LInes of longitude

Today in class we started talking about the lines of longitude.  these lines are called meridians, and they run north to south and are used to measure the degrees east or west of the prime meridian. the prime meridian is 0 degrees east or west.  all of these lines converge at the north and south poles.  then because lines of longitude and time zones are closely related we moved onto to talking about timezones.  Each timezone is about 15 degrees of longitude in size,  but it often caters to the borders of nations or states for convenience of legal, commercial, or social purposes.  these timezones are counted from the prime meridian which runs through Greenwich England.  The time in Greenwich is the standard time of the world and the western hemisphere is negative compared to Greenwich, and the eastern hemisphere counts forwards.  The time in Greenwich is also known as UTC or Coordinated universal time this is the standard time that the rest of the world counts off of.