<Li> Height of the horizon changes the day's length . For an observer atop a mountain the day is longer, while standing in a valley will shorten the day . </Li> <P> Some of the statements above can be made clearer by picturing the day arc (i.e., the path along which the Sun appears to move across the sky). The pictures show this for every hour on equinox day . In addition, some' ghost' suns are also indicated below the horizon, up to 18 ° below it; the Sun in such areas still causes twilight . The depictions presented below can be used for both the northern and the southern hemispheres . The observer is understood to be sitting near the tree on the island depicted in the middle of the ocean; the green arrows give cardinal directions . </P> <Ul> <Li> In the northern hemisphere, north is to the left, the Sun rises in the east (far arrow), culminates in the south (right arrow), while moving to the right and setting in the west (near arrow). </Li> <Li> In the southern hemisphere, south is to the left, the Sun rises in the east (near arrow), culminates in the north (right arrow), while moving to the left and setting in the west (far arrow). </Li> </Ul> <Li> In the northern hemisphere, north is to the left, the Sun rises in the east (far arrow), culminates in the south (right arrow), while moving to the right and setting in the west (near arrow). </Li>

Where do you find day and night equal