Sundial facts for kids

A sundial showing the time

A garden sundial at 9:30am

A sundial is a cool device that tells you the time of day using the sun! It works because the sun seems to move across the sky, and as it moves, it casts a shadow in different spots. By looking at where the shadow falls on the sundial's marked surface, you can figure out the current solar time.

There are many different kinds of sundials, from the common ones you might see in a garden to really fancy designs. The main idea is always the same: a fixed object creates a shadow on a specially marked surface.

The History of Sundials: Telling Time Through the Ages

Sundials are super old! People in Ancient Egypt were using them thousands of years ago. Later, other amazing cultures like the Greeks and Romans also used and improved sundials. They were some of the first ways humans accurately kept track of time during the day.

How a Sundial Works: Shadow Play and Time Telling

So, how does a sundial actually tell time? It's all about a special part called the gnomon and the dial plate.

The Gnomon: The Shadow Caster

The gnomon is the part of the sundial that sticks up and casts the shadow. Think of it like the pointer. For a sundial to be accurate, the gnomon needs to be pointed towards the North (in the Northern Hemisphere) or South (in the Southern Hemisphere) and tilted at an angle that matches the latitude (how far north or south you are) of where the sundial is located. This makes sure the shadow moves correctly throughout the day.

The Dial Plate: Where Time is Marked

The dial plate is the flat or curved surface where the shadow from the gnomon falls. This plate has lines and numbers marked on it, representing the hours of the day. As the sun moves, the gnomon's shadow moves across these lines, showing you the time.

Solar Time vs. Clock Time

It's important to know that a sundial shows solar time, which is based directly on the sun's position. This can be a little different from the time on your phone or watch (which is called mean time or standard time). Sometimes, you might need to make a small adjustment to the sundial's reading to match your clock, especially if you want super precise time.

Different Types of Sundials: Creative Designs

Sundials come in many shapes and sizes, each designed to work in a specific way or place.

• Horizontal Sundials: These are the most common garden sundials, with the dial plate lying flat.
• Vertical Sundials: You often see these on the sides of buildings, with the dial plate standing upright.
• Equatorial Sundials: These have a dial plate that's tilted to be parallel with the Earth's equator. They often have two faces, one for summer and one for winter.
• Polar Sundials: These have a gnomon that points directly to the celestial pole (like the North Star), and their hour lines are parallel.

Amazing Sundial Examples Around the World

Sundials aren't just old tools; they are also beautiful works of art and science. Here are some cool examples:

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  A vertical sundial on the Moot Hall in Aldeburgh, England. Its Latin motto means "I only count the sunny hours."

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  A sundial in the Singapore Botanic Gardens. Its design shows that Singapore is very close to the equator.

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  The world's oldest sundial, found in Egypt's Valley of the Kings (around 1500 BC).

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  A sundial in Perth, Australia. Notice how the hour marks run counter-clockwise because it's in the Southern Hemisphere!

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  The Whitehurst & Son sundial, made in 1812, now at the Derby Museum.

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  The Sunquest sundial at the Mount Cuba Observatory in Delaware.

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  Timepiece, an equinoctial sundial by Wendy Taylor in London (1973).

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  A horizontal sundial in Minnesota, showing the time on June 17, 2007.

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  A simple sundial near the Johnson Space Center in Texas.

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  Two sundials in Nové Město nad Metují, Czech Republic.

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  A polar sundial at the Melbourne Planetarium.

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  This image shows how the hour lines on a vertical sundial change depending on which direction it faces.

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  Two sundials at the Fatih Mosque in Istanbul, from the late 16th century.

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  A vertical sundial in the Southern Hemisphere, facing north, at the Valongo Observatory in Brazil.

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  A ring sundial, a portable type of sundial.

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  An Ottoman-style sundial with a special folded gnomon and a compass, at the Debbane Palace museum in Lebanon.

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  A 19th-century Tibetan Shepherd's Timestick, another way to tell time using shadows.

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  A Navicula de Venetiis (a type of altitude sundial) on display in Geneva.

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  This animation shows how the sun's path changes throughout the year, affecting sundial readings at different locations.

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  A unique diptych sundial shaped like a lute, from around 1612.

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  The Benoy Sun Clock showing 6:00 p.m.

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  A modern stainless steel bifilar sundial in Italy.

Related pages

• Time

See also

In Spanish: Reloj de sol para niños