AcharyaChanakya/simple-wikipedia huggingface dataset:
The Earth has mass. Every particle of matter has mass. So the Earth pulls on every object and person, and they pull on the Earth. This pulling force is called "gravity" and it gives weight.
These words mean almost the same thing in everyday use. Sometimes scientists use "gravity" for the force that pulls objects towards each other, and "gravitation" for the theory about the attraction.
According to one of his students, Galileo did a famous experiment about gravity where he dropped balls from the Tower of Pisa. He later rolled balls down inclines. With these experiments, Galileo showed that gravitation accelerates all objects at the same rate regardless of weight.
Johannes Kepler studied the motion of planets. In 1609 and 1616 he published his three laws governing the shape of their orbits and their speed along those orbits, but did not discover why they moved that way.
In 1687, English mathematician Isaac Newton wrote the "Principia". In this book, he wrote about the inverse-square law of gravitation. Newton, following an idea that had long been discussed by others, said that the closer two objects are to each other, the more gravity will affect them.
Newton's laws were used later to predict the existence of the planet Neptune based on changes in the orbit of Uranus, and again to predict the existence of another planet closer to the Sun than Mercury. When this was done, it was learned that his theory was not entirely correct. These mistakes in his theory were corrected by Albert Einstein's theory of General Relativity. Newton's theory is still commonly used for many things because it is simpler and is accurate enough for many uses.
Why does the Earth not fall into the Sun? The answer is simple but very important. It is because the Earth moving round the Sun is in a dynamic equilibrium. The speed of the Earth's movement creates a centrifugal force which balances the gravitational force between the Sun and the Earth. Why does the Earth continue spinning? Because there is no force to stop it.
Newton's first law: "If a body is at rest it remains at rest or if it is in motion it moves at the same speed "until it is acted on by an external force"".
There is a kind of analogy between "centrifugal force" and "gravitational force", which led to the "equivalence principle" of general relativity.
In free fall an object's motion balances out the pull of gravity on it. This includes being in orbit.
The special theory of relativity describes systems where gravity is not an issue; by contrast, gravity is the central issue of the general theory of relativity.
In general relativity "there is no gravitational force" deflecting objects from their natural, straight paths. Instead, gravity is seen as changes in the properties of space and time. In turn, this changes the straightest-possible paths that objects will naturally follow. The curvature is, in turn, caused by the energy–momentum of matter. Spacetime tells matter how to move; matter tells spacetime how to curve.
For weak gravitational fields and slow speeds relative to the speed of light, the theory's predictions converge on those of Newton's law of universal gravitation. Newton's equations are used to plan journeys in our Solar System.
General relativity has a number of physical consequences.
Gravity influences the passage of time. Light sent down into a is blueshifted, whereas light sent in the opposite direction (i.e., climbing out of the gravity well) is redshifted; collectively, these two effects are known as the "gravitational frequency shift".
More generally, processes close to a massive body run more slowly when compared with processes taking place farther away; this effect is known as gravitational time dilation.
General relativity predicts that the path of light is bent in a gravitational field; light passing a massive body is deflected towards that body. This effect has been confirmed by observing the light of stars or distant quasars being deflected as it passes the Sun.
Closely related to light deflection is the gravitational time delay (or Shapiro delay), the phenomenon that light signals take longer to move through a gravitational field than they would in the absence of that field. There have been numerous successful tests of this prediction.
A parameter called γ encodes the influence of gravity on the geometry of space.
Gravitational waves are ripples in the curvature of spacetime. They move as a wave, travelling outward from the source. Einstein predicted them in 1915 on the basis of his theory of general relativity. In theory, gravitational waves transport energy as gravitational radiation. Sources of detectable gravitational waves might include binary star systems composed of white dwarfs, neutron stars, or black holes. In general relativity, gravitational waves cannot travel faster than the speed of light.
The 1993 Nobel Prize in Physics was awarded for measurements of the Hulse-Taylor binary star system. These measurements suggested gravitational waves are more than mathematical peculiarities.
On February 11, 2016, the LIGO Scientific Collaboration and Virgo Collaboration teams announced that they had made the first observation of gravitational waves, originating from a pair of merging black holes using the Advanced LIGO detectors. On June 15, 2016, a second detection of gravitational waves from coalescing black holes was announced. Besides LIGO, many other gravitational-wave observatories (detectors) are under construction.
Centripetal force
Centripetal force is an accelerating force that acts on any body that revolves around a centre. This force contributes to keeping the body in rotation. This force is always directed towards the centre.
The opposite force (by Isaac Newton's third law of motion) is called centrifugal force. This is the force that acts on the body in a direction away from the centre, which contributes to making the body try to fly away. When you hold a rope with a heavy object attached to it, and rotate it around, the rope becomes tight and keeps the body from flying away. This is caused by centripetal force.
An example is a roller coaster which uses centripetal force to accelerate the carts so they will keep going in a circular motion. Even if an object changes direction but maintains at a constant speed it still counts as acceleration.
In the figure to the right we define the displacement vector formula_2 to represent motion in a circle. The magnitude of formula_2 is denoted as formula_4 and represents the radius of the particle's orbit.
A treaty is a written agreement between two or more parties that consists international law. The parties may be countries or other important groups. A treaty may be about any subject.
