Earth and space
The Sun, Earth and Moon, day and night, the seasons, the phases of the Moon, and the solar system.
📌 Key points
- The Sun is a star at the centre of our solar system. The Earth and the other planets orbit (travel around) the Sun.
- The eight planets, in order from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
- The Earth spins on its axis once every 24 hours. The side facing the Sun has day and the side facing away has night.
- The Sun seems to rise in the east and set in the west because the Earth is spinning. It is the Earth that moves, not the Sun.
- The Earth takes about 36514 days (one year) to orbit the Sun.
- We have seasons because the Earth’s axis is tilted. When your half of the Earth is tilted towards the Sun, it is summer.
- The Moon orbits the Earth about once a month. We see it because it reflects light from the Sun.
- The Moon seems to change shape (its phases: new moon, crescent, half moon, full moon) because we see different amounts of its sunlit side.
- Gravity keeps the planets in orbit around the Sun and the Moon in orbit around the Earth.
📖 Key words
- Orbit
- The path of one object around another, such as the Earth around the Sun.
- Axis
- An imaginary line through the Earth from the North Pole to the South Pole. The Earth spins around it.
- Rotate
- To spin around. The Earth rotates once every 24 hours.
- Solar system
- The Sun and everything that orbits it, including the eight planets.
- Star
- A huge ball of hot gas that gives out light, like the Sun.
- Planet
- A large object that orbits a star.
- Phases of the Moon
- The different shapes of the Moon that we see during a month.
✏️ Worked example
It is daytime in Erbil. Explain why it will be night in Erbil about 12 hours later.
- The Earth spins on its axis once every 24 hours.
- Now Erbil is on the side of the Earth facing the Sun, so it is day.
- After about 12 hours the Earth has made half a turn, so Erbil faces away from the Sun.
- Answer: it is night because the Earth has spun round and Erbil now faces away from the Sun.
Learn the three times: the Earth spins once a day (24 hours), the Moon orbits the Earth about once a month, and the Earth orbits the Sun once a year (about 365 days).
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