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.
Start at the EQUATOR where the lattitude is 0 degrees. The sun rises straight up to above your head at noon, then sets straith down below the horizon. Now go slowly up from the south of the USA to the Canadian border. You go from 0 degrees lattitude 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 lattitude. That is about the same lattitude as France and northern China, just check it out by going around the globe at the same 45 degree lattitude.
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…
Here a person is his own “gnomon”. You can also cast your own shadow and tell the time!
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.