CLASS 7 · LEARNING KNOWLEDGE

Celestial motions from the observer’s perspective – basic principles

How it works

The apparent motions of the Sun, Moon, stars, and planets in the sky are caused by the Earth’s rotation, its orbit around the Sun, and the proper motions of other celestial bodies. From Earth, many celestial objects seem to move across the sky from east to west over the course of the day. This daily motion of the sky is mainly caused by Earth’s rotation. An observer’s location on Earth affects how high celestial bodies are in the sky and when they are visible. The seasons arise from the tilt of Earth’s axis and Earth’s orbit around the Sun. As a result, the Sun’s position in the sky and the length of the day change. In the Northern Hemisphere, Earth’s axis is tilted toward the Sun in summer and away from it in winter; in the Southern Hemisphere, it is the opposite.

Note
The apparent motion of celestial bodies in the sky is the result of Earth’s rotation and revolution as well as the bodies’ own motions. What one sees depends on the location and the time of day.

An example

Why does the Sun rise in the east and set in the west for an observer on Earth?

The Earth rotates from west to east. As a result, it appears to an observer as if the Sun moves from east to west across the sky.

Try it yourself now

50 Exercises · three difficulty levels · selection and number input

To the learning unit →

Own explanation and own practice exercises by AmyMath. Subject reference framework: KMK Educational Standards Mathematics ESA/MSA. The topic assignment may vary by federal state.