Mount Logan Middle School
Mount Logan Discovery Homepage

Our Solar Calendar: 875 North 200 East, Logan, Utah

What is a solar calendar?

Solar calendars are often confused with sundials. Both measure time using the position of the sun. The difference is that sundials mark the time of day and solar calendars mark the time of year.

How do solar calendars work?

Because earth's axis is tilted--and that tilt is always oriented the same general direction in space --the North Pole is tilted towards the sun during our summer (in the Northern Hemisphere) and away from the sun during our winter, causing different regions of the earth to receive more direct sunlight at different times of year. This is the reason we have seasons. Click HERE to see a visual diagram

Near December 21st each year, the North Pole is tilted the furthest away from the sun and direct sunlight shines on the Tropic of Cancer. This event is known as Winter Solstice and is the day that the Northern Hemisphere receives the least amount of sunlight during a twenty-four hour period throughout the year. On this date the sun will appear to rise and set the furthest to the south on the eastern and western horizons. We had to wait three years for clear enough weather to put the marking stones in place (on the perimeter of the solar calendar) that mark the shadow of the rising and setting sun on the Winter Solstice.

Near March 21st each year North and South Poles are tilted neither towards or away from the sun, this event is called the Spring Equinox. On the equinox, direct sunlight strikes the equator, and night and day are equal in length world wide. The sun rises due east and sets due west. If you mark the tip of the shadow from the center pole at intervals throughout the day on the equinox an interesting pattern emerges (that we won't give away here). A second equinox, the Autumnal Equinox, occurs near September 21st of each year as well. Stones on the perimeter of the solar calendar mark the shadow of the rising and setting sun on both equinoxes. On our solar calendar these stones are slightly off from true east and west because the mountains that rim Cache Valley delay the sunrise and sunset at Mount Logan Middle School.

Near June 21st each year, on Summer Solstice, the North Pole reaches its maximum tilt towards the sun and direct sunlight strikes the Tropic of Capricorn. When this occurs we have the longest amount of daylight in a 24 hour period for the year. The sun rises and sets the furthest to the North in the eastern and western skies. Stones on the perimeter of the solar calendar mark the shadow of the rising and setting sun on Summer Solstice as well.

A link to the past

Thousands of years ago, before telephones, satellites, internet, and radio, indigenous people throughout the world noticed the apparent movement of the sun along the horizons caused by the tilt and orbit of the earth described above. Without knowing that other cultures, groups, and tribes, were doing the same thing, many intricate and often daunting monuments were built to track and record the pattern that creates a year. Hundreds of other ancient structures worldwide are aligned with equinox or solstice sunrises or sunsets. A few examples we have been taking a close look at include the Bighorn Medicine Wheel, Stonehenge, the Sun dagger, the Newgrange, the Maeshowe and Yucatan Temples to name a few. We have also learned that ancient Chinese, Egyptians, Mayans, Mexicans, and Polynesians had knowledge of this cycle. They were certainly not the only ones.


March 2008-cemented paver stones in place to mark the shadow lines on the equinoxes and solstices.

March 2007-We marked the shadow line from the center pole back in December on Winter Sostice and again on the Vernal Equinox. These shadow lines will be marked permanantly with cement landscape curbing.

Sept 2007-The center pole of the solar calendar rusted out and fell over. We ordered a new stainless steel pole, had the decorative metal artwork removed from the old pole and welded to the new one. After careful measurements we installed the new pole in the exact spot, careful to ensure it was set exactly one meter tall.

June 2006--Summer school students observed and marked the position of the Summer Solstice sunrise and sunset shadows. Sixth grade science students will set these sunrise and sunset stones in place in September of 2006 to complete the main phase of the solar calendar.

May 2006--Sixth graders completed the sundial! Click HERE to see a time lapse photo of construction.

This spring (2006) we will add a human sundial next to the solar calendar.  A human sundial is simply a sundial that works only when a person is standing in the middle, allowing their shadow to fall on the stone marking the time of day.

Update--December 2005: We have established a connection with a USU exchange student (Thiago) who is from Brazil. He has put us in contact with a school in Bauru, Brazil who just finished building a solar calendar that matches the specs of our solar calendar. We had our first video-conference with the students in Bauru on December 2, 2005 and will continue to communicate with them this school year, comparing shadows from our solar calendars (ours, in the Northern Hemisphere and theirs, in the Southern Hemisphere). Click on the photos link to see the Brazilian solar calendar.

Update--September 28, 2004:  In May of 2004 we were asked to move the solar calendar to make room for a construction project at Mount Logan Middle School.  The solar calendar was moved, brick by brick, to its new (and much better) location just north of the sand volleyball pit.  Students this year will now "re-calibrate" the solar calendar to mark the position of the rising and setting sun on the equinoxes and solstices.  On September 22nd we placed the equinox marking stones in place and on the 27th we mixed and poured cement to fix the  North, East, West, and South stones in place. 


©2006 Eric J. Newell