DIURNAL MOTION Meaning and
Definition
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Diurnal motion refers to the apparent daily movement of celestial bodies, particularly the sun, in relation to the Earth. It is the rotation of the Earth on its axis that causes this phenomenon. As the Earth rotates from west to east, celestial bodies appear to move across the sky in an eastward direction.
The diurnal motion of the sun is evident as it rises in the east, reaches its highest point at noon, and sets in the west. This cycle is repeated each day due to the Earth's rotation on its axis, completing a full rotation in approximately 24 hours.
The angle at which the sun appears in the sky changes throughout the day, resulting in the diurnal arc. At sunrise and sunset, the sun's position appears lower on the horizon, while at noon it is positioned higher in the sky.
Other celestial bodies, such as the stars, also demonstrate diurnal motion. However, due to their immense distance from Earth, this motion is extremely subtle and often imperceptible to the naked eye over short periods. Nevertheless, when observed for more extended periods, stars also exhibit the eastward motion caused by Earth's rotation on its axis.
Overall, diurnal motion is a fundamental concept in astronomy that describes the apparent movement of celestial bodies across the sky throughout the day due to the rotation of the Earth.
Etymology of DIURNAL MOTION
The word "diurnal motion" originates from two Latin words: "diurnus" meaning "daily" and "motio" meaning "motion". In astronomy, diurnal motion is used to describe the apparent daily motion of celestial bodies across the sky caused by the rotation of the Earth on its axis.
