Earth, Sun and Moon · Grade 4
Earth spins on its axis once a day, giving day and night, and orbits the Sun once a year. Its axis is tilted, which gives us seasons – opposite in the two hemispheres. The Moon orbits Earth about once a month; as it does, we see different amounts of its sunlit half, giving the phases. Sometimes the three line up to make eclipses.
Key facts
- Day and night: Earth spins once every 24 hours. The Sun appears to move east → west.
- A year: Earth orbits the Sun in about 365¼ days.
- Seasons are caused by the tilt of Earth’s axis, not by our distance from the Sun.
- Solar eclipse: the Moon blocks the Sun (at new moon). Lunar eclipse: Earth’s shadow covers the Moon (at full moon).
- Earth turns 15° per hour, which sets time zones.
Worked examples
Example 1
It is 10:00 solar time at a place at 30°E. What is the solar time at 75°W?
Answer: 03:00