Two countries might agree to stop a war, or declare war on a common enemy. Very common are treaties where a country promises to come to the aid of another country if the other country is attacked. Treaties about trade are also common. They may allow allow each other's citizens or merchandise to cross borders freely. The European Union is set up by treaties between most of the European nations. It arranges that trade is free between members.
In general, treaties are usually used to settle disputes, or to avoid disputes.
Luxembourg is a country in Western Europe; its official name is the Grand Duchy of Luxembourg (, , ). It is a small country in land area. It was one of the first countries in the European Union. It is also a member of the Benelux. The countries next to Luxembourg are Belgium, Germany, and France. In 2015, its population was 569,700, making it one of Europe's most densely populated countries.
Luxembourg is a parliamentary democracy lead by a constitutional monarch. Under the constitution of 1868, executive power is in the hands of the Governor and the cabinet, which consists of several other ministers.
Luxembourg is divided into 3 districts, which are further divided into 12 cantons and then 116 communes. Twelve of the communes have city status, of which the city of Luxembourg is the largest.
The districts are
Baden-Württemberg
Baden-Württemberg (, ; Alemannic German: "Baade-Wiirdebäärg") is a federal state ("Bundesland") in the southwestern region of Germany. It is the third largest German state by total area (after Bavaria and Lower Saxony) with a size of nearly 35,752 km² and population (after North Rhine-Westphalia and Bavaria) with over 11 million people as of 2017. It shares borders to the east with the state of Bavaria, to the north with the states of Hesse and Rhineland-Palatinate, to the west with the country of France (along the river Rhine), and to the south with the countries of Switzerland and Austria. Its biggest cities are Stuttgart, the capital, Mannheim, and Karlsruhe. The Minister President is Winfried Kretschmann of the party "Alliance '90/The Greens".
In 2017, Baden-Württemberg ranked 2 on the Human Development Index (HDI) among all states in Germany.
In 1952, the three states of Baden, Württemberg-Baden and Württemberg-Hohenzollern joined together to found Baden-Württemberg.
The Minister President is the chief of the government of Baden-Württemberg. The government is made up of ministers and state secretaries.
The CDU was the main political party in the state between 1953-2011, the Ministers President have all been members of the CDU. Between the years 1972 and 1992, the members of the Landtag of Baden-Württemberg were mostly members of the CDU. But the state is also a stronghold of the "Grünen" which were founded in the early 1980s in Karlsruhe. The election results of the Grünen in Baden-Württemberg have always been above the election average for the party in Germany.
Since 2016 there have been 5 parties represented in the Landtag of Baden-Württemberg:
List of Ministers President since 1952:
The Black forest, the Swabian Alb and the Lake Constance are world famous holiday regions. The highest mountain is the Feldberg (1492m).
Other important cities for tourism in Baden-Württemberg besides the capital city of Stuttgart are: Freiburg, Heidelberg, Rastatt, Karlsruhe, Mannheim, Ulm, Ravensburg and Heilbronn.
The Danube, the Neckar and the Rhine are important rivers which are in the state.
Baden-Württemberg has the third largest economy in Germany after the economies of North Rhine-Westphalia and Bavaria. It had a gross regional product (GRP) of €524.33 billion in 2019.
In the northern part of Württemberg and the Kurpfalz the majority are Protestants. But the other parts of the state, especially the south, the majority are Roman Catholics.
Statistics for Baden-Württemberg:
Football is the most popular sport in Baden-Württemberg. The best clubs are the VfB Stuttgart and the Karlsruher SC (Karlsruher SC or KSC). Another popular sport is handball.
Vienna (; ; Central Austro-Bavarian: "Wean", Viennese German: "Wian") is the capital and largest city of Austria.
It is in the east of the country on the river Danube. More than 1,800,000 people live there (2016). It is an administrative district ("Bundesland") of its own.
Before World War I, it was the capital of the Austro-Hungarian Empire. Its centre is a UNESCO World Heritage Site.
The history of the city goes back to the Roman Empire. The Romans started a military camp called Vindobona. The camp was in today's first district on the Danube river. The name came from the Celts, so there was probably a Celtic settlement before the Roman invasion. The Romans stayed until the 5th century. In medieval times, the settlement was still in use. The present name was mentioned in 881 in the Salzburger Annalen, where a battle "ad weniam" is mentioned.
In 976 the House of Babenberg became rulers of the area. They made Vienna their capital in 1155. Vienna was already an important city. In 1156, Austria became a Duchy, and Vienna was where the Duke who ruled the Duchy lived. In 1221, Vienna got municipal rights. It Is the second oldest city in Austria (Enns, in Upper Austria, is the oldest).
In 1278, the Duchy came to the Habsburg family. Rudolf IV started the university in 1365 and while he was duke the nave of the Gothic St. Stephan's Cathedral was built. Quarrels within the Hapsburg family caused an economic decline in Vienna. In 1438, Vienna became the residence of the Holy Roman Emperor.
During the time of the reformation Vienna was a Protestant city, but in the times of the Counter Reformation, Austria and Vienna were mostly Roman Catholic.
In 1529, Vienna was first besieged by the army of the Ottoman Empire, which had a border only 150 km east of Vienna. This hurt Vienna economically, but led to people fortifying the city (making it stronger). After a second siege, the Ottoman Empire could not take Vienna, and the city started getting larger.
