I was wondering this on Sunday. I mean, it was the shortest day of the year, and now days will only get longer. And it rained here yesterday! Winter probably won’t begin in full until January here.
So, eh? 
Because it takes Earth’s atmosphere about 40 days to heat up and 40 days to cool off, thus the seasons lag behind the equinoxes (equinoxi?) by a month to a month-and-half.
I guess I’m dense, but I thought the atmosphere cooled off every night, not only on the ground but all the way up.
Delete sun, insert cool.
It cools down but not all of the way down. There is a daily up and down trend superimposed over a yearly up and down trend. Think of a sine wave on a slope.
Haj
The solstices and the equinoxes fall at the beginning of the calendar seasons that they demarcate.
We might more properly refer to it as the Fall/Winter Solstice, followed 91 days later by the Winter/Spring Equinox.
Well, I know that WS is the offical beginning of winter, I was just wondering why it was the beginning instead of the middle.
I think BE explained it, tho.
It still seems goofy to me.
Animist,
The solstices and the equinoxes have little to so with the seasons. They are an astronomical term. The solstices are when the the Sun reaches its northernmost and southernmost points in the sky. The equinoxes are the days when the Sun is directly over the Equator and sunrise and sunset all over the world at at exactly the same time.
The Sun is actually closer to the Earth on the winter solstice than it is in on the summer solstice.
The seasons do depend on atmospheric heating and the growth of many plants is triggered by the amount of sunlight they receive each day.
The coldest days of the year generally follow the winter solstice by about 30 days, and the warmest days of the year follow the summer solstice by about the same amount. The atmosphere and the oceans – and to some smaller extent the land – are gigantic reservoirs of thermal energy that do not heat up and cool off quickly.
I don’t know why our current calendars define the solstices and the equinoxes as the beginning of the seasons, other than they make convenient reference points.
Personally, I divide the year into two seasons: The good season from about 1 May until 31 October. And the not so good from 1 November until 30 April. That is how many ancient cultures did it also. In Germany, 30 April is known as Walpurgis Nacht when all the bad spirits go underground for six months, and come out again on 31 October – the day we now call Halloween.
Merry Christmas,
Sky
To add to what SkyCowboy says, as far as I know, there are no “official” seasons. The current convention seems to be to have them start at the solstices and equinoxes, although when I was younger, they were on month boundaries, so that winter was just “December, January, and February.” I’m not sure who decided that they needed changing, and I don’t like it the way it is mostly done nowadays.
Cecil made a reference to this in his column about whether summer starts in May in Ireland, and Earth & Sky did a segment on it once, though I can no longer find it in their archives. But when anyone says that the solstice is the “official” first day of winter, I always ask what standards body said that, because I’d like to have a word with them.
Just to confirm what CurtC said summer does begin in May in Ireland. Winter is Nov, Dec, Jan. Spring is Feb, Mar, Apr. And so on. I always assumed the rest of the world did the same.
The Bad Astronomer, Phil Plait has treated the subject.
http://www.badastronomy.com/bad/misc/badseasons.html
Here, it seems to be that winter is Jan, Feb, March. Good times!
I think I finally came to understand it all. What with the earth holding all the heat and all. Thanks.
Here is Cecil’s column about the seasons. Equating (heh) the seasons with the equinoxes and solstices is a very modern and peculiarly American custom.
For the same reason that summer begins on Mid-Summer’s Day.
And the Twenty First Century began at the beginning of the last year of the Twentieth Century.
Go Figure!
“Beware of the Cog”
Now that I think about it, the seasons shouldn’t all be the same length. Because our orbit is an ellipse, in the winter we are traveling faster, so winter should be shorter than summer. (Antipodeans can reverse these)
In other words, we get half way from apogee to perigee before the equinox.
That should be true.
From SkyMap:
2003 Dec 22 07:03 Winter Solstice
2004 Mar 20 06:48 Vernal Equinox
2004 Jun 21 00:56 Summer Solstice
2004 Sep 22 16:29 Autumnal Equinox
2004 Dec 21 12:41 Winter Solstice
So, it looks like winter is about 89 days, and summer will be almost 94 days.
I don’t think that is in other words–that’s not true. Apogee will be around July 5, almost two full weeks after the summer solstice. It won’t be halfway, in time or distance, before Sep 22.
The seasons on Pluto are dictaed by the eccenrticity of its orbit; however the planetoid has long past its closest approach to the Sun, yet is still warming up.
Thermal inertia means that the world is still warming up long after perihelion, and a similar effect happens in the two hemispheres of Earth.
During the summer the Earth is still warming up long after the solstice.
SF worldbuilding at
http://www.orionsarm.com/main.html
Fairly eccentric spelling there, if I do say so myself.
Do you know what, I was mentioning this to a couple colleagues of mine (one from Dublin and the other from Monaghan) and they both absolutely dismissed the idea that summer begins in May here. They acknowledged that that is technically correct but insisted that everybody they know considers summer to be June-July-August.