THE BEGINNING AND THE END OF THE PRAYER TIMES FROM THE POSITION OF THE SUN

The Earth rotates about its axis from west to east. In other words, an overhead view of it, like that of a globe placed on a table (with the North Pole pointing upwards), would reveal that it rotated in a counterclockwise direction. This is called the true (direct, prograde) motion. The Sun and the fixed stars appear to make a revolution per day from east to west. This is called the retrograde motion. The time between two successive meridianal transits of a star at a certain location is defined as one sidereal day. One-twenty-fourth of this period is one sidereal hour. The time interval between two successive transits of the centre of the Sun across the meridian, that is, the time between successive instants of true zawâl is called one true solar day. Meanwhile, the Earth moves from west to east along the ecliptic and completes one revolution per year around the Sun. Due to this motion of the Earth, the Sun appears to move from west to east on the ecliptic plane, rotating about the ecliptical axis through the Earth’s centre perpendicular to the ecliptic plane. The average speed of this translational movement is about 30 kilometres per second, though it is not constant. Since the orbit of the Earth on the ecliptic plane is not circular but elliptical, the angles subtended by the arcs travelled in equal intervals are not equal. The smaller its distance to the Sun, the higher its speed.