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Notes: Earth & Moon
(28.2 & 28.3)
REMEMBER THIS SAYING:
“You don’t have to
believe it, you just have
to learn it”
Everyone has different belief systems about
origins of the universe. . . If you do or don’t
believe any of it, that’s fine! Just learn it so you
can pass tests, OK?
Cosmology: Theories as to
how something began, or where
it came from . . .
1) The Capture Theory : The moon was
flying by, and got trapped in earth’s orbit.
2) The Simultaneous Formation Theory:
Earth and moon formed at the same time.
3) The Impact Theory: The moon was flying
by, hit Earth, and took a chunk of Earth
with it.
(#3) The Impact Theory is the
prevailing theory
• At one time, our solar system could have
had as many as 20 planets
• When the earth was still molten, it got hit
by one of them
• The impacting body
Took some of earth’s
Mantle with it (about
1/3) forming the moon
SYNCHRONOUS ROTATION
• Video:The moon's rotation
• The moon revolves around the earth at the
same speed that it rotates. This causes
us to see only one side of the moon from
earth at any time!
Problems with the first
two theories:
• The earth and the
moon have
differences in their
composition/shape
SOLID
COMPARE/CONTRAST:
Earth & Moon
• Earth has more iron than
the moon.
• The moon has a solid
mantle. (This means the
moon does not have plate
tectonics!)
• The moon is more eggshaped than round.
(This might mean the moon
was moving rapidly when it
cooled off.)
SOLID
CURRENT RESEARCH SHOWS:
• The moon is far older than
previously expected. Maybe
even older than the Earth
or the Sun. The oldest age
for the Earth is estimated to
be 4.6 billion years old;
moon rocks were dated at
5.3 billion years old, and the
dust upon which they were
resting was at least another
billion years older.
The moon does not appear to
have Plate Tectonics
• There are moderate earthquakes there because the solid
mantle sometimes cracks after being impacted
• There are no volcanoes, subduction zones, etc. because
it’s mantle is solid
• There is very little to no atmosphere
• There are lots of impact marks on it’s surface, that are
very very old . . .
TYCHO, the largest crater on the moon, is
85 km in diameter and 4.5 km deep. (This
crater was thought to have been created
by a bolide of the same family as the one
that hit earth and could have caused the
extinction of the dinosaurs.)
The “crumbs”, or broken fragments of
rock on it’s surface are called regolith,
and have also come from bolide
collisions.
Our Earth:
Still forming
• The molten interior of the earth indicates that the
earth is still cooling off today from its time of
formation.
• This cooling process creates our atmosphere
(volcanoes, etc.) and moves our plates on the
lithosphere.
Q: Why does the moon have more
craters than the earth?
Q: Why can’t we find rocks on
earth that are as old as earth is
supposed to be?
Q: Why does the moon have
practically no atmosphere?
Folklore #1:The Harvest Moon
• FACT: The Harvest moon is a low-lying, unusually big
and colorful full moon that lands close to Autumnal
Equinox. It was said to give
farmers extra light to work by.
• FICTION: It
is not the moon
“covered in blood”,
or able to give
people
extra supernatural powers.
Folklore #2:The Man in the
Moon
• FACT: Some cultures
see a face or man in the
moon carrying an
object, which is made
from the low/high plains
(maria) along the
moon’s surface.
• FICTION: It is not a
supernatural face, or a
man banished there for
working on a religious
holiday. There is also
no one living there on
that scale.
Folklore #3:The Moon is Made
of Cheese
• FACT: Craters/maria make the moon look
like swiss cheese from far away.
• FICTION: This doesn’t need any
explaining!
SYNCHRONOUS ROTATION
• Video:The moon's rotation
• The moon revolves around the earth at the
same speed that it rotates. This causes
us to see only one side of the moon from
earth at any time!
Phases of the Moon
• The moon revolves around the earth at the same speed
as it rotates. (SYNCHRONOUS ROTATION)
Sometimes the moon will have a shadow where the
sunlight can’t reach it. This creates “phases” of the moon
that are predictable for telling clock and calendar time.
Tides are from the gravitation influence
of the sun and moon on earth’s fluids
You would
experience high
tide here
You would
experience low
tide here
Solar Eclipse – Blocking the sun
with the moon
Lunar Eclipse– Blocking
the sun with the earth
• The moon’s orbital pathway is tilted 5
degrees. The imaginary flat space the
moon orbits on is called it’s ecliptic plane
• SYZYGY is rare! (The alignment of 3
celestial objects)
Like the earth, the moon has a
close point and far point in it’s
rotation relative to the earth.
Lunar Eclipses happen 2-4
times each year, and are hard
to see.
• The reason: the moon’s orbital pathway is
tilted 5 degrees.
• SYZYGY is rare!
There are 1-2 total/annular solar
eclipses a year, and 1-5 partial
eclipses a year.
The earth has 4 distinct
positions in it’s orbit around the
sun, which mark the middle of a
season. . .
SUMMER and WINTER are from a
hemisphere of the earth being tilted toward
or away from the sun. . . not only it’s orbit!
The Tropic of
Cancer (North) and
Tropic of
Capricorn (South)
are latitude lines of
23.5 degrees. These
lines act like a “fake
equator” in summer
and winter, since the
sun is shining directly
on them while earth
tilts.
The “Arctic / Antarctic Circles” are
circles of latitude at the 60+ North and
South poles of the earth, which are in
complete darkness, or complete
daylight for one whole day during
SOLSTICES (Jan 2 and July 2)
What’s this?
“Foucault Pendulum”: Earth
moves the ground while the pendulum
swings freely in one spot.