Days on Different Lengths

DAYS ON DIFFERENT LENGTHS On June 21 the sun is overhead along the Tropic of Cancer and all parallels in the northern hemisphere have their longest day of the year. At this time the length of the day increases as latitude increases north of the equator until there is continuous day north of the Arctic Circle. South of the equator the length of day decreases with increasing latitude until there is continuous night south of the Antarctic Circle. On Decem­ber 22, the reverse takes place for the two hemispheres.

MIDNIGHT SUN It is a phenomenon, observable in latitudes 661,i° North and South (or the Arctic and Antarctic circles respectively) where the sun does not sink below the horizon during summer. This results due to the tilt of the earth's axis, each hemisphere being inclined towards the sun during its summer. The duration of the phenomenon increases towards the poles, where it may be observed for six months of each year.
TIME
To avoid confusion and make the study of time relations simple, it is necessary to think of the earth as stationary and of the sun as completing one circuit about the earth every 24 hours.