# Earth Space Science: 08 Our Solar System: 08.06 The Earth-Sun-Moon System

### Assignment

The Earth-Sun-Moon System Lab Report

### Introduction

The Earth-Sun-Moon system moves through space in very predictable cycles. Your job will be to simulate this movement by creating a source of light (the sun) and using your head as the Earth. For the moon, you will use a small object, such as a Styrofoam ball on a stick. You will re-create the Earth-Sun-Moon system and its motions using these models.

### Problem:

How do we identify moon phases using a model?

Hypothesis:

Predict the direction of waning and waxing moon phases in your diagram.

For example:

If I move counterclockwise in my Earth-Sun-Moon system, then the phases of the moon will begin waning/waxing until the new moon/full moon.

### Materials:

One Styrofoam ball or white table-tennis ball
One dowel rod, pencil, or another long holder for the sphere
Tape, if needed
A darkened room, preferably without windows
One lamp or source of light

### Procedures:

Poke a hole into your spherical object. If you cannot obtain a Styrofoam ball, another small spherical object will work.
Attach the dowel, pencil, or another long holder to the sphere with tape, if needed. If you have a Styrofoam ball, stick the holder in the hole you created.
Place a bright lamp to one side of a room. Be sure you can darken the room enough to create shadows.
Stand in the middle of the room or in a location where you can hold out your arms and spin unobstructed.
Darken the room and turn your body on its axis counterclockwise, or to your left. (You are acting as the Earth and the sphere is the moon.)

### Follow the photographs illustrating the correct sequence of movement:

Step 1: Face the light source (the sun) and hold the sphere (the moon) between yourself and the light source.
Turn 45 degrees (half-quarter turn) counterclockwise so that the light source is slight to your right. Continue to hold the sphere in front of you.
Step 2: Turn another 45 degrees counterclockwise so that the light source is direct to your right. Continue to hold the sphere in front of you.
Turn another 45 degrees counterclockwise so that the light source is slight to your back. Continue to hold the sphere in front of you.
Step 3: Turn another 45 degrees counterclockwise so that the light source is directly behind you. Continue to hold the sphere in front of you.
Make another 45-degree turn counterclockwise so that the light source is slight to your back (left side). Continue to hold the sphere in front of you.
Step 4: Make another 45-degree turn counterclockwise so that the light source is to your left. Continue to hold the sphere in front of you.
Make another 45-degree turn counterclockwise so that the light source is slight to your left. Continue to hold the sphere in front of you.
As you change positions, you will notice differences in the shadows on the sphere. For instance, in the following image, you can see that one side of the moon is illuminated and the other side has a subtle shadow. You will be drawing the shading of the moon in the diagram provided for each position.

Complete Table 1 describing each position and each moon phase it represents.
Complete the Questions and Conclusion section of the lab report.
As you complete the lab, fill in the following diagram by drawing the appropriate shading on each circle representing the moon at various stages of Earth’s orbit around the sun. You can use the “Draw” tool in your document to shade the spheres.

### Variables:

For this investigation, list the independent, dependent, and controlled variables.

Data and Observations:

Table 1: Moon Phases

### Questions and Conclusion

Why did you spin counterclockwise rather than clockwise?
Describe exactly when a lunar and solar eclipse could occur within your model. Explain why eclipses do not occur during every lunar cycle.
How would you describe the waxing versus the waning portion of the moon’s journey?
How could you change your model to indicate a moon that is at apogee and perigee?
In conclusion, how did your hypothesis of moon phases match your moon phase model?
In what ways could you continue to investigate the changing positions of the Earth-Sun-moon system?
The Earth-Sun-Moon System
You are at your computer studying the sun, moon, and Earth for a homework assignment. Suddenly, you receive an instant message from your friend Ganesh, who lives in Nepal.

Ganesh’s message: I’m standing outside looking at the sky. It’s daytime, but the sun is gone!
On July 22, 2009, people in Nepal and other parts of the world might have sent instant messages just like this one. Although it was daytime, the sun seemed to disappear.

Question: What caused the sun to temporarily disappear from the sky?

A shadow of the moon on Earth
A shadow of the sun on the moon
A change in the position of Ganesh as he observed the sky
The rotation of Earth on its axis

Ganesh would have been in the path of totality for the total solar eclipse that occurred on July 22, 2009, in India, Nepal, China, and Myanmar, as shown in the image below:

image of Earth during a total solar eclipse. See text version.

### Public Domain

In this lesson, you will learn how viewers at different locations on Earth can see the same astronomical events differently. For example, when a shadow is cast on a small portion of Earth, as in solar eclipses, someone in the path of totality will see the sun blacked out. However, people outside the path of totality may be entirely unaware of the eclipse. Throughout the lesson, you will learn how Earth is affected by the motions of the Earth-Sun-Moon system.

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Earth Space Science: 08 Our Solar System: 08.06 The Earth-Sun-Moon System
IntroductionSolar Eclipse 1Solar Eclipse 2Solar Eclipse 3Solar Eclipse 4

To understand moon phases and eclipses, we can use a model of how shadows look depending on the observer’s position on Earth and Earth’s position in space. A shadow on Earth is easy to see. If you stand with your back to the sun, your shadow is in front of you. Your body blocks some of the sunlight from reaching the ground. Your shadow on the ground is not completely dark because light scatters as it bounces between molecules of air in the atmosphere.

In space, shadows are completely dark. The vacuum of space contains no molecules. When light strikes the surface of an object, the object is illuminated; if no light strikes the surface, the object is completely dark. On the moon, which has a little atmosphere, your shadow on the ground would be completely dark.

