The official onset of winter and the beginning of the end for long, dark nights in the northern hemisphere is marked by the winter solstice, which is this year at 5.30am (GMT) on Thursday.
The winter solstice happens because the Earth does not spin upright, but on an axis 23.5 degrees from vertical. As the Earth orbits the sun, it reaches the moment of winter solstice when the north pole is tilted furthest from the sun, making it the shortest day of the year.
The winter solstice is as far south as the sun ever gets, shining directly overhead along the Tropic of Capricorn, 23.5 degrees south of the equator.
Usually, the winter solstice occurs on the 21 December, but that can shift for the same reasons we have leap years: the Earth takes 365.25 days to orbit the sun, but the Gregorian calendar has only 365 days so each year the solstice is pushed back by around six hours.
"At extreme ends of the four year calendrical cycle the solstice can sometimes get shunted into the early hours of the 22nd, as it does this year. Next year is a leap year, which resets the calendar so that the winter solstice will fall on the 21st again," said Marek Kukula at the Royal Observatory in Greenwich, London.
In the northern hemisphere, the winter solstice marks the shortest day and the longest night, but the sun continues to rise later for some days afterwards. The reason is that Earth's orbit around the sun is not circular, but elliptical. As the Earth rotates, it also moves along this curved path, and so sees the sun a little sooner than if it were stationary.
2011: 22 December at 5:30am GMT
2012: 21 December at 11:12am GMT
2013: 21 December at 5:11pm GMT
2014: 21 December at 11:03pm GMT
2015: 22 December at 4:48am GMT
Comments
21 December 2011 4:16PM
Cosmic!
21 December 2011 4:17PM
So we're not done with the shortest day yet? Gah.
21 December 2011 4:27PM
Not looking forward to the very short day in 2012
21 December 2011 4:36PM
Keep this from my wife.
I informed her this morning that today was the winter solstice.
She seemed very impressed that I knew this.
Crushing my innate man-wisdom will not further anyone's causes.
I am now hoping that I can avoid the subject this evening...
21 December 2011 4:40PM
so the elliptical orbit explains why the very darkest evenings are now behind us (yes, it is panto season) whilst the darkest mornings are not until next year (well, very early january)
21 December 2011 4:41PM
Well I'm celebrating it today!
21 December 2011 4:43PM
I blame Nick Clegg.
21 December 2011 4:48PM
The solstice is a moment, not a day, and not the "shortest day of the year" as your caption writer puts.
Sunrise and sunset are determined by the equation of time, which is something else again.
21 December 2011 4:51PM
We're not done with the shortest day yet because the sun always sits still for three days after the solstice. I mean the days stay the same lenght until Sunday. so you have to wait until Monday before they start to get longer. Thats the same every year.
21 December 2011 4:54PM
Much better to celebrate Solstice than New Year.
Solstice is when the days get longer and brighter again.
New Year is just an arbitrary date.
21 December 2011 4:57PM
This is kid's stuff. It shouldn't need spelling out in a broadsheet newspaper.
21 December 2011 4:57PM
It's the same every week! Mondays always seem longer than Sundays.
21 December 2011 5:02PM
"The winter solstice is as far south as the sun ever gets"
The sun is migrating?
21 December 2011 5:03PM
This is kid's stuff. It shouldn't need spelling out in a broadsheet newspaper.
oi fungloo, yr kids are over-educated... let them kick back for a year to give those of us in remedial time to catch up...
21 December 2011 5:11PM
The winter solstice is not the start of winter. It's officially if not in reality mid winter, and has always been celebrated as such in the northern hemisphere.
The start of winter is the first of November. Which the old festival which we now know as Halloween the night before is all about.
21 December 2011 5:18PM
"official" start of winter ???
¿according to whom?
21 December 2011 5:23PM
So, each day gets longer after winter solstice by how much? (per day that is? )
21 December 2011 5:23PM
dang! It's my birthday tomorrow. Shortest bleeding day.
