Beyond the answers - interesting background to this quiz

A physicist's proposal that became the web

Tim Berners-Lee was working at CERN, the European particle physics laboratory near Geneva, when he proposed a system for sharing documents across the internet. In 1990 he wrote the first web browser and server, and the following year the first website went live. Crucially, CERN put the underlying technology into the public domain in 1993, which is a large part of why the web spread so quickly rather than staying locked inside one organisation.

Why the equator is a line on a map, not in the ground

The equator is an imaginary circle, roughly 40,000 kilometres around, drawn at equal distance from the two poles. It crosses Gabon in West Africa along with a string of other countries, including Ecuador, Kenya, Indonesia and Brazil. Places near it tend to be warm and humid year round, and it is also where the Coriolis effect, which helps steer large weather systems, fades to almost nothing.

Roman numerals and the missing zero

Roman numerals grew out of a practical counting system and have no symbol for zero, which is one reason arithmetic with them is awkward. Values are built by adding and subtracting: a smaller numeral before a larger one is subtracted, so 152 becomes CLII - 100 plus 50 plus two ones. The system still turns up on clock faces, film credits and the occasional building date.

Agoraphobia is not really about open spaces

The word agoraphobia comes from the Greek agora, the public gathering place, and it is usually described as anxiety about situations that feel difficult to escape rather than simply a fear of wide-open areas. Many people with the condition are most uneasy in crowds, queues or public transport. It is one of the better-known anxiety disorders, and it is treatable, often with talking therapy.

Rodents: small, numerous and everywhere

Rodents form the largest order of mammals, with roughly 2,000 species, from mice and rats to beavers, porcupines and capybaras. Their defining feature is a pair of continuously growing incisors that must be worn down by gnawing. Their numbers and adaptability make them important seed dispersers and prey animals - and, less happily, carriers of disease and pests in stored food.