Aarushhh/wikipedia-simple-splitted huggingface dataset:
Poyo is a popular Sierra Leonean drink. It is a sweet, lightly fermented palm wine. Poyo bars are areas of lively informal talk about politics, football, entertainment and other issues.

Sports
Football is by far the most popular sport in Sierra Leone. Children, youth and adult are often seen playing street football across Sierra Leone.

The Sierra Leone national football team, popularly known as the Leone Stars, represents the country in international competitions. It has never qualified for the FIFA World Cup. They were in the 1994 and 1996 African Cup of Nations. Many of the national team footballers are celebrities across Sierra Leone. They are often well known by most of the country's general population. Some well known Sierra Leonean international footballers include Mohamed Kallon, Mohamed Bangura, Rodney Strasser, Ibrahim Teteh Bangura, Alhassan Bangura, Sheriff Suma, Mohamed Kamara, Umaru Bangura and Kei Kamara.
Related pages
 List of rivers of Sierra Leone
 Sierra Leone at the Olympics
 Sierra Leone national football team

References

Other websites 

 SierraLeone.com

 
English-speaking countries
Least developed countries
Members of the Organisation of Islamic Cooperation
Commonwealth member states
A door is a hard, flat object a person can open and close so that person can go into a room or other place. It is found in houses and other buildings. Doors are also found in cars and cages.

The reasons for a door are:
 for people, animals, and objects to go through; some doors are for emergencies only (emergency exit)
 to keep cold or hot air outside (or inside, such as the door on a refrigerator)
 so that people cannot see or hear what happens on the other side (privacy and stopping noise)
 so that people do not fall out of the car or other vehicle
 so a person can decide who to let in—many doors have a lock

Types of doors 

A revolving door is a group of doors that turn in a circle as a person pushes one. The person can go through, but wind and rain cannot get in.

A blind door is a fake door that is really part of the wall. People use them to make a room look nice.

An up-and-over door is often used in garages. Instead of hinges, it rolls up on rails so that it stays above the opening.
A fire door is a door that does not let fire go through. They are usually made of heavy steel.

A doggie door is a small door for dogs or other small pets. They are usually on the bottom of people-sized doors.
 

Basic English 850 words
Doors
The 1540s was a decade that started on 1 January 1540 and ended on 31 December 1549.

Events 
 Hernando de Soto is the first European to see the Mississippi River. 
 Ivan IV of Muscovy becomes the first Tsar of Russia. 
 Edward VI succeeds his father Henry VIII as King of England. 
 Wars between Protestants and Catholics in Europe.
 Japan opens up to Europeans.

Births 
 El Greco, Greek-born artist 
 Mary, Queen of Scots
 Miguel de Cervantes, Spanish writer

Deaths 
 Martin Luther, reformer
 Hernando de Soto, Spanish explorer
 Henry VIII, King of England
 Hernán Cortés, Spanish explorer
 Juan Diego Cuauhtlatoatzin, Mexican Catholic saint
Boeing began designing the 737 in 1965. The very first 737-100 flew in 1967. It was first used by an airline in February 1968.  The 737-200 started being used in April 1968. The -200 was basically just a longer version of the 737-100. In the 1980s Boeing made the -300, -400, and -500 models. Boeing called these models the Boeing 737 Classic series. The 737 Classics could carry more passengers, and they had new engines: CFM56 turbofans. The 737 Classic planes also had some improvements made to the wings. In the 1990s, Boeing brought out the 737 Next Generation. The 737 Next Generation planes also had redesigned wings, a better cockpit and a new cabin. The 737 Next Generation is made up of the -600, -700, -800, and -900ER models. These models go from  to  in length.
The 737 is the best-selling jet airliner in history. Boeing has never stopped making 737s since 1967. 7,283 aircraft have been delivered, and the 737 still has 2,759 orders that have not been delivered yet (). Boeing 737s are built at the Boeing Renton Factory in Renton, Washington. The 737's main rival is the Airbus A320 family. On average, 1,250 737s are in the air at any time and two land or leave somewhere every five seconds.

Development

Background
Background

Boeing was looking at designs for aircraft which flew short distances. Boeing wanted to make another aircraft to replace the 727 on short flights. It began designing the 737 on May 11, 1964. Boeing did a lot of research and found that airlines wanted an airliner which could hold 50 to 60 passengers. This airliner would also be able to fly routes  long. Lufthansa was the first airline to order a Boeing 737 on February 19, 1965. They ordered 21 aircraft, worth $67 million (1965, $190.28 million in 2008). After Boeing spoke to Lufthansa in winter 1964, they made the 737 bigger so that it could hold 100 passengers.

On April 5, 1965, Boeing announced that United Airlines had ordered 40 737s. United wanted a plane which was a bit bigger than the 737-100. Boeing made a different type of 737 for United, which was longer. This other plane was called the 737-200. Boeing changed the name of the original 737 to the 737-100.

Making and testing of the 737
The first 737s were made near Boeing Field (now officially called King County International Airport) because the factory in Renton was too busy building the 707 and 727. After 271 aircraft were made at Boeing Field, Boeing moved the 737s to Renton. This was in 1970.

The first Boeing 737-100 prototype was ready in 1966. It made its first flight on April 9, 1967. On December 15, 1967 the Federal Aviation Administration said that the -100 was allowed to fly with passengers. They gave it the Type Certificate A16WE. Lufthansa got its first 737 on December 28, 1967. On February 10, 1968, Lufthansa became the first non-American airline to fly a new Boeing aircraft. It was the only large airline which bought the 737-100. Only 30 -100s were ever made.
The 737-200 first flew on August 8, 1967. The FAA allowed it to fly with passengers on December 21, 1967. The first flight it made for United Airlines was on April 28, 1968. It flew from Chicago to Grand Rapids, Michigan. Airlines liked the 737-200 much more than the 737-100.

