Every place on Earth has an address made of just two numbers.
🌍 Play this lesson on the globe
Every place on Earth has an address made of just two numbers. The first is its latitude. Lines go round the Earth like belts: the equator is 0°, and they count up to 90° at the North and South Poles.
The second number is its longitude. Its lines run from pole to pole. The prime meridian, 0°, runs through Greenwich in London, and you count up to 180° east or 180° west, which meet on the far side of the world.
Put the two numbers together and you have an address. At 0°, 0° the equator crosses the prime meridian. There’s no land here, just open sea off West Africa, where a weather buoy called Soul bobbed on the waves for years.
The Earth’s axis leans over by about 23.4°. Because of that lean, the midday sun can only ever be straight overhead between 23.4° north and 23.4° south. Those lines are the Tropic of Cancer and the Tropic of Capricorn, and the belt between them is the tropics.
The lean also sets the Arctic Circle and the Antarctic Circle, at about 66.6°. Past them, the sun doesn’t set on at least one day each summer. Drag the slider to change the lean and watch all four lines move.
Latitude also tells you roughly how warm a place is (the colours are drawn simply). Near the equator, the midday sun hits the ground almost straight on. Near the poles it comes in low, so the same sunlight spreads thin over much more ground.
Longitude tells you the time. The Earth turns all the way round, 360°, every 24 hours, so it turns 15° every hour. So when the sun is highest over Greenwich, it’s already 2 pm by the sun 30° further east.
The first number says how far north or south of the equator a place is. The second says how far east or west of Greenwich. The 30° lines are marked.
🌍 Play this lesson on the globe
The globe pictures are simplified to show the idea. Earth images: NASA Blue Marble (public domain).