MOON PHASES

The BIG Idea Students will understand

that the appearance of the moon changes in a predictable cycle as it orbits Earth and as Earth rotates on its axis.

Objective 1: Explain patterns of changes in the appearance of the moon as it orbits Earth. Describe changes in the appearance of the moon

during a month. Identify the pattern of change in the moon’s

appearance Use observable evidence to explain the

movement of the moon around Earth in relationship to Earth turning on its axis and the position of the moon changing in the sky.

Design an investigation, construct a chart, and collect data depicting the phases of the moon

Objective 2: Demonstrate how the relative positions of Earth, the moon, and the sun create the appearance of the moon’s phases.

Identify the difference between the motion of an object rotating on its axis and an object revolving in orbit.

Compare how objects in the sky (the moon, planets, stars) change in relative position over the course of the day or night.

Model the movement and relative positions of Earth, the moon, and the sun.

Must Know Vocabulary

Rotation – is the spinning of an object (i.e. planet) around an imaginary center line.

Orbit – is the path that an object follows around a central object.

Revolution – is to move in an orbit around another object.

Axis – is an imaginary line through the middle of an object, around which that object spins.

Reflection – the process of bouncing off.

Planetary Motion

Planets revolve in an orbit around the Sun.

The Moon revolves in an orbit our planet, Earth.

Day and night on Earth are caused by Earth’s rotation on its axis as it revolves around the Sun.

The Moon

The Moon orbits (travels around) Earth.

The revolution of the Moon around the Earth makes the Moon appear as if it is changing shape in the sky.

From Earth we see the Moon grow from a thin crescent to a full disk (or full moon) and then shrink back to a thin crescent again before vanishing for a few days.

The different shapes that the moon appears to have are called the Moon’s phases.

The Moon goes through eight basic phases as it revolves around Earth.

The Moon completes an orbit and a lunar cycle approximately every 4 weeks.

Changes of the Moon

Changes of the Moon

The moon is lit by sunlight reflecting off it. That light reaches Earth as moonlight.

The lit part of the Moon always points the way to the Sun.

The part of the moon facing the sun is lit up. The part facing away from the sun is in darkness.

The phases that you see depends on how much of the sunlit part of the moon you can see.

The lit part you can see depends on the alignment of the Moon and Sun, and your position on Earth.

Changes of the Moon

The phases we will be discussing and observing are as we see the Moon in the Northern Hemisphere.

Did you know the countries near the equator see the crescent moon shaped like a smile?

The Moon

Why are the phases different in each hemisphere?

The Moon orbits near the equator of the Earth. In the northern hemisphere, we're standing on the

opposite side of the globe from countries in the southern hemisphere.

We are essentially "upside down" from each other! Therefore, we see the Moon from a completely

different vantage point from each other.

The Moon

The Moon

FULL

QUARTER

CRESCENT

GIBBOUS

FOUR BASIC SHAPES

The Moon passes through four major phases during a cycle that repeats itself

every 29.5 days.  The phases always follow one another in the same order:

New moonFirst quarter

Full moonThird quarter

New MoonThe new moon occurs when the moon and

the sun are on the same side of Earth. The moon is between the Sun and the Earth

and therefore lost in the glare of the sun. We see the side which is not lit, so the

moon appears dark to us.

We can’t see a New Moon because the lit side is facing directly away from the

Earth. The New Moon rises at dawn and sets at sunset.

New Moon

New Moon

First Quarter Moon

The right half of the Moon appears lighted and the left side of the Moon appears

dark.  During the time between the New Moon and the First Quarter Moon, the

part of the Moon that appears lighted gets larger and larger every day, and will

continue to grow until the Full Moon.

First Quarter Moon

Full MoonThe lighted side of the Moon faces the Earth.  This means that the Earth, Sun, and Moon are nearly in a straight line,

with the Earth in the middle.  The Moon that we see is very bright from the

sunlight reflecting off it.

Full Moon

Third (Last) Quarter Moon

Sometimes called Third Quarter.  The left half of the Moon appears lighted, and the

right side of the Moon appears dark.  During the time between the Full Moon

and the Last Quarter Moon, the part of the Moon that appears lighted gets smaller

and smaller every day. It will continue to shrink until the New Moon, when the

cycle starts all over again.

Third Quarter Moon

Comparing the First- and Third-Quarter Moons

First-quarter Moon Third-quarter Moon

There are also four other phases of the Moon used.

Waxing Crescent Moon "Waxing" means increasing, or growing

larger.

This Moon can be seen after the New Moon, but before the First Quarter Moon. 

The crescent will grow larger and larger every day, until the Moon looks like the First Quarter Moon.

http://btc.montana.edu/ceres/html/birthdayphases.html

Waxing Crescent Moon

Waxing Gibbous Moon

This Moon can be seen after the First Quarter Moon, but before the Full Moon.  The amount of the Moon that we can see

will grow larger and larger every day. 

Waxing Gibbous Moon

Waning Gibbous Moon "Waning" means decreasing, or getting

smaller.

This Moon can be seen after the Full Moon, but before the Last Quarter Moon.  The amount of the Moon that we can see will grow smaller and smaller every day.

Waning Gibbous Moon

Waning Crescent MoonThis Moon can be seen after the Last

Quarter Moon and before the New Moon.  The crescent will grow smaller and

smaller every day, until the Moon looks like the New Moon.

Waning Crescent Moon

Moon Phases Quiz

The movie is an animated GIF created by Antonio Cidadao from a sequence of still images taken during March and April 1998. Copyright Antonio Cidadao.

Let’s Review Moon Phases!

It’s Just a Phase Moonlight is reflected

sunlight. Half the moon’s surface is

always reflecting light. From Earth we see

different amounts of the Moon’s lit surface.

The amount seen is called a “phase.”

The visible light moves (grows or shrinks) in a right-to-left motion.

The Phases

New moon Waxing Crescent moon First Quarter moon Waxing Gibbous moon Full moon Waning Gibbous moon Third Quarter moon Waning Crescent moon New moon

earth

moon orbit`searth

last (third)quarter

gibbous moon

full moon

gibbous moon

first quarter

crescent

new moon

crescent

waning Moon

waxing Moon

SUN

Video

Go to YouTube. Search “The Universe: Phases of the

Moon”

Review Questions

1. How long does it take Earth’s Moon to complete one lunar cycle?

2. What is a new Moon and what causes it?

3. What is the difference between a waxing Moon and a waning Moon?

4. What is the difference between a crescent Moon and a gibbous Moon?

5. Sketch the Moon’s appearance 1 week, 2 weeks, 3 weeks, and 4 weeks after the new Moon.