seasons on earth - weeblywatsonscience.weebly.com/.../4/8/5548081/seasons_on... · investigation 3:...

FOSS Planetary Science Course

© The Regents of the U

niversity of CaliforniaCan be duplicated for classroom

or workshop use.

FOSS Planetary Science Course

© The Regents of the U

niversity of CaliforniaCan be duplicated for classroom

or workshop use.

Investigation 3: SeasonsN

o. 15—N

otebook Master

Investigation 3: SeasonsN

o. 15—N

otebook Master

Wh

at do you im

agine w

hen

you read

these

word

s: sum

mer, sprin

g, fall, win

ter?

Most of u

s come up

with

a men

tal picture

or two. Su

mm

er mean

s shorts an

d T-sh

irts,

swim

min

g, and

fresh fru

its and

vegetables.

Win

ter mean

s heav

y coats and

short

days, p

erhap

s with

a blanket of sn

ow on

everythin

g. Seaso

ns are pretty easy to tell

apart in

most p

arts of the U

nited

States. Th

e

amou

nt of d

aylight, th

e average temp

erature,

and

the beh

aviors of plants an

d an

imals are

a few fam

iliar ind

icators of the season

. But

wh

at causes th

e predictable ch

ange of season

?

Wh

at have you

learned

in class th

at help

s

you explain

the reason

s for the season

s?

As E

arth

TiltsLet’s start w

ith a qu

ick review of som

e basic

inform

ation about Earth

.

Earth sp

ins on

an im

aginary axle called

an a

xis. T

he axis p

asses throu

gh th

e North

and

South Poles. T

his sp

inn

ing on

an axis is

called ro

tatio

n. It takes 24 h

ours for Earth

to make on

e complete rotation

.

Earth travels arou

nd

(orb

its) the Su

n.

Traveling arou

nd

someth

ing is called

revolu

tion

. Earth’s p

ath arou

nd

the Su

n

is not exactly rou

nd

. It is slightly oval. O

ne

revolution takes 365 an

d 1/4 d

ays, wh

ich w

e

call 1 year.

Seasons on Earth

Make a n

oteb

oo

k entry. R

ecord

the reaso

ns fo

r season

s on

Earth. Y

ou

can

add

mo

re after readin

g th

is article, bu

t record

you

r first ideas n

ow

.

10

Wh

at do you im

agine w

hen

you read

these

word

s: sum

mer, sprin

g, fall, win

ter?

Most of u

s come up

with

a men

tal picture

or two. Su

mm

er mean

s shorts an

d T-sh

irts,

swim

min

g, and

fresh fru

its and

vegetables.

Win

ter mean

s heav

y coats and

short

days, p

erhap

s with

a blanket of sn

ow on

everythin

g. Seaso

ns are pretty easy to tell

apart in

most p

arts of the U

nited

States. Th

e

amou

nt of d

aylight, th

e average temp

erature,

and

the beh

aviors of plants an

d an

imals are

a few fam

iliar ind

icators of the season

. But

wh

at causes th

e predictable ch

ange of season

?

Wh

at have you

learned

in class th

at help

s

you explain

the reason

s for the season

s?

As E

arth

TiltsLet’s start w

ith a qu

ick review of som

e basic

inform

ation about Earth

.

Earth sp

ins on

an im

aginary axle called

an a

xis. T

he axis p

asses throu

gh th

e North

and

South Poles. T

his sp

inn

ing on

an axis is

called ro

tatio

n. It takes 24 h

ours for Earth

to make on

e complete rotation

.

Earth travels arou

nd

(orb

its) the Su

n.

Traveling arou

nd

someth

ing is called

revolu

tion

. Earth’s p

ath arou

nd

the Su

n

is not exactly rou

nd

. It is slightly oval. O

ne

revolution takes 365 an

d 1/4 d

ays, wh

ich w

e

call 1 year.

Seasons on Earth

Make a n

oteb

oo

k entry. R

ecord

the reaso

ns fo

r season

s on

Earth. Y

ou

can

add

mo

re after readin

g th

is article, bu

t record

you

r first ideas n

ow

.

