Every place in the world has two numbers: latitude and longitude. Latitude lets you know how many degrees south or north a location is in the equator. It’s a number between 0 and 90. For instance Alexandria in Egypt is 31.25 degrees northwest.
Longitude lets you know how many degrees east or west a location is from London. It’s a number between 0 and 180. Therefore we state Alexandria is 31.25 N, 30 E. Sometimes this is only written as “31.25, 30” where it is understood that the first number is latitude and that negative numbers mean south to get latitudes and west for longitudes.
A degree is a way to quantify how far round a circle you are. A circle contains 360 degrees. Half way round a ring is 180 degrees. A fourth of the manner is 90 degrees. And so Forth.
The equator is a line that divides the earth into two equal halves, a north and a southwest.
Longitudes start at the Royal Observatory at Greenwich in London. When the current system was set up, Britain was the top sea-going nation so their largest city became the starting point.
From the previous days boats set their own clocks to the period of the Greenwich Observatory in London, called Greenwich Mean Time (GMT). Then, wherever they moved, they might tell exactly what their longitude was by viewing what time was on their clock when the sun reached its highest point in the sky at dusk.
Each hour equals 15 degrees of longitude. If noon arrived before 12:00 GMT, then you had been that numerous degrees of longitude east of London. Otherwise you’re to the west. To find your latitude you measured how many levels high the north star was — or another celebrity of known place.
To locate your latitude you quantified the number of levels high the north star was — or even some other star of known place.
All this measuring was performed by means of an astrolabe, All this measuring was performed by an astrolabe, later with a sextant. Even without anything special except a clock you’ll be less than 1,000 km away.
Since 1500 that has allowed Westerners to cross the seas without becoming lost. That meant they could discover and take over new lands. They could also deliver goods faster and cheaper and take over world trade.
These days you can just use a GPS to find out your latitude and longitude. Inspired by the American army, it talks to satellites in orbit round the earth and out of that it can tell where it’s. Most ships and aircraft include you, so do a few cars.
The latitude and longitude of each computer on the Internet can also be understood. So there are sites you can visit to find out the latitude and longitude of the computer that is connecting you to the Internet. This will not be exactly like your own latitude and longitude but it’ll be close.
Latitude and longitude isn’t as fresh as you may think. In Roman times Ptolemy listed the latitude and longitude of all 8,000 places from Spain to China in his book on geography.