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Noise phenomena tend to relate to things that happened a long time ago. The signal from these events bounce around the Universe until it seems to come from everywhere and varies little in intensity. In this way, it resembles "noise", the background signal that pervades every instrument used for astronomy. The most comm... |
There are way astronomers can get better pictures of the heavens. Light from a distant source reaches a sensor and gets measured, normally by a human eye or a camera. For very dim sources, there may not be enough light particles coming from the source for it to be seen. One technique that astronomers have for making it... |
Astronomical sources do not move much: only the rotation and movement of the Earth causes them to move across the heavens. As light particles reach the camera over time, they hit the same place making it brighter and more visible than the background, until it can be seen. |
Telescopes at most observatories (and satellite instruments) can normally track a source as it moves across the heavens, making the star appear still to the telescope and allowing longer exposures. Also, images can be taken on different nights so exposures span hours, days or even months. In the digital era, digitised ... |
Adaptive optics means changing the shape of the mirror or lens while looking at something, to see it better. |
Data analysis is the process of getting more information out of an astronomical observation than by simply looking at it. The observation is first stored as data. This data will then have various techniques used to analyse it. |
Fourier analysis in mathematics can show if an observation (over a length of time) is changing periodically (changes like a wave). If so, it can extract the frequencies and the type of wave pattern, and find many things including new planets. |
Pulsars pulse regularly in radio waves. These turned out to be similar to some (but not all) of a type of bright source in X-rays called a Low-mass X-ray binary. It turned out that all pulsars and some LMXBs are neutron stars and that the differences were due to the environment in which the neutron star was found. Thos... |
This section attempts to provide an overview of the important fields of astronomy. |
Solar astronomy is the study of the Sun. The Sun is the closest star to Earth at around 92 million (92,000,000) miles away. It is the easiest to observe in detail. Observing the Sun can help us understand how other stars work and are formed. Changes in the Sun can affect the weather and climate on Earth. A stream of ch... |
Planetary Astronomy is the study of planets, moons, dwarf planets, comets and asteroids as well as other small objects that orbit stars. The planets of our own Solar System have been studied in depth by many visiting spacecraft such as Cassini-Huygens (Saturn) and the Voyager 1 and 2. |
Galactic astronomy is the study of distant galaxies. Studying distant galaxies is the best way of learning about our own galaxy, as the gases and stars in our own galaxy make it difficult to observe. Galactic astronomers attempt to understand the structure of galaxies and how they are formed through the use of differen... |
Gravitational wave astronomy is the study of the Universe in the gravitational wave spectrum. So far, all astronomy that has been done has used the electromagnetic spectrum. Gravitational waves are ripples in spacetime emitted by very dense objects changing shape, which include white dwarves, neutron stars and black ho... |
Architecture |
Architecture is designing the structures of buildings. It uses both art and engineering. Examples include houses, churches, hotels, office buildings, roads, viaducts, tunnels and bridges. |
Architecture is the profession of an architect. Usually, a person must study at an institution of higher education (university) to become an architect. There were architects long before there was higher education. They learnt by being an apprentice to an established architect. |
Architecture can do small designs, such as for a garage, or large designs, such as for a whole city. The capital cities of Brasília, and Canberra were designed. Architecture often overlaps with structural engineering, and architects and engineers often work together. |
In the past, people built huts and wood houses to protect themselves from the weather. For safety, they were often close together. Great civilizations like the Ancient Egyptians built large temples and structures, like the Great Pyramids of Giza. The Ancient Greeks and Romans made what we now call "Classical Architectu... |
Classical architecture was formal, and it always obeyed laws. It used symmetry, which really means balance, and it used proportion between shapes. The Golden Mean was a rule which said, (to put it simply) if you are making a room, or any other thing, it will work best if you always make the long side 1.6 times as long ... |
