Measuring the Earth with a shadow
Around 240 BC, a Greek scholar in Egypt called Eratosthenes, the head of the great library at Alexandria, heard that at noon on midsummer's day the Sun shone straight down a well in the town of Syene, far to the south, casting no shadow. On the same day in Alexandria, an upright stick did cast a short shadow. From the angle of that shadow and the distance between the two towns, he worked out the size of the whole Earth. His answer was remarkably close to the real figure of about 40,000 kilometres around the EQUATOR, more than 1,700 years before anyone sailed round it.
The word geography itself comes from Greek words meaning writing about the Earth. It covers the physical world, every MOUNTAIN, RIVER, DESERT and COAST, and the human one, every COUNTRY, CAPITAL and BORDER.
Where people live
There are now more than eight billion people on Earth; the figure passed eight billion in 2022. Since around 2007 more than half of them have lived in towns and cities rather than the countryside. People are spread very unevenly. A circle drawn around South and East Asia, taking in India, China, Japan and South-east Asia, holds more than half the people in the world, even though it covers only a small part of the planet's surface.
At the other extreme, huge areas have almost nobody: the frozen TUNDRA of the far north, the great deserts, and the whole of Antarctica, where only scientists spend the winter, in research stations that are resupplied by plane and ship.
Record-breaking places
The spot in the ocean furthest from any land is called Point Nemo, in the South Pacific, more than 2,600 kilometres from the nearest island. It is so remote that the closest people are often the astronauts passing overhead on the space station, about 400 kilometres up, and space agencies steer old satellites down to crash into the sea there, far from anyone.
Saudi Arabia is the largest country in the world with no permanent river at all; its riverbeds fill only after rare storms. The border between Canada and the United States is the longest land border between two countries, nearly 9,000 kilometres, and much of it is a straight line along a single line of latitude.
Climate zones
The CLIMATE of a place depends mostly on how far it is from the equator. Near it, in the TROPICS, the Sun is high overhead all year, and it is hot and often wet. Towards the poles, sunlight hits the ground at a low angle and spreads out, so it is colder. Height matters too, so a GLACIER can sit on a mountain near the equator, and so does the sea, which keeps coastal places milder. Lines of LATITUDE on a map, and in an ATLAS, help show where each zone lies.
Every feature in the grid, from the OCEAN and the CONTINENT to the VOLCANO, VALLEY, CANYON, PENINSULA, PLATEAU, ISLAND and DELTA, has its own page in this category, and a COMPASS will help you find them all.