Science · Year 5 · Earth and Space · Spring Term

The Solar System: Planets and Orbits

Describing the Sun, Earth, and Moon as approximately spherical bodies and their orbital paths around the Sun.

• National Curriculum Attainment Targets
• NC-KS2-Science-Y5-ES-1

About This Topic

The Movement of the Planets introduces students to the structure of our solar system, focusing on the Sun, Earth, and Moon as approximately spherical bodies. Students explore the concept of orbits and the relative sizes and distances of the planets. This topic is a key part of the KS2 Earth and Space curriculum, requiring students to describe the movement of the Earth and other planets relative to the Sun.

This unit is fundamental for developing a sense of scale and our place in the universe. It challenges students to think in three dimensions and understand forces like gravity on a celestial scale. This topic comes alive when students can physically model the solar system, using their own bodies or objects to represent the vast distances and orbital paths of the planets.

Key Questions

1. Explain what causes the different planets in our solar system to stay in orbit.
2. Compare the characteristics of inner and outer planets.
3. Predict how our view of the night sky would change if we lived on Mars.

Learning Objectives

• Compare the characteristics of the inner, rocky planets with the outer, gas giant planets.
• Explain how gravity causes celestial bodies to orbit the Sun and the Moon to orbit the Earth.
• Describe the Sun, Earth, and Moon as approximately spherical bodies.
• Model the orbital paths of the Earth around the Sun and the Moon around the Earth.

Before You Start

Basic Shapes and Properties

Why: Students need to recognize and describe basic 3D shapes like spheres to understand the form of celestial bodies.

Forces and Motion

Why: Understanding that forces cause objects to move or change direction is foundational for grasping the concept of gravity causing orbits.

Key Vocabulary

Orbit	The curved path of a celestial object, such as a planet or moon, as it moves around another celestial body due to gravity.
Gravity	A force of attraction that exists between any two objects with mass. It is what keeps planets in orbit around the Sun.
Sphere	A perfectly round geometrical object in three-dimensional space, like a ball. The Sun, Earth, and Moon are approximately spheres.
Inner Planets	The four planets closest to the Sun: Mercury, Venus, Earth, and Mars. They are rocky and smaller in size.
Outer Planets	The four planets farthest from the Sun: Jupiter, Saturn, Uranus, and Neptune. They are gas giants and much larger.

Watch Out for These Misconceptions

Common Misconception

The planets are all close together in space.

What to Teach Instead

Most diagrams in books show planets clustered together for clarity. By creating a scale model on the playground, students can see that if the Earth were the size of a pea, the outer planets would be hundreds of metres away, correcting their sense of scale through physical experience.

Common Misconception

The Earth is a perfect circle.

What to Teach Instead

Students often think of Earth as a flat circle or a perfect ball. Using the term 'approximately spherical' and discussing how the Earth bulges slightly at the equator helps them understand the more complex reality of planetary shapes, which can be modeled using soft clay.

Active Learning Ideas

Simulation Game: The Human Solar System

In a large outdoor space, students are assigned roles as the Sun and different planets. Using scaled distances, they 'orbit' the Sun at different speeds, helping them visualize the relative distance of each planet and why some take much longer to complete a 'year' than others.

45 min·Whole Class

Inquiry Circle: Spherical Proof

Groups are given historical 'clues' used to prove the Earth is a sphere (e.g., ships disappearing over the horizon, shadows during an eclipse). They must use models and torches to demonstrate how each clue works and present their 'proof' to the rest of the class.

50 min·Small Groups

Think-Pair-Share: Life on Another Planet

Students choose a planet and think about how its distance from the Sun would affect its temperature and length of a year. They pair up to discuss what 'daily life' might look like there, then share their ideas, focusing on the scientific constraints of each environment.

25 min·Pairs

Real-World Connections

• Space agencies like NASA use complex calculations based on orbital mechanics and gravity to send probes and astronauts to planets like Mars and Jupiter, ensuring they reach their destinations safely.
• Astronomers use telescopes to observe planets and their moons, tracking their movements to understand celestial mechanics and discover new celestial bodies. This helps us map our solar system and beyond.

Assessment Ideas

Exit Ticket

Give students a card with the names 'Sun', 'Earth', and 'Moon'. Ask them to draw a simple diagram showing their approximate spherical shape and draw arrows indicating their orbital paths. Include one sentence explaining why they stay in orbit.

Discussion Prompt

Pose the question: 'Imagine you are an astronaut on Mars. How would your view of the night sky, including any moons, be different from Earth's night sky? What would you see?' Encourage students to use vocabulary like 'orbit' and 'gravity' in their explanations.

Quick Check

Present students with a list of planet characteristics (e.g., rocky, gas giant, large, small, close to Sun, far from Sun). Ask them to sort these characteristics into two columns: 'Inner Planets' and 'Outer Planets', demonstrating their understanding of planetary classification.

Frequently Asked Questions

What keeps the planets in orbit around the Sun?

Gravity is the force that keeps planets in orbit. The Sun's massive gravity pulls on the planets, while their own forward motion (momentum) tries to keep them moving in a straight line. The balance between these two forces results in a curved, circular path called an orbit.

Why do we call the planets 'approximately spherical'?

While planets look like perfect balls from a distance, they are not perfect spheres. For example, the Earth's rotation causes it to bulge slightly at the equator and flatten at the poles. Scientists use the term 'oblate spheroid' to be more precise, but 'approximately spherical' is the standard for Year 5.

How can active learning help students understand planetary movement?

Space is too big to see all at once. Active learning, like physical modeling or simulations, allows students to bring the solar system down to a human scale. By 'walking' an orbit or using torches to simulate light, students build a mental map of the solar system that is much more robust than just looking at a 2D diagram.

What is the order of the planets from the Sun?

The order from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. A common mnemonic to help students remember this is 'My Very Easy Method Just Speeds Up Naming.' Note that Pluto is now classified as a 'dwarf planet' and is not part of the main eight.