Only a few parts of the world experience the classic four seasons of spring, summer, autumn and winter. Many parts of the world get only two or even one. So, what's going on? Every day, the Earth spins once on its axis. But our planet isn't perfectly upright when it spins. Thanks to a few collisions during its formation, the Earth is tilted at an angle of 23.5 degrees. This means that as the Earth takes it annual trip around the Sun, different areas of the planet face the Sun more directly during their daylight hours at different times of the year. The tilt also affects the daily amount of light — without it the whole planet would have 12-hour days and nights every day of the year. Summer and winterAustralia has summer at the end of the year when the southern hemisphere is tilted towards the Sun. In summer, days are longer because more hours are spent facing the Sun. And they're hotter because we're facing the Sun more head-on — so we get hit by more rays of sunlight than if we were on an angle. The summer solstice in Australia — about December 22 — is when we have our longest day of the year. On this day the Sun is as far south in the sky as it gets — it passes directly above the Tropic of Capricorn, roughly over Rockhampton.  But while we're busy planning Christmas barbecues, the northern hemisphere is tilted away from the Sun. That means there are fewer daylight hours up there and the light is spread out over a greater surface area, so it doesn't get as warm. Their shortest day — the winter solstice — happens on our longest. The tables turn six months later, when the Earth is halfway around its orbit of the Sun. The northern hemisphere's summer solstice (longest day) matches our winter solstice around June 22, when the Sun is as far north as it goes — above the Tropic of Cancer. Spring and autumnIn spring and autumn the planet isn't tilted towards or away from the Sun — it's roughly side-on. And for two days each year the Earth's tilt is exactly side-on to the Sun. The two days are called equinoxes (equal nights), and they fall in the middle of spring and autumn, usually on September 22 and March 22. On an equinox, night and day are equal length everywhere on the planet. But spring and autumn only happen in mid-latitude areas of our planet. It's a different story in the tropics and at the frozen ends of the planet. Tropics and polesSome parts of the polar regions are so consistently cold — and the tropics so hot — they could pass for having only one season. Even the sunniest Antarctic day is as cold as winter in most places. This is because the light reaching the bottom of the planet is at such a low angle it doesn't carry much heat. On the other hand, the tropics are consistently hot. It doesn't matter if they're tilted towards or away from the Sun, they're still closer to it than anywhere else on Earth and they get plenty of direct light and heat. But both places have two distinct seasons. Only the mid-latitudes experience four seasons.(ABC: Julie Ramsden)In the polar regions, the main difference comes down to the amount of daylight. During 'summer', the whole area is tilted towards the Sun and flooded with sunlight. Daytime at the poles lasts for half the year. And the polar night lasts almost as long — making for one very long, dark winter. In the tropics, the difference between seasons is due to rainfall. The wet is caused by a permanent belt of storm clouds around the middle of the planet that dumps huge volumes of rain on the land or sea below. Thanks to the tilt of the planet and some super-sized sea breezes, the storm belt doesn't stay in one place. During the northern summer, the hot air over the land rises, sucking the storm belt as far north as the Tropic of Cancer, doling out monsoons wherever it goes. As the northern summer ends the storms are dragged down towards the Tropic of Capricorn, driving the southern tour of the monsoons. The belt travels across the equator twice a year, once going south and once on the way back up. If they've got the right combination of mountains, wind and sea temperature, some equatorial areas — such as Kuala Lumpur — can score two wet seasons each year. Fortunately, the Top End is far enough from the equator to just have the one wet season — imagine how crazy Darwin would get with two build-ups each year… Thanks to Dr Blair Trevin from the Bureau of Meteorology.
