Phases, Eclipses, and Tides
I.
Motions of the Moon
A. The positions of the moon, Earth, and the sun cause
the phases of the moon, eclipses, and tides.
B. Moon revolves around Earth
1. 27.3 days to revolve around Earth
2. orbit is a flattened circle or oval shaped
C. Moon rotates on its axis
1. 27.3 days to rotate once on its axis
2. “day” and “year” on the moon are the same
length
D. Same side of the moon always faces Earth
II. Phases of the Moon
A. Moon reflects light from the sun; does not produce
its own light
B. The different shapes of the moon you see from
Earth are called phases.
1. What Causes Phases?
a. Phases caused by changes in relative
positions of:
(1.) moon
(2.) Earth
(3.) sun
b. Phase you see depends on how much of the
sunlit side of the moon faces Earth
2. Cycle of Phases (see diagram)
a. New Moon
b. Waxing Crescent
c. First Quarter
d. Waxing Gibbous
e. Full Moon
f. Waning Gibbous
g. Third Quarter
h. Waning Crescent
III. Eclipses
A. Moon’s shadow hits Earth or Earth’s
shadow hits the moon, an eclipse occurs
B. Eclipse occurs when an object in space comes
between the sun and a third object, a shadow is cast
on that object
C. Two types:
1. solar
2. lunar
IV. Solar Eclipses
A. Occurs when the moon passes between Earth and the
sun, blocking the sunlight from hitting Earth.
B. Occurs during the new moon phase
C. Total solar eclipses
1. Seen only from the umbra; the darkest part of the
moon’s shadow.
2. Light from the sun is completely blocked.
3. Shadow can only reach a small part of Earth’s
surface.
a. sky is dark and you can see the stars
b. solar corona is visible (outer atmosphere of
the sun)
D. Partial Solar Eclipse
1. Penumbra- less dark and larger part of the
moon’s shadow
2. Part of the sun is still visible from Earth
3. Not safe to look directly at the sun
4. People in the penumbra can only see a partial
eclipse
V. Lunar Eclipses
A. Occurs at a full moon when Earth is directly between
the sun and the moon.
1. Earth blocks sunlight from hitting the moon
2. Moon is in Earth’s shadow and looks dark from
Earth
B. Total Lunar Eclipse
1. When the moon is in Earth’s umbra
2. Lunar eclipse can be seen from anywhere on
Earth that the moon is visible, unlike a solar eclipse
C. Partial Lunar Eclipse
1. Occurs when Earth, sun, and the moon are not
quite in line.
2. moon passes partly into the umbra of Earth’s
shadow
VI. Tides
A. What Causes Tides?
1. tide- rise and fall of water
2. force of gravity pulls the moon and Earth toward
each other
3. occur mainly because of differences in how
much the moon pulls on different parts of Earth
4. moon’s gravity pulls water toward the point on
Earth that is closest to the moon
a. that side is experiencing high tide
b. a second high tide is occurring on the
opposite side of the Earth
B. The Tide Cycle
1. Earth rotates one high tide stays on the side of
the Earth that is facing the moon
2. The second high tide stays on the opposite side
of the Earth
3. The low tide occurs in between the high tides
4. Every location on Earth sweeps through 2 high
tides and 2 low tides in a 25 hour cycle
C. Spring and Neap Tides
1. Spring Tides
a. at new moon and full moon
b. gravity of the sun AND moon are pulling on
the high tide
c. greatest difference between high and low tides
d. Earth, sun, and the moon are in- line
2. Neap Tides
a. at first quarter and last quarter phases
b. sun’s pull is at right angles to the moon’s pull
c. least difference between high and low tides
d. moon is at a 90° angle from Earth and the sun