PORTLAND - The shortest day of the year falls on Friday, as the earliest winter since 1896 arrives this year. The Old Farmer’s Almanac says the solstice falls at 3:12 a.m.
Technically, the solstice lasts only a brief moment in time – each year it falls on Dec. 21 or Dec. 22, dependent on other factors.
Around the solstices, the angle of the sun (caused by earth's tilted rotational axis) is changing very little day by day. But the earth's position in its orbit around the sun is changing a lot.
So this factor dominates in determining the change in sunrise and set. Two factors determine sunrise and sunset time: the tilt of the earth's axis relative to its orbit around the sun, and the fact that said orbit is not a circle but an ellipse.
The elliptical orbit means the earth has to travel faster in its orbit when it's closest to the sun, which occurs in early January.
KGW Chief Meteorlogist Matt Zaffino says it's kind of like how a skater spins faster when she or he pulls their arms close in to their body.
Julius Caesar proclaimed a winter solstice celebration across Europe in the year 46 BCE – and he chose the date December 25. Go back 1,800 years and anthropologists believe the ancient Mayans honored the sun and earth around Dec. 25, too.
Later, the Catholic Church moved its Christ masses to fall on the 25th – with the days before and after offering a moment to reflect on a year’s completion, while looking toward the rebirth spring brings.