Final answer:
The apparent motion of stars and constellations over a night is a result of Earth's rotation. Constellations maintain their shape but change position, while planets may show more complex motion due to Earth's orbit combined with their own movements. The concept of the celestial sphere helps us understand these patterns in the night sky.
Step-by-step explanation:
The apparent motion of stars and constellations over a night is primarily due to the rotation of Earth on its axis. As Earth rotates from west to east, stars seem to move from east to west across the sky, tracing circular paths around the celestial poles. Constellations maintain their shape but will rotate and change position in the sky throughout the night. The celestial sphere concept allows us to visualize stars as if affixed to an immense sphere surrounding Earth, which rotates as a whole.
The apparent wandering of planets across the sky, also known as planetary motion, is more complex. This is because the Earth's revolution around the sun and the planets' own motion combine to create patterns that can sometimes make planets appear to move backward, referred to as retrograde motion. The Earth's positional change along its orbit creates an effect known as stellar parallax on nearby stars, which is analogous to watching objects shift as you move head from side to side. However, over the course of a single night, this parallax is barely perceptible, and the stars appear to move uniformly due to Earth's rotation rather than its revolution around the sun.