Earth, Moon and Sun
Earth, the Moon, and the Sun have a special relationship. Earth orbits the Sun, and the Moon orbits Earth. These movements cause day/night, seasons, and lunar phases.
What You Need to Know
Key Concept Diagram
Earth rotates on its axis once every 24 hours, causing day and night
Earth orbits the Sun once every 365.25 days, causing the year and seasons
The Moon orbits Earth every 27-29 days, causing lunar phases
The Moon does not produce its own light — it reflects sunlight
Key Vocabulary
Orbit
The curved path of one object moving around another due to gravity
Rotation
The spinning of Earth on its own axis, causing day and night
Lunar phase
The changing appearance of the lit portion of the Moon as seen from Earth
Axis
The imaginary line through Earth's North and South Poles, around which it spins
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
What causes day and night on Earth?
Question 2
How long does it take Earth to complete one orbit around the Sun?
Question 3
Why does the Moon seem to change shape each night?
Key Concepts Summary
- ●Earth rotates on its axis once every 24 hours, causing day and night
- ●Earth orbits the Sun once every 365.25 days, causing the year and seasons
- ●The Moon orbits Earth every 27-29 days, causing lunar phases
- ●The Moon does not produce its own light — it reflects sunlight