Transcript Phases , Eclipses, & Tides

The Moon (Phases, Eclipses, and Tides)
Our Motion & the Moon
Nutation and Precession
Nutation
Barycenter
Barycenter
What makes our Moon weird?
 Large
in comparison to the planet
that it orbits
 27% the radius of Earth
 Great distance from Earth (most
moons are closer)
 Solid rocky composition (most are
icy)
Moon Vs. Earth
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The moon can get
reallllllly hot and cold
(127°C, -173°C), but
because it has no
atmosphere, it does not
retain heat in the
absence of sunlight
No erosion (no wind or
water)
Differences
Areas of high elevation
(highlands) and low
elevations (maria and
craters)
 Very similar mineral
content
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Similarities
How was the Moon formed?
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Capture Theory: As the solar system was
forming, an object came too close to the
forming Earth and got sucked into our
gravitational pull
Simultaneous Formation Theory: The moon and
Earth formed at the same time and in the
same area (that’s why the compositions are
similar)
Impact Theory: The moon formed as a result
of the collision of Earth and a Mars-sized
object about 4.5 billion years ago. Debris from
both merged together to form the moon (most
widely accepted!)
Phases, Eclipses, & Tides
The moon is Earth’s closest neighbor out in space at
384,400 kilometers out in space or 30 Earths lined up
in a row.
 The moon revolves around the Earth as the Earth
revolves around the sun.
★ The positions of the moon, Earth, & the sun
cause the phases of the moon, eclipses, and
tides.

Motions of the Moon:
As the moon revolves around the Earth it
rotates on its own axis; its orbit similar to
Earth’s as a flat oval, tilted at about 7˚.
The moon takes about 27.3 days to orbit
around the Earth; it also takes 27.3 days to
complete one revolution on its own axis causing
a moon “day” & a moon “year” to be the same
length of time.
The moon & Earth have synchronous rotation,
meaning the same side of the moon always faces
Earth.
The “far side” of the moon always faces
away from Earth & is never seen.
Phases of the Moon:
 The moon does not produce its own light, instead it reflects the light from
the sun.
 The moon has 8 phases and goes through the whole set once a month, or
29.5 days.
 What Causes Phases?
★The phase of the moon you see depends on
how much of the sunlit side of the moon faces
Earth.
The Cycles of the Phases:
 From one full moon to the next it takes about 29.5
days.
 The 8 phases of the moon in order are: New
Moon, Waxing Crescent, First Quarter, Waxing
Gibbous, Full Moon, Waning Gibbous, Third
Quarter, Waning Crescent.
Eclipses
★When the moon’s shadow hits Earth or Earth’s
shadow hits the moon, an eclipse occurs.
 There are 2 types of eclipses: solar (sun) eclipse &
lunar (moon) eclipse.
 The type of eclipse is named for what is being
blocked from Earth.
 Total solar eclipse
Total lunar eclipse
Solar Eclipse
The umbra is the darkest and smallest part of the shadow &
is cone shaped (total darkness).
The penumbra is the largest part of the shadow
(partial darkness).
 Total Solar Eclipse:
○ Only people in the umbra experience a total solar
eclipse.
 Partial Solar Eclipse:
○ In the penumbra, people only see a partial eclipse; since
part of the sun is still visible, it is not safe to look directly at
the eclipse.
Lunar Eclipse
 During a full moon the
Earth blocks the sun’s light
from reaching the moon
making the moon look dark from Earth.
 Total Lunar Eclipse
○ When the moon is in the Earth’s umbra, there is
a total lunar eclipse
 Partial Lunar Eclipse
○ The moon passes partly into the umbra of the
Earth’s shadow.
The Tide Cycle
 The moon’s gravity pulls Earth’s water
toward itself and away from 2 opposite
places, creating low tides.
 All 4 tides rotate in a 25 hour cycle.
Spring & Neap Tides
 Spring tides occur twice a month, one at
full moon & one at new moon.
 The combined force of the sun & moons
gravity make a tide with the most intense
high & low tide.
 Neap tides happen 2 times a month, one at first
quarter moon & one at third quarter moon.
 The sun & Earth are at right angles and creates
tides with the least intense difference between
high & low. (It’s like a tug-of-war between the
moon and sun).