![]() Seasons are defined by astronomy in a very accurate and precise way, down to the minute. The tilt doesn’t change, but the relative orientation of particular regions of the planet will shift during Earth’s orbit around the sun, López-Sánchez says. Seasons occur because the sun heats its orbiting planets unevenly – an effect increased by the Earth’s 23.3 degree tilt. “Seasons are defined by astronomy in a very accurate and precise way, down to the minute,” López-Sánchez says. How the tilt of the earth affects the seasons López-Sánchez says that Australia and New Zealand differ from most European and American countries which use this astronomical definition for seasons. “I was shocked, when I moved to Australia 16 years ago, to see that everyone used the beginning of December, March, June and September as the change of season,” says Macquarie University astrophysicist Dr Ángel López-Sánchez.Īstronomers define the change in seasons by a solstice (when the sun appears at its furthest distance north or south of the celestial equator) or equinox (the moment when the sun crosses the celestial equator). However in Australia, it is meteorologists rather than astronomers who dictate the official change of seasons, and they’ve determined that September 1 is the national start of spring. In Iceland, the first day of summer, a national holiday, falls on the first Thursday after April 18.The wattles are flowering and the days getting longer and slightly warmer – but we’re a few weeks off the start of a new season, according to astronomers, who calculate that spring in the Southern Hemisphere will begin this year on September 23, at 11:03 am, AEST. This means that the seasons within each county start and end on different dates, depending on the regions and their climate. In Finland and Sweden, the dates of the seasons are not based on the calendar at all, but on temperatures. Some cultures, especially those in South Asia have calendars that divide the year into six seasons, instead of the four that most of us are familiar with. In Ireland, St Brigid's Day on February 1 is often thought to mark the beginning of spring in the ancient Celtic calendar system. In many other countries, both definitions are used, depending on the context. For example, Australia and New Zealand use the meteorological definition, so spring begins on September 1 each year. The question which definition to use divides countries and regions around the world. The Sun: Our home star Different Countries, Different Seasons winter starts June 1 and ends August 31.fall (autumn) starts March 1 and ends May 31 and.summer starts December 1 and ends February 28 (February 29 in a Leap Year).spring starts September 1 and ends November 30.The meteorological seasons in the Southern Hemisphere are also opposite to those in the Northern Hemisphere: The same rule applies for the other seasons. For example, under the definition of astronomical seasons, the June solstice marks the start of summer in the Northern Hemisphere, but it is the start of winter in the Southern Hemisphere. Seasons in the Southern Hemisphere are opposite to those in the Northern Hemisphere. ![]() When the Northern Hemisphere gets most sunlight (summer), the Southern Hemisphere gets least (winter).
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