737-200 Advanced
A "thrust reverser" is a part of the engine of a plane. It changes the flow of air through the engine so that it ends up trying to push the plane backwards instead of forwards. The first thrust reversers on the 737 were not very good. They were said to lift the aircraft off the runway when they were used. This meant that the wheels were not being pushed down onto the ground very much, which made the brakes less useful. In 1968, Boeing improved the thrust reverser. This improvement was put onto all aircraft after March 1969. Aircraft which were made before the improvement could have it installed. Boeing also improved the flaps. This improvement allowed the flaps to be used more during takeoffs and landing. All these changes meant that the 737 could hold more cargo and fly further. In May 1971, after the 135th aircraft was built, all of these improvements, as well as better engines and more fuel, were put into the 737-200. This gave it 15% more payload and range than the first 737-200s
. This type of 737-200 became known as the 737-200 Advanced.
In 1970, Boeing only got 37 orders for 737s. Since Boeing were running out of money, they thought about stopping making 737s and selling the design to Japanese companies. Boeing cancelled the Boeing Supersonic Transport and started making less Boeing 747s. By doing this, Boeing kept enough money to keep the 737 project going.

In 1988, Boeing stopped making 737-200s. 1,114 aircraft were made and the last one was delivered to Xiamen Airlines on August 8, 1988.

737 Classic

In 1979, Boeing started working on a large improvement for the 737. Boeing wanted to allow the aircraft to hold more passengers and travel further. It also wanted to make improvements to make the aircraft more modern. However, it also wanted to keep it similar to the older 737s. In 1980, information on this new type of 737 (called the 737-300) was given at the Farnborough Airshow.
The CFM56-3B-1 engine was chosen to be the engine for this new 737 type. This engine burned much less fuel and was much less noisy. However, it was also difficult to fit these engines to the aircraft. This was because the 737's wings were not very high above the ground, and the CFM56 had a bigger diameter than the original engines. Boeing and CFM solved the problem by putting the engine slightly ahead of the wing, instead of right under it. They also moved some parts of the engine, which would normally go on the bottom, to the sides. This made the engine look a bit like a hamster pouch,<ref name="hamster">Brady, Chris. "History & Development of the Boeing 737 - Classics." The Boeing 737 Information Site, 1999. Retrieved: September 5, 2010.</ref> because the engine is not shaped like a circle.
The plane could now carry 149 passengers, because the fuselage of the plane was made bigger. Many changes were made to the wings. The tip of the wing was made longer by . The wingspan was also made bigger. The flaps on the wings were changed. The flight deck (cockpit) was improved with electronic displays. However, airlines could choose not to have these in their planes. The main cabin (where the passengers sit) was also made better. It looked similar to the cabin of a Boeing 757. The prototype of the 737-300 first flew on 24 February 1984. Its pilot was Jim McRoberts.

In June 1986, Boeing said that it was working on the 737-400. The 737-400 made the fuselage even bigger (by ). This change meant that the -400 could carry 170 passengers. The 737-400's first flight was on February 19, 1988. The first airline to use it was Piedmont Airlines.
Boeing made a 737-500 because its customers wanted one. It was a replacement of the 737-200. The -500 is  longer than the 737-200. Up to 132 passengers can travel on the 737-500. Cockpits with electronic displays could be installed on the -500, but airlines could choose the use the older cockpit if they wanted.

The 737-500 was first ordered by Southwest Airlines in 1987. Southwest Airlines ordered 20 aircraft. The 737-500 flew for the first time on June 30, 1989. On February 28, 1990, Southwest Airlines got their first delivery.

After the Boeing 737 Next Generation planes were brought into service, Boeing named the 737-300/-400/-500s the 737 Classic series.

737 Next Generation
The wing was changed again. Many different changes were made. An example of one is a bigger wingspan (made bigger by ). Since the wings were made bigger, 30% more fuel could fit in the plane. CFM56-7B engines were used, which were newer, quieter and burned less fuel. The improvements to the wing, engine and fuel mean that the 737NG can travel 900 nautical miles further. This means it can travel over  in total, which means that the 737NG can travel between different continents. Winglets can be added to most 737NG models. The flight deck was given modern electronics (called avionics). The main cabin was also improved.
The first NG to be built was a 737-700. It was finished on December 8, 1995. This aircraft was 2,843rd 737 built. It first flew on February 9, 1997. The prototype 737-800 was finished on June 30, 1997 and first flew on July 31, 1997. The smallest of the 737NGs, the -600, is the same size as the -500. It was the last NG to be launched (it was launched in December 1997). It first flew on January 22, 1998. The FAA certified it on August 18, 1998.Shaw 1999, pp. 14–15. A
Boeing delivered the 5,000th 737 to Southwest Airlines on February 13, 2006. The 6,000th 737 was delivered to Norwegian Air Shuttle in April 2009. The Airbus A320 family has sold more planes than the 737NG over the past ten years."Airbus 320 Aircraft History, Information, Pictures and Facts." aviationexplorer.com.. Retrieved: September 3, 2010. However, this total includes sales for the A321 and A318. The A321 has been the rival of Boeing's 757 and the A318 has been the rival of the 717. The Next Generation series helped make sure the 737 stayed the bestsellingRobertson, David. "Boeing gets ready for all-new 737." The Times, March 12, 2007. Retrieved: April 22, 2010.  airliner family since it first flew."Boeing airliner deliveries rise 11%." Chicago Tribune, January 4, 2008. Retrieved: April 22, 2010.Rahn, Kim. "B737: Best-Selling Aircraft in the World." Korea Times. Retrieved: April 22, 2010.Jiang, Steven. "Jetset: 'Tianjin Takes Off'." The Beijinger. Retrieved: April 22, 2010
. Quote: A320, the workhorse of many airlines and the second best-selling jetliner family of all time (after Boeing’s venerable B737).
737 MAX