During the baroque era, Vienna was rebuilt. Many residences for the nobility were built. Johann Bernhard Fischer von Erlach was an important architect in Vienna.
At the end of the 18th and the beginning of the 19th century Vienna was the home of important composers like Haydn, Mozart, Beethoven, Schubert.
After the revolution in 1848 Franz Joseph I. became emperor of the Austrian Empire, which was founded in 1806 after the liquidation of the Holy Roman Empire. He ruled till 1916. Vienna became a center of arts, culture and architecture. The city grew because the suburbs became part of the city. After 1858 the walls of the city were destroyed and the Ringstraße replaced them. Along that street houses of the rich citizens were built, as were public buildings like the city hall and the Burg theatre. The industrialisation started at the beginning of the century and made more people live there. In 1870, Vienna had one million people, and in 1910, two million people. With the creation of a large working class and poverty in Vienna the Labour Party (Sozialdemokratische Arbeiterpartei) became stronger.
Karl Lueger was the most important mayor in the time of Emperor Franz Josef. During his time important community plans were realized that made Vienna a modern city. However, Lueger was a radical anti-Semite. He was admired by the young Adolf Hitler, who spent some years before the First World War in Vienna. At this time, Vienna was an important place for the arts. Composers like Arnold Schönberg, Anton Webern, Alban Berg and Ernst Krenek were important for the development of modern music. Also the psychoanalysis was founded in Vienna by Sigmund Freud. Also the so-called Jugendstil in arts was part of Vienna's modern arts scene. Founding fathers of modern architecture lived and worked also in Vienna at this time (Otto Wagner, Adolf Loos)
After the end of the First World War the Austrian-Hungary Empire was dissolved and Vienna became capital of the Republic of Austria. In 1938, Austria was occupied by Germany. In Vienna the suffering of the Jewish inhabitants began. A lot of their properties was given to Austrians (Arisierung).
After the Second World War, which destroyed 20% of Vienna's buildings, Vienna was divided into four parts. The city was controlled by the allies like the other parts of Austria. In 1955 the state treaty between the allies and Austria was signed in Vienna's Belvedere. After that Vienna became an important city for international organisations. The first was 1957 the International Atomic Energy Organisation (IAEO) and 1965 the OPEC followed. 1980 the Vienna International Center was opened and Vienna is now the third UN-city together with New York and Geneva.
There are 23 districts in Vienna. They are:
Vienna has many things worth seeing. Here are a few of them.
There are many old buildings, churches and museums in the city centre. Classical music and opera are popular in Vienna. The composers Wolfgang Amadeus Mozart, Ludwig van Beethoven and Brahms all worked in Vienna. Vivaldi also died in Vienna. The city has two world-famous orchestras: the Vienna Philharmonic and the Vienna Symphony.
Vienna is also the name of a song about the city, by the British group Ultravox.
Vienna is the home of the nationally successful soccer clubs SK Rapid Wien and FK Austria Wien.
A telescope makes astronomical objects appear closer to the naked eye. It is an important tool for astronomy that gathers light and directs it to a single point. Some do this with curved mirrors, some with curved lenses, and some with both. Telescopes make distant things look bigger, brighter and closer. Galileo was the first person to use a telescope for astronomy, but he did not invent them. The first telescope was invented in the Netherlands in 1608. Some telescopes, not mainly used for astronomy, are "binoculars," "camera lenses", or "spyglasses".
When telescopes are used with just your eye, an eyepiece has to be used. These use two or more smaller lenses to magnify an image. Without an eyepiece, an eye can not focus the image. When a telescope is used with a camera or other special scientific tools, eyepiece lenses are not needed.
Most big telescopes for astronomy are made for looking very carefully at things that are already known. A few are made to search for things, such as unknown asteroids. A telescope made to be used with a CCD (Charge-Coupled Devices) camera instead of just your eye are sometimes called "Astrophotography". A Go-to telescope is needed to track Deep Sky objects and must be placed on a Alt-Azimuth Mount for the axis to point towards Polaris, this is called polar alignment.
The bigger the aperture (mirror) the more light the telescope collects. It makes faint objects appear clearer.
Telescopes can be used by normal people too, not just scientists. These are amateur telescopes, and they are usually smaller, and they don't cost too much for a normal person to buy. Some of the most popular amateur telescopes are Dobsonians, a type of Newtonian telescope.
The word "telescope" is usually used for light human eyes can see, but there are telescopes for wavelengths we cannot see. Infrared telescopes look like normal telescopes, but have to be kept cold since all warm things give off infrared light. Radio telescopes are like radio antennas, usually shaped like large dishes.
X-ray and Gamma ray telescopes have a problem because the rays go through most metals and glasses. To solve this problem, the mirrors are shaped like a bunch of rings inside each other so the rays strike them at a shallow angle and are reflected. These telescopes are space telescopes because little of this radiation reaches the Earth. Other space telescopes are put in orbit so the Earth's atmosphere does not interfere.
Telescopes are mostly used for looking at celestial objects such as, the stars, planets, etc.
Homonym
A homonym is a word that has more than one meaning. For example, "right" means moral, the opposite of left, and a personal freedom.