In some parts of the world, like India, the architecture is famous for carving the stone on temples and palaces. Different architectural styles occur in China, Japan, Southeast Asia, Africa, Mexico, and Central and South America. |
Architects in Western Europe in the Middle Ages made Romanesque architecture, then Gothic architecture. Gothic buildings have tall, pointed windows and arches. Many churches have Gothic architecture. Castles were also built at this time. In Eastern Europe, churches usually had domes. People added their own ideas and de... |
In the late 18th century with the Industrial Revolution, people began to invent machines to make things quickly and cheaply. Many factories and mills were built during, or after this revolution. Decades later, in the Victorian era, architects like George Fowler Jones and Decimus Burton still followed the Gothic style t... |
Towards the end of the 19th Century with a second Industrial Revolution, steel became much cheaper. Architects began to use inventions like metal girders and reinforced concrete to build. An example is the Eiffel Tower in Paris. Buildings can now be built taller than ever before. We call them skyscrapers. This new tech... |
Modernism is the name for the architectural style which developed because of these new building technologies, and its beginnings can been seen as early as 1890. Modernism can also refer to a specific group of architects and buildings from the early to late 20th century, and so may not be the proper term to use for many... |
Many of the world's greatest structures were built by modern-day architects such as Frank Lloyd Wright; Sir Hugh Casson; Norman Foster; I. M. Pei; Adrian Smith; Edward Durell Stone; Frank Gehry; Fazlur Khan; Gottfried Böhm; and Bruce Graham. |
Anatomy |
Anatomy is the study of the bodies of people and other animals. Anatomy is the study of the inside of the body and outside the body. Anatomy notes the position and structure of organs such as muscles, glands and bones. A person who studies anatomy is an anatomist. |
The history of anatomy dates back to 1600 BC when Egyptians began studying human anatomy. They discovered the functions of many organs like the liver, spleen, kidneys, heart etc. and were the first to discover the structure and functions of the lymphatic system. |
For long periods the dissection of deceased people was forbidden, and correct ideas about human anatomy was a long time coming. |
Academic human anatomists are usually employed by universities, medical schools and teaching hospitals. They are often involved in teaching, and research |
. Gross anatomy studies parts of the body that are big enough to see. Micro-anatomy studies smaller parts. |
There are different organ systems, such as the cardiovascular system, also known as the circulatory system (the system that gets blood around the body), the muscular system (the system that contains muscles), the nervous system (the system that controls the nerves,and the brain) and the skeleton (the bones). |
Anatomy, physiology and biochemistry are similar basic medical sciences. |
Asteroid |
An asteroid is a space rock. It is a small object in the Solar System that travels around the Sun. It is like a planet but smaller. They range from very small (smaller than a car) to 600 miles (1000 km) across. A few asteroids have asteroid moon. |
The name "asteroid" means "like a star" in the ancient Greek language. Asteroids may look like small stars in the sky, but they really do move around the Sun, while stars only seem to move because the Earth spins. Like planets, asteroids do not make their own light. Because of this, some people think "asteroids" is not... |
Giuseppe Piazzi found the first asteroid, in 1801. He called it Ceres, and it is the biggest object in the asteroid belt. Others, like Juno, Pallas, and Vesta were found later. In the 1850s so many had been found, that they were numbered by a Minor planet designation starting with 1 Ceres. Today, astronomers using comp... |
Asteroids are the leftover rock and other material from the formation of the Solar System. These rocks were too small to come together to make a planet. Some are made of carbon or metal. Depending on what's on the surface, they are classified into various asteroid spectral types including Type M (metal), Type S (stone)... |
Most asteroids in our Solar System are in the asteroid belt between Mars and Jupiter. Many are not in the main asteroid belt. The ones that come close to Earth are called Near-Earth asteroids. Many scientists think asteroids striking the Earth killed off all the dinosaurs and caused some of the other extinction events. |
Afghanistan |
