Guided Notes
Astronomy
Earth’s Moon
Formation
Orbit
Craters
Motions
Phases
Tides
Eclipses
© K. Coder 2015
1. What is the Moon?
• The Moon: the Earth's only natural
satellite. See ESRT page 15 for data on
Earth’s Moon.
o Satellite: an object in space that revolves
around another object due to gravity
© K. Coder 2015
2. How did the Moon form?
• Giant Impact Hypothesis: the Moon was
created from debris left over from a
collision between young Earth and a
Mars-sized body approximately 4.5 billion
years ago.
© K. Coder 2015
3. How does the Moon orbit the Earth?
• The Moon revolves around the Earth in an
elliptical (oval) orbit with the Earth at one
focus.
Perihelion: Moon
is closest to
Earth
Aphelion: Moon
is farthest from
Earth
3. How does the Moon orbit the Earth?
• Evidence: The apparent
diameter of the Moon
changes.
o Photographs A: Moon appears
smaller during Aphelion
o Photograph B: Moon appears
larger during Perihelion
4. Why are there so many craters on the
Moon (and other planets) but not on Earth?
© K. Coder 2015
4. Why are there so many craters on the
Moon (and other planets) but not on Earth?
• Earth has a hydrosphere (water) & atmosphere
(gases).
o The Earth’s atmosphere allows it to have weather
like wind, rain, and snow. All factors that lead to
erosion and weathering, which wear away any
craters on Earth.
4. Why are there so many craters on the
Moon (and other planets) but not on Earth?
• The Moon (and other small planets) have lost
their atmosphere because they are smaller
and have less gravity.
© K. Coder 2015
5. Why do we always see the same side
of the moon?
We always see this side.
We never see this side!
© K. Coder 2015
5. Why do we always see the same side
of the moon?
• The moon’s period of rotation (27.3 days)
is equal to the moon’s period of
revolution (27.3 days). See ESRT page 15.
Synchronous Rotation Animations:
http://www.webassign.net/fkastro9/animations/
Animation03-02.htm
6. Why does the Moon appear
differently on different days?
• Phases of the moon: the observed shape
of the lighted portion of the Moon
6. Why does the Moon appear
differently on different days?
• Caused by the Moon’s revolution around the
Earth which causes the amount of the lit half
of the Moon visible to observers on Earth to
change.
• A complete cycle of phases takes 29.5 days
(one “moonth")
• The phases of the Moon are cyclic and
predictable because they repeat in a pattern.
7. Why is the Moon’s period of revolution not the
same as the amount of time it takes to view one full
cycle of Moon phases?
• As the Moon is orbiting the Earth, the
Earth is orbiting the Sun. Thus, it takes
2.2 more days for the Moon to reach the
same position in relation to the Earth and
the Sun.
© K. Coder 2015
Stop!
Go back to packet for next steps
8. How can you determine the phase of the
Moon as viewed from Earth using a diagram of
the Moon-Earth-Sun as viewed from space?
The diagram below represents the Moon at
eight numbered positions in its orbit around
Earth. The nighttime sides of the Moon and
Earth are shaded.
© K. Coder 2015
Here is what you’re actually seeing…
One half of the
Moon and the
Earth is always
illuminated.
The other half
(facing away
from the Sun)
is always dark.
Moon in 8 orbit
positions around
the Earth.
North
Pole
It takes about 3.5
days for the
Moon to move
from one position
to the next.
Because the
Moon’s
position
relative to
Earth changes,
the amount of
lighted Moon
we see also
changes.
Direction the
Sun is coming from
© K. Coder 2015
View from Space
Completely
dark
Steps to determine the Phase of
the Moon:
1. Draw an arrow from the observer
on Earth’s North Pole to the
selected position.
2. Turn your paper so that the
arrow is pointed directly away
from you.
3. Block the far half of the moon.
4. Draw the amount of light and
dark you see on the same side
as you view it.
© K. Coder 2015
View from Space
Mostly dark on left, a
little light on right Steps to determine the Phase of
the Moon:
1. Draw an arrow from the observer
on Earth’s North Pole to the
selected position.
2. Turn your paper so that the
arrow is pointed directly away
from you.
3. Block the far half of the moon.
4. Draw the amount of light and
dark you see on the same side
as you view it.
Follow the same steps
and complete the rest of
the moon phases in your
packet.
© K. Coder 2015
Practice #1
New
Moon
1st
Quarter
Full
Moon
3rd
Quarter
Answer in Packet
Locations of Major Phases:
1 The New Moon will always be directly
between the Earth and Sun.
2 The Full Moon will always be on the
opposite side of Earth than the Sun.
3 First quarter and third quarter are always
at a right angle to the Earth and Sun.
Here is another perspective with Sunlight coming from the right…
Direction
the Sun is
coming
from
Notice the
same phase
occurs in the
same
position,
relative to the
Earth and
Sun.
© K. Coder 2015
9. How does the Moon affect our
oceans?
• Tides: cyclic rise and fall of sea level
under gravitational pull
9. How does the Moon affect our
oceans?
o Caused by the pull of the Moon’s gravity and
the Sun’s gravity on the Earth
▪ The Moon has more of an effect on the tides
because it is closer to Earth.
© K. Coder 2015
10. How often do the tides change?
• Each day, all coastal locations experience 2 high
tides and 2 low tides.
Lunar Day Animation
o One high tide to the next high tide takes 12 hours
and 26 minutes (or from one low tide to the next
low tide).
o One high tide to the next low tide (or vice-versa) takes
6 hours and 13 minutes.
11. How can you plot a tidal change
graph?
Based on the tidal information, at what time
will the next low tide and high tide occur on
November 27?
Low tide:
High tide:
12. Why does the height of the tide
change throughout the month?
• Spring Tides: highest high tides and
lowest low tides
Highest
High Tide
Lowest
Low Tide
© K. Coder 2015
Mont St. Michel Spring Tides
© K. Coder 2015
Mont St. Michel Spring Tides
© K. Coder 2015
Mont St. Michel Spring Tides
Mont St. Michel Spring Tides
© K. Coder 2015
12. Why does the height of the tide
change throughout the month?
o Occurs when Earth, Sun and Moon are in a
straight line (during New and Full Moons)
Spring Tides = Strong = Straight
Full
Moon
New
Moon
© K. Coder 2015
12. Why does the height of the tide
change throughout the month?
• Neap Tides: lowest high tides and highest
low tides
Lowest
High Tide
Highest
Low Tide
12. Why does the height of the tide
change throughout the month?
o Occurs when Earth, Sun, and Moon are at a 90˚
angle (1st and 3rd Quarter Moons)
Neap Tides = Not Strong = Ninety Degree Angle
1st
Quarter
3rd
Quarter
© K. Coder 2015
13. Why are there eclipses?
• Eclipse: an object is blocked from view
13. Why are there eclipses?
o Solar Eclipse: Cannot see the Sun
• Occurs when Moon is directly between the
Sun and Earth (New Moon)
• Can only see on the daylight side of Earth
13. Why are there eclipses?
o Lunar Eclipse: Cannot see the Moon
• Occurs when Earth is directly between the
Sun and Moon (Full Moon)
• Can only see on the nighttime side of
Earth
© K. Coder 2015
14. Why aren’t there eclipses each month during the Full
Moon and New Moon?
• The Moon orbit around the Earth at a 5˚
incline.
Practice #2 in Packet