Repro ID: Day_Night
Title: Time equals longitude
Description: When it is midday on one side of the earth, it is midnight on the other. Each 15 degrees of longitude is the equivalent to a time difference of one hour. So a sailor found out how far east or west he was from home, by comparing the local time (which could be found from observations of the Sun or the stars) with the time back at home at the same moment.
Creator: Anton Vamplew
Credit line: National Maritime Museum