Since 2006, Boeing has been thinking about replacing the 737 with a completely new design. This was named the Boeing Y1 by people who worked at Boeing. This re-design would be launched after the Boeing 787 Dreamliner. Boeing did not decide on whether or not to go ahead with this. They said they would decide in 2011.

On July 20, 2011, Boeing said that they were working on a new 737 version, which would have the CFM International LEAP engine. American Airlines said they would order 100 of these aircraft.  On August 30, 2011, Boeing said that a new 737 would definitely be launched. It was called the 737 MAX. It would also definitely have CFM International LEAP-1B engines."Boeing officially launches re-engined 737." flightglobal.com, August 30, 2011.

The MAX 8 first carried paying passengers in May, 2017. In 2019 two MAX 8 aircraft crashed, killing all aboard and causing aviation authorities to ban commercial operation of the 737 MAX until they are fixed. 

Design
Design

The 737's main landing gear (wheels) go into holes at the bottom of the plane. The wheels do not have a door to close over them. The tires can be seen easily when a 737 is taking off or is flying low-down.
737s do not have fuel dump systems. A fuel dump system is a system which gets rid of any unneeded fuel if the aircraft needs to make an emergency landing while it still has a lot of fuel on board. This is useful because aircraft can only land safely at a certain weight or below. Getting rid of unneeded fuel helps to get to a safe weight for the plane to land. The first 737s were too small to need these systems. Adding a fuel dump system to the bigger 737s would make the plane much heavier. Instead, if the emergency is not very serious, 737s fly around in circles to get rid of fuel. If the emergency is serious, the 737 just needs to land at an unsafe weight. If it has to land at an unsafe weight, the plane needs to be looked at for damage. If there is no damage, the plane can be put back into service.Cheung, Humphrey. "Troubled American Airlines jet lands safely at LAX."  tgdaily.com, 2 September 2008. Retrieved: August 20, 2011.

Engines
Engines

Engines on the 737 Classic series (300, 400, 500) and Next Generation series (600, 700, 800, 900) are not shaped like a circle like most planes. The 737 Classics had CFM56 turbofan engines. These burned much less fuel and made much less noise than the Pratt & Whitney JT8D engines which were used on the -100 and -200. However, because the 737's wings and fuselage are not very high above the ground, it was impossible to get the engines to fit on the wings. Boeing and CFM fixed this problem by putting the engines slightly ahead of the wings instead of putting them right underneath. They also moved some parts of the engines which would normally go at the bottom to the sides. This is what makes the engines non-circular.
The gearbox of the engine was moved from the bottom of the engine to the side. The gearbox makes the engine look a bit like a triangle. Since the engine is close to the ground, it is possible that they can be damaged by things lying on the ground. The CFM56-7 engine on the 737 Next Generation burns even less fuel than the engines on the 737 Classics.  The Boeing 737 MAX aircraft will have CFM International LEAP-1B engines. These engines are supposed to burn 10-12% less fuel than the CFM56-7B engines on the 737 Next Generation family.

Flight systems

The 737's controls are very safe. If the hydraulics or both engines fail, servo tabs will be automatically used. Servo tabs are small hinges which move important parts of an aircraft. The tabs are controlled by the yoke (the thing used to steer the plane). For the 737 Next Generation, a new cockpit with LCD displays was made. These cockpits also have modern avionics (autopilot etc.).
Most 737 cockpits have "eyebrow windows". These are smaller windows which are above the main windows. There are two on each side. Eyebrow windows were used on the Boeing 707. They helped the pilot see better when the plane was turning. However, because autopilot, advanced radar etc. exist, they are no longer needed. They were removed from the 737 cockpit in 2004. However, 737s used by the military still have them installed. If the customer likes, Boeing will install eyebrow windows for them.

Upgrades

Winglets can be fitted to 737s which do not have them already installed. They can also be added when the aircraft is built. The winglets are about  tall. They are fitted at the end of the wing and help the engines to burn less fuel because they reduce drag. They also help make less noise on takeoff. Winglets can help a plane burn up to 5% less fuel.
the 737 has carbon brakes. These are made by Messier-Bugatti. These new brakes have been allowed by the Federal Aviation Administration. They weigh  less than the steel brakes normally fitted to the 737 Next Generation family. If 700 pounds of weight is taken off a Boeing 737-800, it burns 0.5% less fuel.
Main cabin
How the cabin looks was changed in each different type of 737 (Classic and Next Generation). The cabin design of the 737 Original was changed 737 Classic using designs from the 757. Designs from the Boeing 777 were used to design the cabin for the Next Generation 737. The newest cabin design is called the Sky Interior. It has curved walls. It also has redesigned windows. The Sky Interior has more headroom and LED mood lighting."Check Out Boeing's Swanky New High-Tech Interior." businessinsider.com. Retrieved: November 1, 2011. Overhead bins which move have been installed. These bins are similar to the bins on a 777 and Boeing 787 Dreamliner. They have more space for luggage than the other designs. The Sky Interior is also designed to make the cabin less noisy by 2–4 dB. The first 737 with the Sky Interior was delivered to Flydubai in 2010. Malaysia Airlines, TUIFly and Continental Airlines have also ordered 737s with the Sky Interior.
Types of 737s
The 737 are split into three "generations". These are Original, Classic and Next Generation. The "Original" models are the 737-100, 737-200/-200 Advanced. The "Classic" models are the 737-300, 737-400 and 737-500. The "Next Generation" models are the 737-600, 737-700/-700ER, 737-800, and 737-900/-900ER.

