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The science of winter solstice

  • Author: Doug O'Harra
  • Updated: May 31, 2016
  • Published December 20, 2011

?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.

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