Friday, January 9, 2015 Focus: How does the position and motion of the moon produce moon phases? Explore: Model moon orbit Model moon phases Yesterday, you learned about orbits in the solar system. Today, we will be focusing on the orbit of the moon and what we see as it orbits our Earth.

natural satellite artificial satellite As you read yesterday, a satellite is something that is in orbit. We have both natural satellites and artificial satellites. The moon is a natural satellite, and it orbits the earth. artificial satellite

Moon is in orbit around the Earth We on Earth will only ever see ONE side of the moon.

The Earth, moon, and sun work in a system The Earth, moon, and sun work in a system. As the moon orbits the earth, the earth also orbits the sun. They are both elliptical, but very close to circular, like you learned with Ms. McKenna. The moon does not emit its own light. Instead, the sunlight reflects off of the moon, which is why we can see the moon in the sky.

The orbit of the moon is titled about 5 degrees from the earths orbital plane around the sun. This is the reason the moon reflects sunlight even when the earth is in between the sun and the moon. There are instances called eclipses when the earth gets in the way, but we will talk about that another day. The moon orbits the earth in about 27 days. We call the 27 days a sidereal month.

Model the moon in orbit around the earth Explore! Model the moon in orbit around the earth Revolving? Rotating?

1 Moon revolution = 1 Moon rotation https://www.youtube.com/watch?v=OZIB_leg75Q The Moon revolves around the earth in an orbit in the same amount of time it completes one rotation. 1 Moon revolution = 1 Moon rotation  We only see ONE side of the moon on Earth!

The sunlight will only reflect off the half of the moon that is facing the sun. Because of this, half of the moon is always dark. This is the cause for moon phases. Although half of the moon is always lit up, the moon is at a different spot in relation to our earth each night. From the earth we see a portion of the “lit” moon. The portions we see are what we call phases.

In this picture, we see the half of the moon that is reflecting the sunlight, but we also see the parts of the moon that we see here on earth. If you look at the lines coming from the earth, they show us the frame we see of the moon. Lets take a look at this one (new moon). We see that the half of the moon that is reflecting the sunlight is away from the earth. The half that we see is dark because it is not reflecting any light this is called a new moon. As the moon orbits, the same half is still reflecting the light, but it is now in a position where on earth, we can see a portion of the lit up side. This is called a waxing cresent moon. Waxing basically means the moon is growing. Waxing is when more and more of the light side of the moon is becoming visible to us on earth. We continue to the next phase, which is a first quarter moon. We now see half of the lit side of the moon. The moon is still waxing. As we continue on the moon’s counter clockwise orbit, we see more of the lit side of the moon, which is called a waxing gibbous. A gibbous is what we call the moon in between the quarter moon and the full moon. Next is the full moon. When we see a full moon, we really see half of the moon, but the whole side that is reflecting the sunlight. As the earth continues its orbit, it is now waning. Waning refers to the “shrinking” of the moon. Waning is the opposite of waxing. The waning gibbous shows the moon shrinking, as we see most of the moon. The third quarter moon is another “half moon” as we see in the sky. Notice it is the opposite side of the first quarter moon because we are now on the other side of the orbit. Continung to the waning crescent and back to the new moon.

We classify the moon into 8 distinct phases. It takes about 3 We classify the moon into 8 distinct phases. It takes about 3.5 days to get to the next phase. The amount of time it takes for the moon to orbit the earth is slighly less than the amount of time it takes from one new moon to the next new moon. This happens because the moon is orbiting the earth as the earth is orbiting the sun, so the moon has to travel a bit further to line up to the new moon phase again. This is called the synodic month and is about 29.5 days.