The fourth generation of 737 is called the 737 MAX. It is still being worked on, but when it is finished, it will be made up of the 737-MAX-7, 737-MAX-8 and 737-MAX-9. The MAX-7 will replace the 737-700, the MAX-8 will replace the 737-800 and the MAX-9 will replace the 737-900 and 739-900ER.

737 Original
737-100

The very first 737 model was the 737-100. It was first ordered by Lufthansa in 1965. The -100 was finished on January 17, 1967. It entered service in 1968. The aircraft is the smallest type of 737. Only 30 737-100s were ordered and delivered. No 737-100s are still being used by airlines. The 737-100 prototype is in the Museum of Flight in Seattle.

737-200
737-200

The 737-200 is a 737-100 with a larger fuselage. It was created because of an order from United Airlines in 1965. The -200 was finished on June 29, 1967. It entered service in 1968. The 737-200 Advanced is an improved version of the -200. Its first user was All Nippon Airways. It began using the -200 Advanced on May 20, 1971. The -200 Advanced has many improvements. For example, more powerful engines and more fuel. The 737-200 Advanced can also fly further than the 737-200. The last delivery of a 737-200 aircraft was in August 1988 to Xiamen Airlines. This was the 1,095th 737-200 built."About the 737 Family." The Boeing Company. Retrieved: December 20, 2007. Many 737-200s are still used by airlines.

After 40 years the last 737-200 aircraft in the United States were retired on March 31, 2008. This happened with the last flights of Aloha Airlines.

737 Classic
737 Classic

The Boeing 737 Classic is the name of the 737-300/-400/-500. However, they were only called the 737 Classics after the 737 Next Generation (737-600/700/800/900) aircraft were made. Until then, the 737 Classics were called the 'new generation' of the 737. The 737 Classics were made from 1984 to 2000. 1,988 aircraft were delivered in that time. As of January 1, 2001, 1,945 are in service.

737-300
The 737-300 was brought into service in 1981. It was used by both US Airways and Southwest Airlines. The 737-300 is the first model of the 737 Classic series. The -300 can usually hold 128 passengers. The 737-300 series was made until 1999. The last -300 was delivered to Air New Zealand on 17 December 1999. This was the 1,113th 737-300 made.
737-400
The 737-400 brought into service in 1985. It was just a longer version of the 737-300. Piedmont Airlines was the launch customer. They ordered 25 aircraft in 1986. The first 737-400s were brought into service in 1988 with Piedmont. The last -400 was delivered to CSA Czech Airlines. This was the 486th -400 built.

The 737-400F was a 737-400 changed into a cargo plane. The -400F was not delivered by Boeing. They were changed into cargo planes by the airlines that owned them. Alaska Airlines was the first airline to change a -400 to a -400F. It could carry 10 pallets of cargo.

737-500

The 737-500 was finished 1987. It was brought into service with Southwest Airlines in 1990. The 737-500 is around the same length of the 737-200. It was a modern, complete replacement of the 737-200. The last 737-500 was delivered to All Nippon Airways on July 26, 1999. This was the 389th built.

737 Next Generation
In the 1990s, Boeing realized that the Airbus A320 family was a serious threat. Boeing could lose customers because of it. In November 1991, Boeing began the Next Generation program. The Next Generation aircraft would replace the 737 Classics. The 737-600, 737-700 and 737-800 planes were planned.

737-600

The 737-600 replaced the 737-500. It was also supposed to replace the McDonnell Douglas DC-9. The 737-600 was finished in 1995. The first aircraft was delivered to Scandinavian Airlines on September 18, 1998. The 737-600 is the only Boeing 737 still being made that cannot be fitted with winglets.

The 737-600's rivals are the Airbus A318, Embraer 195 and Sukhoi Superjet 100. The Bombardier CSeries will also be a rival. 69 -600s have been delivered. There have been no orders that have not been delivered (as of 2010).

737-700
737-700

The 737-700 was added to the Next Generation planes when Southwest Airlines ordered one in November 1991. The -700 was based on the 737-300. It was brought into service in 1998. It replaced the 737-300. Its main rival is the A319. 126 people can fit into the 737-700 if there are two classes (first class and economy). However, 149 can fit in if the aircraft only has an economy class. Boeing launched the 737-700ER on January 30, 2006. "ER" stands for "extra range". This means that the plane can fly further than a normal 737-700. All Nippon Airways was the launch customer for the -700ER. It has the body of a 737-700, but the wings and landing gear of a 737-800. It can fly for 5,510 nautical miles (10,205 kilometers). 126 passengers can fit onto the plane.

In July 2008, Delta Air Lines got the first -700 that had Messier-Bugatti's carbon brakes.