Afghanistan (, also pronounced //; Pashto/Dari: , Pashto: , Dari: ), officially the Islamic Republic of Afghanistan, is a country located in Central Asia and South Asia. It has borders with Pakistan in the south and east, Iran in the west, Turkmenistan, Uzbekistan and Tajikistan in the north, and China in the far north... |
In early times people passed through it with animals and other goods as it connected China and India with Central Asia and the Middle East. More recently, Afghanistan has been damaged by many years of war. This has resulted in there not being enough jobs. |
The country is around in size or area. There are 30 million people in Afghanistan. There are about 3 million Afghan refugees (people who had to leave the country) who are in Pakistan and Iran for some time. In 2011, its capital, Kabul, had about 3,691,400 people living in it. |
Afghanistan has many mountains. The mountains are called the Hindu Kush and Himalayas. The big mountain in Afghanistan is Mount Nowshak. There are plains (which have soil that is good for growing plants) and foothills. Part is also dry and called the Registan Desert. |
Afghanistan has snow and glaciers in the mountains. Amu Darya is the big water stream, or river. |
The country has a lot of a valuable stone called lapis lazuli, which was used to decorate the tomb of the Egyptian king Tutankhamun. |
Afghanistan has a continental climate with hot summers and cold winters. Having no water sometimes causes problems for farmers. Sandstorms happen a lot in the desert. |
Southern Afghanistan has not many plants because it is dry. There are more plants where there is more water. Mountains have forests of pine and fir, cedar, oak, walnut, alder, and ash trees. |
Afghanistan's wild animals live in the mountains. There are wolves, foxes, jackals, bears, and wild goats, gazelles, wild dogs, camels, and wild cats such as the snow leopard in the country. The birds are falcons, eagles and vultures. The Rhesus Macaque and the red flying squirrel are also in Afghanistan. |
Many years of war, hunting, and years of no water have killed animals in Afghanistan. There used to be tigers in Afghanistan, but now there aren't any. Bears and wolves are almost gone. |
Many people have moved through or invaded the land of Afghanistan. Today's people of Afghanistan are known as "Afghans". They have many traits passed down from these previous peoples. |
The largest group of people are the Pashtuns. These make up about half the population. Tajiks are the second-largest ethnic group, making up about one-fifth of the population. Before the 20th century, Tajiks were called Sarts and some come from the Iranian peoples. Most Pashtuns are also related to the Iranian peoples.... |
Dari-Persian and Pashto are the official languages of Afghanistan. Many people speak both languages. Both are Indo-European languages from the Iranian languages sub-family. They are usually written with the Arabic alphabet. Uzbek and Turkmen are widely spoken in the north and Nuristani and Pashai are spoken in the east... |
Afghanistan is a largely rural country. This means there are only a few major cities. About one fifth of the population live in cities. Kabul, the capital, is the largest city. It is south of the Hindu Kush range and alongside the Kabul River. Other cities in Afghanistan include Kandahar, Herat, Mazar-e Sharif, and Jal... |
Afghanistan is in the path of important trade routes that connect southern and eastern Asia to Europe and the Middle East. Because of this, many empire builders have decided to rule over the area. Signs that these emperors were near Afghanistan still exist in many parts of the country. Afghanistan is near what used to ... |
Archaeologists digging a cave in what is now northeastern Afghanistan (in Badakhshan), discovered that people lived in the country as early as 100,000 years ago. They found the skull of a Neanderthal, or early human, as well as tools from about 30,000 years ago. In other parts of Afghanistan, archaeologists uncovered p... |
Farmers and herders settled in the plains surrounding the Hindu Kush as early as 7000 B.C. These people may have grown rich off the lapis lazuli they found along riverbeds, which they traded to early city sites to the west, across the Iranian plateau and Mesopotamia. As farms and villages grew and thrived in Afghanista... |
The Oxus civilization expanded as far east as western edge of the Indus Valley during the period between 2200 and 1800 B.C. These people, who were the ancestors of the Indo-Aryans, used the term "Aryan" to identify their ethnicity, culture, and religion. Scholars know this when they read the ancient texts of these peop... |
Zoroaster, the founder of the Zoroastrian religion, the world's earliest monotheistic religion, (meaning a religion believing in one god) lived in the area (somewhere north of today's Afghanistan), around 1000 B.C. |
