Question

Cleveland is located at about 81 degrees W. Is sunrise in Cleveland earlier or later than sunrise at the principal meridian for its time zone?

Answer 1

Meridians are the line joining the north pole and south pole and are perpendicular to the equator. The zero line (0 degree longitude) also known as Prime Meridian passes through Greenwich, England. This line is used as reference to measure longitudes in degrees. Different time zones are based on the position from Prime meridian. Earth rotates 15 degree per hour (360 degree/24 hrs) therefore time zones are set for each 15 degree longitude. Hence there are 24 time zones and the difference between each time zone is 1 hr.  

Now coming to the question, thereotically there is no any time difference between two location in the same time zone. However due to solar time,the sunrise and sunset time are different for different location (even in the same time zone). This leads to the apparent time of sunrise on the clock time at later time in west side of the timezone to that of the east side.