The Sun, Earth and Moon

The Sun, Earth and Moon are part of a system that works together.

• Earth travels around the Sun
• The Moon travels around the Earth
• The Sun stays in the centre of this system

The Sun’s gravity keeps the planets moving around it. This system affects day and night, the phases of the Moon, and life on Earth by providing light and warmth.

Earth travels around the Sun in a path called an orbit. It takes one year (365 days) for Earth to complete one full journey around the Sun.

The Moon also moves in an orbit. It takes about 28 days for the Moon to travel once around the Earth.

Day and night

Earth is always spinning. This spinning movement is called rotation.

• The side of Earth facing the Sun has daytime
• The side of Earth facing away from the Sun has night-time

As Earth spins, different places move into daylight and then into darkness. This is why we have day and night every 24 hours.

Even though it looks like the Sun is moving across the sky, it is actually Earth that is spinning.

Phases of the moon

The Moon seems to change shape in the sky. These changes are called the phases of the Moon.

The Moon does not make its own light. We see the Moon because it reflects light from the Sun. As the Moon moves around Earth, we see different amounts of the sunlit part.

Sometimes the Moon looks like:

• a thin crescent
• a half circle
• a full circle

The Moon itself never changes shape — it only appears to change depending on where it is in its orbit.

Our solar system

The solar system is a huge family of objects that travel through space together. It is made up of:

• the Sun
• eight planets
• moons that orbit some planets
• asteroids (rocky objects)
• comets (icy objects with long tails)

Everything in the solar system is held together by the Sun’s gravity.

The Sun at the Centre

The Sun is at the centre of the solar system. It is a giant star and is much bigger than any of the planets. The Sun gives out light and heat, which provide energy to the whole system.

Without the Sun:

• Earth would be dark and freezing
• plants could not grow
• animals and people could not survive

Some stars are much bigger and hotter than our Sun. The Sun is just a medium-sized star compared to giant stars called supergiants.

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The planets and their order

There are eight planets in our solar system. They are always in the same order from the Sun.

The planets are:

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

Each planet travels around the Sun in its own path called an orbit. It takes different amounts of time for each planet to complete one orbit.

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Types of planets

The planets can be grouped into different types.

Rocky Planets

The four planets closest to the Sun are called rocky planets:

• Mercury
• Venus
• Earth
• Mars

These planets have solid surfaces made of rock and metal. Earth is special because it has water, air, and life.

Gas Giants and Ice Giants

The planets farther from the Sun are much larger.

• Jupiter and Saturn are called gas giants
• Uranus and Neptune are called ice giants

These planets do not have solid surfaces like Earth. They are made mostly of gas and ice and have many moons.

Moons, asteroids and comets

Many planets have moons that move around them. Earth has one Moon, but some planets have dozens.

• Asteroids are rocky objects that mostly travel in a belt between Mars and Jupiter. This is called the asteroid belt.
• Comets are made of ice and dust. When they get close to the Sun, they heat up and grow a glowing tail.

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Space travel and exploration

Humans have always been curious about space. To explore it, scientists and engineers have built rockets and spacecraft that can travel far beyond Earth.

Rockets and Spacecraft

Rockets are powerful machines that use fuel to blast into space. They carry spacecraft, which are specially designed vehicles that can travel in space and keep astronauts safe.

Some spacecraft travel without people on board. These are called space probes and satellites. They send pictures and information back to Earth to help scientists learn more about space.

Astronauts and space stations

Astronauts are people who are trained to travel and work in space. Astronauts have:

• travelled to the Moon
• lived and worked on space stations
• carried out experiments in space

A space station is a large spacecraft that orbits Earth. Astronauts can live there for months while they study how space affects the human body and test new equipment.

Why Do We Explore Space?

Space exploration helps scientists:

• learn more about Earth, the Moon and other planets
• understand how the Sun and space affect our planet
• develop new technology that can be used on Earth

Exploring space also helps us answer big questions about the universe and our place in it.

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Observing the night sky

Not all space exploration needs rockets or astronauts. Scientists can learn a lot just by observing the night sky from Earth.

By watching carefully over time, scientists can:

• track the movement of the Moon
• study stars and planets
• spot patterns, such as planets changing position in the sky

To help them see objects that are very far away, scientists use telescopes. Telescopes make distant objects appear bigger and brighter, so details can be seen more clearly.

Many telescopes are kept in special places called observatories. Observatories are often built on high mountains or in areas with very dark skies, where there is less light from towns and cities. This helps scientists get clearer views of space.

Careful observation using telescopes allows scientists to discover new objects and learn more about our universe.