The Science of Solstice12/01/2019 11:56AM ● By Sandy Kauten
But what exactly is making this happen? To find the answer, let’s zoom out and take a look at Earth from space.
As the Earth orbits around the sun, it also spins on an imaginary line that passes through the North and South Poles, known as the “axis of rotation.” This is what gives us daytime and nighttime. However, our planet doesn’t point straight up and down, spinning like a top—rather, it’s tilted slightly. The direction of that tilt stays the same as it orbits the sun, so certain times of year the North Pole is pointed toward the sun, and other times of year, the South Pole is pointed toward the sun.
During the times when the north is pointed away from the sun, the northern latitudes spend more time in the dark, hence the longer nights and shorter days of winter.
Winter solstice occurs when the sun is at its lowest point in the sky all year. This year, that day will be December 21. The sun will appear to be at the same level at noon for several days before and after the solstice. In fact, this is where the term “solstice” comes from: the Latin word, solstitium, meaning “the sun stands still.”
Because of the Earth’s curvature and axial tilt, the shortest day of the year will be shorter in some places than others. For example, people who live on the equator will have roughly 12 hours of daylight and 12 hours of darkness on the winter solstice. At the North Pole, there will be about 11 weeks of darkness—the sun will set in mid-November, and not rise again until mid-January.
So, what about Oregon? Here, our winter solstice will have 8 hours, 42 minutes, and 10 seconds of daylight, because we are partway between the equator and the North Pole.
With the change in the seasons, try to observe how your local ecosystem adapts. What do you notice about the plants and animals you see every day? You might see leaves turning brown and dropping off the trees, birds migrating south, and squirrels busily collecting food to store up for the winter ahead.
Think about the changes that humans go through during wintertime, too. How do you dress differently in winter versus summer? Do you eat different foods or participate in different activities? What seasonal holidays or traditions do you observe?
Want to learn more about winter? Head to the Museum of Natural and Cultural History! Join us for Second Saturday on December 14, and explore a whole galaxy of celestial events through family-friendly crafts and experiments from 11:00 a.m. to 3:00 p.m. Preschoolers and their adults can come learn about winter, too, at our monthly Little Wonders event on the third Friday, December 20, at 10:30 a.m.
The Museum of Natural and Cultural History is located at 1680 E.
15th Avenue, on the UO campus. Museum hours are Tuesday through Sunday from
11:00 a.m. to 5:00 p.m. and Thursdays from 11:00 a.m. to 8:00 p.m. Visit us
online at mnch.uoregon.edu.
by Andrea Willingham