Aarushhh/wikipedia-simple-splitted huggingface dataset:
Geography
Rome stands on seven hills, with an area of . The city is crossed by two rivers: the Tiber, which runs from east to west, and l'Aniene, which runs from north-east to north – within the city, it flows into the Tiber. Rome was built on Sun Hill, later named Palatine. It grew and covered seven principal hills, which are now the inner city of Rome:
 Palatine
 Aventine
 Capitoline
 Quirinal
 Viminal
 Esquiline
 Caelian

Climate
Rome has a Mediterranean climate (Köppen climate classification: Csa), with cool, humid winters and warm, dry summers. Its average annual temperature is above 20°C (68°F) during the day and 10°C (50°F) at night.

Education
The children in Rome have to go to school from the age of six until 16. This takes them to the middle of high school (Scuola secondaria di secondo grado). Rome has the biggest university in Italy and it is named University of Rome. It was created in 1303. About 200,000 students go to study at this university.
Transport
Rome has an airport, which is named Leonardo da Vinci International Airport (IATA: FCO). There is a fast train that goes between the airport and the city center, the Leonardo Express, and many commuter railway lines to the nearby suburbs, along with long-distance trains to other cities in Italy. In the city itself, public transport consists of three metro lines (A, B, and C), six tram lines, and many bus routes.

Buildings
Rome has many old, famous buildings. In recent centuries, the city has become an important tourist attraction.
 The Vatican
 Cinecittà Studios
 Roman Forum
 Colosseum
 The Temple of Antonius and Faustina (141 )
 The Temple of Julius Caesar (29 )
 The Temple of Vesta (7th century )
 The Temple of Castor and Pollux (484 )
 The Arch of Augustus (29-19 )
 The Forum of Caesar (54 )
 The Forum of Augustus (2 )
 The Temple of Venus and Rome (135 )
 Circus Maximus
 The Baths of Caracalla (212–216 )
 Pantheon

Related pages
 Ancient Rome

Notes

References

Other websites
Other websites

 Rome -Citizendium
 Ancient Rome first days 

 
Olympic cities
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 (, ) is a city in the state of North Rhine-Westphalia in Germany. It is on the Rhine River. 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. It has one of the busiest train stations in Europe. It is the only train station 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 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, and was 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
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
Solidarity can refer to:
 Solidarity (Polish trade union), a Polish trade union originally led by Lech Wałęsa;
 Solidarity, a United States political party from the fusion of the International Socialists, Socialist Unity, and Workers' Power;
 Solidarity, a newspaper published by the Alliance for Workers Liberty in the UK.

 Solidarity = feeling of unity based on respect, support, equality, common values, welcoming actions, diversity, community, etc.
1924 was a leap year starting on Tuesday.

Events 
 January 22 – Ramsay MacDonald becomes the first Labour Prime Minister.
 February 8 – The first execution with gas was in Carson City, Nevada.
 February 14 – IBM founded.
 March 25 – Greece proclaims it is a republic.
 May 4 – The 1924 Summer Olympics begins.
 May 10 – J. Edgar Hoover appointed head of FBI
 December 24 – Albania becomes a republic.

Births

January 

 January 6 – Kim Dae-jung, 8th President of South Korea (d. 2009)
 January 8 – Ron Moody, British actor (d. 2015)
 January 10 – Max Roach, American jazz percussionist, drummer, and composer (d. 2007)
 January 10 – Eduardo Chillida, Spanish Basque sculptor (d. 2002)
 January 14 – Katy Jurado, Mexican actress (d. 2002)
 January 27 – Rauf Denktaş, 1st President of Northern Cyprus (d. 2012)
 January 29 – Dorothy Malone, American actress (d. 2018)
 January 29 - Luigi Nono, Italian composer (d. 1990)
 January 30 – Lloyd Alexander, American writer (d. 2007)

February
February 

 February 6 – Billy Wright, English footballer (d. 1994)
 February 19 – Lee Marvin, American actor (d. 1987)
 February 20 – Gloria Vanderbilt, American businesswoman, fashion designer, socialite and writer (d. 2019)
 February 21 – Robert Mugabe, 2nd President of Zimbabwe (d. 2019)
 February 26 – Noboru Takeshita, 74th Prime Minister of Japan (d. 2000)

March 

 March 3 – Lys Assia, Swiss singer (d. 2018)
 March 3 – Tomiichi Murayama, 81st Prime Minister of Japan

