Saturday is the shortest day of the year, but it’ll be shorter for folks in the northern reaches of Wyoming.
The official time for the winter solstice is 2:21 a.m. on Saturday. However, your results may vary depending on where you are in the Cowboy State.
While the winter solstice is the shortest day of the year everywhere in the Northern Hemisphere, just how little sunlight you get is location-dependent. Technically, only one Wyoming community will experience it the closest to the official time at exactly 2:19 a.m.
“The timing for the true solstice is only valid in Wheatland,” said Max Gilbraith, planetarium coordinator for the University of Wyoming. “It’s the only Wyoming community with a longitude that corresponds with Union Station in Denver, Colorado, which they chose to make the center of the Mountain Standard time zone. So, the timing of your local solstice kind of varies.”
A Longer Shortest Day
Because of the tilt of the Earth’s axis, the winter and summer solstices are the shortest and longest days of the year, respectively. However, the length of these days varies across the globe.
Gilbraith said Wyoming is large enough that how much daylight a place gets varies significantly across the state. The shortest day of the year is longer in Laramie and Rock Springs than in Gillette and Cody.
“We can expect between eight hours and 20 minutes or nine hours and 10 minutes of daylight on Saturday, depending on how far north or south you are,” he said.
According to the website Time and Date, Cheyenne’s sunrise will be at 7:21 a.m. Saturday, and sunset at 4:34 p.m., for a total of nine hours and 12 minutes of daylight.
Meanwhile, Sheridan’s sunrise will happen at 7:42 a.m. and sunset is at 4:29 p.m. That’s eight hours and 47 minutes of daylight, making Sheridan’s shortest day more than half an hour shorter than Cheyenne’s.
In the middle of the state, Casper will have nine hours and a minute of sunlight Saturday.
“As you get beyond 45 degrees north latitude, daylight starts to drop off really precipitously,” Gilbraith said. “That’s what happens when the sun rounds the corner during the solstices.”
Still Sun
Solstice is derived from a Latin word meaning “still sun.” The winter solstice is when the sun appears at its slowest and lowest in the sky.
“The rising and setting position in the sun is slowest close to the solstices and fastest near the equinoxes,” Gilbraith said. “In the Northern Hemisphere, we're actually physically closer to the sun during winter. It's the length of day and the angle of the sun that causes winter.”
Gilbraith said the sun will appear to stand still for several days during and after the winter solstice. Stargazers have recognized this pattern since the beginning of civilization, which is why it has an enduring cultural significance today.
“A lot of our winter traditions today harken back to this,” he said. “The round wreaths of evergreen we put on doors originally symbolized the return of the green and the circle of the sun and the sky. It’s an observation that people have been making for thousands of years.”
Planetary Party
It’s been a stellar year for stellar events in Wyoming, with once-in-humanity comets, a rare planetary party and one of the best years for auroras in recent memory.
While nothing out of the ordinary is happening on the night of the solstice, Gilbraith hopes Wyomingites take advantage of the extended darkness to spot some prominent planets.
“I've been enjoying the planets that have been up lately,” he said. “Venus, Saturn, and Jupiter have been particularly bright over the last few days. Mars will be out by that point, and the Leonids are tapering off. You see lots of really nice things in the dark.”
Meanwhile, the daylight increase will be negligible at first. The daylight gain between Dec. 21 and Dec. 22 is a fourth of a second.
Daylight doesn’t significantly increase until January, and it’ll take some time for that extra sunlight to break the winter cold. Still, there’s something to enjoy and celebrate in the coming and going of another winter solstice in the Cowboy State.
“Meteorologically and climate-wise, water takes a long time to heat,” Gilbraith said. “The Earth's atmosphere will lag behind the amount of solar insulation we're getting, so there will be several months of cold before the Earth catches up with how much sun we're receiving, But the days will get longer from here.”
Contact Andrew Rossi at arossi@cowboystatedaily.com
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