10

FOSS

Pla

neta

ry S

cien

ce C

ours

e©

The

Reg

ents

of t

he U

nive

rsity

of C

alifo

rnia

Can

be d

uplic

ated

for c

lass

room

or w

orks

hop

use.

FOSS

Pla

neta

ry S

cien

ce C

ours

e©

The

Reg

ents

of t

he U

nive

rsity

of C

alifo

rnia

Can

be d

uplic

ated

for c

lass

room

or w

orks

hop

use.

Inve

stig

atio

n 3:

Sea

sons

No.

16—

Not

eboo

k M

aste

rIn

vest

igat

ion

3: S

easo

nsN

o. 1

6—N

oteb

ook

Mas

ter

Eart

h i

sn’t

str

aigh

t up

an

d d

own

on

its

axis

as

it r

evol

ves

arou

nd

th

e Su

n. I

t is

til

ted

at a

23.

5° a

ngl

e.

Th

e av

erag

e d

ista

nce

bet

wee

n t

he

Sun

and

Ear

th i

s ab

out

150

mil

lion

kil

omet

ers

(km

). E

arth

’s o

rbit

is

slig

htl

y ov

al, s

o

Eart

h i

s so

met

imes

far

ther

aw

ay f

rom

an

d

som

etim

es c

lose

r to

th

e Su

n. T

his

dis

tan

ce

is s

o in

sign

ific

ant

that

it i

s n

ot r

elat

ed t

o th

e

seas

ons.

It w

ould

see

m lo

gica

l th

at s

um

mer

wou

ld

be w

hen

Ear

th i

s cl

oses

t to

th

e Su

n. T

hat

idea

is

wro

ng.

Eac

h y

ear

wh

en E

arth

is

clos

est

to t

he

Sun

, th

e N

orth

ern

Hem

isph

ere

exp

erie

nce

s w

inte

r. T

he

reas

ons

for

the

seas

ons

are

lin

ked

to

Eart

h’s

til

t, n

ot t

he

dis

tan

ce f

rom

th

e Su

n.

Th

ink

abou

t Ea

rth

rev

olvi

ng

arou

nd

th

e

Sun

. As

Eart

h r

evol

ves,

it a

lso

rota

tes

on it

s

axis

, on

e ro

tati

on e

very

24

hou

rs. H

ere’

s

som

eth

ing

imp

orta

nt:

Ear

th’s

Nor

th P

ole

poi

nts

tow

ard

a r

efer

ence

sta

r ca

lled

th

e

No

rth

Sta

r. N

o m

atte

r w

her

e Ea

rth

is

in it

s

orbi

t ar

oun

d t

he

Sun

, th

e N

orth

Pol

e p

oin

ts

tow

ard

th

e N

orth

Sta

r, d

ay a

nd

nig

ht,

eve

ry

day

all

yea

r.

Fall

equ

ino

x

Win

ter

sols

tice

Earl

y Ju

ly,

152

mill

ion

km

Earl

y Ja

nu

ary,

14

7 m

illio

n k

m

Sum

mer

so

lsti

ce

Spri

ng

eq

uin

ox

Sid

e-vi

ew d

iag

ram

of

Eart

h-S

un

re

lati

on

ship

, sh

ow

ing

sea

son

s in

th

e N

ort

her

n H

emis

ph

ere.

(N

ot

dra

wn

to

sca

le.)

No

rth

Sta

r

Is E

arth

clo

ser

to t

he

Sun

in

win

ter

or

in s

um

mer

? Is

dis

tan

ce f

rom

th

e Su

n a

re

aso

n f

or

seas

on

s o

n E

arth

?

N

N

N

N

Inve

stig

atio

n 3

: Se

ason

s 1

1

Eart

h i

sn’t

str

aigh

t up

an

d d

own

on

its

axis

as

it r

evol

ves

arou

nd

th

e Su

n. I

t is

til

ted

at a

23.

5° a

ngl

e.