April 

 April 3 – Marlon Brando, American actor (d. 2004)
 April 12 – Raymond Barre, former Prime Minister of France (d. 2007)
 April 13 – Stanley Donen, American film director and choreographer (d. 2019)
 April 23 – Rossana Rossanda, Italian journalist and politician (d. 2020)
 April 28 – Kenneth Kaunda, 1st President of Zambia (d. 2021)
 April 29 – Zizi Jeanmaire, French ballet dancer and singer (d. 2020)

May
May 

 May 1 – Terry Southern, American writer (d. 1995)
 May 16 – Dawda Jawara, 1st President of the Gambia (d. 2019)
 May 22 – Charles Aznavour, French singer, actor and composer (d. 2018)

June 

 June 3 – Torsten Wiesel, Swedish neuroscientist
 June 12 – George H. W. Bush, American politician, 41st President of the United States (d. 2018)
 June 15 – Ezer Weizman, President of Israel (d. 2005)
 June 20 – Audie Murphy, American soldier, actor, songwriter (d. 1971)
 June 20 – Chet Atkins, American guitarist and record producer (d. 2001)
 June 24 –Thelma Rogers, English actress (d. 2000)
 June 25 – Sidney Lumet, American director, producer and screenwriter (d. 2011)

July 

 July 3 – S. R. Nathan, 6th President of Singapore (d. 2016)
 July 4 – Eva Marie Saint, American actress
 July 19 – Pat Hingle, American actor (d. 2009)
 July 20 – Lola Albright, American actress and singer (d. 2017)

August
August 

 August 1 – Abdullah of Saudi Arabia, King of Saudi Arabia (d. 2015)
 August 1 – Georges Charpak, Ukrainian-born French physicist (d. 2010)
 August 2 – James Baldwin, American writer (d. 1987)
 August 2 – Carroll O'Connor, American actor (d. 2001)
 August 8 – Gene Deitch, American illustrator, animator and film director (d. 2020)
 August 13 – Yuri Orlov, Soviet physicist (d. 2020)
 August 24 – Ahmadou Ahidjo, 1st President of Cameroon (d. 1989)

September 

 September 2 – Daniel arap Moi, 2nd President of Kenya (d. 2020)
 September 9 – Jane Greer, American film and television actress (d. 2001)
 September 16 – Lauren Bacall, American actress (d. 2014)
 September 28 – Marcello Mastroianni, Italian actor (d. 1996)
 September 30 – Truman Capote, American writer (d. 1984)

October 

 October 1 – Jimmy Carter, American politician, 39th President of the United States
 October 19 – Lubomír Štrougal, Prime Minister of Czechoslovakia

November
November 

 November 1 – Süleyman Demirel, 9th President of Turkey (d. 2015)
 November 20 – Benoit Mandelbrot, French-American mathematician (d. 2010)
 November 30 – Shirley Chisholm, American politician (d. 2005)

December 

 December 2 – Alexander Haig, 59th United States Secretary of State (d. 2010)
 December 7 – Mário Soares, 17th President of Portugal (d. 2017)
 December 10 – Michael Manley, 4th Prime Minister of Jamaica (d. 1997)
 December 13 – Krishna Prasad Bhattarai, Prime Minister of Nepal (d. 2011)
 December 19 – Cicely Tyson, American actress (d. 2021)
 December 25
Atal Bihari Vajpayee, 10th Prime Minister of India (d. 2018)
Moktar Ould Daddah, 1st President of Mauritania (d. 2003)
Rod Serling, American television scriptwriter (d. 1975)
Deaths 
 January 21 – Vladimir Lenin, first communist leader of the USSR
 February 3 – Woodrow Wilson, 28th President of the United States (b. 1856)
 April 21 – Eleonora Duse, Italian actress
 June 3 – Franz Kafka, writer
 June 10 – Giacomo Matteotti, Italian politician
 3 August – Joseph Conrad, novelist
 November 29 – Giacomo Puccini, Italian grand opera composer

