With just two numbers, you can find any place on Earth. The system is so precise, your left hand is in a different location than your right. To understand how this works, we have to go back more than 3,500 years to the Babylonians.
Degrees and Circles
The Babylonians divided a circle into 360 degrees. The symbol for a degree is °. Long before calculators, they worked with fractions. The number 360 was helpful because it can be divided evenly by 2, 3, 4, 5, 6, and 10, so the math was easier.
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An ancient Greek thinker named Claudius Ptolemy wrote one of the first books on geography. He explained that a sphere can be measured in degrees. The distance from the equator to either pole is 90 degrees—a right angle. The North and South Poles are 180 degrees apart. Using this system, he gave every place on Earth a unique address. Geographers use it to create lines of latitude and longitude.
Latitude and Longitude
The horizontal lines that circle the globe from east to west are called Lines of Latitude. They measure distance north or south of the equator and are also known as parallels because they run in the same direction as the equator. The equator is the imaginary line—a sort of belt around the Earth—that is as far away from the North Pole as it is from the South Pole.
Lines of longitude cross the equator at right angles, and all of them meet at the North and South Poles. They are also called meridians. Meridian comes from a Latin word meaning midday. The sun is directly over each meridian at solar noon—the point halfway between sunrise and sunset.
In 1884, the International Meridian Conference chose to make the line at 0° longitude run through the Royal Observatory in Greenwich, England, though they could have chosen any location on Earth. This line is called the prime meridian.
Meridians are counted east and west from the prime meridian. St. Louis, Missouri, is 90° west of the prime meridian—one-fourth of the way around the Earth. The International Date Line is 180°—as far away as possible—from the prime meridian. When it is noon along the prime meridian, it is midnight along the International Date Line.
Geographers also divide the Earth into hemispheres. Hemi- is a prefix that means half. Everything north of the equator is in the Northern Hemisphere, and everything south of it is in the Southern Hemisphere. The Western Hemisphere is west of the prime meridian, and the Eastern Hemisphere is east of it. Both extend to the International Date Line. The United States is north of the equator and west of the prime meridian, so Americans live in the Northern and Western Hemispheres. The White House in Washington, D.C., is 77° west of the prime meridian and 39° north of the equator. A location is written with latitude first, then longitude—for example, 39°N, 77°W.
Cell phones can identify your exact location using latitude and longitude—even if you move your phone from one hand to the other. The Babylonians divided each degree into 60 minutes and each minute into 60 seconds—the same system we use to tell time. Today, locations are often shown as decimal fractions of a degree. Look at the bottom of Google Earth to see the exact location wherever you place your cursor.
Absolute and Relative Locations
If someone were to ask for the location of the Empire State Building, you might answer that it is at 350 5th Ave, New York, New York in the 10118 zip code. It probably wouldn’t be very helpful, but you could also truthfully answer that the president lives precisely at 40°45’04.35″N, 73°59’10.17″W. These are examples of absolute locations.
It is often more helpful to describe your relative location. For example, the Empire State Building is 25 blocks south of Central Park. We could also say that the Empire State Building is across the street from McDonald’s (it really is!). Both absolute and relative location are useful tools for geographers, and we will use both throughout our study.
Finding Your Absolute Location
You can find the exact location of any place on Earth by clicking on earth.google.com. The coordinates are at the very bottom of the page.
A cellphone can also tell you your exact location. On an iPhone, go to the Compass app that comes installed. On an Android device: Open Google Maps. Tap the blue dot that shows your current location. A screen will slide up from the bottom showing your exact coordinates (latitude and longitude).
Arriving the Day Before You Leave
Russia’s Big Diomede Island is in the Bering Strait, just 2.4 miles from Little Diomede in Alaska. Big Diomede is a Russian military outpost, while about 80 people live on Little Diomede. When it is 2:00 p.m. Wednesday on Big Diomede, it is 2:00 p.m. Tuesday on Little Diomede.
The frigid Arctic water did not stop endurance swimmer Lynne Cox from making the crossing. Even in summer, the water temperature was only about 43°F (6°C), yet she swam without a wetsuit. Clad only in a swimsuit, cap, and goggles, Lynne left Alaska on Friday, August 7 and arrived on Big Diomede Island about two hours later on Saturday, August 8. Because she traveled west across the International Date Line, she arrived on the next calendar day. If she had swum in the opposite direction, she would have arrived nearly a day before she started.
Resources
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Mr. Donn has an excellent website that includes a section on Geography.
Cite this page:
Dowling, Mike, “Longitude and Latitude: Identify Any Place on Earth,” mrdowling.com, September 17, 2026. Web. [Date of access].
Sources:
Claudius Ptolemy, Geographia (c. 150 CE), trans. J. Lennart Berggren and Alexander Jones, Ptolemy’s Geography: An Annotated Translation of the Theoretical Chapters (Princeton University Press, 2000)
International Meridian Conference, Protocols of the Proceedings (Washington, D.C., 1884)