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Posted at 12:54 PM ET, 12/20/2012

Winter Solstice 2012: Myths and facts about the shortest day of the year


Sunrise and sunset times in major world cities on the winter solstice. Locations in the Northern Hemisphere see their shortest daylight period of the year. Click here to explore sunrise and sunset times in other cities. (Justin Grieser)

The world won’t end on December 21, but the 2012 winter solstice is still on the astronomical calendar.

On Friday at 6:12 a.m. (EST), Earth’s north pole will be at its maximum tilt away from the sun, marking the official start of winter and shortest day of the year for the Northern Hemisphere. If you’re looking for some bright sunshine to alleviate the winter blues, head south of the equator, which is now enjoying its longest daylight period of the year.

Think you’ve heard everything there is to know about the solstice? Let’s take a look at seven different statements to see what’s true and what’s not…

True or False?

1. The earth is at its farthest point from the sun on the winter solstice.


On the winter solstice, Earth’s northern hemisphere reaches its maximum tilt away from the sun. Click here for larger image. (NASA)
False. Earth’s orbit is approaching perihelion – its closest distance from the sun – in early January. In fact, the earth is about 3 million miles closer to the sun now than in early July. Our seasons are caused by the planet’s axial tilt, which currently positions the sun’s most direct rays over the southern hemisphere. At the winter solstice, the northern hemisphere continues to lose more incoming solar energy than it receives, which is why winter’s coldest days still lie ahead.

2. The number of daylight hours on the winter solstice depends on latitude.

True. Like the summer solstice in June, daylight hours on the winter solstice vary greatly by latitude. Washington, D.C. sees the sun for 9 hours and 26 minutes on December 21, while in Miami the sun spends over 10½ hours above the horizon. Barrow, Alaska, located far north of the Arctic Circle, does not see the sun rise at all – though it does still have about 3 hours of dreary twilight at midday.

Link: Day and night world map


3. In the Northern Hemisphere, the sun takes its shortest and lowest path across the sky.

True. In Washington, D.C., the winter solstice sun reaches a maximum angle of only 27.7º above the horizon at solar noon. In the more northern city of London, the sun takes an even shorter path, climbing only 15.1º in the sky. And just south of the Arctic Circle, the Icelandic capital of Reykjavik sees the midday sun climb no higher than 2.1º above the horizon.

4. The sun rises and sets at its southernmost points along the horizon on the winter solstice.


View larger (NASA)
True – for all locations on earth, including areas in the tropics and Southern Hemisphere (see image).

Because the Southern Hemisphere is at its maximum tilt toward the sun, our nearest star rises and sets south of due east and due west, respectively. The farther one travels from the equator, the more the sun will rise and set toward the southern horizon.

5. In the Northern Hemisphere, the earliest sunset and latest sunrise are on the winter solstice.

False. The reasons are complex, but most mid-latitude locations see their earliest sunset a week or more before the solstice. Meanwhile, the latest sunrise is typically not until early January. Washington, D.C. saw its earliest sunset at 4:46 p.m. from Dec. 1-12, while the latest sunrise is at 7:27 a.m. from Dec. 31-Jan. 10. The reason for this misalignment is a discrepancy between our clocks and the apparent motion of the sun.

Read more about this topic in our technical discussion from last year .

6. At the Arctic Circle, the sun does not rise on the winter solstice.

False. If you stood at 66.5º north latitude on the winter solstice, you would actually see the sun straddle the horizon for about two hours on a clear day. This happens due to atmospheric refraction, an optical phenomenon that allows us to see the sun even when it’s just below the horizon. Only starting around 67.4º north latitude does the sun remain completely below the horizon, and even then there are still several hours of twilight. To experience 24 hours of complete darkness (absence of any twilight), you would have to travel to about 80ºN – almost to the North Pole.

7. After the solstice, daylight in the Northern Hemisphere increases faster the farther north you are.


True. The higher the latitude, the faster daylight is gained or lost on a daily basis throughout the year. This is true whichever hemisphere you live in.

If you live in a northern city with very short days now, the good news is that you’ll gain daylight at a faster, more noticeable pace than places to your south. So, even though the coldest days of winter have yet to arrive, increasing daylight is something to look forward to.

More from Capital Weather Gang

Autumn Equinox 2012
Summer Solstice 2012
Spring Equinox 2012
Winter Solstice 2011
Autumn Equinox 2011
Summer Solstice 2011

By  |  12:54 PM ET, 12/20/2012

Categories:  Astronomy, Latest

 
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