The Phases of the Moon The Phases of the Moon
Section 25.2
Section 25.2
It has been since ______that the Apollo Mission It has been since ______that the Apollo Mission and Neil Armstrong walked on the Moon.
and Neil Armstrong walked on the Moon.
The Moon is still the ONLY other celestial body The Moon is still the ONLY other celestial body (besides Earth) that humans have walked on.
(besides Earth) that humans have walked on.
“ “ Luna Luna ” our Moon ” our Moon
Moon is our nearest neighbor Moon is our nearest neighbor
2 2
ndndbrightest brightest object in the sky object in the sky
For a planet to have one large moon is unusual. For a planet to have one large moon is unusual.
Galileo first observed the Moon with a telescope in 1609. Galileo first observed the Moon with a telescope in 1609.
What he saw conflicted with the existing theories What he saw conflicted with the existing theories
(made of cheese?!)(made of cheese?!)
He noticed that it had a rough surface, craters, mountains, valleys, He noticed that it had a rough surface, craters, mountains, valleys, and what at the time seemed to be seas (maria).
and what at the time seemed to be seas (maria).
He concluded that the Moon was not all that different from Earth. He concluded that the Moon was not all that different from Earth.
This took away the mystery of the Moon This took away the mystery of the Moon
Cold, Hard Facts
Cold, Hard Facts pg. 557 pg. 557
The Moon’s diameter of 2,160 miles at its The Moon’s diameter of 2,160 miles at its equator.
equator.
1/4 1/4
ththsize of Earth size of Earth
1/8 1/8
ththEarth’s mass, lower density 3.3 g/cc Earth’s mass, lower density 3.3 g/cc
If Earth were the size of your head, the If Earth were the size of your head, the orbiting Moon would be the size of a
orbiting Moon would be the size of a tennis ball 30 feet away.
tennis ball 30 feet away.
Cold, Hard Facts Cold, Hard Facts
The surface The surface gravity on gravity on the Moon is 1/6 that the Moon is 1/6 that
on Earth.
on Earth.
This is why astronauts This is why astronauts can jump as they do.
can jump as they do.
If you weigh 160 lbs. If you weigh 160 lbs.
on Earth, you would on Earth, you would weigh _________lbs weigh _________lbs
on the Moon.
on the Moon.
http://www.youtube.com/watch?v=OSJlL4wqLGo&feature=related
Tides Tides
The moon's The moon's gravitational gravitational pull on the Earth
pull on the Earth is the main is the main cause of the rise and fall of
cause of the rise and fall of ocean tides
ocean tides . .
The moon's gravitational pull The moon's gravitational pull causes two bulges of water on causes two bulges of water on
the Earth's oceans the Earth's oceans
where ocean waters face the where ocean waters face the moon and the pull is strongest moon and the pull is strongest
and one where ocean waters and one where ocean waters
face away from the moon and face away from the moon and
the pull is weakest.
the pull is weakest.
The Moon is in a The Moon is in a synchronous orbit around Earth.
around Earth.
It rotates It rotates once once on its axis every 27.3 days, on its axis every It It revolves
revolves (orbits) around the Earth in 27.3 days. (orbits) around the Earth in
It’s “day” and “year” are the same: synchronized
This means we only see one side This means we only see of the Moon. of the Moon.
http://www.youtube.com/watch?v=OZIB_leg75Q http://www.youtube.com/watch?v=OZIB_leg75Q
The moon orbits in a different plane than the Earth does.
The moon orbits in a different plane than the Earth does.
About 5° difference About 5° difference
The moon’s orbit around the Earth is elliptical The moon’s orbit around the Earth is elliptical
http://www.classzone.com/books/earth_science/terc/content/visualizations/es2 503/es2503page01.cfm?chapter_no=visualization moon’s phases
Sidereal
Sidereal month month
27.3 days 27.3 days
Time it takes for Time it takes for the moon to make the moon to make one one complete complete
revolution around revolution around
the earth and the earth and
return to the same return to the same
starting point.
starting point.
27.3 days
Synodic
Synodic Month Month
29.5 days
Time for the moon to complete one full cycle of phases as seen by earth
Because the earth Because the earth has has moved moved in it’s in it’s
orbit, the moon orbit, the moon must go a little must go a little
farther
farther to complete to complete on full cycle.
on full cycle.
29.5 days
Phases of the Moon
Phases of the Moon
Phases
Phases of the Moon: of the Moon:
the daily changes in the moon’s appearance as viewed from Earth the daily changes in the moon’s appearance as viewed from Earth
•
All but invisible in the sky.
• Moon and sun are lined- up in the same direction as seen from Earth.
• The Sun is behind the moon.