Th

e av

erag

e d

ista

nce

bet

wee

n t

he

Sun

and

Ear

th i

s ab

out

150

mil

lion

kil

omet

ers

(km

). E

arth

’s o

rbit

is

slig

htl

y ov

al, s

o

Eart

h i

s so

met

imes

far

ther

aw

ay f

rom

an

d

som

etim

es c

lose

r to

th

e Su

n. T

his

dis

tan

ce

is s

o in

sign

ific

ant

that

it i

s n

ot r

elat

ed t

o th

e

seas

ons.

It w

ould

see

m lo

gica

l th

at s

um

mer

wou

ld

be w

hen

Ear

th i

s cl

oses

t to

th

e Su

n. T

hat

idea

is

wro

ng.

Eac

h y

ear

wh

en E

arth

is

clos

est

to t

he

Sun

, th

e N

orth

ern

Hem

isph

ere

exp

erie

nce

s w

inte

r. T

he

reas

ons

for

the

seas

ons

are

lin

ked

to

Eart

h’s

til

t, n

ot t

he

dis

tan

ce f

rom

th

e Su

n.

Th

ink

abou

t Ea

rth

rev

olvi

ng

arou

nd

th

e

Sun

. As

Eart

h r

evol

ves,

it a

lso

rota

tes

on it

s

axis

, on

e ro

tati

on e

very

24

hou

rs. H

ere’

s

som

eth

ing

imp

orta

nt:

Ear

th’s

Nor

th P

ole

poi

nts

tow

ard

a r

efer

ence

sta

r ca

lled

th

e

No

rth

Sta

r. N

o m

atte

r w

her

e Ea

rth

is

in it

s

orbi

t ar

oun

d t

he

Sun

, th

e N

orth

Pol

e p

oin

ts

tow

ard

th

e N

orth

Sta

r, d

ay a

nd

nig

ht,

eve

ry

day

all

yea

r.

Fall

equ

ino

x

Win

ter

sols

tice

Earl

y Ju

ly,

152

mill

ion

km

Earl

y Ja

nu

ary,

14

7 m

illio

n k

m

Sum

mer

so

lsti

ce

Spri

ng

eq

uin

ox

Sid

e-vi

ew d

iag

ram

of

Eart

h-S

un

re

lati

on

ship

, sh

ow

ing

sea

son

s in

th

e N

ort

her

n H

emis

ph

ere.

(N

ot

dra

wn

to

sca

le.)

No

rth

Sta

r

Is E

arth

clo

ser

to t

he

Sun

in

win

ter

or

in s

um

mer

? Is

dis

tan

ce f

rom

th

e Su

n a

re

aso

n f

or

seas

on

s o

n E

arth

?

N

N

N

N

Inve

stig

atio

n 3

: Se

ason

s 1

1

FOSS Planetary Science Course

© The Regents of the U

niversity of CaliforniaCan be duplicated for classroom

or workshop use.

FOSS Planetary Science Course

© The Regents of the U

niversity of CaliforniaCan be duplicated for classroom

or workshop use.

Investigation 3: SeasonsN

o. 17—N

otebook Master

Investigation 3: SeasonsN

o. 17—N

otebook Master

Tilt Eq

uals S

easo

nLo

ok at the illu

stration on

page 11. It sh

ows

wh

ere Earth is in

its orbit aroun

d th

e Sun

at

each season

. You w

ill also see that th

e North

Pole poin

ts toward

the N

orth Star in

all four

seasons.

Stud

y the Earth

diagram

in th

e sum

mer

solstice p

osition. B

ecause of th

e tilt, the

North

Pole is “leanin

g” toward

the Su

n.

Wh

en th

e North

Pole is leanin

g toward

the

Sun

, dayligh

t is longer, an

d th

e angle at

wh

ich ligh

t hits th

at part of Earth

is more

direct. B

oth of th

ese factors result in

more

sola

r energ

y fallin

g on th

e North

ern

Hem

isphere. It is su

mm

er even th

ough

Earth

is actually farth

er from th

e Sun

. (An

d w

hen

it

is sum

mer in

the N

orthern

Hem

isphere, it is

win

ter in th

e Southern

Hem

isphere.)