737-800
737-800

The 737-800 is a longer version of the 737-700. It replaces the 737-400. The -800 was finished in 1994. It entered service with Hapag-Lloyd Flug (now TUIfly) in 1998. 162 passengers can fit into a 737-800 if it has two classes. Up to 189 can fit into a 737-800 if it only has one class. Its main rival is the A320.

737-900

The 737-900 is the longest 737. Alaska Airlines was the launch customer for the 737-900 when it was launched in 1997. It got its first aircraft on May 15, 2001.

The 737-900ER is the newest and biggest Boeing 737. It was made so that it could replace the 757-200. It was also made to be a rival to the Airbus A321. 180 passengers can fly on a 737-900ER with two classes. 215 passengers can fly if the plane only has one class. The -900ER can carry more fuel and has winglets. It can fly for around 3200 nm. The 737-900 is no longer made; Boeing only makes the 737-900ER now.

737 MAX
737 MAX

In 2011, Boeing said that it was working on the 737 MAX program. Boeing will make three types of 737 MAX. These are the MAX-7, MAX-8 and the MAX-9. The MAX-7 will replace the 737-700, the MAX-8 will replace the 737-800 and the MAX-9 will replace the 737-900ER. The 737 MAX will have CFM International LEAP-1B engines. The wheel in the nose of the plane has been made longer. Deliveries are supposed to start in 2017. Southwest Airlines became the launch customer on December 13, 2011. Lion Air and others have made orders for 737 MAX planes.

Companies which use the 737

The 737 is used by more than 500 airlines. 737s fly to 1,200 places in 190 countries. Over 10,000 737s have been ordered by airlines. 7,283 have been delivered. Over 4,500 are still being used by airlines. On average, there are always 1,250 737s flying. On average, a 737 takes off or lands every five seconds. 25% of the world's jet airliners are Boeing 737s.

Airlines
As of July 2010, 383 Boeing 737-200s are still being used by airlines.
Military
Many countries use the 737 as a military plane. Some countries with 737s are:

Orders and deliveries
Total

Over 7,400 Boeing 737s have been built and delivered. This is correct as of December 31, 2012.

By type
, over 10,400 Boeing 737s have been ordered. 3,020 planes still need to be delivered. This is a list of how many planes have been built for each type of 737.

This information is from Boeing.com.

 Accidents 
As of April 2012, the 737 has been in 315 incidents. 159 of these have been "hull loss accidents". A hull loss accident is when the plane is damaged so much it can not be used anymore, or if the plane was completely destroyed. 4,236 people have died because of these crashes. The 737 has also been in 106 hijackings. 324 people have died in hijackings.

Features

This information comes from: Boeing 737 specifications, 737 Airport Planning Report, b737.org.uk  site.

 Related pages 

 References 
Notes

References
References

 Anderson, David F. and Scott Eberhardt. Understanding Flight. Chicago: McGraw Hill Professional, 2009. .
 Bowers, Peter M. Boeing Aircraft since 1916. Annapolis, Maryland: Naval Institute Press, 1989. .
 Endres, Günter. The Illustrated Directory of Modern Commercial Aircraft. St. Paul, Minnesota: MBI Publishing Company, 2001. .
 Redding, Robert and Bill Yenne. Boeing: Planemaker to the World. Berkeley, California: Thunder Bay Press, 1997. .
 Sharpe, Michael and Robbie Shaw. Boeing 737-100 and 200. St. Paul, Minnesota: MBI Publishing Company, 2001. .
 Shaw, Robbie. Boeing Jetliners. London, England: Osprey, 1995. .
 Shaw, Robbie. Boeing 737-300 to 800. St. Paul, Minnesota: MBI Publishing Company, 1999. .
 Sutter, Joe. 747: Creating the World's First Jumbo Jet and Other Adventures from a Life in Aviation''. Washington, D.C.: Smithsonian Books, 2006. .

Other websites

Official Boeing page

 737
Tsar is a title for the supreme ruler in several countries.

In Bulgaria, the title was used in 913–1422 and again in 1908–1946. The last tsar to rule Bulgaria was Boris III, who replaced Ferdinand I of Bulgaria 1918.

In Serbia, the title was used in 1346—1371. The last tsar to rule Serbia was Stephen Uroš V.

In the Russian Empire, the title was used from 1546 until 1721. Starting in 1721, the title of Russian emperors was imperator, but the word tsar remained in common use until the Russian Revolution in 1917. The last tsar to rule Russia was Nicholas II, who replaced Alexander III in 1894. The system of government used during the Tsardom of Russia and the Russian Empire was called Tsarist autocracy, also known as Tsarism.

Tsar is also spelled tzar, czar, and csar. It is the Eastern European word for caesar. It can be translated to emperor.

Royalty and nobility
The 1550s was a decade that started on 1 January 1550 and ended on 31 December 1559.

Events 
 Helsinki founded in Finland.
 Rule of Bloody Mary, or Mary I of England from 1553 to 1558.
 São Paulo founded in Brazil. 
 Religious wars continue in Europe.
 Russia breaks peace with Sweden by attacking Finland. 
 The Shaanxi Earthquake, the deadliest earthquake in history.

Births 
 Sarsa Dengel, Emperor of Ethiopia
 King Sebastian of Portugal
 Nurhaci, Chinese founder of the Qing Dynasty

Deaths 
 Tabinshwehti, King of Burma
 Edward VI, King of England 
 Ignatius of Loyola, Spanish founder of the Jesuit priests
1840 was a leap year.

Events 
 The Great Natchez Tornado: A massive tornado hits Natchez, Mississippi. Before it was over, 317 people had died and 209 were injured.

