The 1884 International Meridian Conference decided that time would be standardised based on when the sun passes across the Greenwich Meridian. As everything would be measured from this line it was labelled zero!
In an atlas map, other longitude lines will be marked but they are all measured from the 0° of Greenwich. Most of Europe and Asia are to the east, while the Americas are to the west of Britain. If you find an atlas map of Britain with longitude lines marked, you will see that the British Isles goes from nearly 2° east of the Greenwich Meridian to over 10° west on the west coast of Ireland.
Notice – longitude lines are not parallel. Parallel lines stay the same distance apart but if you look carefully at Britain the longitude lines are closer together in the north. Makes sense if you think about it because the lines all meet at the north pole and the south pole, so they will get closer together as they get closer to the poles. Do you know where they would be furthest apart?
If you use GPS to find your way around, then converging longitude lines are not a problem but they don’t work so well on a paper map. To help locate places on a more detailed paper map, you usually find that it is divided into squares – squares drawn with parallel lines. This means that north isn’t quite where you think it is! I’ll help you find it next week!