Distant Nature: Astronomy Exercises
Objectives
This exercise will help to explain the Earth's diurnal (daily) motion. The apparent motion of the the sky over one day.
Equipment/Materials Needed
Stellarium, Calculator, Small Plastic Protractor.
Subject Introduction
If you ever have looked up in the sky at different times during a night, and noticed that over several hours the stars seem to move? During a sunny day, have you noticed the Sun moving from the East horizon to the West? This "apparent" motion of the sky is called diurnal motion. This diurnal (daily) motion is caused by the rotation of the Earth about its axis. Since it takes the Earth 24 hours to complete one rotation, the diurnal motion caused by this rotation will also take 24 hours to repeat. The direction the sky moves is also related to the rotation of the Earth. If you were looking down on the Earth from space, you would see it rotating from west to east, this is the true motion of the Earth. For a person on the Earth, however, the Earth appears to be stationary. Therefore, for that person, the sky seems to rotate from east to west. We then observe, stars, planets, the Moon and Sun appearing to rise in the east and set in the west.