In the image below, you can see that exactly one half of Earth is always illuminated and one half is always in shadow.

A diagram showing that sunlight strikes half the Earth at any one time. In the half facing the sun, it is the day, and in the half facing away from the sun, it is night.
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If Earth did not have an atmosphere or artificial sources of light, how would you describe its darkness at midnight?

The moon provides light to the surface of Earth at night. However, the sun is the only heavenly body in the solar system that is luminous. Luminous objects emit light and heat. For example, all of the following are luminous:

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How does the moon appear lit if it is not luminous?
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Unlike moon phases, an eclipse is caused by a shadow. Solar eclipses occur when a portion of the sun is blocked by a shadow of the moon. These shadows have specific names.

### Use the activity below to investigate shadows created by objects in space:

When the moon is in the new moon position, between Earth and the sun, the shadow of the moon can cause an eclipse of the sun. The shadow of the moon is projected onto the surface of Earth in a narrow location, as you can see in the images below:

A photograph taken from Earth, which shows the moon obscuring the sun during a solar eclipse, paired with a photograph taken from space, which shows the moon’s shadow on a part of Earth’s surface.
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During a solar eclipse, viewers in a relatively small area on the daylight side of Earth can see the moon’s shadow. Sunlight can be totally blocked for a viewer in one location, but not in another. An eclipse of the sun could be occurring somewhere in the world right now, but you might not see anything unusual.

A solar eclipse, as seen from space, appears very different than when observed from Earth.

This image shows a solar eclipse that occurred in 2006, as seen from the International Space Station. The moon is between the sun and the Earth, blocking the sun’s rays and casting a dark, round shadow on Earth.

A view from outer space during a solar eclipse shows a large, dark area that obstructs the view of the ocean and landmass below it. The dark patch is formed by the shadow of the moon.
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On average, a total solar eclipse occurs somewhere on Earth about every 18 months. For the viewers from Earth, a solar eclipse provides a rare opportunity to see the sun’s atmosphere. Usually, the sun’s surface is too bright to look at, and even during an eclipse, safety precautions must be taken to protect your eyes.

### There are three basic types of solar eclipses. Use the activity below to investigate the types of solar eclipses:

NASA and other agencies predict solar eclipses with a high degree of accuracy. In any given year, there are only a few eclipse events. Usually, these are partial eclipses, whereas a total eclipse occurs only every 18 months. You can see from the following image that only two eclipses will be visible in the United States between 2001 and 2020.

Solar eclipse paths. See text version.
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To see a total solar eclipse in the United States, you will have to be in the path of totality (i.e., the moon’s umbra) as it passes through the middle of the country.

Why don’t eclipses occur during every new moon?

The answer lies in the tilt of the ecliptic plane of the moon. The moon always has a shadow, but the shadow only occasionally covers a part of Earth. This is because the moon’s orbital plane is tilted at 5 degrees from Earth’s ecliptic plane, as shown in the image below:

Moon orbit. See text version.
Public Domain

NASA and other agencies predict solar eclipses with a high degree of accuracy. In any given year, there are only a few eclipse events. Usually, these are partial eclipses, whereas a total eclipse occurs only every 18 months. You can see from the following image that only two eclipses will be visible in the United States between 2001 and 2020.

Solar eclipse paths. See text version.
Public Domain
To see a total solar eclipse in the United States, you will have to be in the path of totality (i.e., the moon’s umbra) as it passes through the middle of the country.

Why don’t eclipses occur during every new moon?

The answer lies in the tilt of the ecliptic plane of the moon. The moon always has a shadow, but the shadow only occasionally covers a part of Earth. This is because the moon’s orbital plane is tilted at 5 degrees from Earth’s ecliptic plane, as shown in the image below:

Moon orbit. See text version.
Public Domain

Start Animation
animation of the moon’s phases, image

Many nights when you look in the sky, the moon is partially obscured and it appears as if part of the moon is in a shadow. These is what we refer to as moon (lunar) phases. Lunar phases refer to the shapes of the sunlit portion of the moon as viewed from Earth. As the moon revolves around Earth each month, it reflects the light of the sun. How we on Earth see this reflection of light depends on the section of the moon exposed to the sun, the position of the moon around Earth, and our viewpoint.

Each phase of the moon has a specific name. The phases of the moon are based on the portion of the moon an observer can see and whether the light reflected from the moon is waxing (“growing”) or waning (“shrinking”) relative to the observer. Let’s explore each one below to learn about the phases of our moon..

Moon phases occur as the positions of Earth, the sun, and the moon change with respect to each other. Remember that one-half of the moon is always illuminated by the sun. But how much of that illuminated half you see from Earth depends on where the moon is in its orbit on a given night.
When Earth casts its shadow on the moon, the event is called a lunar eclipse. This occurs when Earth is positioned at a specific point between the sun and the moon. Only people located on the side of Earth facing the moon can see a lunar eclipse. Lunar eclipses appear red due to the refracted light from Earth’s atmosphere.

Lunar Eclipse
View from Earth
Lunar Eclipses diagram
View from space
Unlike solar eclipses, everyone on the night side of Earth can see a lunar eclipse. A lunar eclipse is caused when Earth’s shadow covers the moon. When Earth is between the moon and sun, a full moon occurs. During a lunar eclipse, the full moon is covered in whole or in part by shadows from Earth.

Similar to solar eclipses, there are also three basic types of lunar eclipses. Use the activity below to investigate the types of lunar eclipses:

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