Before the middle of the sixth century BCE, the land was held by the Medes. |
Then the Achaemenids took over control of the land and made it part of the Persian empire. Alexander the great defeated and conquered the Persian Empire in 330 BCE. He founded some cities in the area. The people used Greek culture and language. After Alexander, Greco-Bactrians, Scythians, Kushans, Parthians and Sassani... |
Kushans spread Buddhism from India in the 1st century BCE, and Buddhism remained an important religion in the area until the Islamic conquest in the 7th century CE. |
The Buddhas of Bamiyan were giant statues, a reminder of Buddhism in Afghanistan. They were destroyed by the Taliban in 2001. There were international protests. The Taliban believe that the ancient statues were un-Islamic and that they had a right to destroy them. |
Arabs introduced Islam in the 7th century and slowly began spreading the new religion. In the 9th and 10th centuries, many local Islamic dynasties rose to power inside Afghanistan. One of the earliest was the Tahirids, whose kingdom included Balkh and Herat; they established independence from the Abbasids in 820. The T... |
In the 10th century, the local Ghaznavids turned Ghazni into their capital and firmly established Islam throughout all areas of Afghanistan, except the Kafiristan region in the northeast. Mahmud of Ghazni, a great Ghaznavid sultan, conquered the Multan and Punjab region, and carried raids into the heart of India. Moham... |
Afghanistan was recognized as "Khorasan", meaning "land of the rising sun," which was a prosperous and independent geographic region reaching as far as the Indus River. |
All the major cities of modern Afghanistan were centers of science and culture in the past. The New Persian literature arose and flourished in the area. The early Persian poets such as Rudaki were from what is now Afghanistan. Moreover, Ferdowsi, the author of Shahnameh, the national epic of Iran, and Rumi, the famous ... |
Timur, the Turkic conqueror, took over in the end of the 14th century and began to rebuild cities in this region. Timur's successors, the Timurids (1405–1507), were great patrons of learning and the arts who enriched their capital city of Herat with fine buildings. Under their rule Afghanistan enjoyed peace and prosper... |
Between south of the Hindu Kush and the Indus River (today's Pakistan) was the native land of the Afghan tribes. They called this land "Afghanistan" (meaning "land of the Afghans"). The Afghans ruled the rich northern Indian subcontinent with their capital at Delhi. From the 16th to the early 18th century, Afghanistan ... |
In 1747, after Nader Shah of Persia was killed, a great leader named Ahmad Shah Durrani united all the different Muslim tribes and established the Afghan Empire (Durrani Empire). He is considered the founding father of the modern state of Afghanistan while Mirwais Hotak is the grandfather of the nation. |
During the 1800s, Afghanistan became a buffer zone between two powerful empires, British India and Russia. As British India advanced into Afghanistan, Russia felt threatened and expanded southward across Central Asia. To stop the Russian advance, Britain tried to make Afghanistan part of its empire but the Afghans foug... |
The Kingdom of Afghanistan was a constitutional monarchy established in 1926. It was the successor state to the Emirate of Afghanistan. On 27 September 1934, during the reign of Zahir Shah, the Kingdom of Afghanistan joined the League of Nations. During World War II, Afghanistan remained neutral. It pursued a diplomati... |
The creation of Pakistan in 1947 as its eastern neighbor created problems. In 1973, political crises led to the overthrow of the king. The country's new leader ended the monarchy and made Afghanistan a republic. In 1978, a Communist political party supported by the Soviet Union seized control of Afghanistan's governmen... |
Most people in Afghanistan opposed the sudden Soviet presence in their country. For nearly a decade, anti-Communist Islamic forces known as "Mujahideen" were trained inside neighboring Pakistan to fight the Soviets and the Afghan government. The United States and other anti-Soviet countries supported the Mujahideen. In... |
After the Soviets left, different Afghan warlords began fighting for control of the country. The warlords received support from other countries, including neighboring Pakistan and Iran. A very conservative Islamic group known as the Taliban emerged in an attempt to end the civil war. By the late 1990s the Taliban had g... |
The Taliban ruled Afghanistan according to their strict version of Islamic law. People whom the Taliban believed violated these laws were given cruel punishments. In addition, the Taliban completely restricted the rights of women. Because of such policies, most countries refused to recognize the Taliban government. Onl... |
