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Phases of the Moon

Find out how to explain lunar phases.

How do we get different phases of the Moon?

We find (and our teacher forum seem to agree) that it is a very difficult topic to tackle unless you have visual resources to help you. With that in mind we created a video that you can use with your students to help explain the phases of the Moon.

Here are some important facts and figures to remember:

  • The Moon rises and sets just like the Sun – this is due to the Earth’s spin.
  • The Moon reflects the light of the Sun, making it visible.
  • The Moon changes phase because it is in orbit around the Earth. This series from one full moon to the next is called the lunar phase cycle.
  • The Earth orbits the Sun every 365.25 days.
  • The lunar orbit around the Earth takes 27.3 days.
  • The lunar phase cycle lasts 29.5 days. It is longer than the lunar orbit because the Earth is continuously moving relative to the Sun and so the Moon takes a few extra days to get into the right position again for us to observe the same initial phase again.
  • We see more or less of the reflected light on the Moon as it makes its way around the Earth. The dark regions are not in the Earth’s shadow but are instead parts of the Moon facing away from the Sun.
  • The Moon’s orbit is tilted by 5 degrees relative to the orbital plane of the Earth around the Sun. It moves up and down slowly with each orbit. This is why we see a bright Full Moon approximately once a month but don’t see a solar eclipse as often.
  • We always see one side of the Moon – this is because the Moon spins at the same rate as its orbit – once every 27.3 days. It turns on its axis just enough for us to never see the far side from Earth.
  • A solar eclipse happens when the Moon lies directly between the Earth and the Sun. The Moon’s shadow is small on the Earth, only people who are directly beneath the shadow witness a total solar eclipse. The phase here is New Moon.
  • A lunar eclipse happens when the Moon moves into the Earth’s shadow (opposite to the Sun). It glows red due to bending of red sunlight by the Earth’s atmosphere onto the face of the Moon. The phase here is Full Moon.

Download our phase of the Moon activity for your class. We recommend this activity for pupils aged 9+. Phases of the Moon classroom resource.

This article is from the free online

Our Solar System and Beyond: Teaching Primary Science

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FutureLearn - Learning For Life

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