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Why can we only see one side of the moon? |
Space
A lot of people talk about the “man in the moon.” From Earth, the moon’s geography looks a little bit like a person’s face. Every time the moon is full or near full, we can see that same face. It’s always there. Why doesn’t the side of the Moon that we see ever change?
The Moon does rotate (spin around its axis,) but it does so in a very special way. The time it takes to spin rotate once is the same amount of time it takes to orbit (travel around) the Earth once: 27.3 days. And that’s not a coincidence.
The Moon’s gravity has an effect on the Earth. It causes our Tides. The Earth has the same sort of effect on the Moon, but since the Earth is much bigger, the effect is stronger. The Earth has actually locked itself to one side of the Moon. One side of the Moon is always pulled toward the Earth, and it’s the side with our friend, the Man in the moon.
Moon Model
The idea that the Moon is rotating may be hard to imagine, but you can make a quick model to help you visualize what’s going on in space. All you’ll need is an apple (or other round fruit).
Take a bite out of one side of the apple. While you chew on some nutrients, hold the apple out in your arm with the bitten side away from you. That’ll be the “dark side” of the Moon or the side we never see from Earth.
With the bitten-side away from you, hold it out to your left. Where is the bitten-side facing? It should also be facing your left. Now, keeping your arm stretched, move the apple so it’s in front of you with that bitten-side still facing away. Where is it facing now? Now keep it moving in a circle around you. Where does it face as it moves?
By the time you get back to where you started, has the bitten-side of the apple faced all sides of the room? Could it have done that without rotating? Think about it while you enjoy the rest of your snack.
