Understanding Latitude: How We Measure Our Position on Earth

Latitude lines, or parallels, are imaginary lines that stretch from east to west across the globe. Although they run east to west, they actually show how far north or south a place is from the equator. The equator sits at 0 degrees and splits Earth into northern and southern halves. As you move toward either the North Pole or the South Pole, the numbers increase up to 90 degrees.

Several important parallels have special names connected to the sun. The Tropic of Cancer sits near 23 degrees north, while the Tropic of Capricorn sits near 23 degrees south. The area between these two lines forms the tropics. Farther away, the Arctic Circle and Antarctic Circle surround the cold polar regions near 66 degrees north and south. These circles help scientists understand climate, weather patterns, and ocean currents.

On Earth, one degree of latitude equals about 111 kilometers. Unlike longitude lines, which meet at the poles, latitude lines always stay the same distance apart. For centuries, sailors used the angle of the sun or stars to find their latitude at sea. For instance, measuring the North Star at 60 degrees above the horizon meant the ship was at 60 degrees north.

Today, satellites have replaced simple hand tools and older observations. More than 30 satellites circle the planet and send signals to receivers on the ground. Organizations like the National Ocean Service use these advanced systems to combine modern data. As a result, modern equipment can quickly measure a position within just a few centimeters.

How did early sailors use the sky to find their position, and how has that technology changed today?