Beyond the answers - interesting background to this quiz

The Danube, a river of capitals

Vienna is not the only capital the Danube touches: Bratislava, Budapest and Belgrade also sit on its banks, which is unusual for a single European river. It rises in Germany's Black Forest and flows east for roughly 2,850 kilometres before emptying into the Black Sea. For centuries it served as a trade route and a natural border between empires, and today it passes through ten countries.

One name, two worlds: Ecuador and the equator

Ecuador takes its name directly from the equator, which runs across the country just north of Quito. The Spanish word "ecuador" simply means "equator", a reminder that the line is an abstract convention rather than a visible feature. It divides the Earth into the Northern and Southern Hemispheres, and crosses a surprising mix of terrain, from Pacific coastline to Andean highlands and Amazon rainforest.

Chaplin and the art of silence

Charlie Chaplin became one of the defining faces of early 20th-century cinema, largely through silent films featuring his Tramp character. What is striking is how long he resisted sound: "City Lights" and "Modern Times" were released well after talking pictures had arrived. His blend of slapstick and pathos showed that comedy could work without a single line of dialogue.

Nitrogen and its easily confused neighbours

Nitrogen carries the symbol N, one of the few single-letter symbols on the periodic table. It makes up about 78 per cent of the air we breathe, yet most of it is chemically unreactive, which is why it took chemists time to understand its role. Its neighbours on the table, niobium (Nb) and neon (Ne), are often mixed up with it in quizzes precisely because their symbols begin with the same letter.

JFK in Dallas, a date that stuck

John F. Kennedy was assassinated in Dallas on 22 November 1963, an event that shocked the world and shaped American politics for years afterwards. The date became one of those moments people remembered by asking where they were when they heard the news. Lyndon B. Johnson was sworn in as president aboard Air Force One just hours later.