Nobel Prize 
 Physics – Karl Manne Georg Siegbahn
 Medicine – Willem Einthoven, (Dutch) invented the ECK
 Literature – Wladyslaw Stanislaw Reymont, polish writer
Hit songs 
 "Alabamy Bound" w. B. G. De Sylva & Bud Green m. Ray Henderson
 "All Alone" w.m. Irving Berlin
 "Amapola" w. Joseph M. Lacalle (Sp) Albert Gamse (Eng) m. Joseph M. Lacalle
 "At The End of The Road" w. Ballard MacDonald m. James F. Hanley
 "Bagdad" w. Jack Yellen m. Milton Ager
 "Big Bad Bill Is Sweet William Now" Ager, Yellen
 "Big Boy" m. Milton Ager
 "The Blues Have Got Me" Silver, Turk
 "California, Here I Come" w.m. Al Jolson, Buddy de Sylva and Joseph Meyer
 "Call Of The South" Berlin
 "Charley, My Boy" w.m. Gus Kahn & Ted Fio Rito
 "Copenhagen" w. Walter Melrose m. Charlie Davis
 "Cover Me Up With The Sunshine Of Virginia" w. Sam M. Lewis & Joe Young m. George W. Meyer
 "Deep In My Heart, Dear" w. Dorothy Donnelly m. Sigmund Romberg
 "Does The Spearmint Lose Its Flavour On The Bedpost Over Night" w. Billy Rose & Marty Bloom m. Ernest Breuer
 "Doo Wacka Doo" w. Clarence Gaskill & Will Donaldson m. George Horther
 "Doodle Doo Doo" w.m. Art Kassel & Mel Stitzel
"Drinking Song (Drink! Drink! Drink!)" w. Dorothy Donnelly m. Sigmund Romberg
 "The End Of The Road" w.m. Harry Lauder & William Dillon
 "Everybody Loves My Baby" w.m. Jack Palmer & Spencer Williams
 "Fascinating Rhythm" w. Ira Gershwin m. George Gershwin
 "Follow The Swallow" w. Billy Rose & Mort Dixon m. Ray Henderson
 "Golden Days" w. Dorothy Donnelly m. Sigmund Romberg
 "The Half Of It Dearie Blues" w. Ira Gershwin m. George Gershwin
 "Hard Hearted Hannah (The Vamp Of Savannah)" w.m. Milton Ager, Charles Bates, Bob Bigelow & Jack Yellen
 "He's The Hottest Man In Town" Owen Murphy, Jay Gorney
 "Honest And Truly" w. Leo Wood m. Fred Rose
 "How Come You Do Me Like You Do?" w.m. Gene Austin & Roy Bergere
 "I Want To Be Happy" w. Irving Caesar m. Vincent Youmans
 "I Wonder What's Become Of Sally" w. Jack Yellen m. Milton Ager
 "I'll See You In My Dreams" w. Gus Kahn m. Isham Jones
 "I'm A Little Blackbird Looking For A Bluebird" w. Grant Clarke & Roy Turk m. George W. Meyers & Arthur Johnson
"I'm Coming At Your Call" w. Dorothy Donnelly m. Sigmund Romberg
 "In Shadowland" w. Sam W. Lewis & Joe Young m. Ruth Brooks & Fred E. Ahlert
 "Indian Love Call" (first published as "The Call") w. Otto Harbach & Oscar Hammerstein II m. Rudolf Friml
 "It Had To Be You" w. Gus Kahn m. Isham Jones
 "Jealous" w. Tommy Malie & Dick Finch m. Jack Little
 "Jimtown Blues" w.m. Fred Rose
 "June Brought The Roses" w. Ralph Stanley m. John Openshaw
 "June Night" w. Cliff Friend m. Abel Baer
 "Just We Two" w. Dorothy Donnelly m. Sigmund Romberg
 "Keep Smiling At Trouble" w. Al Jolson & B. G. De Sylva m. Lewis E. Gensler
 "Lazy" w.m. Irving Berlin
 "Let Me Linger Longer In Your Arms" w. Cliff Friend m. Abel Baer
 "Little Jazz Bird" w. Ira Gershwin m. George Gershwin
 "Mama's Gone, Goodbye" w.m. A. J. Piron & Peter Bocage
 "The Man I Love" w. Ira Gershwin m. George Gershwin
 "Mandalay" w.m. Earl Burtnett, Abe Lyman & Gus Arnheim
 "Mandy Make Up Your Mind" w. Grant Clarke & Roy Turk m. George W. Meyer
"Memory Lane" w. B. G. De Sylva m. Larry Spier & Con Conrad
 "The Mounties" w. Otto Harbach & Oscar Hammerstein II m. Rudolf Friml
 "My Best Girl" w.m. Walter Donaldson
 "My Dream Girl, I Loved You Long Ago" w. Rida Johnson Young m. Victor Herbert
 "My Time Is Your Time" w. Eric Little m. Leo Dance
 "A New Kind Of Man With A New Kind Of Love For Me" w.m. Sidney Clare & Flatow
 "Nobody's Sweetheart Now" w.m. Elmer Schoebel, Ernie Erdman, Gus Kahn & Billy Meyers
 "O, Katharina" w. L. Wolfe Gilbert m. Richard Fall
 "Oh Lady Be Good" w. Ira Gershwin m. George Gershwin
 "Oh! Mabel" Gus Kahn, Ted Fio Rito
 "Oh! Miss Hannah" w. Thekla Hollingsworth m. Jessie L. Deppen
 "The One I Love Belongs To Somebody Else" w. Gus Kahn m. Isham Jones
 "Parisian Pierrot" w.m. Noël Coward
 "Prince Of Wails" m. Elmer Schoebel
 "The Prisoner's Song" w.m. Guy Massey
 "Red Hot Mama" w.m. Gilbert Wells, Bud Cooper & Fred Rose
 "Rhapsody In Blue" m. George Gershwin
 "Riverboat Shuffle" m. Hoagy Carmichael & Irving Mills
"Rose Marie" w. Otto Harbach & Oscar Hammerstein II m. Rudolf Friml
 "See See Rider" w.m. Ma Rainey
 "Serenade from The Student Prince In Heidelberg" w. Dorothy Donnelly m. Sigmund Romberg
 "Shanghai Shuffle" w.m. Larry Conley & Gene Rodemich
 "Shine" w. Cecil Mack & Lew Brown m. Ford T. Dabney
 "So Am I" w. Ira Gershwin m. George Gershwin
 "Somebody Loves Me" w. Ballard MacDonald & B. G. De Sylva m. George Gershwin
 "South" m. Bennie Moten & Thamon Hayes
 "Spain" w. Gus Kahn m. Isham Jones
 "Stack O'Lee Blues" w.m. by Ray Lopez & Lew Colwell
 "Sweet Little You" w.m. Irving Bibo
 "Tea For Two" w. Irving Caesar m. Vincent Youmans
 "Tell Her In The Springtime" w.m. Irving Berlin
 "There's Life In The Old Girl Yet" w.m. Noël Coward
 "Totem Tom-Tom" w. Oscar Hammerstein II & Otto Harbach m. Rudolf Friml
 "Two Little Babes In The Wood" w.m. Cole Porter
 "Wait'll You See My Gal" Sullivan, Wilber
 "What'll I Do?" w.m. Irving Berlin
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 

