Saturday, 21 June 2008

Winter Solstice

I read with interest that 30,000 people gathered at Stonehenge this morning to watch the sun rise at 4.58 am, in celebration of the longest day, or Summer Solstice, also referred to as Midsummer Day.

In Australia we have our shortest day, the Winter Solstice, and that means we are halfway towards Spring and warmer climes even though July is likely to be the coldest month of the year where I live, and there will be snow at some stage. The temperature did not get much above 7 degrees today, and the sun shone briefly between the mists and showers, before it became totally overcast and dull. So far this month we have had more than 65mm of rain, and driving on the dirt road outside my house is like making a slow progress through porridge, leaving my car looking as if it had completed weeks over land in the London to Dakar car rally.

The reason we have solstices, and seasons, is because our planet is tilted at 23 degrees. In June, the southern hemisphere is tilted away from the Sun and the northern hemisphere tilted towards the Sun; in December it's the reverse. In March and September, the hemispheres are not tilted at the Sun, but at right angles to it.
As a result of the tilt, in winter the Sun rises later and sets earlier, leading to less daylight. It also tracks a lower course through the sky, meaning its rays hit Australia at an oblique angle. These factors mean winter is colder.

The (winter) solstice is the point where the Sun reaches the furthest north it will go in the sky, and then it turns back, and the days begin to lengthen. “Solstice" is Latin for "sun stands still" (sol "sun" and sistere "to stand").


There endeth the lesson.


2 comments:

Jane said...

This is actually a bitter sweet time for us up here... Although Summer is more or less beginning and we are into some of the finest weather we can get, as of Monday, the length of the days will start growing shorter and we will again be slipping slowly back towards "darkness"... you made me laugh with your "porridge" statement.... but that is interesting to know that you will see snow there.

Marcie said...

delighted to hear you've had that much rain, only about 25 ml here, but the reservoirs are down your way...