California science grade 3 (9)

Infer What causes the shadows to change position and length?. How does the Sun’s position in the sky seem to change?. Quick Check Summarize How does the Sun’s position in the sky seem

Chapter 4 Chapter 5

The Sun

is the only star in our solar sy stem

.

CHAPTER 4

Our Earth, Sun, and Moon

How do Earth and the Moon

move through space?

174

3 ES 4 Objects in the sky move in regular

and predictable patterns.

175

Poem

ELA R 3.3.5 Recognize the similarities of sounds in words and rhythmic patterns (e.g., alliteration, onomatopoeia) in a selection ELA W 3.2.2 Write descriptions that use concrete sensory details to present and support unified impressions of people, places, things, or experiences.

176

Write About ItResponse to Literature The poet uses rhyme, rhythm, and vivid words to tell how she feels about the Sun and Moon Write a poem about the Sun and Moon Show how they are different Use words that create a strong impression and show how you feel

The Sun is filled with shining light

It blazes far and wide The Moon reflects the sunlight back But has no light inside.

I think I’d rather be the Sun That shines so bold and bright Than be the Moon that only glows With someone else’s light.

from Becoming Myself

Have you ever watched the Sun rise? Bright

light appears on the horizon Slowly, the

Sun rises and night becomes morning The

Sun’s light casts long shadows How do

shadows change during the day?

Lesson 1

Day and Night

3 ES 4.e Students know the position of the Sun in the sky changes during the course

of the day and from season to season.

178

ENGAGE

Time Length of Shadow

Morning Midday Afternoon

Step

Step

How do shadows change?

Form a Hypothesis

How does the location of the Sun in the sky

affect the length of shadows on the ground?

How does it affect the position of the shadows?

Write a hypothesis

Test Your Hypothesis

Work in pairs outside on a sunny morning

Use the chalk to mark an X on the ground

Have your partner stand on the X.

Trace your partner’s shadow

Measure Use the measuring tape to find

the length of the shadow Record your results

in a table Draw a sketch

Predict How do you think the shadow will

change during the day?

Observe Repeat steps 2 and 3 at midday

and in the afternoon on the same spot How

does the shadow change?

Draw Conclusions

Compare Use the data in your table to

answer these questions When is the shadow

very long? When is the shadow very short?

Infer What causes the shadows to change

position and length?

Explore More

How can you find out in which month the Sun’s

position appears highest in the sky? Lowest?

Materials

chalk

measuring tape

3 IE 5.d Predict the outcome of a simple investigation

and compare the result with the prediction.

179

EXPLORE

How does the Sun’s position

in the sky seem to change?

Each day the Sun seems to move across the sky in a giant arc In the morning the Sun appears low on the eastern horizon

(huh•RIGH•zuhn) At midday, it appears high overhead In the evening, it appears low on the western horizon The horizon is an imaginary line where the land seems to meet the sky.

C Main Idea

The position of the Sun

in the sky appears to

change during the day

Earth’s rotation causes

day and night

The Sun’s Position in the Sky

The Sun seems to rise in

the east and set in the west

Looking at these pictures,

you are facing south C

horizon

3 ES 4.e

180

EXPLAIN

A At midday, the Sun is high

overhead and shadows are short

The Sun and Shadows

Have you ever noticed how shadows change during

the day? Sometimes they are long At other times they

are very short Shadows change as the position of the

Sun changes

At midday the Sun is high overhead The angle at

which sunlight strikes Earth is greater than in the

morning or evening The Sun’s light is more direct

and shadows are very short At sunrise and sunset,

the angle at which sunlight strikes Earth is smaller

The Sun’s light is less direct and shadows are very long.

A As the Sun begins to set, shadows get long

Quick Check

Summarize How does the Sun’s position in the sky

seem to change during the day?

Critical Thinking If you wanted to avoid direct

sunlight, when should you stay indoors? Explain.

181EXPLAIN

What causes night

and day?

As you read this book, you are

moving through space You cannot

feel Earth’s movement When you

walk, the ground is still Buildings

and trees seem to stay still too But

you and all things on the surface

of Earth are moving.

Earth rotates (ROH•tayts) like a

giant top that is spinning in space

To rotate means to turn It is the

rotating of Earth that causes day

and night As Earth rotates, one

side faces the Sun That side of

Earth has daytime At the same

time, the other side of Earth faces

away from the Sun That side of

Earth has nighttime.

As Earth turns, the Sun’s

position seems to move in the sky

When you watch the Sun rise and

set, what you see is caused by

Earth’s rotation Earth rotates

from the west to the east.

