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Winter Solstice in the Tropics

December 21st, 2008 · 2 Comments · Hong Kong

I’m something of a calendar wonk. In some previous life or civilization I might have tried to find a job as a priest or astronomical observer watching the sun and the moon and keeping track of their movements. Like the guys in Egypt who figured out the two days a year the sun would shine directly through a crack in a pyramid and light the pharaoh’s burial chamber.

Anyway, I almost always note the two equinoxes and the two solstices. Among other things.

The equinoxes are when the sun is directly over the equator, and the day and night are exactly 12 hours long — everywhere on the planet. Cool concept,  no? Everyone one with a 12-hour day? The equinoxes (equinoci?) generally fall on March 21 and Sept. 21 making the start of spring/fall, depending on your hemisphere.

The solstices are more dramatic because they mark the points when the sun is shining directly on the two tropic latitudes — Cancer and Capricorn — and mark the points when days and nights are at their extremes all over the planet.

Those dates are June 21 and Dec. 21. When the days and nights are as long (or short) as they are going to get.

Which brings us to today, the winter solstice in the Northern Hemisphere, and my first spent in the tropics, here in Hong Kong.

I have been doing some semi-odd things, on the four aforementioned days, the past few years. Right at noon (or 1 p.m., if we were in a daylight savings’ situation), I would find a sunny spot, where I was living, and mark with a pencil the angle that the sun was entering, say, on a window sill. And compare it to the line I drew six months before. That stuff just interests me. How steep the angle is, on Dec. 21 … how less steep it is on June 21.

Inside the tropics, the length of days from one solstice to the other is much less extreme than it is at higher latitudes.

Here in Hong Kong, which is 22 degrees north of the equator (and just in the tropics; the Tropic of Cancer is at 23.5 degrees north), sunrise today was at 6:58 a.m. and sunset is at 5:45.

That is, the shortest day in HK is still 10 hours and 47 minutes. Not really enough to kick us all into Seasonal Affective Disorder (SAD, that is), where you get a little goofy because you don’t see enough light.

Some comparisons:

In Long Beach, California, USA, which is a bit less than 34 degrees north, sunrise is at 6:54 a.m. today and sunset is at 4:48. That makes for a day of 9 hours and 54 minutes. An hour shorter than here, but still not enough to make you weird, probably.

In Paris, which is nearly 49 degrees north of the equator, sunrise today is at 8:41 (!) and sunset at 4:56 — which makes for a day of only 8 hours and 15 minutes. Rather brief. Though we should note that at the higher latitudes the twilight is much longer than it is here in the tropics.

So, anyway, Hong Kong doesn’t have that much swing, in day vs. night. On the short side, like today, the day is 10:47. On the long side, it’s 13:13. That’s not dramatic. Not like in Western Europe, where the sun might set at 10 p.m. in June — and not come up till 9 a.m. in December.

It makes Christmas, which almost certainly was pegged to line up with the pagan celebration of the coming “return” of the sun — and had been retreating alarmingly for six months — somehow a little less dramatic.

Certainly, HK has seasons. But not like we would recognize them in Long Beach,  and certainly not like we would see them in Northern Europe.

Turns out, winter is the good time of year, here. People will happily exchange a few hours of daylight for 4-5 months of temperatures in the 70s and limited rain.

Because when the northern climes are basking in sunshine and luxuriating in those long summer nights, HK will be soaking up 70 inches of rain and living in a perpetual sweat.

If I were here on June 21, the summer solstice would mean a lot more to me than this one does. I would be happy that the days are finally getting shorter, and winter is getting closer. But I also would know that I had at least three and probably four months of hellish weather ahead of me, including a typhoon or five.

Anyway, happy winter solstice to all of you living north of the equator.

And will anyone hire me to gaze at the sun,  the moon and the planets? Didn’t think so.

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2 responses so far ↓

  • 1 Chuck Hickey // Dec 24, 2008 at 1:46 PM

    I’m like that, too, in terms when the solstice/equinox/calendars/etc. One of the cool things was about five years ago, I was in Alaska in late June, and in Fairbanks at the solstice. Didn’t see a dark sky for two-plus weeks. Saw a baseball game at midnight. Without lights.

  • 2 Editor B // Dec 16, 2011 at 9:38 AM

    I was wondering what solstice in the tropics might be like. And so I found your post. Thanks.

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