The distance east and west from the prime meridian is measured in degrees of longitude. The prime meridian is defined as 0 degrees longitude, and it runs through Greenwich, England. As you move east from the prime meridian, the degrees increase up to 180 degrees east, and similarly, as you move west, the degrees increase up to 180 degrees west.
Each degree of longitude corresponds to about 69 miles (111 kilometers) at the equator, but this distance decreases as you approach the poles due to the curvature of the Earth. Thus, if you are located at 30 degrees east, you would be roughly 2,070 miles (3,346 kilometers) away from the prime meridian, while being at 30 degrees west would put you the same distance in the opposite direction. Understanding longitude is crucial for navigation, mapping, and understanding time zones around the world.