What is the coldest continent?

Antarctica, by a wide margin. The lowest air temperature ever measured at the surface, minus 89.2 degrees Celsius, was recorded at the Russian Vostok Station in 1983; satellite readings of the ice surface have since found pockets below minus 98.

Three things make it that cold. It is at the pole, so it gets months of no sunlight at all. It is high - the ice sheet averages over two kilometres thick, which makes it by far the highest continent by mean elevation, and altitude costs temperature. And the ice reflects most of what sunlight does arrive straight back into space.

It also holds around 90 per cent of the world's ice and about 70 per cent of its fresh water, and if all of it melted sea level would rise something like 58 metres. Under the ice there is a whole hidden landscape - mountain ranges the size of the Alps that no one has seen, a canyon longer than the Grand Canyon, and hundreds of lakes of liquid water kept unfrozen by pressure and the Earth's own heat.