Beyond the answers - interesting background to this quiz

Why anniversaries get their own materials

Wedding anniversaries are traditionally linked to materials that grow more valuable with time, and the 40th is commonly known as the ruby anniversary. The idea is that a couple's bond, like a ruby, has become rare and precious after four decades. Different countries and gift lists vary slightly, but the ruby association is widely recognised.

The scale of the Great Barrier Reef

The Great Barrier Reef is the world's largest living structure, stretching for more than 2,300 kilometres off the coast of Queensland, Australia. It is not a single reef but a vast network of thousands of individual reefs and hundreds of islands. It is built by tiny coral polyps and supports an extraordinary range of marine life.

Protons and the identity of an element

The number of protons in an atom's nucleus is what defines its atomic number, and that number determines which element it is. Every hydrogen atom has one proton, every carbon atom has six, and so on. Change the proton count and you have a different element entirely, which is why this number sits at the heart of the periodic table.

The many names of Star Wars: Episode I

When Star Wars: Episode I arrived in 1999, it carried the subtitle The Phantom Menace. It was the first new Star Wars film in over a decade and the beginning of a prequel trilogy. The title refers to the hidden Sith threat lurking behind the film's political events.

A quick look at ammonia

Ammonia has the chemical formula NH3: one nitrogen atom bonded to three hydrogen atoms. It is a colourless gas with a sharp, recognisable smell and is widely used in fertilisers and cleaning products. Its simple formula hides a molecule that is central to modern agriculture.