If you’ve ever looked at a globe or a map of the world, you’ve probably noticed lots of different lines. What do all these lines mean? If you go to those parts of the world, can you see the lines? Could you trip over them?

Don’t worry! None of those lines are actual lines that you can see on the ground. They’re just imaginary lines we use on maps to help us measure and understand the world we live in.

The lines you see on a globe or a map of the world are called lines of latitude and longitude. Latitude lines run east and west (side to side) and help us measure distances north and south. Longitude lines run north and south (up and down) and help us measure distances east and west.

Latitude and longitude lines measure distances in units called degrees. The lines of latitude and longitude where we start measuring from have special names. The equator is 0 degrees latitude, and the prime meridian is 0 degrees longitude.

The equator is the halfway point between the North Pole and the South Pole. It runs from side to side across the middle of the Earth through parts of South America, Africa and Asia.

The prime meridian runs through the United Kingdom, France, Spain, parts of Africa and Antarctica. Its position was not determined by choosing a halfway point between particular natural features, like the Earth’s poles.

In fact, although the earliest maps have the equator marked on them, the prime meridian wasn’t officially named and marked until the late 1800s. Before that time, over a dozen different locations were being used to mark 0 degrees longitude. The International Meridian Conference of 1884 chose a single line of longitude running through Greenwich, England, as the prime meridian.

The earth is a sphere and the equator and the prime meridian divide the Earth into four hemispheres: north, south, east and west. For example, the United States is in both the Northern Hemisphere (because it’s north of the equator) and the Western Hemisphere (because it’s west of the prime meridian).

Because of the equator’s position halfway between the Earth’s poles, its climate is warm and sunny. Tropical rainforests thrive near the equator because of the sun and rain areas receive along the equator.

If you wanted to travel all the way around the Earth along the equator, you’d need to travel about 25,000 miles! It’s difficult to measure the exact length of the equator, though, because it travels up and down hills and mountains throughout South America and Africa.