where do lines of longitude intersect on the globe?
http://education.nationalgeographic.com/encyclopedia/longitude/
Lines of longitude, also known as meridians, are imaginary vertical lines that run from the North Pole to the South Pole on the globe, measuring the east-west direction. Unlike lines of latitude, which are parallel, lines of longitude intersect at two points on the Earth. These two points are called the Prime Meridian and the Antimeridian.
The Prime Meridian, which corresponds to a longitude of 0 degrees, is globally recognized as the reference point for measuring longitude. It runs through Greenwich, London, in the United Kingdom. This is the location where the Royal Observatory is situated. Therefore, the Prime Meridian is commonly referred to as the Greenwich Meridian.
On the opposite side of the Earth, 180 degrees away from the Prime Meridian, lies the Antimeridian. It is an imaginary line that runs through the Pacific Ocean and serves as the dividing line between the Western Hemisphere and the Eastern Hemisphere. The Antimeridian marks the transition point between the regions where the longitude measurements move from 180 degrees East to 180 degrees West.
In summary, lines of longitude intersect at two points on the globe: the Prime Meridian at 0 degrees longitude, which passes through Greenwich, London, and the Antimeridian at 180 degrees longitude, which runs through the Pacific Ocean.