Sudoku puzzles contain numbers that are already filled in by the puzzle’s author, called clues, which allow the puzzle to be solved. The sudoku on the left is unsolved, and the numbers in black are the clues. The sudoku on the right has been solved, and the numbers in blue are the answers for the puzzle.
Credit: World Book illustration

Today, September 9th (or 9/9 depending on how you write the date), is International Sudoku Day. Sudoku is a logic puzzle. A standard Sudoku consists of a grid of 81 squares, made up of nine rows and nine columns. The grid is further divided into nine 3-by-3 boxes. Each puzzle comes with some numbers in place. A player solves the puzzle by filling the grid with numbers so that every row, column, and box contains the digits 1 through 9 without repeating a number. If the puzzle was properly made, it has only one solution. The amount of nines involved in the puzzle is why today was chosen to celebrate the beloved pastime!

There are some variations of standard Sudoku, with smaller or larger grids. Also, because no arithmetic is needed for Sudoku, letters or symbols can be used in place of numbers. Puzzles that use letters are sometimes called Wordoku.

The earliest examples of Sudoku were number logic puzzles called Number Place, first published in the United States in 1979. A Japanese company called Nikoli began publishing the puzzles in 1984. The puzzles became popular in Japan, where they were called Su Doku—a shortened form of a Japanese phrase meaning, roughly, “the numbers can only be used once.”

The Times of London published its first Sudoku in November 2004. Soon, rival London newspapers followed The Times, each attempting to outdo the others by supplying more Sudoku, or by claiming to offer better Sudoku. Magazines of the puzzles first appeared in the United Kingdom early in 2005. Within months, Sudoku had gained widespread popularity. To give Sudoku a try, grab your local newspaper to find the daily Sudoku puzzle next to the crossword or download an application to play it on a phone or computer. If you are working on paper, it is best to start learning by using a pencil instead of a pen!

June 21, 2018

In 2018, London’s famed Royal Academy of Arts (RA) is celebrating the 250th anniversary of its founding in 1768. The RA operates an art school and organizes exhibitions of fine arts. The academy campus recently completed an expansion and thorough modernization, melding new architecture and technology with the existing 1660′s structure, the palatial Burlington House and surrounding Burlington Gardens. King George III founded the RA as an association of artists and architects, and Sir Joshua Reynolds, a great portrait painter, was the academy’s first president.

London’s Royal Academy of Arts is celebrating the 250th anniversary of its founding in 1768. Credit: © Alex Segre, Shutterstock

The RA expansion includes new indoor and outdoor galleries and free art displays. The additions include space for more art courses, debates, lectures, and workshops, and larger studios for students in the RA Schools. For students and visitors alike, the RA has increased the exhibition and performance areas and opened new cafés and a large newsstand.

RA anniversary events include a special “Great Spectacle” exhibition detailing the 250-year history of the Summer Exhibition, an annual display of new notable works of contemporary art—or, as the RA describes it, “art made now.” A special installation of 250 flags is spilling out of the RA and into London’s West End this summer, and notable exhibits in 2018 include displays from artist Chris Orr’s “The Miserable Lives of Fabulous Artists;” a feature on the art of Oceania that recalls Captain James Cook’s 1768 voyage of discovery to the South Pacific Ocean; and a special exhibition of the works of Gustav Klimt and Egon Schiele marking the 100th anniversary of their deaths in 1918.

Beyond London, RA 250 events will be held in museums throughout the United Kingdom, including special exhibits at the Holburne Museum in Bath, the Royal West of England Academy in Bristol, the Manchester Art Gallery, the Turner Contemporary in Margate, the Newport Museum and Art Gallery in Wales, and the Royal Scottish Academy in Edinburgh.

January 17, 2018

Yesterday, January 16, a new United States Embassy opened in the Nine Elms area of Wandsworth, a borough of central London, England. The flashy, chunky, ice cube of a building is an architectural wonder, and a security-first but environmentally friendly construction. The decision to move the U.S. Embassy to a new London location was made in the waning months of the presidency of George W. Bush in 2008. Construction of the new embassy began in 2013, and tinkering continued right up to the morning it opened.

