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Junior School: Earth, Sun and Moon

“Books are a uniquely portable magic.”





Earth is the fifth largest planet in the solar system. It appears bright and bluish in colour when viewed from outer space. Earth is the only planet in the solar system that can support life. Millions of different species of living things are able to thrive on the planet Earth because of its large amounts of liquid water, its atmosphere containing a mixture of oxygen and nitrogen, and its moderate temperatures.




Every day, the Earth spins once around its axis, making sunrises and sunsets a daily feature of life on the planet. It has done so since it formed 4.6 billion years ago, and it will continue to do so until the world ends — likely when the sun swells into a red giant star and swallows the planet.




satellite is an object that orbits another object. In space, satellites may be made by man, or they may be natural. The moon is a natural satellite that orbits the Earth. Most man-made satellites also orbit the Earth, but some orbit other planets, such as SaturnVenus or Mars, or the moon.




Weather satellites can see very long distances because they fly hundreds and sometimes thousands of miles above the Earth. They don't have eyes to see with, but they do use special tools called radiometers (pronounced ra-di-o-me-ters), which are made up of sensors that allow them to scan the Earth and detect different types of energy.



  • The Sun is a star found at the center of the Solar System.

  • It makes up around 99.86% of the Solar System’s mass.

  • At around 1,392,000 kilometres (865,000 miles) wide, the Sun’s diameter is about 110 times wider than Earth’s.

  • Around 74% of the Sun’s mass is made up of hydrogen. Helium makes up around 24% while heavier elements such as oxygen, carbon, iron and neon make up the remaining percentage.

  • Light from the Sun reaches Earth in around 8 minutes.




Sunrise (or Sun up) is the moment when the upper limb of the Sun appears on the horizon in the morning.

Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation.




rocket may be a missilespacecraftaircraft or other vehicle which is pushed by a rocket engine. Some rockets are manned (e.g. Saturn V). Other rockets, for example missiles, are unmanned. ("Manned" means that a person is in it; "unmanned" means that the machine can go without a person.)




Although the Moon may seem small and insignificant compared to the rest of the universe, its size and location make it very important to Earth. Other than the Sun it is the most visible body in the sky. Because of this, humans have been fascinated by the Moon since ancient times. It has been studied both from Earth and from space. In fact, more than 70 spacecraft have been sent on missions to the Moon. In addition, the Moon is the only place outside Earth that has been visited by humans.

The average distance of the Moon from Earth is about 384,400 kilometres (238,900 miles). This may seem like a great distance. However, compared to the distance of Earth from other planets,the Moon is actually quite close.





As the moon orbits or circles the Earth, the phase changes. We'll start with what is called the New Moon phase. This is where we can't see any of the lit up side of the moon. The moon is between us and the sun (see the picture). As the moon orbits the Earth we can see more and more of the lit up side until finally the moon is on the opposite side of the Earth from the sun and we get a full moon. As the moon continues to orbit the Earth we now see less and less of the lit up side.




A star is a massive, bright, sphere of very hot gas called plasma which is held together by its own gravity.




The Milky Way galaxy is a disc shaped spiral galaxy with a huge collection of stars, about 100-400 billion. We don’t know exactly, but we know it’s over 200 billion. Wow. Not bad for a mid-size galaxy! But compared to other galaxies and star clusters The Milky Way is small.