Where can you find pictures of lines of longitude?
Look at a globe, or map of the world, or any large scale map (Not a road map or street plan) and there are horizontal lines (marked in degrees) & these are Latitude. The vertical lines are Longitude & they show the degrees that anywhere in the world is either East or West of Greenwich (The Prime Meridain) which is in London, England. The reason that Longitude is measured from Greenwich is because that was the HQ of the Admiralty (The British Royal Navy) when Longitude measurement was first established. Latitude had been known for centuries because itn depends entirely where the sun is in relation to the horizon in any given place. Longitude was different to measure: you need to know direction, speed & time difference & a correlation of these 3 things will tell you where you are in relation to another place. 180 degrees East & West of Greenwich is where the International Date Line runs from Pole to Pole through the Pacific Ocean