Beyond the answers - interesting background to this quiz

The river that drains a continent

The Amazon carries more water than any other river on Earth, and its basin spreads across several South American countries, with most of it lying in Brazil. Its tributaries begin high in the Andes and cross Peru, Colombia and Ecuador before the main channel empties into the Atlantic. The river's scale is hard to picture: its outflow is so vast that it measurably dilutes the ocean's saltiness far from shore.

A planet with a magnetic field far bigger than Earth's

Jupiter's magnetic field is the strongest of any planet in the Solar System, generated by the movement of electrically conducting material deep inside it. The field is so large that its magnetosphere would appear bigger than the full Moon if it were visible in the night sky. It also traps intense radiation belts, which is one reason spacecraft visiting the Jovian system must be carefully shielded.

When the web became public

The World Wide Web was made publicly available in 1991, after Tim Berners-Lee developed it at CERN in the late 1980s. His early system combined hypertext documents, a browser and a server, and the first website described the project itself. What followed was not an overnight explosion of users, but a gradual spread as universities, then companies and households, got connected.

The machine that sped up thread-making

James Hargreaves is credited with the spinning jenny, patented in 1770 but developed around 1764. The device allowed a single operator to spin several threads at once, a leap from the traditional one-thread spinning wheel. It became one of the defining machines of the early Industrial Revolution, transforming textile production in Britain. Its success also unsettled workers who feared it would replace their livelihoods, and some spinning jennies were destroyed in protests.