Births 
 January 3– Father Damien, priest
 January 18 – Edmund Barton, 1st Prime Minister of Australia (d. 1920)
 May 7 – Pyotr Ilyich Tchaikovsky, Russian composer
 Kuroda Kiyotaka, Prime Minister of Japan

Deaths 
 May 27 – Niccolò Paganini, Italian violinist and composer
Engelbert Dollfuss (German: Dollfuß) (October 4, 1892 – July 25, 1934) was the Chancellor of Austria from 1932 until 1933. He led the country as a dictator from early 1933 until 1934.

He studied law in Vienna, and Economics in Berlin. During World War I, he served in the Alps and briefly became a Prisoner of War in 1918. 

He became Chancellor on May 20, 1932 as head of a right-wing coalition government. He wanted to solve the problems caused by the Depression. He had problems finding majorities in parliament. The measures he liked to take to deal with inflation were not well liked. In March 1933, he suspended the Austrian parliament. He then governed by decree. 

With Adolf Hitler as Chancellor in Germany, Dollfuss feared that the influence of the NSDAP would grow. This would then lead to a growth in popularity for its Austrian counterpart. Because of this, he banned the NSDAP in June 1933. He also banned the SDAPÖ in February 1934.
In September 1933 he formed an umbrella grouping to support the regime, the Vaterländische Front (Fatherland Front) and merged the Christian Social Party with the para-military Heimwehr (Home Guard), a Nationalist paramilitary group. The regime which was put into power by him and remained in power until 1938 is often called Austrofascism. The form of state he employed was called the Ständestaat.

On July 25, 1934, eight Austrian Nazis entered the Chancellery building and shot and killed Dollfuss in an attempted coup, as a prelude to Anschluss. The Nazis surrendered and were executed. Kurt Schuschnigg became the new dictator of Austria.

References

Other websites 
 Video: Dollfuß holds a speech in Burgenland 1933 (mpeg, 6,1 kb)

 

1892 births
1934 deaths
Chancellors of Austria
Government ministers of Austria
Murders by firearm
A language isolate is a language that is not known to be related to any other language.

Many languages are related to other languages by coming from an older language, and both are still similar. Languages that are related are language families. Most languages are known to belong to a language family. However, some are not known to be related to other languages and are called language isolates.

Some spoken language isolates are Basque, Zuni, Burushaski, Ainu and Mapudungun. Some extinct language isolates are Sumerian, Elamite and Urartian.

Language isolates
A species is a kind of organism. It is a basic unit of biological classification, and a formal rank in taxonomy. Originally, the word was used informally in a rather vague way, but now there are at least 26 different ways it is used.

All animals or plants that are the same kind belong to the same species. Wolves (Canis lupus) are one species. Humans (Homo sapiens) are another species. Broadly, the idea is that, for example, cats breed with cats and produce more cats. This is the basis for deciding to have a species called Felis catus. However, to give a simple definition of 'species' is difficult, and many people have tried.
Species is a word for a particular kind of living thing, for example, a jackdaw. Jackdaws and ravens are similar, so they are together in a larger group (taxon) called a genus, in this case Corvus. Then there is a family (such as the crow family, which includes crows and ravens as well as jays and magpies). Families are put together into orders such as the songbirds, which includes many families of birds. The next group is the class; all birds are in the same class. After that is the phylum, such as vertebrates, which is all animals with backbones. Last of all is the kingdom, like the animal kingdom. These are ways to classify living things.

There is a mnemonic to help people remember the order of the divisions which are listed again below: "King Phillip Came Over For Great Spaghetti".
Example
Take as an example the bird called a Common Loon or Great Northern Diver:
 Kingdom: Animalia
 Phylum: Chordata
 Class: Aves
 Order: Gaviiformes
 Family: Gaviidae
 Genus: Gavia
 Species: Gavia immer
 Common name: Common Loon or Great Northern Diver.

Historical changes in the term
There is a long history of disagreement over whether species are objective things, or whether they are man-made labels. Those who think species are objectively different point to things which 'good' species do. They look similar, and they breed true, that is, mate with their own kind, and have offspring which are obviously in the same species.

Against this are the many exceptions. There are species which shade gradually into other species, and which interbreed in overlapping populations (see ring species). On the other hand, there are species which look absolutely identical, but which do not breed together (sibling species).
The greatest change in the species concept was made by Charles Darwin, for evolution meant that hard-and-fast lines could not be drawn between species. Another shift came when Ernst Mayr proposed the biological species concept, which emphasized the interbreeding population as the heart of the species concept. This meant that, in his view, species were objective, that is not just the subjective opinion of a taxonomist. His explanation of the process of speciation was geographical isolation between populations which had once been interbreeding. Today, emphasis has moved back closer to Darwin's ideas.

Numbers
According to the most recent estimate, there are about 8.7 million species on Earth. This counts only eukaryote organisms. It leaves out bacteria, archaea and viruses.

Fewer than a quarter of the species have not been identified, named and catalogued. At the present rate, it might take over 1000 years to complete this job. Some will become extinct before this count is complete.
Related pages
 Subspecies
 Wikispecies

References

Taxonomy
An ancestor is a person (or another organism or thing) from whom (or which) another is descended. Usually, it refers to a person far in the past, rather than the parents or grandparents in the close family. A very similar word is forebear. A female ancestor may be called an ancestress. The line of ancestors from which an organism descends is referred to as its ancestry. 

A second meaning relates to evolution. There, it is used of a species or group of species of animals or plants from which others have evolved. In a similar way, the word ancestor can be used for an early prototype or forerunner of a later device. 