This artist’s rendering of the new U.S. Embassy shows the building under a somewhat-typical rainy London sky. Credit: KieranTimberlake, U.S. Embassy London

The new 12-story embassy, designed by Philadelphia-based architectural firm  KieranTimberlake, has nearly twice the floor space as the old one. The building is powered by renewable energy and maximizes the use of natural light as well as natural wind currents through cross ventilation. Solar panels line the embassy’s glass roof, absorbing both sunshine and rainwater for irrigation and flushing.

The building’s trademark façade uses laminated glazing with an outer layer of pressurized ethylene tetrafluoroethylene (ETFE), a highly durable plastic. The transparent exterior ensures a uniform distribution of light while screening excessive solar glare and heat. The windows are clearly visible to birds, however, greatly reducing accidental flying collisions. The façade is also self-cleaning and limits downdrafts on the outside, effectively reducing wind in the adjacent plaza and sidewalks.

Like castles of old, the embassy has stone walls and is protected by a moat. Other security measures include bollards (posts to block vehicles) camouflaged by plants, blast-proof walls and ceilings, a 100-foot (30-meter) open perimeter, and a garrison of armed security personnel.

The new U.S. Embassy earned the highest platinum certification by Leadership in Energy and Environmental Design (LEED), the most widely used green building rating system in the world. It was also rated outstanding by the Building Research Establishment Environmental Assessment Method (BREEAM), the world’s longest established method of assessing, certifying, and rating building sustainability.

The building’s $1-billion dollar price tag was paid for by the sale of the previous embassy—located across the River Thames on Grosvenor Square in the Mayfair district—and other U.S. properties in London. The U.S. Embassy had been on Grosvenor Square (in more than one location) since future president John Adams became the first U.S. minister to the Court of St. James in 1785. Interestingly, four other future presidents—James Monroe, John Quincy Adams, Martin Van Buren, and James Buchanan—all served as London ministers prior to occupying the White House. In 1893, Delaware Senator Thomas F. Bayard was the first to hold the rank of ambassador to the United Kingdom.

The Bureau of Overseas Building Operations (OBO)—did you know there was one?—directs the foreign building program for the Department of State and the U.S. government community serving abroad. Other recent OBO projects have included new embassies in N’Djamena, Chad; Nouakchott, Mauritania; and Oslo, Norway. New embassies will soon go up in Guatemala, Honduras, Kenya, Lebanon, Mexico, Paraguay, South Korea, Sri Lanka, Turkey, and Uganda.

July 20, 2017

Last month, on June 14, a fire destroyed much of Grenfell Tower, a 24-story apartment building in London, England. The fire, which took place in the city’s Kensington district, killed at least 80 people—the deadliest fire in London since World War II (1939-1945). The tragedy devastated many families and brought harsh criticism on local and national government as well as London’s fire safety laws and emergency response management.

The Grenfell Tower burns out of control as firefighters hose the building’s lower floors early on June 14, 2017, in London, England. Credit: Natalie Oxford (licensed under C BY 4.0)

The Grenfell fire started around midnight in a malfunctioning refrigerator freezer on the building’s fourth floor. That small fire ignited the building’s exterior cladding, a protective layer on the outside of the building’s structure. In this case, the cladding consisted of aluminum plates with a polyethylene core and polyisocyanurate insulation. Polyethylene and polyisocyanurate are types of plastic. The flammable cladding accelerated the fire, which quickly engulfed the building’s upper stories. The cladding—which also released deadly cyanide fumes—was blamed for the fire’s rapid outside-in path that trapped so many people, leading to the terrible death toll (people died from cyanide fumes as well as from flames and smoke). The fire burned intensely for many hours, and was not completely extinguished until June 16.

Some 250 firefighters responded to the Grenfell Tower fire, and they were credited with rescuing 65 people. Riot police worked alongside the firefighters, using their shields to protect firefighters from cascades of burning debris. Other police helped firefighters break down doors into locked apartments. Many people remained trapped in the building, however, as intense heat, flames, smoke, and toxic fumes continually forced rescuers to slow or alter their advance. Eighty people are known to have died in the fire. However, full analysis of remains will not be completed for some time, and the death toll is likely to rise.