Every 24 hours, Earth makes one

complete rotation A full day is 24

hours long, or all of the daytime

hours plus all of the nighttime hours.

Day and Night

A Model of Earth Make a Model

Be Careful.

Push a pencil through

a foam ball The pencil represents Earth’s axis Press a paper clip into the side of the ball The ball represents Earth

The paper clip represents you

Observe In a darkened room shine a light on the paper clip The light represents the Sun.Where is it day on the model?

Experiment Show how Earth rotates by turning the pencil What happens to the light on the paper clip? Where is it day

on the model? Where is it night?

Communicate How does this model help explain what you know about day and night?

north

183EXPLAIN

What is an axis?

Have you ever seen a ball spinning on a fingertip?

Think of a line drawn from the fingertip to the top

of the ball The line would be straight up and down

The ball spins around this line This line is called

an axis (AX•is) An axis is a real or imaginary line

through the center of a spinning object

Earth is shaped like a ball This shape is called

a sphere (SFEER) Earth also spins on an imaginary

axis As you can see here, Earth’s axis is not straight

up and down It is slightly tilted The North Pole is at

the north end of Earth’s axis The South Pole is at the

south end.

Quick Check

Summarize Describe Earth’s axis.

Critical Thinking What if you put a pencil through

a ball to model Earth and its axis? How is the model

like the real thing? How is it different?

axis

North Pole

South Pole Earth’s axis

184

EXPLAIN

California north

North Pole

South Pole

Ac[[O`g

Think, Talk, and Write

Main Idea Why does the position of the Sun in the sky seem to change?

Vocabulary What does it mean

to rotate?

Summarize How long is a day?

Describe the motion of Earth that makes up one day

Summarize the Main Idea

Earth spins on its

axis, the imaginary

line through its center (p 184)

Critical Thinking If it is 9:00 A.M in California, is it the same time, later,

or earlier in New York? Why? Use a model to explain your answer

Test Practice What causes day and night?

A The Sun rotates on its axis

B Earth rotates on its axis

C Earth moves around the Sun

D The Sun moves around Earth

Solve a Problem

How many times has Earth rotated

in your lifetime? Explain how you

could solve this problem Then

try to solve it You can use a

calculator to help

Conduct an Interview

Ultraviolet light (UV) from the Sun causes skin to tan or burn

Interview adult family members

to find out how they protect their skin from the Sun Write down what they tell you

- Review Summaries and quizzes online @ www.macmillanmh.com

Math Link Health Link

185EVALUATE

Analyze Data

Have you ever noticed that some days seem

longer than others? This happens because the

Sun rises and sets at different times on different

days Some days seem longer because they have

more hours of daylight than others How did

scientists figure this out? One way is to analyze

data from past years.

Learn It

When you analyze data, you use information that has

been gathered to answer questions or solve problems It

is easier to analyze the data if it has been organized and

placed on a chart or a graph That way you can quickly

see differences in the data

Try It

You learned that scientists analyze data Scientists

collect information about sunrise and sunset in certain

places They use the data to figure out the number of

daylight hours we have at different times of the year

You can organize and analyze their data to draw

conclusions, too

Average Sunrise and Sunset Data for Los Angeles, California

Month Sunrise Sunset Approximate Hours of Daylight

Apply It

It is your turn to analyze data Measure the air

temperature every hour for one day Begin at 8 A.M. and

end at 6 P.M Record your data in a chart Use the data

chart to make a bar graph

Now you can use your bar graph to analyze your data

When during the day is the air temperature the warmest?

When is the air temperature the coolest?

First, organize the data by making a bar graph Use

the graph to show the number of daylight hours there

are in each month Follow these steps to make your

bar graph

C List the months along the bottom of the graph

Write the numbers along the left side of the graph

C Draw a bar to match each of the numbers from

the data

C Write a title for the graph and label the sides Use

the column headings of the chart to help you

Now you can use the bar graph to analyze the

data About how many hours of daylight will there

be tomorrow? Explain

187EXTEND

The Seasons

Lesson 2

Do you have a favorite season? Some places on Earth have longer and warmer days at certain times of the year Some places stay the same or almost the same How come? What happens when seasons change?

3 ES 4.e Students know the position of the Sun in the sky changes during the course

of the day and from season to season.