 January 15 – Martin Luther King Jr., American civil rights activist (d. 1968)
 January 31 – Jean Simmons, British actress (d. 2010)
 January 31 – Rudolf Mössbauer, German physicist (d. 2011)

February 
 February 21 - Chespirito, Mexican actor, director and screenwriter (d. 2014)

March

April 

 April 1 – Milan Kundera, Czech writer
 April 6 – André Previn, German-born American musician (d. 2019)
 April 22 – Michael Atiyah, British mathematician (b. 2019)

May
May 

 May 4 – Audrey Hepburn, Belgian-born British actress (d. 1993)
 May 25 – Beverly Sills, American soprano (d. 2007)

June 

 June 12 – Anne Frank, German-Dutch diarist who died in the Holocaust (d. 1945)

July 

 July 28 – Jacqueline Kennedy Onassis, First Lady of the United States (d. 1994)

August 

 August 2 – K.M. Peyton, English writer
 August 24 – Yasser Arafat, leader of the Palestinian Authority (d. 2004)

September 

 September 28 – Lata Mangeshkar, Indian playback singer, composer and politician (d. 2022)

October 

 October 22 – Lev Yashin, Russian footballer (d. 1990)

November 

 November 12 – Grace Kelly, American actress and Princess of Monaco (d. 1982)
 November 14 – McLean Stevenson, American actor (d. 1996)

December 

 December 13 - Christopher Plummer, Canadian actor (d. 2021)

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 a decade in the Anno Domini and Common Era in the Gregorian calendar. It began on January 1, 1920 and ended on December 31, 1929. It is distinct from the decade known as the 193rd decade which began on January 1, 1921 and ended on December 31, 1930. This decade was known as the Roaring Twenties or the Jazz Age.

