Diurnal motion refers to the apparent daily movement of celestial objects across the sky from east to west due to the Earth’s rotation on its axis. This rotation causes the sun, stars, planets, and other celestial bodies to seemingly rise in the east, reach their highest point (culmination) in the sky, and then set in the west. The term “diurnal” comes from the Latin word “diurnalis,” meaning “daily.” This motion is primarily caused by the Earth’s rotation, completing a full rotation approximately every 24 hours. As the Earth turns, observers on its surface experience different celestial bodies appearing and disappearing over the horizon at different times. Notably, the diurnal motion is responsible for the alternation of day and night.