In law an ancestor can mean the person from whom an estate is lawfully obtained. No blood relationship is necessarily implied. More commonly, however, it is the person from whom an estate is obtained based on law and blood.
Two people have a genetic relationship if one is the ancestor of the other, or if they share a common ancestor. Each of someone's ancestors will have contributed to their DNA. In evolution, species that have evolved from the same ancestor are said to be of common descent. However, this concept of ancestry does not apply to some bacteria and other organisms capable of horizontal gene transfer. DNA testing is used in determining ancestry. This can be for paternity testing, to determine the parents of a child for legal purposes. DNA is also used to better understand the ancestry and history of all humans over the last 50,000 years. This was one of the benefits of the Human genome project.
In some cultures ancestors may have relatively little importance. Many today have no knowledge of their own great-great-grandparents. China is an example of a culture that in general has a deep respect for ancestors. Korea is an example of a culture that engages in ancestor worship where ancestors are revered. But genealogy (the study of one's ancestors) is growing in popularity and includes both amateur and professional genealogists.

Related pages

 Ethnicity
 Kinship
 Generation
 Human Genome Project

References

Family
South Asian river dolphins (two sub-species)
Ganges river dolphin, Platanista gangetica gangetica – Lives in Nepal, Republic of India and Bangladesh
 Indus river dolphin, Platanista indicus minor – Lives in Pakistan; National mammal of Pakistan.
South American river dolphins (three species)
 Amazon river dolphin (or Boto), Inia geoffrensis – Largest of river dolphins, lives in Peru and Brazil.
Araguaia river dolphin, Inia araguaiaensis  – Recently discovered in the river basin in Brazil after which it is named. Identified as a separate species by genetic sequence analysis.
 La Plata dolphin (or Franciscana), Pontoporia blainvillei – Lives in Argentina.
 Chinese river dolphin (or Baiji), Lipotes vexillifer – Lives in the Yangtze River in China (one of the most endangered of all dolphins and whales). Recent counts have come up with 17 remaining individuals. Scientists now want to raise some dolphins in a lake.
Differences between marine and river dolphins 
Both river dolphins and marine dolphins belong to a group of mammals called cetaceans. The snout of a river dolphin measures about 58 centimeters (2 ft) long, approximately four times as long as that of most marine dolphins. They use their long snout to search for fish on the muddy bottom of the river. River dolphins have smaller eyes than marine dolphins, and their vision is poorly developed because they live in dark, muddy water. River dolphins are less active than marine dolphins because they do not need to search so widely to find fish. Marine dolphins work in pods (packs) because when they find a shoal of fish then they work together to make the most of their find. River dolphins work mostly as individuals or small groups.

Taxonomy 
The following is the taxonomy of river dolphins, or how dolphins are classified:
River dolphin classification 
 Superfamily Platanistoidea
 Family Platanistidae
 South Asian river dolphin Platanista gangetica (two subspecies)
 Ganges river dolphin P. g. gangetica
 Indus dolphin P. g. minor
 Family Iniidae
 Amazon river dolphin (or Boto) Inia geoffrensis
 Family Lipotidae
 Chinese river dolphin (or Baiji) Lipotes vexillifer
 Family Pontoporiidae
 La Plata dolphin (or Franciscana) Pontoporia blainvillei

References

Other sources 
River-Dolphins-and-their-habitat
An estuary is where a river meets the sea. There, saltwater mixes with freshwater. The river becomes wider and wider and flows slowly to the ocean.

Bays, marshes, swamps, and inlets can all have estuaries. A view of an estuary from the air is usually an interesting sight: many estuaries meander (curve and bend) to find their way to the sea. Estuaries come in all sizes and shapes, each according to its location and climate. Where rivers meet the sea and fresh water mixes with salt water, the mixture is called brackish water.

Some estuaries are very large. They may be large ocean bays that have more than one river flowing into them.  For example, Chesapeake Bay is a large estuary, and several different rivers meet the Atlantic Ocean there.
In simple terms it is where a river meets with a large body of water only with ((one)) outlet and not  many like a ((delta)).
Habitat 
Estuaries are usually filled with shallow waters, and sunlight reaches all levels of the water. Marsh grasses, algae, and other kinds of plants live in estuaries and provide food for a variety of fish, crabs, oysters, and shrimp. Estuaries are especially important since they act as nurseries for many different types of young fish and other animals before they head out toward the open ocean. Many sea birds also nest in estuaries.

The United States government has a program to study and protect the natural environment in many different estuaries, called the National Estuarine Research Reserve System. One reason that the natural environment in so many estuaries is in danger is because they are also good places for people to live and build cities. Unfortunately, many of world's largest cities are at or near estuaries.

References 

Bodies of water
Ecosystems
James Bond is a fictional British spy created by Ian Fleming in 1953.

History

1950s-1960s 
In 1953, Fleming wrote Casino Royale, the very first James Bond novel. The novel made a lot of money, and he continued to write one James Bond novel each year until he died in 1964. In a 1956 South African radio program Moonraker he was voiced by Bob Holness. In 1962 Albert. R. "Cubby" Broccoli and Harry Saltzman started to produce the first James Bond movie, Dr. No, starring Sean Connery as James Bond. The movie became extremely popular, and they continued to make more Bond movies. In the end of the 1960s Connery did not want to do any more Bond movies, and many thought that Bond was now dead. In 1969, George Lazenby appeared in one movie as the Bond character, but the movie was not successful.
1970s-1980s 
In 1971 Sean Connery stepped back into the role for one movie "Diamonds are Forever". After this in 1973, producers came up with the Live and Let Die movie, starring Roger Moore as Bond. The movie became a very big success. The series continued throughout the 1970s and 1980s with Roger Moore playing the role of Bond.

