Moon Phases, and Eclipses

• Motions of the Moon– Moon revolves around

the Earth and rotates on its axis.• Takes 27.3 days to

revolve around Earth.• Rotates slowly on its

axis, once every 27.3 days.

– Earth only sees the same side of the moon.• “Far side” always faces

away.

• Phases of the Moon– We see the moon

because it reflects light from the sun.

– The moon’s shape changes during the month causing the phases.

Moon Menu

• Phases of the Moon

– New Moon• The sun lights the side

of the moon facing away from Earth. This side of the moon that faces the Earth is dark.

Moon Menu

• Phases of the Moon

– Waxing Crescent• You see more and

more of the lighted side of the moon.

Moon Menu

• Phases of the Moon

– First Quarter• You see half of the

lighted side of the moon.

• The moon is ¼ of the way through it’s orbit.

Moon Menu

• Phases of the Moon

– Waxing Gibbous• The moon continues

to wax. • The moon is called a

waxing gibbous.

Moon Menu

• Phases of the Moon

– Full Moon• The whole lit side of

the moon can be seen from Earth.

• This is known as a Full Moon.

Moon Menu

• Phases of the Moon

– Waning Gibbous• The Moon now

becomes darker each day. This is known as a waning gibbous

Moon Menu

• Phases of the Moon

– Third Quarter Moon• You can see half of the

moon’s lit side. The moon is ¾ of the way through it’s orbit. This is called a third quarter moon, or last quarter moon.

Moon Menu

• Phases of the Moon

– Waning Crescent• The last phase before

new moon.

Moon Menu

C

E

BI

H

F

D

A

Phases

Cause

Eclipses

• Phases of the Moon– Phases are caused by

changes in the relative positions of the moon, Earth and sun.• As the moon revolves

around the Earth, we see the moon from different angles.

– The phase of the moon depends on how much of the sunlit side of the moon faces Earth.

Moon Menu

• Phases of the Moon– The cycle begins at

new moon.– The amount of light on

the moon will gradually increase (Waxing) to full moon.

– After full moon, the light will gradually decrease (Waning) back to new moon.

Moon Menu

• Phases of the Moon– One lunar

cycle lasts 29.5 days.

Objective: I will be able to describe how the Moon moves and what causes the phases.

Moon Menu

• Eclipses– The moon’s orbit is

slightly tilted.

– As a result, the moon doesn’t always

pass into the Earth’s shadow or the shadow from the moon isn’t cast on the Earth.

Moon Menu

• Eclipses– When the moon’s shadow

hits the Earth or the Earth’s shadow hits the moon, an eclipse occurs.

– An eclipse occurs when an object in space comes between the sun and a third object and casts a shadow on that object.

Moon Menu

• Solar Eclipse– Occurs when the moon is in the new moon

phase and it passes between the Earth and the sun.

– Blocking sunlight from the Earth.– The moon’s shadow hits the Earth.

Moon Menu

• Total Solar Eclipse– Occurs when the

darkest part of the moon’s shadow, “the umbra” hits the Earth.• Sunlight is completely

blocked in any part of this shadow.

• Must be in the shadow of the umbra to see a total solar eclipse.

• Stars, and the corona are visible.

Moon Menu

• Partial Solar Eclipse– Occurs when the less

dark shadow “the penumbra” hits Earth.

– People in the penumbra only see a partial eclipse.

– Part of the sun is still visible.• It is not safe to look

directly at the sun.

Moon Menu

• Lunar Eclipse– Occurs at a full moon when the Earth is

directly between the moon and the sun.– Earth blocks sunlight from reaching the moon.– The moon is in the shadow and looks dark.– Can only occur during a full moon.

Moon Menu

• Total Lunar Eclipse– Occurs when the moon

is in the Earth’s “umbra”• The dark shadow.

– Can be seen anywhere on the dark side of the Earth where the moon is visible.

– More likely to see a lunar eclipse than a solar eclipse.

Moon Menu

• Partial Lunar Eclipse– Occurs if the Earth,

moon and sun are not quite in a line.

– The moon only partially passes into the umbra of the Earth’s shadow.• Edge of shadow appears

blurry.• Last up to 2 or 3 hours.

Moon Menu