This photo shows a devastated corner apartment in the burned-out Grenfell Tower on June 18, 2017. Credit: London Metropolitan Police

Grenfelll Tower was constructed in 1974. It had 129 apartments and space for some 600 residents. Grenfell had just one entrance and one staircase, and residents often complained that this could be a problem in an emergency evacuation. British regulations, however, require just one staircase in a building of that size, unlike rules in most countries that require two. Residents also complained of exposed natural gas pipes in the building, and the installation of fire-retardant boxing around the pipes had begun but was not yet completed at the time of the fire. (Several gas lines burst during the fire, which worsened the situation.)

In 2015 and 2016, Grenfell Tower—which also lacked a sprinkler system—was renovated and the new cladding was added to improve the tower’s exterior appearance. Fireproof zinc cladding was passed over in favor of much cheaper aluminum cladding. After the fire, the cladding used at Grenfell—which has long been banned on high-rise buildings in the United States and other countries—failed fire safety tests. The cladding was then banned in the United Kingdom and is in the process of being removed and replaced in hundreds of buildings throughout the country.

The local Kensington council was blamed for ignoring safety complaints from Grenfell, which was populated by largely poor, immigrant, and ethnic-minority tenants in an otherwise affluent area. The British government was blamed for deregulating the building industry and for cutting funding for fire prevention, as well as for its slow response in helping survivors of the fire. A public inquiry into the fire is scheduled to begin in September.

February 1, 2017

In December 2016, an exhibition of the works of Australia’s greatest Impressionist painters opened at the National Gallery, an art museum in London, England. The museum, home to a broad collection of paintings by mostly European artists, is showing 41 works by such Australian artists as Tom Roberts (1865–1931), Arthur Streeton (1867–1943), Charles Conder (1868–1909), and John Russell (1858–1930). “Australia’s Impressionists,” in collaboration with the Art Gallery of New South Wales, runs through the last Sunday of March 2017.

Tom Roberts’ Bourke Street West catches a bright glimpse of 1880′s Melbourne, Australia’s fastest-growing and largest city at the time. Credit: Allegro con brio, Bourke Street West (1885-6), oil on canvas by Tom Roberts; National Gallery of Australia, Canberra and the National Library of Australia

Much of the exhibit concentrates on the works of Charles Conder, Tom Roberts, and Arthur Streeton. These artists formed the backbone of the Heidelberg School, a group of painters who worked on the tree-covered hills overlooking the Yarra River in what is now the Melbourne suburb of Heidelberg. The group, later known as the Australian Impressionists, flourished from 1886 to about 1900. During that time, the group developed a distinctly Australian landscape style showcasing the continent’s light-filled outback and seacoasts as well as the sun-baked streets of Melbourne and Sydney.

The vibrant paintings of Sydney’s John Russell, who lived in France for much of his life, get an exhibit section to themselves. His works reveal the colorful influences of such contemporary European artists as Vincent van Gogh and Claude Monet. Russell’s paintings often portray the landscapes and rocky shorelines of Belle-Île, an island off the coast of Brittany. Russell’s paintings received little attention during his life and for many years after his death. Interest in “Australia’s lost Impressionist” first emerged in the 1960′s.

Taken as a whole, “Australia’s Impressionists” depicts an emerging sense of artistic and national identity as the Australian colonies neared federation on New Year’s Day 1901. The exhibit was inspired by the 2015 loan of Streeton’s Blue Pacific, the first painting by an Australian artist to be displayed at the National Gallery.

London voters elected Labour Party candidate Sadiq Khan as the city’s new mayor on May 5, 2016.
Credit: © Hannah McKay, Reuters

Yesterday, May 5, in London, England, voters elected the Labour Party’s Sadiq Khan as the city’s new mayor. Khan, a London native, is a Muslim of Pakistani descent. His election win makes him London’s first Muslim mayor and just the second Muslim mayor (after Rotterdam’s Ahmed Aboutaleb) of a major European city. Khan’s win reflected the choice of Londoners to focus on issues and a candidate’s policies and abilities rather than a candidate’s race, religion, or ethnic identity. Billionaire Conservative Party candidate Zac Goldsmith—who lost with just 35 percent of the vote—tried to use Khan’s religion against him, hoping his Islamic faith would turn voters away. Goldsmith also tried to link Khan—and the liberal Labour Party in general—to Islamist extremists. The tactics fell flat, however, and Khan’s electoral support—strong from the start—never faltered, carrying him to a comfortable victory.