The most important events 

 1920 – Prohibition began in the United States. Criminal activity associated with alcohol.
 1922 – The Soviet Union was founded as a dictatorship.
 1922 – Howard Carter discovered the tomb of the Egyptian King Tutankhamun.
 1922 – Southern Ireland gained independence from the United Kingdom.
 1929 – Black Tuesday, which lead to the Great Depression. 
Role of the depression in stimulating the career of Adolf Hitler in Germany

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), later replaced by Adolf Hitler.
 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)
 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)
Outer space, commonly shortened to space, is the near-vacuum between celestial bodies. It is where all of the planets, stars, galaxies and other objects are found. It is the expanse that exists beyond Earth and its atmosphere.

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: it 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 in 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 by direct travel is difficult, and more or less impossible beyond the near planets. Space contains no air beyond the Earth. It takes three days of travelling to reach the Moon and, depending on speed, it would take a very long time to reach the closest star (Proxima Centauri). Manned spacecraft are designed to keep air inside them and to protect astronauts from extreme temperatures. It is widely thought that people will not be able to travel to nearby stars. A serious problem for humans is the great times taken for interstellar flights, and the danger of radiation to human life.

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 distant.

Related pages 
 Space-time
 Black hole
 Galaxy
 Universe
 Astronomy

References 

Astrophysics
Space
A natural satellite in astronomy is a smaller body which moves around a larger body. The smaller body is held in orbit by gravitation. The term is used for moons which go around planets, and it is also used for small galaxies which orbit larger galaxies.

Bodies which orbit planets are called moons. They vary in size. The Earth has only one moon. Some other planets have many moons, and some have none. When people write just "the moon", they are usually talking about the moon of the Earth. Earth's moon is written with a capital letter, Moon. The Latin word for the moon is luna, which is why the adjective used to talk about the moon is "lunar". For example, lunar eclipse.

Anything that goes around a planet is called a satellite. Moons are natural satellites. People also use rockets to send machines into orbit around the Earth. These machines are called artificial (man-made) satellites.

Earth's moon
Earth's moon

Moons do not make their own light. We can see the Earth's moon because it acts like a mirror, and reflects the light of the Sun.  The same half of the moon faces toward Earth at all times, no matter where it moves. This effect is called tidal locking. But different parts of the moon are lit up by the Sun, so it looks different at different times of the month. This change as seen from Earth is called the phases of the moon, or lunar phases.

A moon's cycle is the time the moon takes to change from looking very bright and round to looking very small and thin, and then back to bright and round again. In the case of the Earth's moon, this is about four weeks. It does this about 13 times in one year. The moon's cycle is about 28 days, a bit shorter than a calendar month.

The Apollo 11 mission helped Neil Armstrong and Buzz Aldrin become the first people to walk on the Moon. They did this on July 20, 1969.
Orbits
The orbit of a moon or other satellite is affected by two forces: gravity, and the centripetal force.
For example, the Earth's moon is kept in orbit by the gravitational pull from the Earth. This is also the way the Earth is attracted to the Sun, and stays in its orbit. The orbit of the Earth's moon actually causes the tides and waves on Earth.

Moons of moons

No moons that belong to moons have been found. In most cases, the tidal effects of the main body would make such a system unstable.

However, calculations completed after the recent finding  of a possible ring system around Saturn's moon Rhea show that Rhean orbits would be stable. The rings are thought to be narrow, something that is known with shepherd moons.

Asteroid moons
The finding of 243 Ida's moon Dactyl in the early 1990s was the proof that some asteroids have moons; indeed, 87 Sylvia has two. Some, such as 90 Antiope, are double asteroids with two same-sized parts.
Moons of the Solar System
The biggest moons in the Solar System (those bigger than about 3000 km across) are Earth's moon, Jupiter's Galilean moons (Io, Europa, Ganymede, and Callisto), Saturn's moon Titan, and Neptune's captured moon Triton.

The following is a table grouping the moons of the solar system by diameter. The column on the right has some notable planets, dwarf planets, asteroids, and Trans-Neptunian Objects for comparing.  It is normal for moons to be named after people from mythology.

Planets that have moons
Planets in our Solar System that have moon(s):
 Earth, 1 moon
 Mars, 2 moons
 Jupiter, 92 moons
 Saturn, 83 moons
 Uranus, 27 moons
 Neptune, 14 moons

Dwarf planets that have moons
 Orcus, 1 moon
 Pluto, 5 moons
 Haumea, 2 moons
 Quaoar, 1 moon
 Makemake, 1 moon
 Gonggong, 1 moon
 Eris, 1 moon

Planets not known to have moons
Planets in our Solar System that do not have moons:
 Mercury
 Venus
 Ceres
 Sedna
Galaxies 
Galaxies are found in groups called galaxy clusters which are also held together by gravitation. Our own Milky Way is the second largest galaxy in our Local Group (the largest is Andromeda). Many smaller galaxies and star clusters are also held in the Local Group, outside the two main galaxies. They are all in orbits round one of the centres of gravity. That means most of them move round either Andromeda or the Milky Way. so it seems natural for astronomers to use the term 'satellite' for these as well.

