Until recently there was many debates on how the moon, our nearest planetary neighbor was formed. Well we believe that at some point in Earth's early history, a rogue planet, larger than Mars, struck the Earth in a great, glancing blow. Instantly, most of the rogue body and a sizable chunk of Earth were vaporized. The cloud rose to above 13,700 miles altitude, where it condensed into innumerable solid particles that orbited the Earth as they aggregated into ever larger moonlets, which eventually combined to form the moon. Studies also show that by measuring the ages of lunar rocks, we know that the moon is about 4.6 billion years old, or about the same age as Earth. So this seems to be a pretty accurate theory as to how the moon was formed. Many people today still have many questions about the moon such as, “Why do we only see one side of it?” “Why does the moon change shape?” and “How does it affect our ocean tides?” Well to answer the first question, the rotation of the moon, the time it takes to spin once around on its own axis, takes the same amount of time as the moon takes to complete one orbit of the Earth, about 27.3 days. This means the moon's rotation is synchronized in a way that causes the moon to show the same face to the Earth at all times. One hemisphere always faces us, while the other always faces away. The lunar far side (aka the dark side) has been photographed only from spacecraft.
Then we wonder why it changes shape and this is because the shape of the moon appears to change in a repeating cycle when viewed from the Earth because the amount of illuminated moon we see varies, depending on the moon's position in relation to the Earth and the sun. We see the full moon when the sun is directly behind us, illuminating a full hemisphere of the moon when it is directly in front of us. The new moon, when the moon is darkened, occurs when the moon is almost directly between Earth and the sun, the sun's light illuminates only the far side of the moon...
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