time
The highest longitude lines are the prime meridian at 0 degrees longitude and the 180 degrees longitude line. These lines mark the starting point for longitude measurements to the east and west, respectively.
The northern and southern hemispheres each have 360 degrees of longitude. The eastern and western hemispheres each have 180 degrees of longitude. You can use as many or as few 'lines' as you want, to mark off any number of degrees.
0 Degrees
Degrees.
Yes, but they only go up to the 90 degrees mark. On the other hand, the longitude line spreads out further to the 180 degrees mark.
Every point at that location has a longitude of zero. If you mark a dot at every point there, they form the line known as the "Prime Meridian".
Degrees.
75 degrees longitude.
"240 degrees east of the Prime Meridian" places you at 120 degrees west longitude.
On my large-scale map, the mark for the center of London is located at about 51.5 degrees north latitude, 0.17 degrees west longitude. I'll bet it's the one you're thinking of.
The Prime Meridian marks the zero degree line of longitude. The Equator marks the line for zero degrees latitude.
longitude