Position 1 Day 1
Phases of the Moon Phases of the Moon
Day 4 Day 4
Waxing Waxing crescent crescent moon moon
(‘wax on’) (‘wax on’)
The moon appears The moon appears to to grow grow brighter brighter
each night each night
http://youtu.be/h9rWQGtznW0?t=2m37s
Position 2
Phases of the Moon Phases of the Moon
7 days old, the 7 days old, the
Moon is at its first Moon is at its first
quarter.
quarter.
This is the optimum This is the optimum night to look at the night to look at the
Moon.
Moon.
Lunar features are Lunar features are in their most deeply in their most deeply
shadowed relief.
shadowed relief.
Position 3
Phases of the moon Phases of the moon
10 days old 10 days old
As the Moon enters As the Moon enters is is waxing gibbous waxing gibbous
phase beyond first phase beyond first
quarter, quarter,
It is nearly full, and It is nearly full, and it becomes very
it becomes very bright.
bright.
Position 4 Position 4
Phases of the moon Phases of the moon
Full moon Full moon
14 days old 14 days old
Sun and moon are Sun and moon are at opposite sides of at opposite sides of
the Earth.
the Earth.
The moon is The moon is brightest and brightest and
“shines” by
“shines” by
reflected sunlight reflected sunlight
Position 5
Phases of the Moon Phases of the Moon
18 days old 18 days old
Waning (away) Waning (away)
Slowly getting Slowly getting darker.
darker.
Waning Waning gibbous gibbous
Position 6
Phases of the moon Phases of the moon
22 days old 22 days old
3 3
rdrdquarter quarter moon moon
It continues to wane It continues to wane
The Apennine Mountains The Apennine Mountains are clearly visible.
are clearly visible.
These were the These were the
mountains that Galileo mountains that Galileo
studied the most studied the most
intensely.
intensely.
Position 7
Phases of the moon Phases of the moon
26 days old 26 days old
Waning crescent Waning crescent moon moon
Position 8
Phases of the moon Phases of the moon
• Day 28
• New moon again
• All but invisible
Quiz! Name that phase!
Quiz! Name that phase!
Waxing or Waning?
Phase…..
Crescent
Name that phase!
Name that phase!
Waxing or Waning?
Phase…..
Gibbous
Name that phase!
Name that phase!
Waxing or Waning?
Phase…..
1
stQuarter
Name that phase!
Name that phase!
Day_____:
Day_____:
Day_____:
Day_____:
Day_____:
Day_____: Day_____:
New Moon
Moon Phases Text page 563
How did we get our Moon?
How did we get our Moon?
We still don’t know with certainty how the Moon was formed.
There are four theories of how the Moon was formed.
1. The oldest theory: the Moon was originally part of Earth, due to Earth’s fast rotation it and was spun off.
Theory was rejected because the Earth could
not have spun quickly enough.
2. 2. Another theory holds that the Moon Another theory holds that the Moon formed separately
formed separately from Earth around from Earth around the same time
the same time (4.6 bya) (4.6 bya) and out of the and out of the same stuff.
same stuff.
This was rejected after lunar rock samples revealed This was rejected after lunar rock samples revealed different “stuff” than Earth.
different “stuff” than Earth.
3. The third theory is that the Moon formed independently and it was
pulled in by Earth’s gravity when it
passed too close.
4. 4. The final, and favored, theory is known The final, and favored, theory is known as the
as the impact theory impact theory . .
States that a very large object (roughly States that a very large object (roughly the size of Mars) collided with Earth 4.5 the size of Mars) collided with Earth 4.5
bya ago when it was still forming.
bya ago when it was still forming.
The debris from the Earth and the The debris from the Earth and the
colliding object combined into an object colliding object combined into an object
with a stable orbit.
with a stable orbit.
A Cold, Hard Place A Cold, Hard Place
The Moon is not massive enough to The Moon is not massive enough to hold on to an atmosphere, so there is hold on to an atmosphere, so there is
no atmosphere.
no atmosphere.
One of the first observations you will One of the first observations you will make about the moon is all of the
make about the moon is all of the craters
craters on its surface. on its surface.
Most craters are the result of asteroid Most craters are the result of asteroid
and and meteoroid impacts meteoroid impacts . .
A Cold, Hard Place A Cold, Hard Place
Most meteoroids burn up in Earth’s Most meteoroids burn up in Earth’s
atmosphere. This can’t happen on the atmosphere. This can’t happen on the
Moon.
Moon.
Also, weathering and erosion has Also, weathering and erosion has
covered up most of the craters here covered up most of the craters here
on Earth.
on Earth.
The Moon preserved a nearly perfect The Moon preserved a nearly perfect record of every impact.
record of every impact.
A Cold, Hard Place A Cold, Hard Place
Meteoroid collisions release terrific amounts of energy. Meteoroid collisions release terrific amounts of energy.
They create an They create an ejecta blanket ejecta blanket of debris, of debris, including large including large boulders and dust.
boulders and dust.
