Earth, Moon, and the Sun

Overview

The Earth, Moon and Sun move in regular patterns that cause day and night, the phases of the Moon and the seasons. This chapter explores these astronomical relationships.

Key concepts

• The Earth rotates on its axis, causing day and night.
• The Earth revolves around the Sun, causing seasons.
• The Moon revolves around the Earth.
• Phases of the Moon are the changing shapes we see.
• The Moon shines by reflecting the Sun's light.

Important terms / formulae

• Rotation: spinning of Earth on its axis (about 24 hours).
• Revolution: Earth orbiting the Sun (about 365 days).
• Phases of the Moon: changing lit shapes of the Moon.
• Satellite: a body that revolves around a planet.

Solved example or key process

As the Earth rotates once in about 24 hours, the side facing the Sun has day while the other side has night. As the Earth keeps spinning, places move from day into night and back, giving us the regular cycle of day and night.

Important questions

1. What causes day and night?
2. Why do we see different phases of the Moon?
3. Difference between rotation and revolution?
4. Does the Moon produce its own light?

Quick revision

Earth rotates to give day and night and revolves around the Sun to give seasons. The Moon orbits Earth and shines by reflecting sunlight, producing its phases.