The following post was written by 2015 Grosvenor Teacher Fellow Jesse Lowes following his expedition to the Galápagos Islands. The Grosvenor Teacher Fellow Program is a professional development opportunity made possible by a partnership between Lindblad Expeditions and National Geographic Education.
With its finely indented coastline and unflinching wildlife, the Galápagos is a place that beckons you to look closely and meet it eye-to-eye.
Yet, on this day, my aim was to step back and envision my position as a point on a planet whirling around the sun. It was approaching noon on September 23rd, 2015, and I was holding myself steady on the deck of the National Geographic Endeavour. We were on the Equator, and I was about to take the photograph I’d been waiting for.
Within this photograph, written in the tight disk of shade around my feet, is a geographic story whose elements extend beyond the Endeavour, beyond the Galápagos, and even beyond our own planet.
Back in the classroom weeks later, my students were unimpressed when first viewing this photo—after all, there’s not a single iguana, tortoise or blue-footed booby to be seen. But, a quick walk outside pointed out that something truly peculiar was going on that day in the Galápagos.
“Where did your shadow go?”
“Why did it look like that?”
I remind my students that if you know how to read it, a shadow can tell you the time, reveal which direction you’re traveling, help pinpoint your location on Earth, and even tell you where Earth is in orbit around the sun.
I challenged my students to brainstorm the variables that would affect the length and direction of their shadows. They begin filling up a whiteboard with ideas: “the time of day,” “how tall you are,” “where the sun is,” “time of year,” “maybe where you are on the planet.”
I had no intention of revealing the true answer to the riddle of my hiding shadow. Instead, I introduced my students to a set of models: Styrofoam spheres skewered on small dowels and carefully set into wooden blocks, not entirely upright, but tilted at an earthly 23.5-degree angle. Each sphere—each Earth—is scribed with a central line, and on that line a single pin pokes out. This pin is me standing on the deck of the Endeavour at the Equator. A bare lightbulb—the sun—shone from a table. We gathered around the table to mimic Earth’s orbit.
I handed out the spheres to groups of students, alerted them to the mini compasses glued to the bases, and reminded them that the top of the dowel (the North Pole) must always point north.
They remembered from an earlier activity that the Earth both rotates and revolves counterclockwise (at least when viewed from above the North Pole). Now it was time to present the challenge: Can you position your model Earth so that the pin recreates the shadow (or lack thereof) from my picture?
Time passed with everyone engrossed in the puzzle. Eventually, a group of students hollered, “We’ve found it! There’s no shadow here!” Another group, directly across from them and bisected by the lightbulb sun, argued that they had actually found the spot. In looking closely at the two spheres, it was clear that they both could be right. The class gathered around the models, squinting at the nearly nonexistent shadows and discussing the significance of these two special points on Earth’s orbit—the only two times of year when the sun’s rays shine directly upon the equator and the points in time and space that we have come to call the equinoxes.
This puzzle was a gateway exercise for my students as we work together to explore the dynamic relationship between the sun and Earth and investigate how this cosmic dance, coupled with the tilt of Earth’s axis, creates seasons and even stabilizes the diversity of life. Most importantly, it reminded my students that, no matter where they stand, there are invaluable clues that may reveal both the nature of the planet and of the cosmos beyond.
Using YOUR shadow to find YOUR Place
Consider engaging your students in one of the following “Shadow Geography” activities.
Shadow Journaling: Bring students to a selected location throughout the year and have them measure and record the length and compass bearing of their shadows (or of the shadow cast by a meter stick or other gnomon). Look for and discuss patterns that you observe. What planetary motions cause these patterns?
Sundial or Solar Calendar Construction: Record the location of shadows cast by a class-constructed gnomon (or a flagpole, tree, light post, important school landmark, etc.) throughout a day or at the same time over the year. Use these measurements to create a sundial or solar calendar.
Global Shadow Tracking: Using a shadow tracking program (such as http://www.findmyshadow.com/), investigate how shadows change around the world at different times of a day or throughout the seasons. It’s particularly interesting to have students focus on the longitudinal line of their location and research and record changes in the day length and shadow characteristics from the North to South Pole on a given day. What does this tell us about planetary motion?
Shadow Sleuthing: Collect images containing shadows with all but one of the following variables identified: date, time, and location. (Google Earth is a great source for this.) Challenge your students to predict the missing information using a sun-Earth shadow model and/or a shadow tracking website (such as http://www.findmyshadow.com/).
To learn more about Jesse’s expedition, click here.
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