But longest night. Time to party.
21 December 2011 5:24PM
Yeah, the sun's actually a bird. It goes south for winter.
21 December 2011 5:24PM
So "christmas" is on Thursday! I thought it was today... feasting twice over, so!
21 December 2011 5:27PM
and probably explains why the powers that be (all those years ago) chose 25th December to be Christmas Day instead of, say, the 21st.
21 December 2011 5:28PM
..not sure about that. Myself and allot of my friends thought today was solstice, so this article has educated me.
But then again, I've always been a big kid.
21 December 2011 5:29PM
Are you bemoaning the spellers or the idiots who need it spelled out? I'm in the latter camp.
21 December 2011 5:36PM
@whitworthflange
21 December 2011 05:11PM
The winter solstice is not the start of winter. It's officially if not in reality mid winter, and has always been celebrated as such in the northern hemisphere.
The start of winter is the first of November. Which the old festival which we now know as Halloween the night before is all about.
-
Today IS the start of the Meteorological winter. The seasons are thus.
21st December = Winter
21st March = Spring
21st June = Summer
21st September = Autumn
If you want to be pedantic, today is the last day of the old year. Which runs 22nd June to 21st December. And the new year starts tomorrow, 22nd December to 21st June. One is the dark year, with the dark increasing, and the other the light, with the light increasing. This was commonly used by the Celts / Britons before the Roman calendar came into affect.
21 December 2011 5:38PM
* - the Earth takes 365.25 days to orbit the sun
365.2<u>4</u>, surely?
21 December 2011 5:38PM
Likewise...
Happy Birthday to us, Happy Birthday to us... :-)
21 December 2011 5:39PM
Little known fact: The winter solstice is in the middle of the halcyon days.
21 December 2011 5:40PM
By about 90 seconds. But I think we've three days of the same amount of daylight. So, from Monday, you should see 90 seconds more light each evening. I usually start to notice it about mid-Jan.
21 December 2011 5:41PM
This a great site for that info
http://www.timeanddate.com/
Days start off by getting just 6 seconds more daylight than the previous day just after the Winter solstice but by March it goes up to a whopping 5 extra minutes per day before dipping off again heading towards the Summer solstice.
21 December 2011 5:44PM
It's all to do with those bloody sine waves that scientists are happy with.
To start with, the days only get a little longer each day.
Then they suddenly seem to get much longer day on day.
Then towards summer solstice they start to slow down, and only get a little longer each day.
I have a line of poetry forming in my mind....
21 December 2011 5:48PM
"Footnote Becomes Full Story Shocker!"
Gerry Hattrick, Daily Cobblers
The Guardian today reported that the winter solstice varies between the 21st and 22nd of December and managed to make a complete article out it! Ian Sample, aged 19, reported that "blah blah blah" which caused shock across the entire nation, nay, the world. This caused the rotation of the earth to speed up due to the increase in levels of energy and the shortest day was left being the 20th of December.
Ian, whose favourite music is some bland R&B clone stuff, was left in dismay when this was discovered. "Blimey," he said as he ruffled his golden locks. "I weren't expecting that, like!"
Nex year, the winter solstice will...oh, forget it...
(Sorry, Ian, nothing personal. I don't know you at all and I bet you're highly desirable and dead clever. I'm just having a laugh.)
21 December 2011 5:53PM
If you think I'm going to get up at 5:30 tomorrow morning to sacrifice 11 virgins you must be joking. I'll leave it to next year. It also means I can start to recycle all that Virgin junk mail again.
21 December 2011 5:55PM
This is when you not only get into Leap Years, but also Leap Seconds.
There has been an international conference on this as computers and the like need to know exactly how long a year is. Otherwise (?) your sat-nav fails.
21 December 2011 5:55PM
hmmm..... "Vertical"? There is no such definition in the solar system. That would assume the Earth's orbital plane is "horizontal", but there is really no reason to call it that except that it usually gets drawn that way in diagrams.
