Why does the moon shine?

The moon is made up of large dark volcanic rock. The moon is not like earth, instead of a hot core, the moon is completely cold and dead. It doesn’t rotate or turn around like the earth either; it faces us in one direction. One thing that the moon does do is that it has an orbit around the earth. The reason that we see the moon with a glow or shine, is because the light of the sun is reflecting off of the moon that is visible to us.

Moon in direct sunlight

Think of the moon as a mirror. In the case of the moon, it’s really a bad mirror. Due to the fact that it is made up of such dark material, it reflects only about 12% of the light that hits it. The amount of light that gets bounced back to earth also depends on the time and place of the orbit of the moon. When the moon’s orbit puts it in direct forward facing to the earth, we get a larger amount of light bounced back.

This is when we have a ‘full moon’. It appears larger and brighter and we can usually see the man-in-the-moon face really clearly. As the orbit changes, the angle of the light changes and less and less light bounces back to earth. During the various quarter stages of the moon it is actually only reflecting around 8% of the light. Due to the elliptical orbit, the moon occasionally gets even closer. When this happens, and it is facing the earth, we see the moon at a 20% reflection and this is called a super moon. The light of a super moon is so bright, that astronomers have to put away their telescopes because the light hides a lot of the surrounding night sky, including the light of smaller stars.

Moonlight illuminates a lake and surroundings

The moon is made up of volcanic rock that is 4.5 billion years old. Since there isn’t any atmosphere, which would cause rain and wind, the surface only changes when it is hit by another space object, such as an asteroid. This has caused the moon to have a lot of craters and mountains. As the angle changes in the orbit of the moon the angle of the mountains and craters also changes and the light that is reflected from them becomes dimmer. When there is a sharper angle from the light of the sun, it will cause the craters and mountains to cast shadows. This is why the moon is less bright at certain times in its orbiting cycle.

You might be surprised to know that the amount of light we see today is a lot less than what our ancestors saw. This is because the moon is also ever so slowly moving away from the earth. The earth and moon both have a gravitational ‘pull’. The moon’s gravitational pull causes our ocean tides. Thousands of years ago, the moon was closer to the earth and people saw it in the night sky as larger and brighter. This is because the amount of light reflected was more than it is today.