Lecture 11
Moon Phases
and Eclipses
Full Moon near
Saturn
The Moon will be full
on Sunday, 4/17/11 so
on Saturday and
Sunday night it will
be near Saturn, which
reached opposition
last week and, like the
full Moon, is on the
opposite side of the
sky as the Sun.
In each phase of the Moon, how much of the Moon is
lit up by the Sun?
Half the Moon is always
lit by the Sun
Except . . .
When the Earth’s shadow hits the Moon we have a …….
Lunar Eclipse
Eclipses occur ONLY when the Moon crosses
the plane of Earth’s orbit around the Sun AND
ONLY during the NEW or FULL phases
Lunar Eclipse
• When Earth blocks most of the sunlight from
illuminating the Moons surface for several
hours when in the full moon phase
When the Moon’s shadow hits the Earth, we have a ….
Solar Eclipse
Solar
Eclipse
Annular Eclipse
Partial Eclipse
Total Eclipse
Eclipses occur ONLY when the Moon crosses
the plane of Earth’s orbit around the Sun AND
ONLY during the NEW or FULL phases
Which positions cause which eclipses
Moon is in the _____
full
• When the ______
phase and is
Earth and the ____
Sun , you get
directly in line with the _____
lunar eclipse?
a ______
new phase and is
Moon is in the _____
• When the ______
Earth and the ____
directly in line with the _____
Sun , you get
a ______
solar eclipse?
When the full Moon is rising in
the East, what is the Sun always
doing?
The Sun is always setting in the
West.
Therefore the Sun and Moon
180
are exactly ________
degrees
apart…try a human animation
if you are having difficulty
visualizing this.
The only exception is …
…if there is a lunar eclipse,
with the Moon crossing the
line of nodes.
How are the motions and positions of
Earth and the Sun connected to what
happens on Earth?
• Earth’s rotation on its axis determines the
length of the day.
• Earth’s orbit around the Sun determines the
length of the year.
• The tilt of Earth’s rotational axis with respect
to the plane of Earth’s orbit causes the
seasons.
The changing phases of the Moon originally
inspired the concept of the month
Watch Movie at:
http://antwrp.gsfc.nasa.gov/apod/image/9911/lunation_ajc.gif
Moon Phase Names
•
•
•
•
•
•
•
•
New Moon
Waxing Crescent
First Quarter
Waxing Gibbous
Full Moon
Waning Gibbous
Third Quarter
Waning Crescent
The Causes of Moon Phases
• Think to yourself about the answer to this question:
What causes the phases of the Moon?
Take out a piece of paper and quickly write out a
brief answer.
How long does it take to complete
the full cycle of Moon Phases?
A. About a day
B. About a week
C. About a month
D. About a year
E. None of the above
Check your answer with your partner!
Solar Period vs. Sidereal Period of
the Moon
Synodic (Solar) vs. Sidereal Period
of
the Moon
Sidereal Period is 27.32 days, Moon
rotates to the purple line (which should
be parallel to the leftmost red dotted
line), 360 degrees; not back to New
Moon - same phase as leftmost image
Synodic Period is 29.53 days, Moon
rotates to the orange line, more than 360
degrees; back to the same phase (new
moon) as leftmost image.
Right now our Moon is just…
What phase is our Moon in right now?
Just a day past First Quarter
Discuss light fills in from the right-ish side.
Lunar Calendar
http://yasirlioneljordan.blogspot.com/2011/04/moon-phases2011-february.html
http://www.clarkplanetarium.org/pages/nightSky
http://meteorshowersonline.com/lyrids.html
Let’s Watch some Moon Phase
Animations!
Pay attention to where the Moon, Sun and Earth are
located and how the Moon appears from Earth at each of
these positions.
Look at how much of the Moon is illuminated when at
each position.
Look at which side of the Moon is illuminated when at
each position.
Animation
ZOOM IN
http://www.sumanasinc.com/webcontent/animations/content/
moonphase.html
Prepare for Human Animation! Get
volunteers! Look at tidal locking.
Discuss plane of Moon’s orbit and angle.
What is a
monthly cycle
& what is a
daily cycle?
Label the daily
times and how
the Moon
phases are
broken up over
time. Name
the phases of
the Moon that
are shown.
Discuss rising
and setting.
Although the
Moon is always
½ lit by the
Sun, we see
different
amounts of the
lit portion from
Earth
depending on
where the
Moon is
located in its
month-long
orbit.
1) How many phases shown in the
picture will the Moon go through in one
day?
2) How long does it take the Moon to
complete one orbit? How many of the
phases will the Moon have gone through
in this time?
3) How long does it take the Earth to
complete one rotation? How far will the
Moon have moved?
4) How much of the Moons total surface
is illuminated when it is in the New
Phase? Full Phase?
5) How much of the illuminated surface
of the Moon is visible from Earth when
it is in the First Quarter Phase, Full
Phase?
6) What time is it when the Waxing
Gibbous Phase is highest in the sky,
Rising? Setting? What phase will it be
in one week later….see next slide for
answer. SKIP RED PORTION.
A Moon Phase is highest in the
sky at 9 pm today. What phase
will the Moon have in three
weeks after today?
Lecture Tutorial: Cause Moon Phases
• Work with a partner!
• Read the instructions and questions carefully.
• Discuss the concepts and your answers with one
another. Take time to understand it now!!!!
• Come to a consensus answer you both agree on.
• If you get stuck or are not sure of your answer, ask
another group.
• If you get really stuck or don’t understand what the
Lecture Tutorial is asking, ask one of us for help.
A few more resources you might enjoy!
Animations:
more complex demo.
http://jove.geol.niu.edu/faculty/stoddard/JAVA/moonphase.
html
Useful information and tables as covered in class:
http://home.hiwaay.net/~krcool/Astro/moon/moonphase/
Gives information on the different moon phases and the
times of day when they are visible.