Moon Phases

animated GIF created by Antonio Cidadao

Barbara Gage PSC 1210 Prince George’s Community College

Intro to the moono The moon does not produce its own

light - we see the moon because it is reflecting light from the Sun.

Moon Phases

o Like Earth, the moon moves through space in 2 ways:

o The Moon revolves around the Earth in 27.3 days

o The Moon also rotates on its own axis in 27.3 days

Moon Phases

o A day and a year on the moon are the same length

o For this reason, the same side of the moon always faces earth

Moon Phases

o As the moon revolves around Earth, the relative positions of the moon, Earth, and sun change

o The changing relative positions of the moon, Earth, and sun cause the phases of the moon and eclipses

Moon Phases

o The different shapes of the moon you see from Earth are called phases

o In about 29.5 days, the cycle is completed

Moon Phaseso The phase of the moon you

see depends on how much the sunlit side of the moon faces earth

1) New Moon

o The sunlit side faces away from the Earth

2) Waxing Crescento The portion of the moon you

can see is waxing, or growing, into a crescent shape.

3) First Quarter

o You can see half of the sunlit side of the

moon.

4) Waxing Gibbouso The moon

continues to wax. The visible shape of the moon is called gibbous.

5) Full Moono The

entire sunlit side faces the Earth.

6) Waning Gibbous

o The portion of the moon you can see wanes, or shrinks.

7) Third Quarter

o You can see half of the moon’s lighted side

8) Waning Crescent

o You can see a crescent once again.

How do you know if it is a Waning or Waxing phase?

Eclipses

Intro to Eclipseso When the Sun or Moon is blocked

from the Earth an eclipse occurs.o When the sun is blocked, it is

called a solar eclipseo When the moon is blocked, it is

called a lunar eclipse

Solar Eclipseo The moon (in new

moon phase) passes directly between the earth and the sun blocking the sunlight

o Remember “SME”The shadow of the Moon falling on the Earth. Anyone under the shadow will

see the solar eclipse.

umbra

penumbra

penumbra

o People within the umbra (or dark shadow region) see the total eclipse

o People within the penumbra (or lighter shadow region) see only a partial eclipse

o It is not safe to look directly at a solar eclipse (you need special glasses)

o In a total solar eclipse, the outer layer of the sun’s atmosphere, the solar corona, is visible surrounding the dark disk of the moon

o The sky grows dark as night, and an eerie color and you can see the stars

Lunar Eclipseo The Earth passes directly between

the Moon and the Sun (during the Full Moon phase)

o Remember “SEM” o Earth casts a shadow on the Moono Everyone on Earth (at night) will

see the Lunar Eclipse

penumbra

penumbra

umbra

Lunar EclipseoWhen the moon is in the Earth’s umbra, you see a total lunar eclipseoWhen the moon is not totally in the Earth’s umbra, you see a partial lunar eclipse

Lunar Eclipseo During a total lunar eclipse, the moon obtains a reddish tint (also called blood moon) because the Earth’s atmosphere bends the red part of the visible sun light toward the moono You do not need special glasses to see a lunar eclipse

Question?

Shouldn’t there be a lunar eclipse every time we have a full moon? (Once per month)

The Earth revolves around the Sun on a flat plane.

The Moon revolves around Earth on a tilted plane. This means that when the moon is full, it may be above or below the shadow of the Earth and no eclipse will occur. Two times a year, the sun, earth, and moon will align, causing an eclipse.

Earth’s

Earth’s

o The Earth moves through space in 2 major ways: rotation and revolution

o Rotation is the spinning of the Earth on its axiso It takes Earth about 24 hours to rotate once. This

24 hour cycle of day and night is called a day

Day and Nighto An Earth’s rotation causes day and nighto It is day on the side of the Earth facing the

sun. o It is night on the side of the Earth facing

away from the sun.

sunlight

Day Night

Yearo Revolution is the movement of one object around

anothero The earth travels around the sun in one year

(365.24 days) o The earth’s path or orbit around the sun is not

circular (it is an ellipse or elongated circle)

SunEarthMoon Vocab Review

Axis Ellipse

365 ¼ days24 hours

Day/Night 1 year