188

ENGAGE

What happens to the length of shadows as the

seasons change? Write a prediction

Test Your Prediction

Make a Model Stick the clay

on the globe over California

Stand the straw up in the clay

Your teacher will place

the lamp in the center of a

darkened room so the light hits the middle of

the globe The lamp represents the Sun

Experiment The globe represents Earth

Hold Earth and walk around the Sun Tip Earth

to show its tilted axis Keep the tilt pointed in

the same direction Keep the straw pointed at

the Sun as Earth moves around the Sun

Observe How does the amount of light

hitting your part of Earth change? What

happens to the length of the straw’s shadow

as the globe moves?

Draw Conclusions

Analyze Data Where was the shadow

shortest? Where was it longest?

Infer Where was the light most direct?

Explore More

How do you think this model might help explain

the changing seasons?

Materials

small lump of clay

drinking straw

lamp

3 IE 5.d Predict the outcome of a simple investigation

and compare the result with the prediction.

189EXPLORE

Why do seasons change?

You learned that Earth rotates around its axis This is not the only way Earth moves in space It also revolves (ri•VOLVZ)

An object that moves around another object revolves Earth travels, or revolves,

in a regular path around the Sun This path is called Earth’s orbit (AWR•bit) It takes Earth one year, or about 365 days, to complete one orbit around the Sun

Seasons change as Earth rotates and revolves around the Sun because of Earth’s tilted axis Look at the diagram No matter where Earth is in its orbit, its axis is always tilted in the same direction

C Main Idea

Earth’s tilted axis and

orbit around the Sun

causes the seasons The

position of the Sun in

the sky seems to change

from season to season

In June, the North Pole is tilted toward the Sun

This means sunlight is more direct More of the

Sun’s energy reaches the North Pole Days are longer

Temperatures are warmer It is summer there.

By December, Earth has moved to a different

position in its orbit Now the North Pole is tilted

away from the Sun Less direct sunlight and less

energy reach the North Pole Days are shorter and

temperatures are cooler It is winter there The South

Pole is now tilted toward the Sun It is summer there.

Quick Check

Cause and Effect Why do seasons change?

Critical Thinking How would seasons change if

Earth took longer to revolve around the Sun?

summer (begins June 21–22)

Seasons in the Northern Hemisphere

fall (begins September 22–23)

What is the same about Earth’s axis as it moves around the Sun?

Clue: Compare the drawings of Earth during each of the

winter

winter (begins December 21-22)

N

191EXPLAIN

How does the Sun’s path change

from season to season?

You learned that on a single day, the Sun appears

to rise and follow a path across the horizon Day, night,

and changing shadows are caused by Earth’s rotation

The Sun’s position also seems to change from

season to season When it is summer in California,

the Sun is high overhead at noon That is because the

northern half of Earth is tilted toward the Sun This

tilt makes the Sun’s path seem higher in the sky.

When it is winter in California, the path of the Sun

appears low in the sky California is tilted away from

the Sun The Sun at noon is lower The southern half

of Earth is tilted toward the Sun.

summer

winter

Path of the Sun in Summer and Winter

The Sun’s path appears lower in the sky during winter and higher in the sky during summer

192

EXPLAIN

Sunset Times Use research materials to find the average time of sunset for each month where you live.

Record this information in

a chart

Draw Conclusions During which month is sunset the latest? The earliest?

Quick Check

Cause and Effect What causes

the Sun to appear higher in the

sky during the summer?

Critical Thinking When it

is winter in the Southern

Hemisphere, does the Sun’s

path appear high or low?

Explain.

In the spring and fall, the path

of the Sun is in between high and

low In the spring days are growing

longer, and temperatures are higher

in California In the fall days are

growing shorter and temperatures

are lower in California

A During the summer, temperatures

are warmer, and there are more

hours of daylight It is still daytime

at 4 P.M in California

A During the winter, temperatures are cooler, and there are fewer hours of daylight At 4 P.M in California, the Sun is already setting

winter summer

.POUI 5JNF
PG
4VOTFU

+BOVBSZ 'FCSVBSZ BSDI

"QSJM BZ

El Capitan, Yosemite

National Park, California

193EXPLAIN

Quick Check

Cause and Effect What causes

places near the equator to have the

same temperature most of the year?

Critical Thinking Why are the

seasons in places further from the

equator different from the seasons

The equator (ee•KWAY•tuhr) is an

imaginary line around the middle of

Earth It separates Earth into two

parts The top part is the Northern

Hemisphere The bottom part is the

Southern Hemisphere

Places near the equator have about

the same temperature most of the year

That is because the amount of sunlight

that hits the equator stays the same

all year Here the Sun’s rays are

stronger and the temperature

is higher Places farther

away from the equator

have different seasons

Places closest to the

poles have cold weather

for most of the year.

Equator

Northern Hemisphere

Southern Hemisphere

194

EXPLAIN