Summer Solstice Brings Sunlight, Sundials, & SOLIDWORKS

by Nic Rady

Over the last year, many interesting events in the upper atmosphere of the earth have made the news, including:

  • The last of the tetrad (4 total lunar eclipses in a row) was September 28, 2015
  • Six “super moons” (when a full moon happens during perigee) in 2015
  • Solar eclipse on the spring equinox

Plus, Summer Solstice is no less exciting as it is the longest day of the year (at least for those of us in the northern hemisphere). Yes, it’s the Summer Solstice.

As a physicist, I have always looked to the stars a bit more often than the average person. In college, while studying the life and times of Galileo, I took a trip to Italy where quite a few churches were built with the sun in their design. For example, Santa Maria Novella in Florence was the source of measurements taken by monk Egnazio Danti to create our current calendar, named after Pope Gregory XIII.

The façade of Santa Maria Novella, which eloquently combines art with science, has numerous sundials, an armillary sphere, and a gnomonic hole for a never completed meridian line that were used to find the 11 extra minutes in the Julian calendar that had caused Easter to fall 10 days later than expected by 1582.

Our new Gregorian calendar is fascinating in that this small discrepancy was measured to an accuracy of 1 day in 3,236 years before the father of physics, Galileo Galilei, published his finding on pendulums, free fall motion, and celestial mechanics.

As a tribute to these great minds, I set out to model the main sundial on Santa Maria Novella in SOLIDWORKS to share with others a glimpse into how this device works.

A newer feature of SOLIDWORKS is the ability to add sunlight into a model and show how the sun will move over time: Solar Access Study. After modeling the quadrant sundial, I went to View->Lights and Cameras->Add Sunlight and put in the coordinates for Santa Maria Novella – 43.78°N 11.25°E. Now with the sunlight added, I created a motion study, and using the Animation Wizard, set up a Solar Access Study to see how the sundial should look throughout the year at local noon, and how it will look on the Summer Solstice this year.

The first study simulates the measurement of the solar declination each day at local noon. I only show the motion from the Summer Solstice to the Winter Solstice, but you can see the full range of motion from a 20° to 67°.

Solar Declination from Summer to Winter Solstice Video

The second study is of the solar time clock. Now, this is an interesting device in that it is divided into twelve ‘hours,’ but this does not necessarily coincide with an hour of the day. Rather, it breaks the time equally between sunrise to sunset into twelve equal parts. Either way, it is a really cool phenomenon to see the passage of time in a day using SOLIDWORKS. Because the sun is partially behind the church during the Summer Solstice, I used the Fall Equinox in this study.

Hourly Sundial at Equinox Video

There are numerous uses for a Solar Access Study:

  • Placement of solar panels
  • Optimizing the overhang on a shade structure
  • Designing a solar analemma calendar

For the fathers out there, you might consider using SOLIDWORKS to teach your children something new on your special day since Sunday also happens to be Father’s Day. Either way, enjoy the extra daylight!

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