21 December 2011 6:01PM
The winter solstice happens because the Earth does not spin upright, but on an axis 23.5 degrees from vertical
What is "vertical" in space? I assume you mean 23.5 degrees from the orthogonal to the plane of orbit of the earth around the sun.
21 December 2011 6:29PM
@BrianLewis
"What is "vertical" in space?"
"Up" or "North". I thought that obvious, and you should go back to Sunday school for a better grasp of the world.
21 December 2011 6:29PM
yes
21 December 2011 6:46PM
Nice to see the Christmas spirit in such evidence. Spread that good-will.
21 December 2011 6:55PM
Please desist from talking about things that you know nothing of. The so-called seasons that you state are those as defined by astronomers, but the standard meteorological seasons are simply December - February, March - May, etc.
It's also worth noting that for various purposes meteorologists define different seasons for different purposes. So, for example, when looking at the effect of La-Nina on British climate it can be useful to consider a late-winter season [Feb - Mar] separately from an early winter season [Dec - Jan]. Or, you can look at long winter/summer seasons [Nov - Mar and May - Sep], with one month long spring and autumn.
The noted British climatologist Hubert Lamb actually created five seasons for the British climate, which included an early winter from about 20 Nov - 20 Jan, and a late winter thereafter.
So, today, or tomorrow, may mark the start of many things, but it most certainly does not mark the start of any meteorological season.
21 December 2011 6:59PM
Here is some more information on the definitions of the seasons. THere also appears to be an interesting paper by Alpert (2004) that I intend to read...
21 December 2011 7:07PM
It's all very well to compare relative dates for the seasons - but until three weeks ago there were geraniums, lobelia, sweet peas and nasturtiums all in flower in pots in the yard, and roses in bud - with attendant greenfly - in the garden. Daffodils are well up and almost all the other spring bulbs are showing ready to flower...
Dates seem rather arbitrary - nobody's told nature.
21 December 2011 7:09PM
Bugger!
Dec 22 is my birthday. Now I have to go to Stonehenge instead!
21 December 2011 7:09PM
@ThermoStat
"Today IS the start of the Meteorological winter. The seasons are thus.
21st December = Winter
Please desist from talking about things that you know nothing of. "
Nice one. But it just makes you look like an ass. I meant astronomically, but I didn't tell you that you didn't know what you were talking about.
"Time period of winter
Astronomically, it starts with the winter solstice (around December 21 in the Northern Hemisphere and June 21 in the Southern Hemisphere), and ends with the spring equinox (around March 21 in the Northern Hemisphere and September 21 in the Southern Hemisphere). In meteorology, it is by convention counted instead as the whole months of June, July and August in the Southern Hemisphere and December, January and February in the Northern Hemisphere.
21 December 2011 7:24PM
The sun appears to stand still for three days at the solstice, afterwhich it begins its return journey into light and warmth. Hmm, three days after solstice, a celebration of the newborn sun ;-)
21 December 2011 7:29PM
It might actually be simple harmonic motion, but I stand to be corrected.
Not to be confused with a simple harmonic moron, e.g. a Liberal going along with Tories.
21 December 2011 7:54PM
I’m having a winter solstice party in Glastonbury tomorrow night. Drumming and chanting round the campfire whilst naked. The odd rams skull on a stick being thrust wildly through the flames. Brian I would be honoured if you could come along and spice things up a bit.
21 December 2011 8:04PM
Ah, but in California the solstice is at 21:30 on 21 Sept. For us the solstice is today.
21 December 2011 8:10PM
Cool it !
If you read the link that "Thermostat "kindly provided you will see it is, as always, a bit more complicated than appears at first sight .
21 December 2011 8:11PM
Wolcum Yule.
21 December 2011 8:12PM
Actually it's simpler (and more complicated) than that (well, according to Wikipedia.) Essentially, when they came to decide the date for Christmas at the Council of Nicea, they thought December 25 was the solstice: