cahya/simple-wikipedia huggingface dataset:
A light year (symbol: ly)  is the distance that light travels in empty space in one year. Since the speed of light is about 300,000 km per second (about 186,000 miles per second), then a light year is about 10 trillion kilometers (about 6 trillion miles). A light year is not a length of time.

The light year is used in astronomy because the universe is huge. Space objects such as stars and galaxies may be hundreds, thousands or millions of light years away.

Example
Think of a star at a distance of 100 light years from us on Earth. Light leaves the star and takes 100 years to get to us. When we see the star's light, we are seeing that star as it was 100 years ago.

Similar distance measurements
Light minute - The distance that light travels in one minute (about 18,000,000 km per minute, or 11,160,000 miles per minute).
For example, our Sun is about 8 light minutes from Earth
Light second - The distance that light travels in one second (about 300,000 km per second, or 186,000 miles per second)
For example, our Moon is about 1¼ light seconds from Earth

References

Units of length
Astronomical distances
English as a second language is a common phrase which has related acronyms, including
ESL, which means "English as a Second Language". This is most often used in a country where English is the primary language
EFL, which means "English as a Foreign Language". This is most often used in a country where English is not the primary language
EAL, which means "English as an Additional Language". This is rarely used.
ESOL, which means "English for Speakers of Other Languages". This is rare.
ELF, which means "English as a Lingua Franca", a term relating to Globalization.
Each of these acronyms means roughly the same thing. In each, the learners already have another native or "mother" language, and they want to learn English as well.

History
The teaching of English as a second language has a long history. For example, the official introduction of English into India's education system began in 1835.

Use
English as a second language is the single most popular subject in the world, after mathematics. English is a very important language in business. Many people study English as a foreign language, because they want a better job. English is also very important in education. Many pages on the internet are in English.

Many people who can not go to English language classes study on the internet, using websites like BBC Learning English.

Many people study English in a country where the people speak English. This way, many students learn to listen and speak English better.

Testing
There are many English exams. These English exams are important for learners. They may show how well a person can use English. It is very difficult to compare different English exams. Every exam is a little different. Read Testing English as a foreign language for more information.

Global Scale of English 
Global Scale of English (GSE) is a test for learners of English as a second or foreign language.   The GSE is a list of can-do statements based on the Common European Framework of Reference (CEFR) for English. Learners' abilities are rated on a 10-to-90 point scale for each of the four basic skills (speaking, listening, reading, and writing). A learner reaches a level on the scale when she or he can correctly perform 50% of the can-do tasks at that level. The education company Pearson PLC developed the scale.

Teaching 
Teaching English as a foreign language (TEFL) is referred to the practice of teaching the English language to the students with different first languages. It is taught in the state school system or privately with a language school or with a tutor. TEFL can also take place in an English-speaking country for people who have immigrated there. 

TEFL teachers may be native or non-native speakers of English. Other forms of TEFL are TESL (Teaching English as a second language), TESOL (Teaching English to speakers of other languages), and ESL (English as a second language).

Additional types of TEFL certification include: CTBE (Certificate in Teaching Business English), CTYL (Certificate in Teaching Young Learners), CTO (Certificate in Teaching Online).

Related pages
 ELTon Award

References

Other websites 
 TESOL

English language
LOL, or lol, is an internet slang term that means "laugh(ing) out loud". It is commonly mistaken for "lots of love." LOL is often used in messages meaning "That is really funny."  

It also means mute in Persian and is a native Dutch word (not an acronym) which means "fun" ("lollig" means "funny"). In Welsh, lol means nonsense - e.g., if a person wanted to say "utter nonsense" in Welsh, they would say "rwtsh lol". LOL is usually used on the internet or when text messaging.

Words similar to "LOL"
 lolz, lulz, lul, lawls, or lawl/lawlzies: Sometimes used instead of LOL, but can have other meanings.
 LOOOOOL: For more emphasis. Any amount of "OL"s can be added to the end of LOL.  
 LMAO: Stands for "Laugh my ass off". Another way to say it is LMFAO ("Laugh my fucking ass off").
 ROFL: For "rolling on the floor laughing". It is often combined with LMAO to make ROFLMAO ("Rolling on the floor laughing my ass off"). Another way to write this is ROTFL.
ROTFLOL: Rolling on the floor laughing out loud; used by Weird Al in the song "White and Nerdy".
LEL: Basically lol; except used by those wanting to be different from the millions of internet users.
kek: The Japanese version of saying Lol.
LEL: Basically lol; except used by those wanting to be different from the millions of internet users

Related page
 Lolcat

References

Internet slang
Here are some words for small numbers. Words in bold are irregular.

When writing other numbers between 21 and 99, you must use a hyphen (-).
 21: twenty-one
 29: twenty-nine
 64: sixty-four
 99: ninety-nine

The number 100 is written as "one hundred", but sometimes people say "a hundred".

The way numbers are written and spoken differs between American English and other forms of English, such as British English and Australian English, as follows.

American English 

To write a whole number from 100 to 999 in American English:
  First write how many hundreds.
  Then write the word "hundred".
  Then write the name of the two-digit number after the digit in the hundreds place.

In standard, written, American English, the word "and" is not in the word-name of any whole number even though many speakers insert it.

Examples:

 101: one hundred one
 102: one hundred two
 175: one hundred seventy-five
 200: two hundred
 300: three hundred
 512: five hundred twelve
 987: nine hundred eighty-seven

British and Commonwealth English 

To write a whole number from 100 to 999 in British and Commonwealth English:
  First write how many hundreds.
  Then write the words "hundred and".
  Then write the name of the two-digit number after the digit in the hundreds place.

In standard, written, British English (and the English spoken in many other places), the word "and" is in the word-name of many whole numbers.

Examples:

 101: one hundred and one (NOT: one hundred one)
 102: one hundred and two (NOT: one hundred two)
 175: one hundred and seventy-five (NOT: one hundred seventy-five)
 200: two hundred
 300: three hundred
 512: five hundred and twelve (NOT: five hundred twelve)
 987: nine hundred and eighty-seven (NOT: nine hundred eighty-seven)

Related pages
 Names of ordinal numbers in English
 Names for large numbers
 Names for small numbers

Numbers
The shape of the Universe cannot be discussed with everyday terms, because all the terms need to be those of Einsteinian relativity. The geometry of the universe is therefore not the ordinary Euclidean geometry of our everyday lives.

According to the special theory of relativity, it is impossible to say whether two distinct events occur at the same time if those events are separated in space.  To speak of "the shape of the universe (at a point in time)" is naive from the point of view of special relativity. Due to the relativity of simultaneity we cannot speak of different points in space as being "at the same point in time" nor, therefore, of "the shape of the universe at a point in time".

What astrophysicists do is ask whether a particular model of the universe is consistent with what is known through observations and measurements of the universe. If the observable universe is smaller than the entire universe (in some models it is many orders of magnitude smaller or even infinitesimal), observation is limited to a part of the whole. 

Consideration of the shape of the universe can be split into two:
 local geometry, which relates especially to the curvature of the universe, especially in the observable universe, and
 global geometry, which relates to the topology of the universe as a whole, measurement of which may not be possible.

The observable universe is the basis for testing any model of the universe. It is a spherical volume (a ball) centered on the observer, regardless of the shape of the universe as a whole. Every location in the universe has its own observable universe, which may or may not overlap with the one centered on Earth.

Recent measurements have led NASA to state, "We now know that the universe is flat with only a 0.4% margin of error".  Within one model, the FLRW model, the present most popular shape of the Universe found to fit observational data is the infinite flat model. There are other models that also fit the data.

References 

Geometry
Cosmology

zh:宇宙#宇宙的形状
A meteor shower is an event when many meteors seem to come from one point in the night sky. These meteors are caused by meteoroids entering Earth's atmosphere at extremely high speeds on parallel paths. Most meteors are smaller than a grain of sand, so almost all of them burn up and never hit the Earth's surface.

A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet. Comets are dirty snowballs, made up of rock embedded in ice, orbiting the Sun. Each time a comet swings by the Sun in its orbit, some of its ice vaporizes and meteoroids will be shed. The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a "dust trail".

Most of our short-period meteor showers are the product of rare disintegrations, when large chunks break off a mostly dormant comet. Examples are the Quadrantids and Geminids. They originated from a breakup of asteroid-like objects, 2003 EH1 and 3200 Phaethon, respectively, about 500 and 1000 years ago. The fragments tend to fall apart quickly into dust, sand, and pebbles, and spread out along the orbit of the comet to form a dense meteoroid stream, which later moves into Earth's path.

The most visible meteor shower in most years are the Perseids, which peak on 12 August each year at over one meteor per minute. NASA has a useful tool to calculate how many meteors per hour are visible from your observing location.

The Leonid meteor shower peaks around 17 November of each year. About every 33 years, the Leonid shower produces a big meteor storm, peaking at thousands of meteors per hour. Leonid storms gave birth to the term "meteor shower" when it was first realised, during the November 1833 storm, that the meteors radiated from near the star Gamma Leonis. The last Leonid storms were in 1999, 2001 (two), and 2002 (two). Before that, there were storms in 1767, 1799, 1833, 1866, 1867, and 1966. When the Leonid shower is not storming it is less active than the Perseids.

References
Communication is when information is passed from a sender to a recipient using a medium. There are different media that can be used:
Visual communication (using body language or gestures)
Communicating with sounds (like human language, but may also be the barking of a dog)
Communication using touch
Using smell
Using writing

Communication can be spoken (a word) or non-spoken (a smile). Communication has many ways, and happens all the time. Not only humans communicate, most other animals do too. Some communication is done without thinking, such as by changing in posture.

Communication that tries to change somebody's mind may be called persuasion or propaganda.

How communication works 
Communication works by exchanging information or messages. In very basic terms
The sender makes a message, from an idea. This is usually called encoding
The sender transmits the message through the medium.
The recipient receives the message and decodes it.

Besides the content of the message, there are other things that are important. These are not part of the message itself, but rather of its context
Who is communicating, and what status does the communicator have?
Communication messages usually do not come alone, but are accompanied by other messages. These are also interpreted.

For a message exchange to be successful, the sender and the recipient must have agreed on a vocabulary. The word hedge can mean completely different things based on the context. In biology a hedge is a row of shrubs or trees that make a barrier or form a border. In finance, a hedge is an investment made to reduce the risk of another investment. In linguistics a hedge is a word or set of words that make other words less important. Without any information it is therefore very difficult to know which hedge is really meant by the speaker.

Related pages

References 
 Communication protocol
Language
Sign language
A Miracle is an amazing, beneficial event that goes (or at least seems to go) against natural laws.  Some people say that a miracle is always an act brought about by God or other supernatural force (such as an angel). Others say that there can always be another explanation for it. And thirdly, some say the event is myth and never actually even happened in the first place.

According to the Bible
In the Bible a miracle is an act by God, where God's presence is shown. They can be an act that affects one person, or a gigantic disturbance of nature that changes the world.

Examples in the Bible
Here are seven types that can be found. These are just some of the many miracles in the Bible.

God’s authority
Moses parts the Red Sea so that the people of Israel could escape from Egypt
Jesus commands the storm winds to stop blowing
Healing
A man crippled since birth gets up and walks after Jesus heals him
Jesus makes a man who was born blind to see
Judgment for evil
People became so evil that God destroys them with a flood; Noah and his family are saved
Two members of the Jerusalem church are struck dead for lying
Provision
God gives manna to the Israelites as they traveled through the desert
Jesus feeds thousands of people with only five loaves of bread and two fish
Raising the dead
By the power of God, Elijah raises a widow’s dead son back to life
Jesus raises his friend, Lazarus, to life
Safety
King Nebuchadnezzar tries to burn Shadrach, Meshach and Abednego to death in a fiery furnace, but God keeps them from burning
Visions
The prophet Isaiah has a vision of God seated on his throne surrounded by angels
Saul has a vision of Jesus that changed his life

In other books
Other religious books, like the Quran, Mahabharata and the Avesta, contains many references to this definition of miracle. An example of a miracle in the Quran is when Muhammad splits the moon into halves.

References

Theology
Kami (神) is a Japanese word for the spirits that are worshipped in the Shinto religion. Not all of Kami are gods of the personified type. Instead, they have to do with phenomena and events like the growth of trees, or rain, or wind, or other aspects of Nature; it is believed that these kami live in those natural things. 

It is usually said that there are . In Japanese the number "eight-million" is normally used to mean infinity.

Though the word kami can be translated multiple ways into English, no English word expresses its full meaning.

Some important kami  
 Amaterasu, the sun goddess 
 Inari, god of foxes
 Kotoamatsukami, the primary kami trinity
 Izanagi, the first man 
 Izanami, the first woman 
 Shinigami, kami of death
 Ryūjin, god of the sea
 Susanoo, god of storms
 Sarutahiko, kami of Earth

Related pages 
 Shinto 
 Shinto shrine
 Inugami

Other websites  
 Kami at Onmark database

Japanese deities
Shinto
Cardboard is a heavy type of paper, notable for its stiffness and durability. It was first invented in China some time in the 15th century, and is used for a wide variety of purposes. One of its more common uses is as a packaging material.

Cardboard boxes were first produced commercially in 1817 in England. Corrugated (also called pleated) paper was patented in England in 1856, used as a liner for tall hats, but corrugated cardboard would not be patented and used as a shipping material until 20 December 1871. The patent was issued to Albert Jones of New York City, New York for single-sided corrugated cardboard. Jones used the corrugated cardboard for wrapping bottles and glass lantern chimneys. The first machine for producing large quantities of corrugated cardboard was built in 1874 by G. Smyth, and in the same year Oliver Long improved upon Jones' design by inventing corrugated cardboard with liner sheets on both sides. This was now cardboard as we know it today.

American Robert Gair was a Brooklyn printer and paper-bag maker during the 1870s, and while he was printing an order of seed bags a metal ruler normally used to crease bags shifted in position and cut the bag. Gair discovered that by cutting and creasing cardboard in one operation he could make prefabricated cartons. Extending this to corrugated cardboard was a straightforward development when the material became available. By the start of the 20th century, corrugated cardboard boxes began replacing the custom-made wooden crates and boxes previously used for trade.

The Kellogg brothers first used cardboard cartons to hold their flaked corn cereal, and later when they began marketing it to the general public a heat-sealed waxed bag of Waxtite was wrapped around the outside of the box and printed with their brand name. This marked the origin of the cereal box, though in modern times the sealed bag is plastic and is kept inside the box rather than outside.

Cardboard packaging has undergone minor changes in recent times due to the trend towards environmentalism. It is now common for cardboard to be manufactured with a large percentage of recycled fibers.

Paper
The Moselle River (German: Mosel)  is a river which flows through  France and Luxembourg, then becomes part of the Rhine River after it flows into Germany. It is  long.

Important cities at the Moselle river are Metz, Thionville, Trier, Bernkastel-Kues and Koblenz.

The valley of the Moselle river is famous for the wine of Elbling, Riesling, and Müller-Thurgau - grapes in the wine growing region Moselle-Saar-Ruwer.

Tributaries 
From the left:
Madon,
Terrouin,
Esch,
Rupt de Mad,
Orne,
Fensch,
Gander,
Syre,
Sauer,
Kyll,
Salm,
Lieser,
Alf,
Endert,
Brohlbach,
Elz.

From the right:
Moselotte,
Vologne,
Meurthe,
Seille,
Saar,
Olewiger Bach,
Avelsbach,
Ruwer,
Feller Bach,
Dhron,
Ahringsbach,
Kautenbach,
Lützbach,
Flaumbach,
Altlayer Bach,
Baybach,
Ehrbach.

Other websites 
 German page

Geography of Rhineland-Palatinate
Geography of Saarland
Rivers of France
Rivers of Germany
Rivers of Luxembourg
Grand Est
Bavaria (; , ), officially the Free State of Bavaria (, ; ), is a State (Bundesland) of Germany. The territory of this state is the largest of the 16 German states. The state capital is Munich with 1.3 million people. About 12.5 million people live in Bavaria.  

Like many German states, Bavaria was once independent. Ludwig II of Bavaria was its last independent king. Bavaria joined the German Empire in 1871.

Structure 
Bavaria has seven parts: Oberbayern (Upper Bavaria), Niederbayern (Lower Bavaria), Schwaben (Swabia), Mittelfranken (Middle Franconia), Unterfranken (Lower Franconia), Oberfranken (Upper Franconia) and Oberpfalz (Upper Palatinate). Bavaria has 71 districts and 25 free cities.

The highest point is the Zugspitze, which is also the highest mountain in Germany. Munich is the largest city, the second biggest city is Nuremberg (Nürnberg), which is famous for its gingerbread, a kind of Christmas bread that is often shaped like a Christmas tree, a snowman or Santa Claus.

Pope Benedict XVI was born in Bavaria.

Administrative divisions

Administrative regions

Bavaria is divided into seven administrative regions called  (singular ). For every Administrative regions exist a state agency called  (district government).
Altbayern:
 Upper Palatinate
 Upper Bavaria
 Lower Bavaria
Franconia:
 Upper Franconia
 Middle Franconia
 Lower Franconia
Swabia:
 Swabia

Districts (Bezirke)
Bavaria has "Bezirke" or districts; the others are the  and the  or . The  in Bavaria are identical with the . In the other larger states of Germany, there are only  as administrative divisions and no self-governing entities at the level of the  as the  in Bavaria.

Population and area

Districts
Bavaria is made up of 71 rural districts that are comparable to counties, as well as the 25 independent cities, both of which share the same administrative responsibilities and duties.

Rural districts:

Independent cities:

Municipalities
The 71 rural districts are on the lowest level divided into 2,031 regular municipalities. Together with the 25 independent cities, there are a total of 2,056 municipalities in Bavaria.

 

In 44 of the 71 rural districts, there are a total of 215 unincorporated areas (as of 1 January 2005), not belonging to any municipality, all unsettled and unpopulated, mostly forested areas, but also four lakes (-without islands, -without island , , which are the three largest lakes of Bavaria, and ).

Major cities and towns

Source: Bayerisches Landesamt für Statistik und Datenverarbeitung

Notes

References

Sources

Other websites

 Official government website
 Official website of Bayern Tourismus Marketing GmbH
 Bavarian Studies in History and Culture
 Außenwirtschaftsportal Bayern
 Statistics
 

 
States of Germany
For animals of the mammal order, see Carnivora.

A carnivore is an animal which eats only meat.  Predators commonly hunt and kill their own prey. Scavengers are carnivores which eat animals they did not kill themselves. Carnivores which eat mainly or only insects are called insectivores. Carnivores which eat mainly or only fish are called piscivores.

The word "carnivore" describes more than just the scientific order Carnivora. However, almost all animals in the Carnivora do eat meat, though a few do not.

List of living carnivores 

Mammals
 All feliforms, such as domestic cats, big cats, hyenas, mongooses, civets
 Almost all caniforms, such as the dogs, wolves, foxes, ferrets, seals and walruses
 All cetaceans, such as dolphins, whales and porpoises
 All bats except fruitbats
 The carnivorous marsupials, such as the Tasmanian devil

Birds
 All birds of prey, such as hawks, eagles, falcons and owls
 All vultures, both old world and new
 Most waterfowl, such as gulls, penguins, pelicans, storks, and herons

Reptiles
 All crocodilians, such as alligators, crocodiles, gharials and caimans
 All snakes, such as cobras, vipers, pythons and boas
 Some lizards, such as most skinks and all monitor lizards
 Some turtles, including the snapping turtle and most sea turtles

Fish and amphibians
 All frogs and toads
 Almost all sharks, such as tiger, great white, nurse and reef sharks
 Most teleosts, such as tuna, marlin, salmon, and bass

Invertebrates
 Most crustaceans, such as the coconut crab are mainly omnivorous, but eat some prey and carrion
 Many molluscs, such as octopus and squid, and some gastropods
 All arachnids, such as spiders and scorpions
 Many insects, such as mantises, dragonflies and most wasps
 All jellyfish and sea stars

Related pages 
 Theropod
 Insectivore
 Herbivore
 Omnivore

References
Cologne (, Kölsch: Kölle) is a city on the Rhine River in the state of North Rhine-Westphalia in Germany. About 1,060,000 people live there, making Cologne the biggest city in North Rhine-Westphalia. It is in the southern part of the 'Rhine-Ruhr agglomeration' of cities with a combined total population of about 10 million people. This is one of the most densely populated areas of the world.

Cologne has an oceanic climate (Cfb in the Koeppen climate classification).

History
The city was founded by the Romans in the year 50 AD. Before that, it was a Roman castle ("castellum") and a town inhabited by a local German tribe named Ubier at least for 100 years. Archaeologists have found out that the surrounding area was populated already during the Stone Age.

Traditionally, the city was always Roman Catholic. That changed only recently after the Second World War,as a result of massive immigration of Protestants from the East of Germany. Still the largest number of people, 41.6%, are Roman Catholic, compared to 17% Protestant. 10% of the people are Muslim.

Sights
The most interesting thing to see there is Cologne Cathedral. This church was built from about 1248 to about 1550, but completed only in 1880. The United Nations list it as 'World Cultural Heritage'. Cologne's archbishop Rainald von Dassel brought the relics of the biblical Three Wise Men there in 1164. They are kept in a very beautiful golden shrine in the cathedral. Three golden crowns in the coat of arms of the city symbolize them. They made Cologne a major place of pilgrimage.

The University of Cologne alone has more than 50,000 students. It was founded 1919 and is one of the biggest universities in Germany. There are several specialized Schools in addition to the university. The Hochschule für Musik is the biggest Academy of Music in Europe. Cologne has two Colleges of Arts and the Sports College again is one of the biggest institutions of its kind worldwide.

Cologne has 31 museums and has one of the busiest train stations in Europe. It is the only train station located next to a big cathedral.

Culture
People in Cologne and nearby have their own dialect. They call it Kölsch. During carnival time it even appears on nationwide broadcasts.

Cologne has a handful of broadcasting stations. The Westdeutscher Rundfunk, part of the network ARD, is the biggest producer of television and radio programs in Germany.

Cologne is also famous for Eau de Cologne (Kölnisch Wasser).

Related pages
 Berlin
 Bonn (nearby city)
 Düsseldorf (nearby city)
 Frankfurt/Main
 Hamburg
 Leverkusen (nearby city)
 Munich

References

Other websites 

 German page on the city
 German page of the University
 German page of the cathedral
 German page of the broadcasting station Westdeutscher Rundfunk

Cities with more than a million inhabitants
Cities in North Rhine-Westphalia
 
1st-century establishments in Europe
Establishments in Germany
50 establishments
The Republic of Senegal (French République da Sénégal) is a country in West Africa. The capital is Dakar. 
Senegal covers a land area of almost 197,000 square kilometres. It has population of about 13 million. The climate is tropical with two seasons: the dry season and the rainy cold  season. Senegal was given independence by France in 1960.

Major industries are fish processing, phosphate mining, fertilizer production, petroleum refining, construction materials, ship construction and repair. Peanuts, sugarcane, cotton, green beans, industrial tomato, cherry tomato, melon, and mango are important cash crops.

French is the official language. Since April 2012, Senegal's president has been Macky Sall.

History
In the 15th century, Portuguese people came to Gorée Island off the coast of Dakar. In the 17th century, French people and Dutch people came there, too. These European countries used the island as a trading post in slaves from the mainland, controlled by the Muslim Wolof Empires. Slavery was later made illegal by France, but soon after, around 1850, the French started to conquer the Wolof. By 1902 Senegal was a part of the French colony French West Africa.

In January 1959, Senegal and the French Sudan became one to form the Mali Federation, which became fully independent on June 20, 1960, as a result of the independence and transfer of power agreement signed with France on April 4, 1960. This did not last long and Senegal and Mali broke apart into separate nations. Between 1982 and 1989, Senegal and The Gambia joined together to make Senegambia.

Geography
In the north of Senegal is the Senegal River. To the north of the river is Mauritania. The nation borders Mali in the east, Guinea-Bissau in the south, and Guinea in the south-east. The Gambia is another country inside of Senegal, along the Gambia River. It is about 300 km long.

The north of Senegal is part of the Sahel. The highest mountain is 581 m high. The rainy season is between June and October. The average temperature on the coast is about 24° C, and inland about 27° C.

Regions

 Dakar
 Diourbel
 Fatick
 Kaffrine
 Kaolack
 Kédougou
 Kolda
 Louga
 Matam
 Saint-Louis
 Sédhiou
 Tambacounda
 Thiès
 Ziguinchor

References

 
French-speaking countries
Least developed countries
Members of the Organisation of Islamic Cooperation
Developmental biology is the study of how organisms grow and develop. 

Modern developmental biology studies the genetic control of cell growth, differentiation and morphogenesis. These are the processes which turn a zygote into an adult animal.

Cell differentiation 
Differentiation is the formation of cell types, from what is originally one cell – the zygote or spore. The formation of cell types like nerve cells occurs with a number of intermediary, less differentiated cell types. A cell stays a certain cell type by maintaining a particular pattern of gene expression.293-5 This depends on regulatory genes.

Embryonic development 

Embryogenesis is the step in the life cycle after fertilisation – the development of the embryo, starting from the zygote (fertilised egg). Organisms can differ drastically in the how embryo develops, especially when they belong to different phyla.

Growth 
Growth is the enlargement of a tissue or organism. Growth continues after the embryonic stage, and occurs through cell division, enlargement of cells or accumulation of extracellular material. In plants, growth results in an adult organism that is strikingly different from the embryo. The dividing cells tend to be distinct from differentiated cells (see stem cell). 

In some tissues dividing cells are restricted to special areas, such as the growth plates of bones.467-482 But some stem cells move to where they are needed, from the bone marrow to form muscle, bone or adipose (fat) tissue.

Metamorphosis 

Many animals have a larval stage, with a body plan different from that of the adult organism. The larva abrubtly develops into an adult in a process called metamorphosis. For example, caterpillars (butterfly larvae) are specialized for feeding whereas adult butterflies (imagos) are specialised for flight and reproduction. When the caterpillar has grown enough, it turns into an immobile pupa. Here, the imago develops from imaginal discs found inside the larva.575-585

Regeneration 
Regeneration is the reactivation of development so that a missing body part grows back. This phenomenon has been studied particularly in salamanders, where the adults can reconstruct a whole limb after it has been amputated. Researchers hope to one day be able to induce regeneration in humans. There is little spontaneous regeneration in adult humans, although the liver is a notable exception. Like for salamanders, the regeneration of the liver involves reversing some cells to an earlier state.592-601

Related pages 
Evolutionary developmental biology

References
Year 1929 (MCMXXIX) was a common year starting on Tuesday in the Gregorian calendar. By January 1 of this year, every state in the entire world had adopted the Gregorian calendar, having abandoned the Julian calendar.

Events 
 February 20 – American Samoa becomes organized as a territory of the United States 
 July 16 – The first Oscar-event
 August 8 to August 29 – The German airship Graf Zeppelin makes a round-the-world flight. It was 49.000 km.
 October 24 – The Black Friday
 October 29 – The Black Tuesday

Births 
 January 15 – Martin Luther King Jr., civil rights leader
 January 31 - Jean Simmons, actress
 February 21 - Roberto Gómez Bolaños, actor, screenwriter, director, producer and comedian
 April 1 – Milan Kundera, writer 
 April 6 – André Previn, composer, conductor
 May 4 – Audrey Hepburn, actress
 May 25 - Beverly Sills, American soprano
 June 12 – Anne Frank, Dutch diarist of Jewish descent
 June 18 - Carlo Airoldi, Italian marathon runner 
 June 20 - Edgar Bronfman, Sr., Canadian-American businessman 
 July 25 - Manuel Olivencia,  Spanish lawyer and economist 
 July 28 – Jacqueline Kennedy Onassis, First Lady of the United States, 1961-63
 August 2 – K.M. Peyton, English writer
 August 24 – Yasser Arafat, leader of the Palestinian Authority
 November 12 - Grace Kelly, actress and later Princess of Monaco
 November 14 – McLean Stevenson, actor
 December 13 - Christopher Plummer, Canadian-American actor

Deaths 
 February 8 – Maria Christina, Queen Regent of Spain 
 March 20 – Marshall Ferdinand Foch, (French)
 April 4 – Karl Benz, German automobile pioneer
 October 1 – Antoine Bourdelle, sculptor

Nobel Prize winners 
 Physics – Louis-Victor de Broglie, French physicist 
 Chemistry – Arthur Harden and Hans Karl August Simon von Euler-Chelpin 
 Medicine – Christiaan Eijkman (Dutch physicist) and Frederick Gowland Hopkins 
 Literature – Thomas Mann, German writer 
 Peace – Frank Billings Kellogg

Hit songs 
 "Am I Blue?" by Ethel Waters
 "Button Up Your Overcoat" by Helen Kane
 "Heigh-Ho, Everybody, Heigh-Ho" by Rudy Vallee
 "I Want To Be Bad" by Annette Hanshaw
 "I'll Get By, As Long As I Have You" by Aileen Stanley
 "I'm The Medicine Man For The Blues" by Ted Lewis & His Jazz Band
 "If I Had A Talking Picture of You" by Johnny Hamp's Kentucky Serenaders
 "Louise" by Maurice Chevalier
 "Louise/So The Bluebirds And The Blackbirds Got Together" by Paul Whiteman's Rhythm Boys, featuring Bing Crosby
 "Makin' Whoopie" by Eddie Cantor
 "Maybe, Who Knows?" by Kate Smith
 "Nobody Knows You When You're Down and Out" by Bessie Smith
 "Piccolo Pete" by Ted Weems & His Orchestra
 "Singin' In The Rain" by Cliff Edwards
 "Stardust" by Isham Jones & His Orchestra
 "What Did I Do To Be So Black and Blue?" by Louis Armstrong & His Orchestra
 "You'll Do It Someday, So Why Not Now?" by Rudy Vallee
The 1920s was the decade that started on January 1, 1920 and ended on December 31, 1929. This decade was known as the Roaring Twenties or the Jazz Age.

The most important events 

 Golden Twenty
 1920 – Prohibition began in the United States.
 1922 – March on Rome
 1922 – Howard Carter discovered the tomb of the Egyptian King Tutankhamun.
 1922 – Southern Ireland gained independence from the United Kingdom.
 1922 – The Soviet Union was founded.
 1929 – The Black Tuesday, which leads to Great Depression.

Important people

World leaders 
 Prime Minister Stanley Bruce (Australia)
 Prime Minister William Lyon Mackenzie King (Canada)
 President Sun Yat-sen (Republic of China)
 President Chiang Kai-shek (Republic of China)
 President Friedrich Ebert (Germany)
 President Paul von Hindenburg (Germany)
 Ahmad Shah Qajar of Qajar dynasty (Persia/Iran)
 Reza Shah Pahlavi of Pahlavi Dynasty (Iran)
 King Victor Emmanuel III (Italy)
 Prime Minister Benito Mussolini (Italy)
 President W.T. Cosgrave (Irish Free State)
 President Mustafa Kemal (Atatürk) (Turkey)
 Emperor Hirohito (Japan)
 Pope Pius XI
 Józef Piłsudski (Poland)
 Vladimir Lenin (Soviet Union)
 Joseph Stalin (Soviet Union)
 King Alfonso XIII (Spain)
 King George V (United Kingdom)
 Prime Minister David Lloyd George (United Kingdom)
 Prime Minister Andrew Bonar Law (United Kingdom)
 Prime Minister Stanley Baldwin (United Kingdom)
 Prime Minister Ramsay MacDonald (United Kingdom)
 President Woodrow Wilson (United States)
 President Warren G. Harding (United States)
 President Calvin Coolidge (United States)
 President Herbert Hoover (United States)

 Charlie Chaplin (entertainer)
 Albert Einstein (German physicist)
 Paul von Hindenburg (president of Germany)
 King George V (King of the United Kingdom)
 Vladimir Lenin (leader of the USSR)
 Pope Pius XI (Pope in the 1920s)
 Joseph Stalin (leader of the USSR)
 King Victor Emmanuel III (king of Italy)
Space, also known as outer space, is the near-vacuum between celestial bodies. It is where everything (all of the planets, stars, galaxies and other objects) is found.

On Earth, space begins at the Kármán line (100 km above sea level). This is where Earth's atmosphere is said to stop and outer space begins.  This is not a natural boundary but is a convention used by scientists and diplomats.

However, the space near Earth is quite crowded by astronomical standards. A list of spaces goes like this: 
Geospace is the region of outer space near Earth; Geospace includes the upper region of the atmosphere and the magnetosphere.  The Van Allen radiation belt lies within the geospace. The space inside the magnetosphere is protected from radiation from the Sun. It has a low level of electrically charged particles.
Interplanetary space is the space around the Sun and planets of the Solar System. It has  the solar wind, a continuous stream of charged particles from the Sun. This stream creates a very thin atmosphere (the heliosphere) for billions of miles or kilometers into space. Interplanetary space has the magnetic field generated by the Sun.  Planets such as Jupiter, Saturn, Mercury and the Earth also have magnetospheres.  These magnetic fields can trap particles from the solar wind and other sources, creating belts of magnetic particles such as the Van Allen radiation belt. Planets without magnetic fields, such as Mars, have their atmospheres gradually stripped off by the solar wind.
Interstellar space is the physical space within a galaxy not occupied by stars or their planetary systems. It continues to the edges of the galaxy, where it fades into the intergalactic void. Most of the mass in this space is made up of single hydrogen atoms, fewer helium atoms and a few heavier atoms formed in stars. Supernovae blow some of their atoms huge distances. A number of molecules and tiny 0.1 μm dust particles do exist in interstellar space. About four new types of molecule are discovered each year. Large regions of higher density matter known as molecular clouds allow chemical reactions to occur. This includes organic polyatomic species. Much of this chemistry is driven by collisions.
Intergalactic space does have 'cosmic voids' between the large-scale structures of the universe.

Exploration 

Exploring space is very difficult because it contains no air and is so large that even the fastest ships can only explore a tiny part of it. It takes 3 days of traveling to reach the Moon and, depending on speed, it would take a long time to reach the closest star Proxima Centauri. 

Manned spacecraft are designed to keep good air inside them and to protect astronauts from extreme temperatures.

We gain most of our information about the items in space from different kinds of telescopes. Some of them are space telescopes, put in outer space for a better view. Space probes also explore planets, comets and other space objects that are not too far.

Related pages 
 Space-time
 Black hole
 Galaxy
 Universe
 Astronomy

References 

Astrophysics
Space
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.

Geometric proof for uniform circular motion

In the figure to the right we define the displacement vector  to represent motion in a circle.  The magnitude of  is denoted as  and represents the radius of the particle's orbit.

Force
Mechanics
A treaty is a written agreement between two or more parties. International treaties are covered by 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. For example, the European Union is set up by treaties between most of the European nations. It arranges that trade of products and services is free between the member states of the European Union.

In general, treaties are usually used to settle disputes, or to avoid disputes.

Famous treaties 
 1494 - Treaty of Tordesillas
 1783 - Treaty of Paris (1783)
 1814 - Congress of Vienna
 1840 - Treaty of Waitangi
 1919 - Treaty of Versailles
 1928 - Kellogg-Briand Pact
 1935 - Roerich Pact
 1938 - Munich Agreement
 1944 - Bretton Woods Agreement
 1945 - United Nations Charter (not strictly a treaty)
 1947 - General Agreement on Tariffs and Trade
 1949 - North Atlantic Treaty
 1955 - Warsaw Pact
 1957 - Treaty of Rome
 1968 - Nuclear Non-Proliferation Treaty
 1992 - Treaty of Maastricht
 1993 - United Nations Framework Convention on Climate Change
 1998 - Good Friday Agreement

Related pages
 Peace treaty
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.

Timeline
 963 - Luxembourg was founded. Sigefroid, Count of Ardennes, came to own the ruins of an old Roman fort called "Castellum Lucilinburhuc" ("Little Castle") from the monks of the Abbey of St. Maximin in Trier.
 1354 - The emperor Charles IV made Luxembourg a duchy.
 1437 - There were no people in the ruling family alive. The castle was given to the Habsburgs.
 1443 - Luxembourg was captured by Philip of Burgundy.
 1482 - Mary of Burgundy died. Luxembourg was ruled by the Habsburgs again.
 1795 - After the French revolution Luxembourg was taken over by France. It became a département of France.
 1815 - Luxembourg became a grand duchy. It was ruled by the king of the Netherlands.
 1815-1866 - Luxembourg became a member of the German Confederation.
 1890 - After the death of William III, Luxembourg passed to the House of Nassau-Weilburg.
 1914-1918 - Luxembourg was conquered by Germany during World War I.
 1940 - The Germans returned during World War II, and in 1942 Luxembourg became part of the Third Reich.
 1944 - Luxembourg became independent in September because the United States Army arrived.
 1945 - Luxembourg joined the United Nations
 1957 - Luxembourg became one of the first six members of the European Economic Community. That is now called the European Union.
 2020 - Luxembourg became the first country in the world to make all public transport free to use.

Government
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.

Districts, cantons, and communes
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.

Districts
The districts are
Diekirch
Grevenmacher
Luxembourg

Related pages
List of rivers of Luxembourg
Luxembourg at the Olympics
Luxembourg national football team

References

 
European Union member states
Benelux
Current monarchies
French-speaking countries
German-speaking countries
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.

History 
In 1952, the three states of Baden, Württemberg-Baden and Württemberg-Hohenzollern joined together to found Baden-Württemberg.

Politics 
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:
 Greens
 Christian Democratic Union (CDU)
 Alternative for Germany (AfD)
 Social Democratic Party (SPD)
 Free Democratic Party (FDP/DVP)

List of Ministers President since 1952:

Tourism 

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.

Economy 
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.

Religion 
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:

Sports 
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.

References

Other websites 
 www.baden-württemberg.de
 www.baden-württemberg.de/en/home
 Webportal Baden-Württemberg 

 
1952 establishments in Europe
1950s establishments in Germany