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Moon Works



What do you see when you look at the Moon? Do you see a man in the Moon? Some people think that what they see looks like a man's face. What they are noticing are the light and dark patches of the Moon. Scientists used to think that the dark patches were filled with water and named them seas. The ancient Greek word for sea was mare or maria. Maria is plural for mare. After astronauts visited the Moon, we discovered that there is no water on the Moon. These dark areas are just lower, flat plains that appear in shadow. However, they are still called seas today. Mountains and craters surround some of these dark areas. That is what makes some people think they see a man's face. 

The “seas” on the Moon are actually what?


      Maybe you have noticed that on some nights there is a full moon and on other nights you can only see a sliver of it. What happened? The different shapes of the Moon are related to the positions of the Moon, the Earth, and the Sun. The Moon does not produce any of its own light. What you are really seeing is the reflection of the Sun's light. It takes the Moon 27.3 days, about a month, to revolve around the Earth.  Now we already know that the Earth is orbiting the Sun, so while the Moon is orbiting the Earth, the Earth is also moving forward in its orbit.  If the Earth was sitting still in space, it would take the Moon 27.3 days, but because the Earth is moving, it takes the Moon a little longer to catch up.  This makes it actually take 29.5 days to make one orbit.
       As it is revolving around the Earth, the Moon is also spinning on it own axis. The Moon spins very slowly. In fact it takes the Moon 29.5 Earth days to make one rotation. SO! One Moon day is actually 29.5 Earth days. Now, because the Moon is rotating and revolving around the Earth at the same speed that it is rotating on its axis, the same side of the Moon is always facing the Earth. Only the astronauts have seen the back side of the Moon. One other thing about the Moon's rotation, is that throughout the month, you will notice that the portion of the Moon that is lit up changes the shape of the Moon in the sky. These changes are called the Moon's phases.

Explain how long it takes the Moon to orbit the Earth and why it takes longer than it should.


Explain why we don’t see the back side of the Moon.


As the Moon revolves around the Earth, different parts are lit up.  These changes in the Moon are called what?


      Let's begin on a cloudless night when you cannot see the Moon. This first phase of the Moon is called the new moon. This occurs when the Moon is between the Earth and Sun, the Moon actually comes up at the same time that the Sun comes up. The side of the Moon that is not lit up by the Sun faces the Earth at this time. This makes the Moon look dark. Sometimes, we can see a faint outline of the new moon. This is caused by sunlight that is reflected from the Earth back to the Moon. However, most of the time we do not see anything when there is a new moon. 
      A few days later, you would see a sliver of the moon called the waxing crescent moon. By the end of the week, you would see half of the Moon's surface lit up. This is called a quarter moon. A few more days later, you could see an area of the Moon's surface that is larger than half of the Moon but less than a full moon. This is called a waxing gibbuous moon. Two weeks into the cycle, you would see a full moon. A full moon occurs when the Earth is between the Moon and the Sun. These are the brightest nights of the month. These nights you can walk outside in most areas and see in fron of you without using a flashlight.

What is the first phase of the Moon called and why can’t we see it?


What is a full Moon and when does it occur?


      On the day of the New Moon, the Moon rises at the same time as the Sun so we can't see it. The next day, the Moon rises about an hour later. If you know where to look, you might be able to see a tiny sliver of the Moon. Two days after the New Moon, the Moon rises about 2 hours later and three days later, about 3 hours later. There is a pattern here. Every day, the Moon comes up at least an hour later than it did the day before. As the Moon rises later and later, more and more of it becomes visible. During the first two weeks of the Moon's cycle, it is getting brighter and brighter. This phase is called waxing. (a newly waxed car is very bright) Once the full Moon appears, the Moon begins to disappear. It will be less and less bright. This is called waning. Waning means going away! 

The phases of the Moon between New Moon and Full Moon are...


What is causing the Moon to get brighter as it is waxing?


      Now, a few days after the Moon is full, it starts to become less and less full. A few days after the full Moon, we have the waning gibbous moon, a few more days brings another quarter moon. We call this the last quarter. A few more days later, we get the waning Crescent Moon, and then we see no moon, which is once again, the New Moon.  The cycle then starts over.

      The Moon's phases take place in a lunar month (lunar means month). This is shorter than a month on our calendar. So, every couple of years there will actually be two full moons in one month. This is called a blue moon. Some calendars list the phases of the Moon so you can observe them. You can also get that information in a daily newspaper or on the internet.

How is it possible for us to have two Full Moons during the same calendar month?


What is the difference between a waxing Moon and a waning Moon?

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