This Friday (December 21) marks the December solstice—the shortest day of the year in the Northern Hemisphere, and the longest day of the year in the Southern Hemisphere. The maximum difference in daylight between the June solstice and the December solstice is a whopping five hours and 50 minutes!
As schools wind down for holidays, take some time to introduce the solstice through Earth science, geography, and culture. Consult a list of key resources in our Teachers Toolkit.
Science of the Solstice
Photograph by NASA and Robert Simmon, using data ©2010 EUMETSAT
A solstice is an event in which a planet’s poles are most extremely inclined toward or away from the star it orbits. At Nat Geo headquarters in Washington, D.C., the precise time of the December 2018 solstice—when solar declination hits the Tropic of Capricorn—is 5:23pm.
Teach the science of the solstice:
- Discuss our comprehensive encyclopedic entry to help students get a handle on key concepts like solar declination, axial tilt, orbital eccentricity, and the subsolar point, as well as how different latitudes experience (or, in the case of equatorial regions, don’t experience) the December solstice.
- Use MapMaker Interactive or Google Maps to have students find locations at different latitudes, and hypothesize how the region might experience the solstice.
- Adapt one of our most popular activities, “The Reason for the Seasons,” to help students investigate the sun’s intensity on the surface of the Earth. The activity introduces concepts like weather, temperature, and seasonality, and uses round fruits or polystyrene balls to help students model the solstice and Earth’s orbital behavior.
- Take a look at how sunlight is reflected during the solstices with the amazing satellite images below. Use our questions (aligned to the National Geography Standards) to quiz your students: Why do they think the Southern Hemisphere reflects so much more solar radiation than the Northern Hemisphere during the December solstice? Why do they think the Southern Hemisphere reflects more solar radiation?
Images courtesy Takmeng Wong and the CERES Science Team at NASA Langley Research Center
Shadow Geography
Photograph by Jesse Lowes
The winter solstice is a shadowy subject. So throw some shade!
One of our Grosvenor Teacher Fellows, Jesse Lowes, offers a terrific lesson on shadow geography—or, how “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.”
Jesse’s class modeled Earth’s orbital path around the sun using polystyrene balls tilted at an earthly 23.5° angle. (Polystyrene balls are apparently indispensable for studies of solar shadows and the solstices.)
In Jesse’s example, students were able to deduce where he was in a photograph based on the positioning of his shadow. He encourages other educators to have students do some similar “shadow sleuthing” by collecting images containing shadows with all but one of the following variables identified: date, time, and location. (Google Earth is a great source for collecting these real-life images.) Have students predict the missing information using a sun-Earth shadow model and/or a shadow tracking website, such as Find My Shadow.
Io, Saturnalia and Stonehenge!
Photograph by WolfgangRieger, courtesy Wikimedia. Public domain
Why would ancient Romans greet each other with a “yo, Saturnalia” in the week preceding the bleak midwinter? Saturnalia was a wild carnival that marked the final passage of autumn into winter. During Saturnalia festivities, Romans enjoyed banquets, gambling, jokes, gifts, and a tradition of usurping strict social structures.
Read through “The Culture of the Solstices” from our encyclopedic entry to introduce students to Saturnalia, then celebrate, yo! Here are some foods for a certified Saturnalian banquet:
- an appetizer of crackers or breadsticks
- a traditional Saturnalia snack—roasted dormice! (OK, OK, chicken drumsticks can substitute.)
- Saturnalia cake
- bite-sized, deep-fried cheesecakes known as globi that would be familiar at an Ancient Roman feast or a Midwestern state fair
Saturnalia is hardly the first celebration associated with the December solstice, of course. The sacred site of Stonehenge, for instance, was probably created at least in part to honor the solstices thousands of years before the Romans were celebrating. Its central “avenue” is aligned to the sunset of the December solstice, and, looking toward the famous circle, the December solstice sunset appears directly in front of the Heelstone. (Some archaeologists think this has more to do with geology than astronomy or ancient Britons, however. Use our study guide to learn more about that.)
Like the Romans, the ancient Britons of Stonehenge feasted during the solstice. Cater your winter party to their tastes:
- Salisbury granola: hazelnuts, dried cherries, and berries
- soft cheese plate with cottage cheese, yogurt, and butter
- pork (ideally imported from Scotland)
- apples, likely sweetened with honey
Photograph courtesy The Stones of Stonehenge. CC-BY-NC-ND-4.0
To Sum Up the Solstice
Whether you’re planning a fresh approach to a winter feast, coming out of the shadows with model geography, or learning the reason for the seasons … don’t forget the solstice!
TEACHERS TOOLKIT
Nat Geo: What is a solstice?
Nat Geo: The Reason for the Seasons
Nat Geo: Solstice Solar Radiation
Nat Geo: Use ‘Shadow Geography’ to Find Your Place
Nat Geo: Parts of Stonehenge May Have Been In Place Long Before Humans
Judith Geary: A “Certified” Roman Banquet for Saturnalia
The Romans in Britain: Recipe for Gliris or Glis-Glis (Dormice)
Texas Classical Association: Recipe for Saturnalia Cake
Stephanie Dray: Io Saturnalia! A Holiday Party Tray, Ancient Roman Style
English Heritage: Food and Feasting at Stonehenge
Time and Date: Shortest Day of the Year in the Northern Hemisphere