Sadiq Khan was born in London on Oct. 8, 1970, the son of Pakistani immigrants. His father was a bus driver and his mother a seamstress. Khan joined the Labour Party while still in high school. He practiced as a human rights lawyer before entering Parliament in 2005 as representative for Greater London’s Tooting constituency (where he grew up) in the House of Commons. He held different ministry positions before concentrating on his run for London mayor in 2015.

April 11, 2013

Fabulous artifacts from around 2,000 years ago—dating to the time when London was called Londinium and was ruled by the Romans—have been discovered in the city’s financial district. The find was made by archaeologists working in advance of construction on a new headquarters for Bloomberg L.P., the media company owned by Michael Bloomberg, current mayor of New York City. More than 50 archaeologists from the Museum of London Archaeology are working on the Roman site.

Hadrian's Wall, built by the Romans in the A.D. 120's, protected England from northern raiders. Roman ruins remain in many parts of England, including London and Bath. (c ZEFA)

The artifacts found at the building site were much more numerous and much better preserved than archaeologists had imagined. The site is so well preserved because of its location. Being encased in the heavy mud created by the Walbrook, one of London’s many underground rivers, helped to save the Roman antiquities, which would have simply rotted away in ordinary soil. Some of the Roman objects found include pottery, jewelry, shoes (hundreds of them), and coins. Archaeologists were especially excited to find tablets with writing, since few written documents from this period and area have survived. They also found a carved amber amulet, or luck charm, in the shape of a gladiator’s helmet. In addition to objects, an entire streetscape of wooden structures was discovered 40 feet (12 meters) beneath the ground. This preserved Roman street led the media to dub the site the “Pompeii of the North.”

The building site is also home to the Temple of Mithras, Walbrook, which was discovered in the 1950′s. Mithra, or Mithras, was a Persian god of light. His mystery cult became popular among Roman soldiers and slaves from around A.D. 100 to 300.

When completed, the Bloomberg headquarters will include an entrance to the Roman temple and a museum to house the artifacts found on the site.

Additional World Book articles:

• Ancient Rome
• Archaeology
• Archaeology (1954 Back in time)

August 15, 2012

Pessimistic notes were being sounded throughout the United Kingdom in the weeks before the start of the 2012 Summer Olympic Games in London. The media carried stories about inadequate security and the threat of terrorism. Some people predicted gridlock traffic congestion complicated by fears of bad weather that would ruin the Olympic experience. But the Games turned out to be a triumph, from the extravagant opening ceremonies on July 27 to the even more spectacular closing ceremonies on August 12.

In-between these spectacles, the world was treated to more than two weeks of dazzling athletic competition in 302 events, led by memorable performances from sprinter Usain Bolt of Jamaica and swimmer Michael Phelps of the United States. Phelps ended the Games with four gold medals, making him the all-time recordholder of Olympic gold–with a total of 18 medals from the 2004, 2008, and 2012 Games. Gabby Douglas of the United States won gold medals in both the individual and team all-around gymnastic competitions. She is the first African-American and the first woman of color to become the Olympic champion in the individual all-around event.

Usain Bolt (© Kyodo/Landov)

The United States and China led in medals, as they did in the 2008 Olympics, but other countries had glorious victories as well. Host United Kingdom outdid itself in medal accumulation, with 65 total and 29 gold compared with 47 total and 19 gold in the last Summer Games in 2008. The individual stars of the Australian team were gold medal winners Sally Pearson in the 100-meter hurdles and cyclist Anna Meares in the women’s sprint. Rosie MacLennan was the star of the Canadian team with her gold-medal performance in the women’s individual trampoline event. The Games were more than satisfying for Team New Zealand, which captured 13 medals, including 6 gold, the country’s best showing since the 1988 games in Seoul, South Korea. Five of the six gold medals were won on the water, in rowing and canoeing. Valerie Adams took the women’s gold medal in the shot-put. Adams was awarded the medal after the announced winner, Nadezhda Ostapchuck of Belarus, was disqualified for failing a drug test.

Additional World Book Article:

• The Winning Edge (a special report)

July 30, 2012

The 2012 Summer Olympic Games in London boast some impressive numbers. About 10,500 athletes from 205 countries are competing in 300 events spread over 26 sports, from aquatics to wrestling. The action will entertain the hundreds of thousands of visitors to London, plus billions more on worldwide television, from July 27 through August 12.