The Taliban also angered other countries by allowing suspected terrorists to live freely in Afghanistan. Among them were Osama bin Laden and members of the al-Qaeda terrorist network. In September 2001, the United States blamed bin Laden for the terrorist attacks on the World Trade Center in New York City and the Penta... |
In December 2004, Hamid Karzai became the first democratically elected president of Afghanistan. NATO began rebuilding Afghanistan, including its military and government institutions. Many schools and colleges were built. Freedom for women has improved. Women can study, work, drive, and run for office. Many Afghan wome... |
Afghanistan is a newly formed democracy. Under the new constitution, the president and two vice presidents are elected every five years. The International Security Force Assistance (ISAF) helps the government maintain peace and rebuild the country. |
The government still faces problems with the Taliban, internal security, and public services. |
As of 2004, there are thirty-four provinces. Each province is divided into districts. (For cities see List of cities in Afghanistan.) |
Angola |
Angola, (), officially the Republic of Angola, is a country in southern Africa. It shares borders with Namibia in the south, the Democratic Republic of the Congo in the north, and Zambia in the east. Its west border touches the Atlantic Ocean. Its coastline is 1600 kilometers. Angola's capital is Luanda. The country ha... |
Angola is a member state of the African Union, the Community of Portuguese Language Countries, the Latin Union, South Atlantic Peace and Cooperation Zone and the Southern African Development Community. |
Portugal built up its power in Angola from the late 15th to the middle 20th century. |
After independence there was a civil war from 1975 to 2002. Cuba and the Soviet Bloc supported the ruling People's Movement for the Liberation of Angola (MPLA). South Africa supported the insurgent anti-communist National Union for the Total Independence of Angola (UNITA). The war ended after the rebel leader was kille... |
Angola is the world's twenty-third largest country. Angola is bordered by Namibia to the south, Zambia to the east, the Democratic Republic of the Congo to the north-east, and the South Atlantic Ocean to the west. |
Angola's average temperature on the coast is in the winter and in the summer. It has two seasons; dry (May to October) and hot rainy (November to April). |
Angola had a population of 25,789,024 in 2014. |
Angola is divided into eighteen provinces. |
See List of settlements in Angola for the cities and towns in the country. |
Argentina |
Argentina (officially the Argentine Republic) is a country in South America. Argentina is the second-largest country in South America and the eighth-largest country in the world. |
Spanish is the most spoken language, and the official language, but many other languages are spoken. There are minorities speaking Italian, German, English, Quechua and even Welsh in Patagonia. |
In eastern Argentina is Buenos Aires, the capital of Argentina, it is also one of the largest cities in the world. In order by number of people, the largest cities in Argentina are Buenos Aires, Córdoba, Rosario, Mendoza, La Plata, Tucumán, Mar del Plata, Salta, Santa Fe, and Bahía Blanca. |
Argentina is between the Andes mountain range in the west and the southern Atlantic Ocean in the east and south. It is bordered by Paraguay and Bolivia in the north, Brazil and Uruguay in the northeast, and Chile in the west and south. It also claims the Falkland Islands (Spanish: "Islas Malvinas") and South Georgia an... |
The name Argentina comes from the Latin "argentum" (silver) as the Spanish conquistadors believed the area had silver. In the Americas (South and North), Canada, US, Brazil and Argentina are the largest countries (in that order). |
The oldest signs of people in Argentina are in the Patagonia (Piedra Museo, Santa Cruz), and are more than 13,000 years old. In 1480 the Inca Empire conquered northwestern Argentina, making it part of the empire. In the northeastern area, the Guaraní developed a culture based on yuca and sweet potato however typical di... |
Other languages spoken are Italian, English and German. Lunfardo is Argentinean slang and is a mix of Spanish and Italian. Argentinians are said to speak Spanish with an Italian accent. |
Argentina declared independent from Spain in 1816, and achieved it in a War led by José de San Martín in 1818. Many immigrants from Europe came to the country. By the 1920s it was the 7th wealthiest country in the world, but it began a decline after this. In the 1940s, following the "infamous decade" where the country'... |
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