How does the position of Earth,
the Moon, and Sun create the
appearance of the Moon’s
phases?
Utah OER DOE
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Printed: April 12, 2016
AUTHOR
Utah OER DOE
www.ck12.org
Chapter 1. How does the position of Earth, the Moon, and Sun create the appearance of the Moon’s phases?
C HAPTER
1
How does the position of
Earth, the Moon, and Sun create the
appearance of the Moon’s phases?
The Moon is Earth’s only natural satellite—a body that moves or revolves around a larger body in space. The Moon
is kept in orbit around Earth by the pull of the Earth’s gravity on the Moon. The Moon is 3,476 km in diameter, about
one-fourth the diameter of Earth. The mass of the Moon is only 1.23% the mass of Earth. Gravity on the Moon is
only one-sixth as strong as it is on Earth due to the smaller mass of the Moon. If you weigh 120 pounds on Earth,
how much would you weigh on the Moon? That’s right! You would weigh 20 pounds. You can jump six times as
high on the Moon as you can on Earth if you weren’t wearing a spacesuit with weighted boots. The rock the Moon
is made from is not as dense as Earth.
The Moon rotates on its axis in the same amount of time it takes to make one orbit around Earth. What does this
mean? The same side of the Moon always faces Earth, so we always see that side of the Moon in the sky. The side
of the Moon that always faces Earth is called the near side. The side of the Moon that always faces away from Earth
is called the far side. From Earth, people have only seen the Moon’s near side. The far side has only been seen by
spacecraft and Apollo astronauts as they orbited the Moon.
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The rotation of Earth gives the Sun the appearance of moving across the sky. The Sun is actually in the same place in
the sky. As Earth rotates on it’s axis, it brings the Sun in and out of view giving us daylight and darkness. Remember:
The Sun is stationary. It is the rotation of Earth that brings the Sun into view. When sunlight is hitting the part of the
Moon that is facing away from Earth, we see only the dark side of the Moon. When we cannot see any part of the
Moon’s lighted reflection, the Moon is invisible to us when we look up into the sky. We call this a New Moon. The
New Moon phase only takes place during daylight hours because the Moon rises and sets with the Sun. As Earth
rotates to nighttime, the New Moon is no longer in view, having disappeared behind the horizon.
Science Language Students Need to Know and Use
•
•
•
•
Revolution: the circling of an object in space around another object in space.
Orbit: the path of a planet or a moon around an object.
Axis of rotation: the spinning of objects around an imaginary center line.
Natural satellite: a body that moves around a larger body in space.
Online Interactive Activities
• This interactive will allow students to view the moon, earth, and sun’s relative motion, and answer questions
related to phases of the moon. http://tinyurl.com/ut6th1-1
• This interactive will allow students to test their knowledge of the phases of the moon, by dragging the phase
to their place in their cycle. http://tinyurl.com/ut6th6-1b
Think like a Scientist
1.
2.
3.
4.
Why does the same side of the Moon always face the Earth?
How long does it take the Moon to rotate on its axis?
How long does it take the Moon to revolve around the Earth?
How is the orbit of the Moon around Earth different from the orbit of Earth around the Sun?
Additional Recommended Resources
• Animation of the movement of Earth, Moon and Sun. https://www.youtube.com/watch?v=W47Wa7onrIQ
MEDIA
Click image to the left or use the URL below.
URL: https://www.ck12.org/flx/render/embeddedobject/178671
• Moon Phases slideshow. http://teachers.henrico.k12.va.us/staffdev/clough_d/Moon/Photos.html
• Mr. Parr “I can see the Phases of the Moon”. http://www.youtube.com/watch?v=WArvitCA1j0
MEDIA
Click image to the left or use the URL below.
URL: https://www.ck12.org/flx/render/embeddedobject/178673
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Chapter 1. How does the position of Earth, the Moon, and Sun create the appearance of the Moon’s phases?
• Space School: The Moon. http://www.youtube.com/watch?v=0HtG9opCmOE
MEDIA
Click image to the left or use the URL below.
URL: https://www.ck12.org/flx/render/embeddedobject/178675
• Moon Read online. https://www.ck12.org/earth-science/Moon/lesson/Moon-Basic/
• Moon Double Entry Diary. https://www.ck12.org/earth-science/Moon/whileread/Moon-Double-Entry-Diar
y/?referrer=concept_details
• Moon Study Guide. https://www.ck12.org/earth-science/Moon/studyguide/Moon-Study-Guide/?referrer=co
ncept_details&conceptLevel=&conceptSource=ck12
• NASA: Evolution of the Moon (from CK-12). https://youtu.be/UIKmSQqp8wY
MEDIA
Click image to the left or use the URL below.
URL: https://www.ck12.org/flx/render/embeddedobject/178677
• Space School - The Moon. https://www.youtube.com/watch?v=0HtG9opCmOE
MEDIA
Click image to the left or use the URL below.
URL: https://www.ck12.org/flx/render/embeddedobject/178675
• The Universe: The Phases of the Moon video by the History Channel. https://www.youtube.com/watch?v=
nXseTWTZlks
MEDIA
Click image to the left or use the URL below.
URL: https://www.ck12.org/flx/render/embeddedobject/178679
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References
1. . https://commons.wikimedia.org/wiki/File:Aldrin_Apollo_11.jpg .
2. . http://goo.gl/FY657T .
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