WINTER IS COMING. ACCORDING TO THE CALENDAR IT STARTS ON JUNE 1, BUT THE WEATHER MIGHT SAY OTHERWISE. DESPITE THE YEAR GENERALLY BEING DIVIDED INTO FOUR SEASONS (ACCORDING TO A MODEL ESTABLISHED IN EUROPE), THERE ARE PLACES IN AUSTRALIA WHERE THE FOUR SEASONS ARE NOT SO CLEAR CUT HOW THE SEASONS WORK ALTHOUGH it is a common misconception that the seasons are the result of the Earth moving closer or further away from the sun, they are actually caused by the angle of the planet to the sun and how the light rays hit the atmosphere.
The Earth is always inclined at an angle of 23.5 degrees to the sun as it travels in an orbit around it. This means that the sun is directly over different hemispheres at different times of the year, or different points in the orbit.
The Earth's atmosphere acts as a filter for heat rays and also traps some of the heat. The angle at which the sun hits the atmosphere determines how much heat makes it through. In summer, as sunlight hits more directly, more heat penetrates. In winter less rays make their way to Earth. In spring, temperatures on average get warmer, while in autumn they get cooler. 
LANDS close to the equator tend not to experience a winter, but there will be other changes such as increasing humidity, storms or monsoonal rains marking distinctions between seasons.
On a daily basis temperatures will also be affected by local weather patterns and climate, so winter can sometimes become "unseasonably" warm and cold snaps sometimes interrupt summer's heat. Various other factors have also affected the changing of the seasons, such as volcanic eruptions, expanding glaciers or changes in the composition of atmospheric gases.
LOCAL DIFFERENCES IT takes a light ray from the sun about 8.3 minutes to reach Earth. The light has to travel 147.5 million km, when the Earth is at its closest point to the sun (perihelion) and 152.6 million km at aphelion (the furthest point from the sun). Those few thousand kilometres make negligible difference to the amount of heat energy that reaches the Earth at perihelion or aphelion.
What does make a major difference is how many particles of gas or dust can absorb or deflect the heat radiation.
Light travels at 299,792,458m per second through a vacuum but it travels slower through the gas, dust and other particles in our atmosphere. The more obliquely the rays hit our atmosphere, the more the heat rays will be deflected or absorbed by particles in the atmosphere. At the north and south poles, the angle of deflection means very little heat reaches the surface there, while at the equator light hits the atmosphere square on, bringing maximum heat. The heat is redistributed by currents and weather across the globe.
LIGHT RAYS FROM THE SUN IN the northern hemisphere the seasons are the reverse of those in Australia. When it is warmer there it is cooler here and vice versa. Their seasons also begin on different dates to our seasons, according to when the northern hemisphere is at the solstice or the equinox.
The solstice is the extreme of tilt away from (winter) or toward the sun (summer). The equinox is the exact point halfway between winter and summer, the name meaning equal night or when there are the same number of daylight and dark hours in the day. The dates vary depending on where the calendar is between the cycle of leap years.
According to the northern hemisphere calendar, winter begins on the winter solstice, which is either   December 21 or 22, spring starts on the vernal equinox   March 20 or 21, summer begins on   June 21 or 22, and autumn on   September 22 or 23.
NORTHERN HEMISPHERE WE divide the year into four seasons, with spring beginning on   September 1, summer on   December 1, autumn on   March 1 and winter on   June 1, but the seasons are not as well defined as in some other parts of the world.
The heat of summer often lingers through autumn, and spring can often see temperatures soar long before summer is due to begin. While northern Europe experiences freezing temperatures and snowfalls in winter, in some parts of Australia, like Sydney, winter days can be bright and sunny, with snow falling regularly in the Snowy Mountains and less regularly in areas like the Blue Mountains.
Summer is generally hot but this can also be variable - in Hobart some summer days have been known to be chilly enough to bring snowdrifts.
