Earth & Moon l Why does the Moon change its Shape l DIY Science Experiment

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E for Earth & Moon

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A fundamental understanding of the Earth and Moon cycle is important to be explored in the childhood years. It’s not surprising that adults as well might in fact stagger for an answer when asked why the Moon changes its shape every night. One of the common answers is that the part of the Moon that goes to the other side of the Earth is not visible. And all it takes to experiment the phases of the moon are a globe (or a big ball), a small ball, a flash light, a dark room, and a few minutes of your time.

Tips to introduce

  • Children naturally have an affinity to the night sky – the glowing stars, the bright Moon that keeps changing its position and appearance every night. As adults, one of the small steps we can do to get children involved into the science of nature is to explore the night sky.
  • Before you plunge into this experiment, I suggest you to take your children to the terrace and observe the shape of the Moon for a few nights, if not for one whole month (preferably starting from either the full moon day or no moon day).
  • To make it interesting and to record your observations, the children can draw the shape of the Moon as they see it every night. They can as well make a flip book out of the drawings they did for a month.
  • In the mean time, you can get familiar with terms such as waxing moon, waning moon, gibbous moon, and crescent moon.
  • When you have done this, to understand in close quarters what exactly happens with the Moon’s shape, set up this phases of the moon experiment.
  • Do it slowly and most importantly, view it from the right angle, and bet me you and your children will never ever stagger to explain the science behind the phases of the Moon.

Things you’ll need

  1. A globe/ a big ball
  2. An old bulb/a small ball
  3. A long-medium-sized stick
  4. Flashlight/ candle/Lamp

pictures of things needed - globe, flash light, bulb tied to a stick

How do you do it?

1. Place a globe (bigger the better) or a big ball on a table or floor in a dark room. This is our Earth.

2. Place a bright source of light – flashlight, candle, mobile flash – whatever works fine, that directly sends its beams on to the globe. This is going to be the Sun.

3. Tie a small ball or an old light bulb to the end of the long stick or scale. The ball or bulb is going to be our Moon. You can skip this step if its complicated. Doing this can prevent the shadow of your fingers or hand falling on the Moon.

4. Hold the small ball (hanging from the stick) at a few centimeter distance from the globe and slowly make the Moon rotate around the Earth. Remember to hold the Moon high above the Earth, else Earth’s shadow will fall upon the Moon.

5. Fix a location on the globe to observe the Moon as it goes around the Earth.


Say you start from the side of the Earth that’s darker. While the Moon is exactly near the middle of the darker side of the Earth, it will appear the brightest and in full circle, what we call the Full Moon.

As you turn anti-clockwise, you can observe that the bright part on the Moon starts narrowing down (Waning Moon), while the dark part gets larger. The bright part is what we see from the Earth. And that’s exactly why the Moon seems to change its shape every night.

image showing the phases of the moon

As the Moon comes closer to the Sun, and when near the middle of the bright side of the Earth, its brighter half is facing entirely toward the Sun and the darker half is facing toward the Earth. And we don’t see the Moon, what we call the No Moon or New Moon (‘New Moon’ actually refers to the first crescent Moon after the No Moon).

Further turning, the Moon begins to grow its brighter side (Waxing Moon) and comes back to the Full Moon form when it’s again near the middle of the darker side of the Earth.

The Science Behind

It’s simple. From Earth, we see that part of the Moon where sunlight directly falls upon and illuminates the Moon. Keep in mind that the other part of the Moon is still there right in front of us, but just that since it is not receiving light from the Sun, we don’t see it. For example, a black object against a black background may not be visible, but upon illuminating the object, we would be able to see it. Similarly, the part of the Moon that’s darker gets hidden from our view within the dark, night sky.

Share your experience

Did you observe the different phases of the Moon? Did it work? Or didn’t? Leave a word in the comment section. I would love to hear!

Here’s the full list of DIY Science Experiments in this series:

A for Air – Does Air has Weight?

B for Buoyancy – Can Egg float on Salt Water?

C for Capillary action – Rainbow Walking

D for Density – 3 Layer Density Experiment

E for Earth & Moon – Why does the Moon change its shape?: Phases of the Moon

F for Fire – Does Fire need Oxygen to Burn?

G for Gravity – Defying Gravity

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