In the 1980s, Bond movies were not as successful at the box office. Unlike the 1960s and 1970s, in the 1980s there were many other action movies being produced that could compete with the Bond series.

After Moore left the role as Bond, he was replaced with Timothy Dalton in the late 1980s. Dalton tried to make a serious, "down to earth" Bond, closer to the Fleming novels. Fans did not like Dalton's interpretation of the Bond character, and the movies made little money.

1990s 
The Cold War ended in 1991. Since Bond almost always fought Communists, many now thought that the Bond series of movies was finally dead.
2000s 
In 2002, the James Bond character was used in the 20th movie, Die Another Day, the 40th anniversary of the movies and the 50th anniversary since Fleming wrote his first Bond novel.
In 2006, the 21st movie, Casino Royale, was released. Pierce Brosnan, who played James Bond in the previous four movies, was replaced by Daniel Craig, the first James Bond to have blonde hair. The movie is based on the first Ian Fleming novel of the same name, but is set in the present day. The movie features a cameo appearance by Richard Branson, a British billionaire. It has a new model of Aston Martin DB9, the car that made James Bond so famous in the 1960s. Many fans think that whilst this movie is different than other movies, it is much better, and movies in the future (however few there will be) will be in this new format. In 2008, Craig appeared in a second Bond movie, Quantum of Solace and a third, Skyfall, in 2012. His fourth appearance as Bond was with Spectre in 2016. His fifth and final appearance as Bond is with No Time to Die in 2021.
Movies 

Many of the James Bond movies were massive hits. However, there are two movies classed as unofficial Bond films and not recognised as part of the series. The 1967 version of Casino Royale was a spoof, featuring "Jimmy Bond". Also, Never Say Never Again was not made by Albert R. Broccoli's production company, EON Productions. Connery is the tallest actor to play James Bond to this day.

Representation 

Visually and musically, but also artistically overall, James Bond and the British way of being a gentleman repeatedly serve as inspiration, or artists like Marc Engelhard and other protagonists resemble each other in this style.

References

Other websites 
 The Official James Bond Website
 Ian Fleming Publications official website 

Fictional British people
Fictional characters introduced in the 1950s
Fictional orphans
James Bond characters
English-language television programs
A Streetcar Named Desire is a 1951 movie. It is based on the 1947 play by Tennessee Williams. The movie stars Marlon Brando and Vivien Leigh.

Other websites 

1951 drama movies
1950s American drama movies
United States National Film Registry movies
Multilingual movies
Movies directed by Elia Kazan
American plays
1947 works
A tetrahedron or triangular pyramid is a polyhedron (a three-dimensional shape). It has four corners and six edges. All four of its faces are equilateral triangles. Every two edges meet on one of those corners forming a sixty-degree angle.

Formulas for a regular tetrahedron 

A regular tetrahedron is a tetrahedron whose edges are the same length. If the length of an edge is a:

Other properties 
A regular tetrahedron's faces are all the same, and so are all its edges, as well as its corners. This makes it a regular polyhedron. It is also convex (its faces do not go through one another), which makes it a Platonic solid.

The dual of regular tetrahedron is another regular tetrahedron. This is called being self-dual.

References

Platonic solids
Robert Hooke FRS (Isle of Wight, 18 July 1635 – London, 3 March 1703) was an English naturalist, architect and polymath. Hooke played an important role in the birth of science in the 17th century with both experimental and theoretical work. He was a colleague of Robert Boyle and Christopher Wren, and a rival to Isaac Newton. Hooke was a leader in the plans to rebuild after the Great Fire of London in 1666.

There is no surviving portrait of Hooke.

Hooke's achievements

Physics 

He discovered Hooke's Law of elasticity. He designed and ordered the making of telescopes and microscopes, and used both instruments. He reported on this work in a book called Micrographia in 1665. He was the first person to see biological cells. He made drawings of bodies in the Solar System, and made the first attempts to measure the distance of certain stars.
Robert Hooke was appointed the Royal Society's first Curator of Experiments in 1662, and he rose to be Secretary of the Royal Society. He took responsibility for experiments performed at its weekly meetings. This was a position he held for over 40 years.

In 1664 Hooke also was appointed Professor of Geometry at Gresham College in London and Cutlerian Lecturer in Mechanics.

On 8 July 1680, Hooke observed the nodal patterns associated with the mode of vibration of glass plates. He ran a bow along the edge of a glass plate covered with flour, and saw the nodal patterns emerge.p101

Hooke did some fundamental work on gravitation and the motion of the planets. Forever after, he was convinced that Newton and the world had cheated him of the creditp389
Natural history 
He was also known for his work in natural history  (biology and geology). He reported on his microsope use in a book called Micrographica in 1665. He was the first person to see biological cells, and was the first to use the word 'cell' to describe them.

In 1668, in a talk to the Royal Society, he recognised that fossil shells of unknown marine animals suggested that some species had become extinct.

Architecture 

Hooke achieved fame in his day as Surveyor to the City of London and chief assistant of Christopher Wren. Hooke helped Wren rebuild London after the Great Fire in 1666.

He also worked on the Royal Greenwich Observatory, and the infamous Bethlem Royal Hospital (which became known as 'Bedlam'). Many other buildings were designed by Hooke, including the Royal College of Physicians (1679).