Ch. 10: Phases of the Moon

Vocabulary:

revolve, orbit, phase, reflect, waxing, waning

Phases of the Moon

• Why is it that sometimes the moon looks full and round, and other times you can’t see it in the sky at all?

• Sometimes it is a thin sliver and sometimes it is partly glowing and partly dark.

• Why does this happen?

The Earth-Sun-Moon System

• Earth revolves (moves in a path) around the sun.

• The path that it takes is called an orbit.

• The Moon revolves around the Earth.

• Both the moon and the Earth travel together around the sun.

What Are Phases of the Moon?

• Phases are the different shapes of the moon that we can see from Earth.

• Really, the moon does not change shape.

• The light from the sun reflects of the surface of the glowing part of the moon, while the shadow from the Earth covers the dark part of the moon.

• Since the Earth and the moon both move, the moon looks like it is changing shape.

Why Do We See Phases?

Why Do We See Phases?

• Sunlight always lights half of the moon’s surface.

• When the moon moves around the Earth, the shadow of the Earth falls on the moon’s surface causing us to see the phases of the moon.

Moon Phases

• When the bright side of the moon faces away from the Earth we call that a NEW MOON.

Moon Phases

• As the moon travels around the Earth the shadow that falls on the surface of the moon moves making it look like the moon is getting bigger.

• This moon is called a WAXING CRESCENT MOON.

• Waxing means to get bigger.

• Crescent means a thin slice.

Moon Phases

• As the moon travels around the Earth more of the moon’s surface is exposed out of the shadow of the Earth.

• When it reaches the half way point it is called a FIRST QUARTER MOON.

Moon Phases

• When most of the Earth’s shadow is off the surface of the moon, it is called a WAXING GIBBOUS MOON.

• Waxing means bigger.• Gibbous mean three-

quarters.

Moon Phases

• When there is no shadow on the moon and you can see the entire surface, it is called a FULL MOON.

• After the full moon, the moon appears to get smaller again.

Moon Phases

• When Earth’s shadow starts to cover the surface of the moon again, it is called a WANING GIBBOUS MOON.

• Waning means to get smaller.

• Gibbous means three-quarters.

Moon Phases

• The LAST QUARTER MOON is when the moon’s surface is half way re-covered by the Earth’s shadow.

Moon Phases

• When the Earth’s shadow almost covers the entire moon, again, it is called a WANING CRESCENT MOON.

• Waning means to get smaller.

• Crescent means a thin slice.• After the WANING

CRESCENT MOON, all the phases restart with the NEW MOON, again.

Sequence of the Moon Phases

• As the moon waxes, it appears that the moon is getting bigger, and as the moon wanes, it looks like the moon is getting smaller.

• It is very important that you are able to tell the phases of the moon, in order.

Questions About Chapter 10

1. During which phase does the moon look like a bright, round circle?

2. Where does the moon’s light come from?

3. What phase comes immediately after the new moon?

4. What phase comes before the last quarter?

5. During which phase would it be easiest to see the stars around the moon?