Beyond the answers - interesting background to this quiz

The composer who could not stop writing variations

Sergei Rachmaninoff wrote his Rhapsody on a Theme of Paganini in 1934, casting it as a set of 24 variations for piano and orchestra. The theme comes from Niccolo Paganini's 24th Caprice for solo violin, a melody that had already tempted Liszt, Brahms and others. Rachmaninoff's twist is that he also weaves in the plainchant melody known as the Dies Irae, a musical signature of mortality that runs through much of his work. The 18th variation, a warm inversion of Paganini's theme, became one of his most beloved pieces.

Why copper carries a Cypriot name

The chemical symbol Cu comes from cuprum, the Latin word for copper, and that in turn is linked to the island of Cyprus, where the metal was mined in antiquity. Copper was one of the first metals humans worked, valued because it is soft, conducts electricity well and can be alloyed with tin to make bronze. That discovery helped define an entire era of human history.

A river that keeps changing its name

The Mekong begins on the Tibetan Plateau and runs through China, Myanmar, Laos, Thailand, Cambodia and Vietnam before emptying into the South China Sea. Its name changes from country to country: it is the Lancang in China and the Mekong further south. The river supports one of the world's richest inland fisheries and provides water and transport for tens of millions of people, which is why dams and water management along its course are such a sensitive subject.

Jupiter, the giant with the biggest magnet

Jupiter's magnetic field is roughly 20,000 times stronger than Earth's, making it the most powerful of any planet in the Solar System. It is generated by the movement of electrically conducting material deep inside the planet, and it drives spectacular auroras near Jupiter's poles. NASA's Juno spacecraft has been studying this magnetic environment at close range since 2016.