Our Local Group is itself part of an even larger group, the Virgo Supercluster. There are other, even larger, groups of galaxies: see the Great Wall for an example.

References
Gravity, or gravitation is one of the fundamental forces of the universe. It is an attraction, or pull, between any two objects with mass. We discuss it in three parts:

 Everyday sense: the force which causes objects to fall to the ground
 Newton's laws: how gravity keeps the Solar System and most major astronomical objects together
 Einstein's theory of general relativity: the role of gravity in the universe

Some physicists think gravity is caused by gravitons, but they are still unsure.

Everyday gravity
Everyday gravity

Weight vs mass 
In everyday talk, we say things fall because the Earth's gravity pulls on them. We talk as if our weight was a "given". Actually, weight changes when the pull of gravity changes. The Moon is much smaller and the pull of gravity on the Moon is about 1/6th that of Earth. So any object on the Moon weighs 1/6th of its weight on Earth. What does not change is the amount of matter in an object. That is called conservation of mass. On Earth, mass and weight are the same for most purposes, though a sensitive gravimeter can detect the difference. The difference can be very different on other extraterrestrial objects such as the moon, and other planets.

From this we learn two things.
 The <u/l>weight</u/l> of an object is variable; its <u/l>mass</u/l> is constant.
 The pull of gravity varies according to the mass of an object. The Earth pulls more strongly than the Moon. A person also exerts a gravitational pull, but it is so tiny it can be ignored for all practical purposes.
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.

Gravity vs gravitation 
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.

Gravitational theory

Galileo 
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.

Kepler 
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.
Newton 
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.

According to Newton's law of universal gravitation, gravity is a force between any two objects with mass. Three numbers affect its strength: the mass of each object, and the distance between them. These two objects will both pull on each other with the same force. However, a force has a greater effect on objects with less mass. The force between the Sun and the Earth makes the Earth orbit the Sun, but it only moves the Sun a small amount.
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.

Dynamic equilibrium 
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.

Weightlessness 
In free fall an object's motion balances out the pull of gravity on it. This includes being in orbit.

General relativity 
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.

Time dilation and frequency shift 

Gravity influences the passage of time. Light sent down into a gravity well 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.

Light deflection and gravitational time delay
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
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.

Related pages 
 Escape velocity
 General relativity
 Newton's laws of motion

References

Other websites 
 Gravity Probe B experiment The Einstein website from Stanford University
 Gravity for kids  (useful Q & A)
 How stuff works: How does gravity work?
 NOVA - PBS NOVA. Galileo's experiments
 Gravity  - Kepler and Newton: excellent summary
 Newton's Law of Universal Gravitation   on Project PHYSNET
 PhysOrg.com. Alternative theory of gravity may explain large structure formation—without dark matter

Force
Basic physics ideas
Centripetal acceleration is a force that acts on a body that revolves around a centre of a circular path. This force keeps the body in circular motion.  Newton's first law is that a moving object will continue in its motion in a straight path unless acted on by an external force.  

When you hold a rope with an object attached to it, and spin it in a circular motion around the hand of the person holding the rope, the rope becomes tight and keeps the body from flying away. This force acts towards the center of motion, not away from it. 

An object changes direction, but may maintain a constant speed, if acted upon by a centripetal acceleration.  In such a case, we know from its  angular frequency that . From Newton's second law we know that force equals mass times acceleration. Here acceleration is the negative of the radius coming from the centre of the circular motion.
In this formula, think that the centripetal force and the centripetal momentum are the same thing because they are both measured in Newtons. 

If, however, the angular frequency is not constant (as might be the case in a roller-coaster ride) then  does vary with respect to time. Here 

 

Thus 

 

as  and  , which we know from the angular frequency.

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
 Ratification
 Vienna Convention on the Law of Treaties
Luxembourg (official name is the Grand Duchy of Luxembourg (, , ) is a landlocked country in Western Europe. It is a small country by land area. 

In 2023, its population was 660,809, making it one of Europe's most densely populated countries. 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. The main language is Luxembourgish.
History 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.