Definition: one of a group of words that share the same spelling and pronunciation but have different meanings.
The point is that homonyms are both homophones (they sound the same) and homographs (they look the same).
A principal is a person who is in charge of something. The person is usually in charge of a school, or a research project, or a business.
Peru is a country in South America. The capital is Lima. The ruins of Machu Picchu, the Andes mountains, and the source of the Amazon River are all found in Peru.
Peru is bordered to the north by Ecuador and Colombia, to the east by Brazil, to the south by Chile, and to the southeast by Bolivia. Peru is a representative democratic republic divided into 25 regions and over 33 million people live in it.
Peruvian territory was home to the Norte Chico civilization, one of the oldest in the world, and to the Inca Empire, the largest state in Pre-Columbian America. The Spanish Empire conquered the region in the 16th century and established a Viceroyalty, which included most of its South American colonies. After achieving independence in 1821.
Peru suffered a terrible guerrilla war in the 1980s. The communist (Maoist) Shining Path tried to take over the country. But after the leader of the group was captured in 1992, Shining Path was not a threat anymore. During the 1990s, it was ruled by President Alberto Fujimori. During this time, the economy of Peru got better, and it became easier to start a company or operate a business. After Fujimori, Alejandro Toledo was elected President, and then Alan Garcia, who was President from 1985 to 1990, was elected again in 2006. Ollanta Humala was elected President in 2011 and Pedro Pablo Kuczynski was elected President in 2016. In March 2018, Kuczynski resigned following political scandals and Vice President Martín Vizcarra was sworn-in as the next president.
Peru's most important exports, products that it sells to other countries, are fish, gold and other metals, oil, coffee, sugar, and cotton. Also, the food in Peru is very diverse, including typical dishes like Ceviche and Broiled Chicken.
Tourists from other countries like to come to Peru because of the history and also to enjoy nature. Many people come to climb mountains in the Cordillera Blanca in the Ancash Region, and many people visit Peru's long Pacific coast or the Amazon jungle. Cuzco and Macchu Picchu are just two of the places where many buildings built by the Incas are still standing after hundreds of years, and these are some of the most visited places. The Incas were not the only tribe in Peru who left buildings and artifacts, but they were the most powerful.
Peru is divided into 25 regions of Peru regions. Lima is the capital and other main regions are Cuzco, Arequipa and Lambayeque. In the Amazon jungle region, we can find many important rivers and different animals, plants and people of many indigenous cultures.
Population: 29, 5 mill.
The currency of Peru is the Nuevo Sol.
The population of Peru is approx. 30 million. The ethnic composition of Peru is like the following:
As of 2018, about 22.3% of the population lives below the national poverty line
Peru was the home of the Inca Empire. The Incas were a well-organized Indian civilization that began the city of Cuzco (now called Cusco). Beginning in the 1400s, they defeated many nearby tribes and built an empire in the Andes. The Inca forced the people to work for the king for a certain number of days every year. They used this "work tax" to build roads and terraces on the sides of the mountains to grow crops, and huge cities with rich palaces for the rulers and their queens. Records were kept on quipa, knotted ropes, since the Incas never invented writing. These could be quickly sent anywhere in the empire by a series of relay runners set up along the roads. Heavier loads were sent by llamas, the pack animals of the Andes.
The Incas were rich in gold and silver which could be found in the mountains. The Spanish wanted that treasure when they discovered the nation in the 1500s. Francisco Pizarro, a Spanish man, kidnapped and killed the Inca ruler in 1532, even after his people paid a huge amount of treasure for his release. The Incas fought the Spanish for many years, but the last Inca king was killed in 1572.
Peru was a Spanish colony until 1821. Spanish is still the main language of the people, although many also speak Quechua, the Inca language.
States of Germany
The Federal Republic of Germany (FRG) has 16 states (). The biggest is Bavaria and the smallest is Bremen. Most of them were created after the Second World War, although their historical roots can be traced back to the early Middle Ages in some cases.
State creation since 1949:
Population and area in km² as of November 2014.
Munich ( ; German: "München" ; ]) is the third biggest city of Germany (after Berlin and Hamburg), and the capital of Bavaria. It has a population of 1,407,000. The metropolitan area of Munich includes the city itself, and all the suburbs around it, and has about 2.6 million people in it. It is one of the most important centres of the economy in Germany. It has an oceanic climate ("Cfb" in the Koeppen climate classification).
The official population of Munich city proper at 310.43 km is 1,368,840 inhabitants only with principal residence as of 31st January 2009. Around 176,000 inhabitants with secondary residence also live in administrative city limits but they are not calculated in this official census. According to some estimates that population counts around 200,000 people. The fast growing Munich urban area has 2,667,000 inhabitants (2008 estimate). Munich city with all suburbs at 12,000 km has 4,700,000 inhabitants and Munich metropolitan region that covers 27,700 km and includes Augsburg, Ingolstadt, Landshut, Rosenheim and Landsberg has around 6,000,000 inhabitants. Munich is the 12th largest city in EU by population within city limits and the 14th largest urban area in Europe. Its metropolitan area ranks among largest metro areas in Europe. As of December 2008, 47.3% of Munich's residents belong to no religious group, 38.3% are Roman Catholic, 14.0% are Lutheran Protestants and 0.3% are Jewish. There is also a small Old Catholic parish and an Episcopal Church.
Munich has the strongest economy of any German city. They have the lowest unemployment rate (5.6%) of any German city with more than a million people.
Munich is the largest publishing city in Europe. It is home to the Süddeutsche Zeitung, one of Germany's largest daily newspapers. Munich is also home to Germany's largest public broadcasting network, ARD, and its largest commercial network, Pro7-Sat1 Media AG. The headquarters of the German branch of Random House, the world's largest publishing house, is in Munich.
The Bavaria Film Studios are in the suburb of Grünwald. They are one of Europe's biggest and most famous movie production studios.
Lufthansa has opened a second hub at Munich's Franz Josef Strauss International Airport. It is the second-largest airport in Germany, after Frankfurt International Airport.
Munich Airport - Franz Joseph Strauss (IATA: MUC, ICAO: EDDM)
Munich has one of the most comprehensive systems in the world. There are subways, suburban trains, trams and buses.
Munich is the most successful city in Bundesliga history. FC Bayern Munich have won 20 national championship along with 13 DFB Cups, 5 UEFA Champions League/European Championship, 1 UEFA Cup and 1 UEFA Cup Winners Cup for 39 trophies.
Munich hosted the 1972 Summer Olympics. They were one of the host cities for the 2006 Football World Cup. Munich bid to host the 2018 Winter Olympic Games but lost to Pyeongchang. In September 2011 the DOSB President Thomas Bach said that Munich would bid again for the Winter Olympics in the future.
Munich's universities are known for their high ranking in Germany.
Berlin (; ) is the capital city of Germany. It is the largest city in the European Union by population, with more than 3.7 million people. The city is in the eastern part of Germany. It is about west of Poland. Berlin has an area of . The rivers Havel, Dahme and Spree run through Berlin. It has an oceanic climate.
Berlin is home to many famous buildings and monuments, like the Siegessäule, the Brandenburger Tor, the Reichstag and the boulevard Unter den Linden. On the boulevard are the Humboldt University and the State Opera of Berlin. The Governing Mayor of the city is Michael Müller (SPD).
Berlin is a world city of culture, politics, media and science. There are a lot of technology companies in the city. They are important for the city's economy. Many planes and trains travel to and from Berlin because the city is an important place for tourism and business.
Berlin is an important city for the history of Germany. The King of Prussia and the Emperor of Germany lived in Berlin. The government of Germany was in Berlin for many years. Bombs destroyed many buildings in the city in World War Two. The city was split into West Berlin and East Berlin after World War Two. After the Berlin Wall was built in 1961 very few people were allowed to cross from East Berlin into West Berlin. The wall divided the city until 1989 when the East German government decided to allow anyone to cross, and people decided to destroy the wall.
In 2001 the 23 boroughs of Berlin were changed into 12
Berlin has partnerships with 17 cities. Each of the 12 boroughs also has their sister cities, sometimes called twin cities.
The 1930s was the decade that started on January 1, 1930 and ended on December 31, 1939.
The 1930s was a bad time because of the depression, where people were sad.
1940s
The 1940s was the decade that started on January 1, 1940, and ended on December 31, 1949.
1950s
The 1950s was the decade that started on January 1, 1950, and ended on December 31, 1959.
Hamburg, or in full Free and Hanseatic City of Hamburg (, Low German: "Friee un Hansestadt Hamborg"), is a city in the north of Germany on the banks of the River Elbe, 18 km away from the North Sea. It is also one of the States of Germany.
With a population of about 1.85 million (1850000), it is the biggest German city after Berlin and the sixth largest city of the European Union. The religion is about 37% Protestant, 10% Catholic, 8% Muslim, 38% agnostic, 2% Pagan.
Since it was an important member of the Hanseatic League, the city's official name still includes "Hansestadt" (Hanseatic city). Other German cities that do the same today are: Lübeck, Rostock, Wismar, Stralsund, Bremen, Greifswald and Demmin. The membership in this trade alliance has influenced the architecture of the city to a great extent. It has also left some marks in the region around the city. Strategic bombing in World War II devastated the city.
In 2017 a consulting company ranked it 17th for best place to live in the world.
The area of Hamburg is . It has an oceanic climate ("Cfb" in the Koeppen climate classification).
Hamburg's harbour is, by shipments, the second largest harbour in Europe (after Rotterdam) and among the ten largest in the world. It is a very important gate to the countries along the Baltic Sea and Eastern Europe.
There are about 120,000 businesses in Hamburg. The company Airbus has an assembly plant for large civil aircraft in Hamburg. 30,000 people are employed in Hamburg's aircraft industries. There are only two other locations worldwide in this scale, Seattle in the United States and Toulouse in France.
About half of Germany's nationwide newspapers and magazines are made in Hamburg. Germany's most-viewed television news "Tagesschau" is broadcast from Hamburg.
Hamburg's red-light district (in Sankt Pauli) is the largest in Europe.
Emphysema
Emphysema is a disease of the lungs.
It is one of the diseases that make up chronic obstructive pulmonary disease (COPD). This is a set of diseases where the flow of air in the lungs is obstructed. Emphysema is most often caused by smoking but can be caused by other diseases or have no known cause at all.
It occurs when the very small air sacs (called the alveoli) at the ends of the airways in the lungs start to break down from many sacs to form much bigger sacs. The alveoli are the areas of the lung where oxygen and carbon dioxide are exchanged into and out of the blood. Emphysema makes it hard for people to blow air out of the lungs because air gets trapped inside the broken alveoli due to the collapse of the walls. The trapped air in the lungs creates the characteristic "barrel chest" of emphysema.
There is no cure for emphysema. Treatment includes stopping smoking and taking medicines ('broncho-dilators' and sometimes corticosteroids). Supplemental oxygen is recommended in those with low oxygen levels at rest. It decreases the risk of heart failure and death if used 15 hours per day, and may improve people's ability to exercise. In those with normal or mildly low oxygen levels, oxygen supplementation may improve shortness of breath. There is a risk of fires and little benefit when those on oxygen continue to smoke.
Emphysema is commonly associated with chronic bronchitis. As it is rather difficult to delineate "pure" cases of emphysema or chronic bronchitis they are classed together into chronic obstructive pulmonary disease (COPD).
Oxygen is a chemical element. It has the symbol O and atomic number 8. It is the third most common element in the universe, after hydrogen and helium. Oxygen is more than a fifth of the Earth's atmosphere by volume. In the air, two oxygen atoms usually join to make dioxygen (), a colourless gas. This gas is often just called oxygen. It has no taste or smell. It is pale blue when it is liquid or solid.
Oxygen is part of the chalcogen group on the periodic table. It is a very reactive nonmetal. It makes oxides and other compounds with many elements. The oxygen in these oxides and in other compounds (mostly silicate minerals, and calcium carbonate in limestone) makes up nearly half of the Earth's crust, by mass.
Most living things use oxygen in respiration. Many molecules in living things have oxygen in them, such as proteins, nucleic acids, carbohydrates and fats. Oxygen is a part of water, which all known life needs to live. Algae, cyanobacteria and plants make the Earth's oxygen gas by photosynthesis. They use the Sun's light to get hydrogen from water, giving off oxygen.
Oxygen gas () was isolated by Michael Sendivogius before 1604. It is often thought that the gas was discovered in 1773 by Carl Wilhelm Scheele, in Sweden, or in 1774 by Joseph Priestley, in England. Priestley is usually thought to be the main discoverer because his work was published first (although he called it "dephlogisticated air", and did not think it was a chemical element). Antoine Lavoisier gave the name "oxygène" to the gas in 1777. He was the first person to say it was a chemical element. He was also right about how it helps combustion work.
At the top of the Earth's atmosphere is ozone (), in the ozone layer. It absorbs ultraviolet radiation, which means less radiation reaches ground level.
Oxygen gas is used for making steel, plastics and textiles. It also has medical uses and is used for breathing when there is no good air (by divers and firefighters, for example), and for welding. Liquid oxygen and oxygen-rich compounds can be used as a rocket propellant.
One of the first known experiments on how combustion needs air was carried out by Greek Philo of Byzantium in the 2nd century BC. He wrote in his work "Pneumatica" that turning a vessel upside down over a burning candle and putting water around this vessel meant that some water went into the vessel. Philo thought this was because the air was turned into the classical element fire. This is wrong. A long time after, Leonardo da Vinci worked out that some air was used up during combustion, and this forced water into the vessel.
In the late 17th century, Robert Boyle found that air is needed for combustion. English chemist John Mayow added to this by showing that fire only needed a part of air. We now call this oxygen (O). He found that a candle burning in a closed container made the water rise to replace a fourteenth of the air's volume before it went out. The same thing happened when a live mouse was put into the box. From this, he worked out that oxygen is used for both respiration and combustion.
Robert Hooke, Ole Borch, Mikhail Lomonosov and Pierre Bayen all made oxygen in experiments in the 17th and 18th centuries. None of them thought it was a chemical element. This was probably because of the idea of the "phlogiston theory". This was what most people believed caused combustion and corrosion.
J. J. Becher came up with the theory in 1667, and Georg Ernst Stahl added to it in 1731. The phlogiston theory stated that all combustible materials were made of two parts. One part, called phlogiston, was given off when the substance containing it was burned.
Materials that leave very little residue when they burn, like wood or coal, were thought to be made mostly of phlogiston. Things that corrode, like iron, were thought to contain very little. Air was not part of this theory.
Polish alchemist, philosopher and physician Michael Sendivogius wrote about something in air that he called the "food of life", and this meant what we now call oxygen. Sendivogius found, between 1598 and 1604, that the substance in air is the same as he got by heating potassium nitrate. Some people believe this was the discovery of oxygen while others disagree. Some say that oxygen was discovered by Swedish pharmacist Carl Wilhelm Scheele. He got oxygen in 1771 by heating mercuric oxide and some nitrates. Scheele called the gas "fire air", because it was the only gas known to allow combustion (gases were called "airs" at this time). He published his discovery in 1777.
On 1 August 1774, British clergyman Joseph Priestley focused sunlight on mercuric oxide in a glass tube. From this experiment he got a gas that he called "dephlogisticated air". He found that candles burned more brightly in the gas and a mouse lived longer while breathing it. After breathing the gas, Priestley said that it felt like normal air, but his lungs felt lighter and easy afterwards. His findings were published in 1775. It is because his findings were published first that he is often said to have discovered oxygen.
French chemist Antoine Lavoisier later said he had discovered the substance as well. Priestley visited him in 1774 and told him about his experiment. Scheele also sent a letter to Lavoisier in that year that spoke of his discovery.
Lavoisier did the first main experiments on oxidation. He was the first person to explain how combustion works. He used these and other experiments to prove the phlogiston theory wrong. He also tried to prove that the substance discovered by Priestley and Scheele was a chemical element.
In one experiment, Lavoisier found that there was no increase in weight when tin and air were heated in a closed container. He also found that air rushed in when the container was opened. After this, he found that the weight of the tin had increased by the same amount as the weight of the air that rushed in. He published his findings in 1777. He wrote that air was made up of two gases. One he called "vital air" (oxygen), which is needed for combustion and respiration. The other (nitrogen) he called "azote", which means "lifeless" in Greek. (This is still the name of nitrogen in some languages, including French.)
Lavoisier renamed "vital air" to "oxygène", from Greek words meaning "sour making" or "producer of acid". He called it this because he thought oxygen was in all acids, which is wrong. Later chemists realised that Lavoiser's name for the gas was wrong, but the name was too common by then to change.
"Oxygen" became the name in the English language, even though English scientists were against it.
John Dalton's theory of atoms said that all elements had one atom and atoms in compounds were usually alone. For example, he wrongly thought that water (HO) had the formula of just HO. In 1805, Joseph Louis Gay-Lussac and Alexander von Humboldt showed that water is made up of two hydrogen atoms and one oxygen atom. By 1811, Amedeo Avogadro correctly worked out what water was made of based on Avogadro's law.
By the late 19th century, scientists found that air could be turned into a liquid and the compounds in it could be isolated by compressing and cooling it. Swiss chemist and physicist Raoul Pictet discovered liquid oxygen by evaporating sulfur dioxide to turn carbon dioxide into a liquid. This was then also evaporated to cool oxygen gas in order to turn it into a liquid. He sent a telegram to the French Academy of Sciences on 22 December 1877 telling them of his discovery.
At standard temperature and pressure, oxygen has no colour, odour or taste. It is a gas with the chemical formula called dioxygen.
As "dioxygen" (or just "oxygen gas"), two oxygen atoms are chemically bound to each other. This bond can be called many things, but simply called a covalent double bond. Oxygen gas is very reactive and can react with many other elements. Oxides are made when metal elements react with oxygen, such as iron oxide, which is known as rust. There are a lot of oxide compounds on Earth.
The common allotrope (type) of oxygen on Earth is called dioxygen (O). This is the second biggest part of the Earth's atmosphere, after dinitrogen (N). O has a bond length of 121 pm and a bond energy of 498 kJ/mol Because of its energy, O is used by complex life like animals.
Ozone (O) is very reactive and damages the lungs when breathed in. Ozone is made in the upper atmosphere when O combines with pure oxygen made when O is split by ultraviolet radiation. Ozone absorbs a lot of radiation in the UV part of the electromagnetic spectrum and so the ozone layer in the upper atmosphere protects Earth from radiation.
Above the ozone layer, (in low Earth orbits), atomic oxygen becomes the most common form.
Tetraoxygen (O) was discovered in 2001. It only exists in extreme conditions when a lot of pressure is put onto O.
Oxygen dissolves more easily from air into water than nitrogen does. When there is the same amount of air and water, there is one molecule of O for every 2 molecules of N (a ratio of 1:2). This is different to air, where there is a 1:4 ratio of oxygen to nitrogen. It is also easier for O to dissolve in freshwater than in seawater. Oxygen condenses at 90.20 K (-182.95°C, -297.31 °F) and freezes at 54.36 K (-218.79 °C, -361.82 °F). Both liquid and solid O are see-through with a light-blue colour.
Oxygen is very reactive and must be kept away from anything that can burn.
There are three stable isotopes of oxygen in nature. They are O, O, and O. About 99.7% of oxygen is the O isotope.
Oxygen is the third most common element in the universe, after hydrogen and helium. About 0.9% of the Sun's mass is oxygen.
Apart from iron, oxygen is the most common element on Earth (by mass). It makes up nearly half (46%
to 49.2% of the Earth's crust as part of oxide compounds like silicon dioxide and other compounds like carbonates. It is also the main part of the Earth's oceans, making up 88.8% by mass. Oxygen gas is the second most common part of the atmosphere, making up 20.95% of its volume and 23.1% of its volume. Earth is strange compared to other planets, as a large amount of its atmosphere is oxygen gas. Mars has only 0.1% by volume, with the other planets having less than that.
The much higher amount of oxygen gas around Earth is because of the oxygen cycle. Photosynthesis takes hydrogen from water using energy from sunlight, which gives off oxygen gas. The hydrogen combines with carbon dioxide to make carbohydrates. Respiration then takes oxygen gas out of the atmosphere and turns it into carbon dioxide and water. This happens at the nearly same rate, so the amount of oxygen gas and carbon dioxide doesn't change much because of it.
O is a very important part of respiration. Because of this, it is used in medicine. It is used to increase the amount of oxygen in a persons blood so more respiration can take place. This can make them become healthy quicker if they are ill. Oxygen therapy is used to treat emphysema, pneumonia, some heart problems, and any disease that makes it harder for a person to take in oxygen.