The Southern Hemisphere is the half (hemisphere) of Earth that is south of the Equator. It contains all or parts of five continents[1] (Antarctica, Australia, about 90% of South America, approx. one third of Africa, and some islands off the continental mainland of Asia) and four oceans (Indian Ocean, South Atlantic Ocean, South Pacific Ocean, and Southern Ocean), as well as New Zealand and most of the Pacific Islands in Oceania. Its surface is 80.9% water, compared with 60.7% water in the case of the Northern Hemisphere, and it contains 32.7% of Earth's land.[2] Owing to the tilt of Earth's rotation relative to the Sun and the ecliptic plane, summer is from December to February (inclusive) and winter is from June to August (inclusive). September 22 or 23 is the vernal equinox and March 20 or 21 is the autumnal equinox. The South Pole is in the center of the southern hemispherical region. Southern Hemisphere climates tend to be slightly milder than those at similar latitudes in the Northern Hemisphere, except in the Antarctic which is colder than the Arctic. This is because the Southern Hemisphere has significantly more ocean and much less land; water heats up and cools down more slowly than land.[3] The differences are also attributed to oceanic heat transfer and differing extents of greenhouse trapping.[4] Aurora australis appearing in the night sky of Swifts Creek, 100 km (62 mi) north of Lakes Entrance, Victoria, Australia Aurora australis appearing from Stewart Island / Rakiura in the south of New Zealand In the Southern Hemisphere, the Sun passes from east to west through the north, although north of the Tropic of Capricorn the mean Sun can be directly overhead or due north at midday. The Sun follows a right-to-left trajectory through the northern sky unlike the left-to-right motion of the Sun when seen from the Northern Hemisphere as it passes through the southern sky. Sun-cast shadows turn anticlockwise throughout the day and sundials have the hours increasing in the anticlockwise direction. During solar eclipses viewed from a point to the south of the Tropic of Capricorn, the Moon moves from left to right on the disc of the Sun (see, for example, photos with timings of the solar eclipse of November 13, 2012), while viewed from a point to the north of the Tropic of Cancer (i.e., in the Northern Hemisphere), the Moon moves from right to left during solar eclipses. The Coriolis effect causes cyclones and tropical storms to spin clockwise in the Southern Hemisphere (as opposed to anticlockwise in the Northern Hemisphere).[5] The southern temperate zone, a subsection of the Southern Hemisphere, is nearly all oceanic. The Sagittarius constellation that includes the galactic centre is a southern constellation as well as both Magellanic Clouds. This, combined with clearer skies, makes for excellent viewing of the night sky from the Southern Hemisphere with brighter and more numerous stars. Forests in the Southern Hemisphere have special features which set them apart from those in the Northern Hemisphere. Both Chile and Australia share, for example, unique beech species or Nothofagus, and New Zealand has members of the closely related genera Lophozonia and Fuscospora. The eucalyptus is native to Australia but is now also planted in Southern Africa and Latin America for pulp production, and increasingly, biofuel uses. One of the most notable animals to be found almost exclusively in the Southern Hemisphere is the penguin. A species is found around Isabela Island on the Galápagos archipelago in the Pacific Ocean, which straddles the equator.[6] However, most of Isabela and the rest of the archipelago is located in the Southern Hemisphere, and it is deemed by the International Hydrographic Organization as being wholly within the South Pacific Ocean, rather than the North Pacific.[7] A photo of Earth from Apollo 17 (Blue Marble) with the south pole at the top and the continent of Africa More than 800 million people live in the Southern Hemisphere, representing around 10–12% of the total global human population.[8][9] Of those 800 million people, more than 200 million live in Brazil, the largest country by land area in the Southern Hemisphere, while 145 million live on the island of Java, the most populous one in the world. The most populous country in the Southern Hemisphere is Indonesia, with 267 million people (roughly 30 million of whom live north of the Equator on the northern portions of the islands of Sumatra, Borneo, and Sulawesi, as well as the most of North Maluku, while the rest of the population lives in the Southern Hemisphere).