AUSTRALIAN SEASONS KAKADU National Park in the Northern Territory defies the usual stereotype of the four-season year. It has a tropical monsoon climate with six distinct seasons, all given different names by the indigenous people: Yegge:   May to mid-  June, comparatively cool with low humidity. The indigenous people use this time to burn off woodlands to encourage new growth for grazing animals.
Wurrgeng: Mid-  June to mid-  August is as close to winter as it gets. Humidity is low, daytime temperatures are lower, but still about 30C, and night-time temperatures average 17C. Drier weather causes most creeks to stop flowing or dry up, and flood plains, once covered with water, also dry out. Animals crowd around the shrinking waterholes.
Gurrung: Mid-  August to mid-  October, Kakadu is hot and dry.
Toward the end of the season the thunderclouds gather.
Gunumeleng: Mid-  October to late   December, the climate builds toward the monsoons. The hot weather becomes increasingly humid. Thunderstorms and showers begin to bring green to the parched land. Temperatures are often above 40C and at night still average above 25C.
Gudjewg: Late   December to   March is when the monsoons arrive bringing thunderstorms, heavy rain and flooding.
Banggerreng:   April, the clouds clear and floodwaters recede. Plants produce fruit and animals have babies to look after.
There are also violent windstorms that flatten speargrass fields.
KAKADU'S SIX SEASONS IN ancient times some people measured the length of their lives by the number of winters they had lived through.
Many cultures devised myths to explain the change of seasons but some also took a more practical approach.
It was vitally important to keep track of the passage of the seasons because it would allow hunter-gatherers to know when certain seasonal plants were available for foraging and migratory or hibernating animals would return to be hunted.
By watching the skies, the ancient people were able to predict upcoming changes in seasons. The Egyptians knew that when the so-called dog star Sirius rose near the sun (known as a heliacal rising) that it would herald the beginning of the Nile floods, which allowed them to prepare to farm the floodplains, and kicked off the first of their three seasons Akhet (inundation), which was followed by Peret (growth = winter) and then Shemu (harvest = summer).
The ancient Mesopotamians devised the signs of the zodiac to predict the changes in seasons so that farmers could be ready for each season. Some of the original zodiac signs were farm implements such as Apin the plough (formed by Gamma Andromeda and the constellation Triangulum).
DID YOU KNOW?
Unseasonably warm weather that lingers through autumn is often called an Indian summer. The expression is thought to have originated in North America where the tranquil, hot, hazy, smoky days in autumn gave the Native Americans, then known as Indians, a final chance to hunt and forage for winter food stocks
DID YOU KNOW?
In the US autumn is more widely known as "fall", which comes from"the fall of the leaf" once used by English migrants to America. The word autumn is of unknown origin but is thought to have come from an Etruscan word meaning increase, referring to the increase of crops heading toward the harvest. For many years the season was known as harvest.
DID YOU KNOW?
Winter was once considered to be the last season in the year, symbolic of death, and spring the rst, symbolising new life.
DID YOU KNOW?
The word winter may be derived from a word meaning wet, because it was considered the wet season. However another theory says that it may be from an Old Irish word meaning white, because of the snow.
Because of the angle, during winter the energy from the sun must travel through more atmosphere to reach the poles. Also the sun's energy is spread over a larger area.
  September 23 Autumnal equinox in the northern hemisphere, spring in the south   December 22 Winter solstice in the northern hemisphere   June 21 Summer solstice in the northern hemisphere, winter in the south   March 21 Vernal equinox. Spring in the northern hemisphere, autumn in the south
The Earth rotates on an axis that is tilted at 23.5 degrees
SOURCES AND FURTHER STUDY " Nature Explorers: Seasons by Annabelle Lynch (Windmill Books) " Ways Into Science: Seasons by Peter D. Riley (Hachette) WEBSITES BOOKS ANCIENTS AND THE SEASONS " The Six Seasons in Kakadu environment.gov.au/topics/national-parks/ kakadu-national-park/natural-environment/six-seasons " What causes the seasons http://spaceplace.nasa.gov/seasons/en/ Encyclopaedia Britannica: Seasons www.britannica.com/science/season
Editor: Troy LennonDesign: Fadzil Hamzah