The solar system is the Sun and everything that travels around it: eight planets, their moons, and countless smaller rocky and icy objects. The Sun sits at the centre, and its gravity holds everything in a path called an orbit. In order outward from the Sun, the eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A trick many students use to remember the order is "My Very Easy Method Just Speeds Up Naming".
The four planets closest to the Sun, Mercury, Venus, Earth and Mars, are called rocky planets. They are small, made of rock and metal, and have a solid surface you could stand on. The four planets furthest out, Jupiter, Saturn, Uranus and Neptune, are called gas giants. They are enormous but made mostly of gas, with no solid surface. Scientists split this group further: Jupiter and Saturn are the true gas giants, while Uranus and Neptune hold far more water, ammonia and methane ice, so they are also called ice giants. Both are still giant planets with no solid surface to stand on.
The further a planet is from the Sun, the further it has to travel to complete one orbit, and the more slowly it moves. This means orbit time grows a great deal with distance.
Label the Sun and the eight planets on the diagram below, in order outward from the Sun. Then answer the questions using the diagram to help you.
Complete the table below by writing each planet's name in the correct column: rocky planet or gas giant. Then answer the questions.
| Rocky planets | Gas giants |
|---|---|
Explain one difference between rocky planets and gas giants. Use the words rocky, gas and surface in your answer.
Earth is always moving in two different ways at once, and it is easy to mix them up. Rotation is Earth spinning like a top, turning all the way around once every 24 hours on an imaginary line called its axis, running from the North Pole to the South Pole. Revolution, or orbit, is Earth travelling all the way around the Sun, which takes about 365 days, or one year.
Day and night are caused by rotation, not by the Sun moving. The Sun does not rise, cross the sky and set: it stays roughly in the same place while Earth spins. The half of Earth facing the Sun has daytime, and the half facing away has night, as the diagram below shows. As Earth keeps spinning, every place moves gradually from the lit side to the dark side and back again, which is why the Sun only appears to rise in the east and set in the west.
Answer each question below in full sentences.
1. What is the difference between Earth's rotation and Earth's orbit?
2. Explain what causes day and night. Use the word rotation in your answer.
3. A classmate says, "The Sun moves across the sky each day." Explain why this is not quite right.
4. How long does it take Earth to complete one full rotation? How long does it take Earth to complete one full orbit of the Sun?
Earth's axis is not upright: it leans over at an angle, called Earth's tilt, of about 23.5 degrees. This tilt keeps pointing in the same direction in space all year, even as Earth orbits the Sun. Because of this, different parts of Earth lean towards the Sun at different times of the year, and that is what causes the seasons.
When the Southern Hemisphere, where Australia is, tilts towards the Sun, it gets more direct sunlight and longer days, so it is summer. Six months later, Earth has moved to the far side of its orbit, and the Southern Hemisphere now tilts away from the Sun, so it is winter. At the very same time, the Northern Hemisphere tilts the opposite way, which is why the two hemispheres always have opposite seasons: when Australia has summer in December, places like Canada and the United Kingdom are having winter.
Read each statement. Write T for true or F for false in the space provided.
This is a challenge activity: use everything you have learnt about orbit, rotation and tilt to answer these questions about Australian seasons.
Why is Australia in summer in December, while the United Kingdom is in winter at the same time?
A pen pal in Canada writes: "It must be strange that Earth moves closer to the Sun to make it hot in summer." Write a reply explaining what really causes the seasons, and correct their mistake. Mention Earth's tilt and orbit in your answer.
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Same Year 6 Science outcomes, printed on A4 with a parent answer sheet, rebuilt around whatever your child is into this week - dinosaurs, Minecraft, horses, you name it.
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