sun, we see it the other way. The sun appears to move from east to west across the sky, and local noon is when it's vertically overhead. But if you live 100 miles west of me, my noon is still your late morning, and your noon is my early afternoon. This would be inconvenient if we used our sundials to arrange a lunch date, but a real problem if I had a plane to catch in another city.

Solar Time and Official Time

People managed to live with this problem until communications and transport became faster. Imagine calculating train timetables when Boston, New York and Buffalo all worked on different local times.

The answer was the development of local time zones. US Railways did this in 1883, but in 1914 the world's governments agreed to divide the globe into 24 zones, each 15 degrees of longitude in width, and each one hour different in time to its neighbours. Boundaries were altered slightly to account for state and national borders.

There are four time zones in the contiguous 48 states of the USA: Eastern, centred on 75 degrees W longitude; Central, on 90 degrees; Mountain, on 105 degrees; and Pacific, on 120 degrees. Noon was identified astronomically for each of these meridians (now it's done by atomic clocks), and accepted everywhere else in the zone.

Noon on sundials in places very close to these longitudes will correspond to official noon. For every degree east or west of the central meridian, for 7.5 degrees either side, you will need to add or subtract four minutes respectively to correct your sundial.

A few other adjustments are necessary to compensate for irregularities in the earth's path around the sun - not too difficult to make but the theory is beyond this article.

They add to the inconvenience, and that's why sundials have been superceded by more convenient and reliable forms of time keeping. But problems with time zones and orbital paths can be corrected, and there's no reason why you can't find the correct time from your sundial.

No reason, that is, provided it has been properly installed in your garden. And that's the subject of another article.

Copyright 2005, Graham McClung.

A retired geologist, Graham McClung has had a lifelong interest in the outdoors. And where there's outdoors there's weather. He is the editor of http://Home-Weather-Stations-Guide.com, where you can find reviews and advice to help you choose and use your own home weather station. You can contact him by email at information@home-weather-stations-guide.com

Other Article Sites

findabook.com  moneycd.info  a-mortgage.info   about-lemon-laws.info  aboutstudentloans.info
all-about-publishing.info  auctions-articles.info  bestcollege-university.com  bestispconnection.com
biblefolder.com  blogger-website.com  books-used.info  brokers-guide.info  buywindows.info  cable-dsl.info
career-miner.com  carpel-tunnel.info  cashinaflash.info  cashloanreviews.info  casinobell.com  chat-house.info
clearmycredit.info  collegeloantips.info  crones.info  depression-articles.info   dirnic.net  dishguides.info
divers-below.com  expodog.info   financewizz.com  fire-insurance.info  getgood.info  handleit.net   it-idea.info
health-supplies.info  hosting-right.com  insidealert.com  insurance-facts.info  jobs-employment.info
justgood.info  lookgold.net   lowcost-travel.info  money-source.info  myhostzone.info  numisblog.com
peoplesearchfinder.info  pr-articles.info  realeas.com   refinancing-guides.info  spyware-remove.info
telelot.info  the-law.info   toppaid.info  travel-deals.info  travelcorrect.com  wedding-guide-site.com
your-blog.info  your-credit.info

MORE ARTICLES:

Exotic Flowers: Luxurious and Impressive for Your Home and Garden Decor
There are several types of exotic flowers to best suit any occasion. And of course, depending on your personal taste, you will want to choose the best exotic flowers you can obtain to be the perfect flowers, the most adequate for the purpose they will be serving. For example: at someone?s funeral, you may want to choose bouquet of flowers that the deceased would have loved. Here are some other examples (after all, these flowers are for happy occasions as well as the more tragic ones.

Flower Gardening
Flower gardening is becoming more and more popular every day. Flowers can brighten everyone?s day, they smell nice, and are a great hobby. Flower gardening is simple, inexpensive, and loads of fun. Flower gardening can be done for yard decoration, simply as a hobby, or even professionally.

Fall Garden Chores for Spring Flowering Bulbs
As the school busses begin to rumble down the road again we are reminded that the gardening season is drawing to a close. For the gardener with an eye toward next spring, however, the season still promises plenty to be done in preparation of a showy spring to come.

Town & Country Conservatories Designs Custom English Skylight for Rockefeller Center's Flower & Garden Show
EnglishSkylights.com, a division of Town & Country Conservatories designs and builds a custom conservatory-inspired skylight for Rockefeller Center's annual Flower & Garden Show.

Wild Flower Garden - Make Amends...Your Plants Will Love It
A wild flower garden, just like any garden you wish to plant, requires good quality soil that will meet the needs of the plants you put in it. That means that your garden soil may need some amendment.

How to Choose the Right Bulbs for Your Spring Flower Garden
Choosing the right bulbs involves more than just selecting colors and cultivars. Timing, bulb size, and most importantly, bulb health are equally significant factors in designing your spring garden.

Converting a Weed Garden to a Manageable Flower Garden
Recently I must have had sucker tattooed on my forehead because just when I thought my summer gardening season was winding down into a nice relaxed not hard labor kind of fall a friend baited me into a conversation about their landscaping and the outcome was I ended up helping them redesign a garden

Wild Flower Garden - Plan to Plant
In the previous article I discussed design for your new wild flower garden. The next stage is planning the planting.

Wild Flower Garden - Yours to Design and Plan
To design a wild flower garden, you do not need to be a specialist or an artist, you just need to be observant and let your creative juices flow. Look around you, what is unique about your surroundings? Do you wish to enhance or compliment these things.

New Ways to Use Flowering Clematis in the Home Garden
As a lifetime horticulture professional, Vicki Smith (www.LGYP.com) has exciting news and guidance for using Clematis in today's low maintenance landscapes.

Flowering Field Farm of NJ Announces Association with Garden Spot Structures
Flowering Field Farm has announced a new business relationship with Garden Spot Structures of Lancaster County, Pa. The NJ farm is located on Highway 34, just south of the Holmdel border and Route 520. Garden Spot Structures of Leola, Pa. has been delivering fine, Amish-crafted structures for 30 years.

Chocolate for the Home and Garden ~ Chocolate Flower Farm Launches New Candle Division
Chocolate Flower Farm, a specialty nursery featuring dark foliaged and flowering plants, launches a new candle division with the acquisition of the exclusive rights to a distinctively different "Essence of Chocolate" candle. The candles along with their popular series of Chocolate Garden Seed Kits will be offered to retailers worldwide.

5 Most Popular Flowers for Your Garden
When planting a garden there are many questions which you must ask yourself before you begin. Where are you going to plant it, do you have the garden equipment to do so and how big do you want your garden to be? When do flowers bloom and what are their heights? These are all very important questions, however they mean very little if you have not yet decided which types of flowers you want to plant.

Flowers That Beautify Your Home and Garden
To help gardeners choose flowers, various systems for rating hardiness have been developed. A plant is considered hardy in a region if it can grow and thrive there without requiring special protective measures such as insulating with straw mulch.