The science of winter solstice

Doug O'Harra
Winter solstice sunshine! Photo taken from Lisa's front deck about 11:15 a.m. on solstice in Houston, Alaska.
Lisa Johansen
Breaking trail on winter solstice, Dec. 21, 2011, in the backcountry near Homer, Alaska.
Jeff Szarzi photo
Winter solstice sunrise over Chugach Mountains in Anchorage, Alaska
Christopher Constant photo
The morning sun colors the Talkeetna Mountains and Hatcher Pass on December 21, 2011.
Stephen Nowers photo
Winter solstice sun in Healy, Alaska
Bob Lype photo
Winter solstice sun at high noon in Bethel, Alaska's old cemetery
Joe Prince photo
The sun rises over the Chugach range on the 2011 winter solstice. Pioneer Peak is on the left.
Stephen Nowers photo
Winter solstice sun in Akiak, Alaska
Chris Grooms photo
Winter solstice sunrise in Midtown Anchorage, 2011
David Snyder photo
2011 winter solstice sun rises behind Pioneer Peak in Palmer, Alaska
Alaska Dispatch reader-submitted photo
Winter solstice sun tries to rise at Alpine Oil Field on Alaska's North Slope
Photo tweeted by @LEANNAak
Sunrise about 10:15 a.m. on winter solstice 2011 in Anchorage, Alaska
Photo tweeted by @TheMenu12
Sun comes up on winter solstice in Palmer, Alaska
Alaska Dispatch reader-submitted photo
Sunset hues bouncing off of frigid tidal flats on winter solstice 2011 at Chapel by the Sea.
Dave Harbour photo

At 8:30 p.m. Alaska Standard Time on Dec. 21, take a deep breath.

That is the precise moment of winter solstice.

You will be more than four hours into the longest night of the year, said to be 18 hour and 33 minutes long in Anchorage by the U.S. Naval Observatory.  The sun won’t rise for another 13 hours and 30 minutes.

In astronomical terms, winter solstice in the northern hemisphere isn’t a day but an instant — the very moment that the Earth’s axial tilt has leaned the geographic North Pole farthest away from the Sun.

This seasonal reach toward the cold abyss of space and away from the solar furnace — the source of our seasons, and the cause of our long winter nights — climaxes when we reach 23 degrees and 26 minutes off plumb, sometime on the Solstice Day.

Here’s what the Earth looks like right now.

On Dec. 21, Anchorage sunrise occurs at 10:14 a.m. with sunset following five hours and 27 minutes later at 3:41 p.m., says the U.S. Naval Observatory calculator for sunrist and sunset times.

But we quickly start to lean back. As the home planet spins three more times, we will travel along the orbit to a position where the tilt has eased just a bit. By Christmas, we will have gained two minutes of possible direct sunlight, and it accelerates from there.

More than other states, Alaska celebrates summer and winter solstices with gusto. This week’s version may mean a ski by moonlight in Russian Jack Park, or a few hours in an outdoor hot tub staring at the stars.

For those who prefer a bit of company, here are a few celebrations:

Homer -- Center for Alaskan Coastal Studies hosts a moonlight family snowshoe at the Carl Wynn Nature Center 6-9 p.m. Wednesday. Snowshoes can be rented and a bonfire will roar. Hot chocolate will be served. Call 907-235-6667 for information.

Anchorage - Winter Solstice Torchlight Skating Party, 6-8 p.m. Thursday at the Cuddy Midtown Park Skating Oval.  Music, a bonfire and ice skating highlights the gathering hosted by Anchorage Skates, which reports on its website: “The warm winds and melting and refreezing have smoothed out the ice. It’s as good as it’s been so far this Chinooky year.” Alaska Mountaineering and Hiking will offer demonstration speed skates and light tiki torches. Non-skaters are asked to park at the far back (southwest corner) of the Loussac Library lot.

Another outdoor gathering is 7-9:30 p.m. Wednesday at the McHugh Creek Trailhead. The Anchorage Adventurers Meetup Group will gather with warm drinks and snacks about 100 yards up the hill from the lower parking lot. Because of limited parking, car-pooling is required.

Eagle River -- The Eagle River Nature Center decorates with ice lanterns during its annual Lantern Walk and Solstice Celebration on Dec. 17th. There will be a bonfire and participants should bring a dessert for the end of the walk.  Free program, but $5 parking for non-members.  Call 907-694-2108 for more information.

In Fairbanks -- Fairbanks Community Museum will celebrate noon to 8 p.m. Wednesday with hot cocoa served all day. There’s also a special holiday art show commemorating the history of Fairbanks through watercolor. Call 907-457-3669 for information.