That's a line that joins the north and south poles, called the Prime Meridian.
the prime meridian
The name of the line that has 0 longitude is the prime meridian
0 Longitude is for the reference of the Prime Meridian and the 0 Latitude is for the reference of the Equator.
they call parells
meridians
They are also called Meridians.
name all the continents found at longitude
prime meridrian
Prime Meridian
0 longitude is the prime meridian. 0 latitude is the equator.
The Prime Meridian itself is defined as zero longitude. (0°) You can't get any closer to it than that. The higher the number of degrees of longitude, the farther a given longitude is from the prime meridian. The maximum is 180° either east or west. There is no minimum. Whatever longitude you name, no matter how close it is to the Prime Meridian, I can always name one that's closer to it than yours is. It's like asking "What is the smallest number ?" There's no such thing.
Prime Meridian. 180 longitude is the Iinternational Date Line, and the equator is 0 degrees latitude