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Thank you Marie Mayer for being an intelligent person.
Hi Rick, in Australia we're in the 1st month of winter. Our 'seasons' officially start: winter, 1st June; spring, 1 September; summer 1 December; Autumn (fall) 1 March.
Cate, glad to hear from "down under" (another northern conceit, though, isn't it; who decided the s. hemisphere is the "bottom" anyway?). By official start, I assume you mean by arbitrarily agreeing to call it so rather than based on the way the planet is moving along in its orbit, right? It doesn't suddenly get cooler on June 1, does it?
Yep, it's just an arbitrary date. Most people realise that it doesn't really start changing temperatures until the solstices/equinoxes.
But, really, none of the calendar dates for what we call the seasons is associated with any kind of sudden temperature change. At the Autumnal equinox, maple leaves don't suddenly turn red. We basically move gradually between warm weather to cool weather to back again over and over. The idea of four separate, distinct seasons is really related more to social customs and human activity like agriculture (for planting, growing, harvesting and fallow times) isn't it?
There is a great site that details the actual progress of the seasons as based on the quarters and cross-quarters: http://www.archaeoastronomy.com/ - it also provides an animated star clock that shows where we currently are in the orbit of the earth as of today and the tilt of the earth as it progresses through the orbital cusp point. Also, it was earlier mentioned that the tilt of the earth's axis is 23.5 degrees - that is incorrect - the current tilt of the earth's axis (as of mid-2013) is 23.439 degrees. The tilt of the earth's axis is affected by many factors, some regular and predictable (related to the precession of the equinoctes and the effecct of lunar gravity) and others unpredicatble (e.g. redistribution of mass due to earthquakes) - for instance, the great earthquakes of 2004 in the Indian Ocean basin and in 2011 at Japan in the Pacific Ocean basin actually slightly affected the tilt of the earth by moving larges masses of the Earth's material closer to the centre of the Earth. The Earth's axial tilt is currently decreasing, and may vary between 22.1 and 24.5 degrees. It is postulated that when the Earth's tilt is at the maximum point of 24.5 degrees is when ice ages typically occur - and as well, ice ages also have an effect on the axial tilt, since they redistribute large amounts of mass (i.e., ice) towards the geographic poles. The after-affect of this mass redistribution is still being felt due to crustal rebound of areas of the Earth that were under massive volumes of ice during the most recent ice age (for instance, the Hudson Bay basin in Canada is currently rebounding by close to 2cm per annum due to the removal of the Laurentian ice sheet following this most recent period of global climate warming [unrelated, BTW, to any human-induced warming of the climate]).
Thank you so much for the educated answer on the tilt of the earth. I knew the earth changed it axis recently but did not know it was linked to major earthquakes. I will be visiting the website you suggested. Great explanation. I too live 'downunder' and yes our date for the beginning of seasons is different to the north. Does anyone know the history of this fact?
Are there different first days of seasons in different countries? Im doing a report and can't answer what date spring starts in Greece.
In Russia winter officially starts on 1 of Jan, spring on 1 of March, summer - on 1 of June and Autumn on 1 of September.
The astronomical definition of when a season begins (such as the March equinox: spring in the Northern hemisphere; fall in the southern) applies everywhere around the world (a set point in time, converted to local time zone).
However, different countries may celebrate the seasons at different times. For example, in Bulgaria, March 1 is often celebrated as the beginning of spring. Also on March 1, Helidonismata is a traditional Greek observance that celebrates the return of the swallows, marking spring's return, as well.
You might also be interested in Greek mythology as it relates to spring: the story of Demeter and Persephone.
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