The games had its preopening glitches, notably the discovery, a few days before the opening, that the private firm contracted to supply security for the Olympics had failed to recruit and train enough staff. To make up the shortfall, the British government deployed 3,500 members of the armed forces to fill the gap.

The Olympic flame is lit during the Opening Ceremony. The fire is ignited in Olympia, Greece, and transported by relay to the site of the games. The flame symbolizes the light of spirit, knowledge, and life, and it is a herald of peace. Here, torchbearer Cathy Freeman stands triumphant after lighting the flame at the 27th Olympiad in Sydney, Australia. (AP/Wide World)

But any pre-Games embarrassments were swept away by the dazzling opening ceremonies at Olympic Stadium the night of July 27. The 80,000 people in attendance, plus billions more watching on TV around the world, saw a stunning celebration of British pop culture, from Lord Voldemort and the Sex Pistols to Mary Poppins. Skydivers dressed as Queen Elizabeth II and James Bond parachuted into the stadium. British football star David Beckham piloted a speedboat carrying the Olympic flame down the River Thames to the stadium where the flame ignited a giant cauldron of fire. Fireworks illuminated the sky for miles. It was all a glorious introduction to the two weeks of world-class athletic competition to follow.

Additional World Book Article:

• The Winning Edge (a special report)

June 1, 2012

Millions of people across the United Kingdom are preparing for Queen Elizabeth’s Diamond Jubilee, a celebration of her 60 years on the throne. Elizabeth became queen when her father, King George VI, died in 1952. She has reigned longer than any other British monarch with the exception of her great-great grandmother, Victoria, who ruled from 1937 to 1901. Her diamond jubilee was celebrated in 1897.

The festivities include two national holidays, on June 4 and 5. The main events marking the Diamond Jubilee include a pageant on the Thames River on June 3. The pageant will feature a flotilla (a fleet of small ships) of 1,000 boats escorting the queen down the river. The queen’s party, aboard the royal barge, Spirit of Chartwell, will include her husband, the Duke of Edinburgh, her son Prince Charles, and his sons, William and Harry.

On the night of June 3, a televised Diamond Jubilee concert will be performed in the Buckingham Palace park. Among other artists, Elton John, Tom Jones, Annie Lennox, Paul McCartney, and Stevie Wonder will perform. The concert will end with the lighting of more than 4,000 beacons around the world to mark the 60 years of the queen’s reign.

The celebration will culminate on June 5 with a national service of thanksgiving at St. Paul’s Cathedral. At the service, the queen and the Duke of Edinburgh will be joined by 57 members of the royal family, current and former prime ministers, senior military and religious figures, and dignitaries from around the world.

Queen Elizabeth, accompanied by her husband, Prince Philip, the Duke of Edinburgh, waves to a joyous crowd in London in 2002 on the occasion of her Golden Jubilee, which marked the 50th anniversary of her reign. In 2012, she celebrates her Diamond Jubilee. (AP/Wide World)

The queen and members of the royal family will return to Buckingham Palace on June 5 in a carriage procession. She will travel in the open-topped 1902 State Landau carriage, used for the Duke and Duchess of Cambridge’s wedding procession in 2011. The procession will end with the queen making an appearance on the balcony at the palace as the Royal Air Force stages a jet fly over.

With millions of people expected to crowd into London for the events, train companies are adding extra cars to their London-bound trains to meet demand. Eurostar reports a 30-percent increase in bookings for the weekend. (Eurostar is the high-speed railway service connecting London with Paris and Brussels through the tunnel under the English Channel.) Officials at Heathrow expect 410,000 people to pass through the airport over the weekend.

Retailers report amazing sales in anticipation of the celebration. Sales of picnic or party paper ware are up 182 percent at the grocery chain Sainsbury’s, which has also sold 364 miles (585 kilometers) of Union Jack flag bunting. (Bunting is long pieces of cloth having the colors and designs of a flag, used to decorate buildings and streets on holidays and special occasions.) The famous London luxury store Marks & Spencer (M&S) has sold more than 50,000 commemorative jubilee biscuit (cookie) tins and is expecting to sell nearly 10 million servings of strawberries. M&S has sold enough bunting to line London’s Mall– down which the carriage procession will travel–155 times.

Additional World Book articles:

• Royal family of the United Kingdom
• The Queen Mother: Creator of the Modern Monarchy (a special report)