Look at th

e position

of Earth 6 m

onth

s

later (at win

ter solstice). Now

the op

posite

is true. Even

thou

gh Earth

is closer to the

Sun

at this tim

e, the N

orthern

Hem

isphere

is tilted aw

ay from th

e Sun

. Dayligh

t hou

rs

are shorter, an

d su

nligh

t does n

ot come as

directly to th

e North

ern H

emisph

ere, so

it gets less solar energy. It is w

inter in

the

North

ern H

emisph

ere.

Four d

ays in th

e year have n

ames based

on Earth

’s location

aroun

d th

e Sun

. In th

e

North

ern H

emisph

ere, sum

mer solstice is

Jun

e 21 or 22, wh

en th

e North

Pole tilts

toward

the Su

n. W

inter solstice is D

ecember

21 or 22, wh

en th

e North

Pole tilts away

from th

e Sun

.

Th

e 2 days w

hen

the Su

n’s rays sh

ine

straight dow

n on

the equ

ator are the

equ

inox

es. On

these 2 d

ays, Earth’s axis is

tilted n

either aw

ay from n

or toward

the Su

n.

Equinox mean

s “equal n

ight.” D

aylight an

d

darkn

ess are equal (or n

early equal) all over

Earth. T

here are tw

o equin

oxes each year,

the sprin

g (also called vern

al) equin

ox in

March

and

the fall (also called

autum

nal)

equin

ox in Sep

tember.

12

Tilt Eq

uals S

easo

nLo

ok at the illu

stration on

page 11. It sh

ows

wh

ere Earth is in

its orbit aroun

d th

e Sun

at

each season

. You w

ill also see that th

e North

Pole poin

ts toward

the N

orth Star in

all four

seasons.

Stud

y the Earth

diagram

in th

e sum

mer

solstice p

osition. B

ecause of th

e tilt, the

North

Pole is “leanin

g” toward

the Su

n.

Wh

en th

e North

Pole is leanin

g toward

the

Sun

, dayligh

t is longer, an

d th

e angle at

wh

ich ligh

t hits th

at part of Earth

is more

direct. B

oth of th

ese factors result in

more

sola

r energ

y fallin

g on th

e North

ern

Hem

isphere. It is su

mm

er even th

ough

Earth

is actually farth

er from th

e Sun

. (An

d w

hen

it

is sum

mer in

the N

orthern

Hem

isphere, it is

win

ter in th

e Southern

Hem

isphere.)

Look at th

e position

of Earth 6 m

onth

s

later (at win

ter solstice). Now

the op

posite

is true. Even

thou

gh Earth

is closer to the

Sun

at this tim

e, the N

orthern

Hem

isphere

is tilted aw

ay from th

e Sun

. Dayligh

t hou

rs

are shorter, an

d su

nligh

t does n

ot come as

directly to th

e North

ern H

emisph

ere, so

it gets less solar energy. It is w

inter in

the

North

ern H

emisph

ere.

Four d

ays in th

e year have n

ames based

on Earth

’s location

aroun

d th

e Sun

. In th

e

North

ern H

emisph

ere, sum

mer solstice is

Jun

e 21 or 22, wh

en th

e North

Pole tilts

toward

the Su

n. W

inter solstice is D

ecember

21 or 22, wh

en th

e North

Pole tilts away

from th

e Sun

.

Th

e 2 days w

hen

the Su

n’s rays sh

ine

straight dow

n on

the equ

ator are the

equ

inox

es. On

these 2 d

ays, Earth’s axis is

tilted n

either aw

ay from n

or toward

the Su

n.

Equinox mean

s “equal n

ight.” D

aylight an

d

darkn

ess are equal (or n

early equal) all over

Earth. T

here are tw

o equin

oxes each year,

the sprin

g (also called vern

al) equin

ox in

March

and

the fall (also called

autum

nal)

equin

ox in Sep

tember.

