by Landy » Tue Dec 21, 2010 9:56 pm
Ron wrote:Just for the record, the season of summer in Australia is generally quoted as beginning at the start of December, not the Summer Solstice.
All the other seasons begin at months beginning too.
Perhaps someone could could quote the historical reasoning behind this ?
It does seem to provide a fair correlation with the seasons.....
Marvellously illustrative picture of the skyward passage of the sun here.
(why do only 3 sun images flare ?).
Perhaps that's the way the months of the calendar were originally set up? I am also in Australia, and ever since I was a nerdy kid reading astronomy books, it never made any sense to me why the astronomical definition of the beginning of seasons were set at the solstices/equinoxes. If you think about it astronomically, summer should be defined as that quarter of the year where the hemisphere you are in receives the greatest amount of insolation. The summer solstice (which is today here - 22nd Dec) should mark the precise
middle of summer - not the start of it! This argument is put forward very elegantly by Phil Plait on his "Bad Astronomy" website
http://www.badastronomy.com/bad/misc/badseasons.html.
Therefore the more correct astronomical definition of when the seasons begin is some six weeks before the solstices/equinoxes. For the southern hemisphere summer (northern hemisphere winter), that would be the 7th of November, which could also be called "Beltaine" (or "Samhain" for the northerners) - see
http://www.archaeoastronomy.com/2010.html. By the way that site is a very useful resource for the timing of these events.
However, speaking meteorologically, it takes a few weeks for weather systems, atmospheric temperatures etc to respond to changing insolation, and so the beginning of December marks the beginning of that quarter of the year which has the ~90 warmest days (on average). So from a human/geographical perspective, the start of the seasons is best marked by the 1st of the month.
Hope this makes sense!
And I agree - it is an excellent picture. Not sure about the flaring thing, but i suspect the photographer put a flaring filter on the camera for those three exposures.
[quote="Ron"]Just for the record, the season of summer in Australia is generally quoted as beginning at the start of December, not the Summer Solstice.
All the other seasons begin at months beginning too.
Perhaps someone could could quote the historical reasoning behind this ?
It does seem to provide a fair correlation with the seasons.....
Marvellously illustrative picture of the skyward passage of the sun here.
(why do only 3 sun images flare ?).[/quote]
Perhaps that's the way the months of the calendar were originally set up? I am also in Australia, and ever since I was a nerdy kid reading astronomy books, it never made any sense to me why the astronomical definition of the beginning of seasons were set at the solstices/equinoxes. If you think about it astronomically, summer should be defined as that quarter of the year where the hemisphere you are in receives the greatest amount of insolation. The summer solstice (which is today here - 22nd Dec) should mark the precise [b]middle [/b]of summer - not the start of it! This argument is put forward very elegantly by Phil Plait on his "Bad Astronomy" website [url]http://www.badastronomy.com/bad/misc/badseasons.html[/url].
Therefore the more correct astronomical definition of when the seasons begin is some six weeks before the solstices/equinoxes. For the southern hemisphere summer (northern hemisphere winter), that would be the 7th of November, which could also be called "Beltaine" (or "Samhain" for the northerners) - see [url]http://www.archaeoastronomy.com/2010.html[/url]. By the way that site is a very useful resource for the timing of these events.
However, speaking meteorologically, it takes a few weeks for weather systems, atmospheric temperatures etc to respond to changing insolation, and so the beginning of December marks the beginning of that quarter of the year which has the ~90 warmest days (on average). So from a human/geographical perspective, the start of the seasons is best marked by the 1st of the month.
Hope this makes sense!
And I agree - it is an excellent picture. Not sure about the flaring thing, but i suspect the photographer put a flaring filter on the camera for those three exposures.