SUNDIAL THEORY

The sundial assembled, note the paper time scales have been cut from the printout and glued to the base, the gnomon is also inserted and glued in the slot.

Our sundial has a GNOMON with a 45 degree angle between the upper edge and the base. This is the same angle as the LATITUDE of the place on earth where you want to use the sundial.

Gnomon is an ancient Greek word. It means shadow maker, or indicator.  

This design of a horizontal sundial was first used in Egypt more than 3500 years ago…Wow!

The Romans used sundials in their gardens which were enclosed spaces inside the large houses.

To really understand all the science of sundials you must study astronomy, geometry and other special areas of science. But you can enjoy the sundial you made by understanding that it works with the sun and the rotation of the earth around the sun: sunrise, then at noon the sun is highest in the sky AND it is in the south, then it moves lower and sets below the horizon in the late afternoon or early evening.

When you try your sundial set it up with the gnomon pointing to the north and if you do this at noon the shadow should be at 12.

Actually if you set it up at noon with the shadow at 12 then you point the gnomon automatically to the north. This way your sundial is a compass!

Let’s have a look at the globe and try to understand LATITUDE.

The globe, North American continent, Atlantic Ocean and part of Europe.

The globe, North American continent, Atlantic Ocean and part of Europe.

Start at the EQUATOR where the latitude is 0 degrees. The sun rises straight up to above your head at noon, then sets straight down below the horizon. Now go slowly up from the south of the USA to the Canadian border. You go from 0 degrees latitude at the equator to 10 degrees, 20 degrees, 30 and 40 degrees. Then further north to Toronto and Montreal. Between those two large cities is Kingston at about 45 degrees latitude. That is about the same latitude as France and northern China, just check it out by going around the globe at the same 45 degree latitude.

Phew, that is a lot …

ALL THE SUNDIALS AT THIS LATTITUDE HAVE A GNOMON THAT HAS A 45 DEGREE ANGLE!

Now we show you something just for fun and to add a special touch to our sundial theory…

A person as \”gnomon\”, you can be your own shadow caster and tell the time!

Here a person is his own “gnomon”. You can also cast your own shadow and tell the time!

There is even a Sundial Bridge in California! Can you see the gnomon and its shadow?

This beatiful bridge is supported by cables that attach to the high mast or pylon on the left. This mast is also the gnomon or shadow caster. This is a great example of civil engineering, architecture, art and science, all in a public object. We hope you like it.

++++++++++++

And here is another large sundial, you can stand in it. What makes the gnomon in this one?

Yes, the person standing in the dial!

Here you can be your own "GNOMON"! See the shadow the person casts on the hour lines? You can be your own shadow caster and tell the time.

Here you can be your own “GNOMON”! See the shadow the person casts on the hour lines? You can be your own shadow caster and tell the time.

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s