[citation needed] Portuguese is the most spoken language in the Southern Hemisphere, with over 230 million speakers in eight countries – mostly in Brazil.[10] The largest metropolitan areas in the Southern Hemisphere are Jakarta (33 million people), São Paulo (22 million), Kinshasa-Brazzaville (17 million), Buenos Aires (16 million), Rio de Janeiro, Surabaya (12 million each), Johannesburg (11 million), Nairobi, Lima (10 million each), Bandung (9 million), Luanda (8 million), Dar es Salaam (7 million), Santiago, Semarang (6 million each), Sydney, Belo Horizonte and Melbourne (5 million each). Important financial and commercial centers in the Southern Hemisphere include São Paulo, where the B3 (stock exchange) is headquartered, along with Sydney, home to the Australian Securities Exchange, Jakarta, seat of the Indonesia Stock Exchange, Johannesburg, home to the Johannesburg Stock Exchange, and Buenos Aires, headquarters of the Buenos Aires Stock Exchange, the oldest stock market in the Southern Hemisphere. Common tourist destinations in the Southern Hemisphere include Bali, Buenos Aires, Cape Town, Easter Island, Lima, Rio de Janeiro, Sydney and Tahiti.[11][12] According to a 2017 report, the most popular Southern Hemisphere "bucket list" destinations among Australians were Antarctica, New Zealand, Galápagos Islands, South Africa and Peru.[13] Among the most developed nations in the Southern Hemisphere is Australia, with a nominal GDP per capita of US$51,885 and a Human Development Index (HDI) of 0.944, the eighth-highest in the world as of the 2020 report. New Zealand is also well developed, with a nominal GDP per capita of US$38,675 and an HDI of 0.931, putting it at number 14 in the world in 2020. The least developed nations in the Southern Hemisphere cluster in Africa and Oceania, with Mozambique and Burundi at the lowest ends of the HDI, at 0.456 (number 181 in the world) and 0.433 (number 185 in the world), respectively. The nominal GDPs per capita of these two countries do not go above US$550, a tiny fraction of the incomes enjoyed by Australians and New Zealanders. The Southern Hemisphere has long been secondary in the global distribution of demographic, economic and political power, as it has less land than the Northern Hemisphere.[14] In recent times however, countries such as Australia have made greater efforts to economically engage with those from their own hemisphere.[14] Prior to the Age of Discovery, the Southern Hemisphere was largely cut off from cultural constructs of the Western and Eastern worlds.[14] Some view both the West and the East as being Northern Hemisphere-centric concepts.[15] The most widespread religions in the modern Southern Hemisphere are Christianity in South America, Africa, Australia, Oceania, and East Timor, followed by Islam in East Africa and Indonesia, and Hinduism, which is mostly concentrated on/around the islands of Bali, Mauritius, and Fiji. The oldest continuously inhabited city in the Southern Hemisphere is Bogor, in western Java, which was founded in 669 CE. Ancient texts from the Hindu kingdoms prevalent in the area definitively record 669 CE as the year when Bogor was founded. However, some evidence shows that Zanzibar, an ancient port with around 200,000 inhabitants off the coast of Tanzania, may be older than Bogor. A Greco-Roman text written between 1 and 100 CE, the Periplus of the Erythraean Sea, mentioned the island of Menuthias (Ancient Greek: Μενουθιάς) as a trading port on the east African coast, which is probably the small Tanzanian island of Unguja on which Zanzibar is located. The oldest monumental civilizations in the Southern Hemisphere are the Norte Chico civilization and Casma–Sechin culture from the northern coast of Peru. These civilizations built cities, pyramids, and plazas in the coastal river valleys of northern Peru with some ruins dated back to 3600 BCE. Easter Island, located about 3,500 kilometers from Chile and French Polynesia, is considered to be the most remote place on Earth to have been permanently inhabited by humans before the Age of Discovery.[16] It was settled by a Polynesian group known as the Rapa Nui. Areas of the Southern Hemisphere that had no contact with humans prior to the Age of Discovery include Christmas Island and Mauritius (in the Indian Ocean), the Galápagos Islands, Juan Fernández Islands and Lord Howe Island (in the South Pacific), the Falkland Islands and Tristan da Cunha (in the South Atlantic) and the continent of Antarctica.
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Why is it summer in the Southern Hemisphere when it is winter in the Northern Hemisphere the Southern Hemisphere is ____?
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