Low-pressure O is used in space suits, surrounding the body with the gas. Pure oxygen is used but at a much lower pressure. If the pressure were higher, it would be poisonous.
Smelting of iron ore into steel uses about 55% of oxygen made by humans. To do this, O gas is injected into the ore through a lance at high pressure. This removes any sulfur or carbon from the ore that would not be wanted. They are given off as sulfur oxide and carbon dioxide. The temperature can go as high as 1,700 °C because it is an exothermic reaction.
Around 25% of oxygen made by humans is used by chemists. Ethylene is reacted with O to make ethylene oxide. This is then changed to ethylene glycol, which is used to make many products such as antifreeze and polyester (these can then be turned into plastics and fabrics).
The other 20% of oxygen made by humans is used in medicine, metal cutting and welding, rocket fuel, and water treatment.
The oxidation state of oxygen is −2 in nearly every compound it is in. In a few compounds, the oxidation state is −1, such as peroxides. Compounds of oxygen with other oxygen states are very uncommon.
Water () is an oxide of hydrogen. It is the most common oxide on Earth. All known life needs water to live. Water is made of two hydrogen atoms covalent bonded to an oxygen atom (oxygen has a higher electronegativity than hydrogen). (this is the basic principle of covalent bonding)
There are also electrostatic forces (Van de'r Waals forces) between the hydrogen atoms and adjacent molecules' oxygen atoms. These pseudo-bonds bring the atoms around 15% closer to each other than most other simple liquids. This is because Water is a polar molecule (Net asymmetrical distribution of electrons) due to its bent shape, giving it an overall net field direction, mainly due to oxygens 2 non bonding pairs of electrons, pushing the bonding H's further together than the linear arrangement with lower enthalpy (see CO). This property is exploited by microwaves to oscillate polar molecules, especially water. And its responsible for the extra energy needed to disassociate H0.
Because of oxygen's high electronegativity, it makes chemical bonds with almost all other chemical elements. These bonds give oxides (for example iron reacts with oxygen to give iron oxide). Most metal's surfaces are turned into oxides when in air. Iron's surface will turn to rust (iron oxide) when in air for a long time. There are small amounts of carbon dioxide () in the air, and it is turned into carbohydrates during photosynthesis. Living things give it off during respiration.
Many organic compounds have oxygen in them. Some of the classes of organic compounds that have oxygen are alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and amides. Many organic solvents also have oxygen, such as acetone, methanol, and isopropanol. Oxygen is also found in nearly all biomolecules that are made by living things.
Oxygen also reacts quickly with many organic compounds at, or below, room temperature when autoxidation happens.
One hundred million tonnes of O are gotten from air for industrial uses every year. Industries use two main methods to make oxygen. The most common method is fractional distillation of liquefied air. N evaporates while O is left as a liquid. O is the second most important industrial gas.Because it is more economical , oxygen is usually stored and transported as a liquid. A small steel tank of 16 liters water capacity with a working pressure of 139 bar (2015 psi) holds about 2150 liters of gas and weighs 28 kilograms (62 lb) empty. 2150 liters of oxygen weighs about 3 kilograms (6.6 lb).
The other main method of making oxygen is by passing a stream of clean, dry air through a pair of zeolite molecular sieves. The zeolite molecular sieves soaks up the nitrogen. It gives a stream of gas that is 90% to 93% oxygen.
Oxygen gas can also be made through electrolysis of water into molecular oxygen and hydrogen.
Oxygen's NFPA 704 says that compressed oxygen gas is not dangerous to health and is not flammable.
At high pressures, oxygen gas (O) can be dangerous to animals, including humans. It can cause convulsions and other health problems. Oxygen toxicity usually begins to occur at pressures more than 50 kilopascals (kPa), equal to about 50% oxygen in the air at standard pressure (air on Earth has around 20% oxygen).
Premature babies used to be placed in boxes with air with a high amount of O. This was stopped when some babies went blind from the oxygen.
Breathing pure O in space suits causes no damage because there is a lower pressure used.
Concentrated amounts of pure O can cause a quick fire. When concentrated oxygen and fuels are brought close together, a slight ignition can cause a huge fire. The Apollo 1 crew were all killed by a fire because the air of the capsule had a very high amount of oxygen.
If liquid oxygen is spilled onto organic compounds, like wood, it can explode.
Blood is a liquid in humans and many animals. Blood is pushed through the organism by the heart, and brings nutrients and oxygen to our tissues. It also takes away waste and carbon dioxide from tissues.
Blood is made up of blood plasma and various cells — red blood cells, white blood cells and platelets. "Platelets" help blood to clot. Hemoglobin is in red blood cells. White blood cells help fight infections and heal wounds.
Blood plasma is the yellow liquid in which blood cells float. Plasma is made up of nutrients, electrolytes (salts), gases, non-protein hormones, waste, lipids, and proteins.
These proteins are albumin, antibodies (also called "immunoglobulins"), clotting factors, and protein hormones. Plasma that does not have the protein fibrinogen is called serum and cannot clot. Adults have about 3 liters of plasma. Plasma is a liquid, mostly water (90%). Plasma takes up 55% of blood volume.