12

FOSS

Pla

neta

ry S

cien

ce C

ours

e©

The

Reg

ents

of t

he U

nive

rsity

of C

alifo

rnia

Can

be d

uplic

ated

for c

lass

room

or w

orks

hop

use.

FOSS

Pla

neta

ry S

cien

ce C

ours

e©

The

Reg

ents

of t

he U

nive

rsity

of C

alifo

rnia

Can

be d

uplic

ated

for c

lass

room

or w

orks

hop

use.

Inve

stig

atio

n 3:

Sea

sons

No.

18—

Not

eboo

k M

aste

rIn

vest

igat

ion

3: S

easo

nsN

o. 1

8—N

oteb

ook

Mas

ter

Day a

nd

Nig

ht

We

take

day

an

d n

igh

t fo

r gr

ante

d. T

hey

alw

ays

hap

pen

. Ear

th r

otat

es o

n it

s ax

is, a

nd

the

Sun

ap

pea

rs t

o ri

se; t

hen

th

e Su

n a

pp

ears

to s

et. T

his

cyc

le h

as h

app

ened

at

leas

t as

lon

g as

hu

man

s h

ave

been

on

Ear

th. I

t w

ill

mos

t li

kely

con

tin

ue

for

mil

lion

s of

yea

rs.

Bec

ause

Ear

th i

s ti

lted

, th

e le

ngt

h o

f

day

an

d n

igh

t fo

r an

y on

e pl

ace

on E

arth

chan

ges

as t

he

year

pas

ses.

Th

is t

able

sh

ows

how

hou

rs o

f d

ayli

ght

chan

ge a

t d

iffe

ren

t

lati

tude

s du

rin

g th

e ye

ar. W

hen

it’s

su

mm

er

in t

he

Nor

ther

n H

emis

pher

e, t

he

Nor

th P

ole

tilt

s to

war

d t

he

Sun

. Du

rin

g th

is t

ime

at t

he

Nor

th P

ole,

th

e Su

n n

ever

set

s. A

bove

th

e

Arc

tic

Cir

cle

(66.

5° n

orth

), d

ayli

ght

can

last

up t

o 24

hou

rs o

f th

e d

ay i

n t

he

sum

mer

.

Dar

knes

s ca

n la

st u

p t

o 24

hou

rs o

f th

e d

ay

duri

ng

the

win

ter.

Thin

k Q

uest

ion

sG

o ba

ck t

o yo

ur

not

eboo

k en

try

abou

t

the

reas

ons

for

the

seas

ons

that

you

mad

e at

th

e be

gin

nin

g of

th

is a

rtic

le.

Wh

at d

o yo

u n

eed

to

add?

Wh

at d

o

you

nee

d t

o ch

ange

?

Len

gth

of

Dayli

gh

t in

th

e N

ort

hern

Hem

isp

here

Lati

tud

eSu

mm

er

sols

tice

Win

ter

sols

tice

Eq

uin

oxes

0° N

12 h

r.12

hr.

12 h

r.

10°

N12

hr.

35 m

in.

11 h

r. 25

min

.12

hr.

20°

N13

hr.

12 m

in.

10 h

r. 48

min

.12

hr.

30°

N13

hr.

56 m

in.

10 h

r. 4

min

.12

hr.

40°

N14

hr.

52 m

in.

9 h

r. 8

min

.12

hr.

50°

N16

hr.

18 m

in.

7 h

r. 42

min

.12

hr.

60°

N18

hr.

27 m

in.

5 h

r. 33

min

.12

hr.

70°

N24

hr.

0 h

r.12

hr.

80°

N24

hr.

0 h

r.12

hr.

90°

N24

hr.

0 h

r.12

hr.

Inve

stig

atio

n 3

: Se

ason

s 1

3

Day a

nd

Nig

ht

We

take

day

an

d n

igh

t fo

r gr

ante

d. T

hey

alw

ays

hap

pen

. Ear

th r

otat

es o

n it

s ax

is, a

nd

the

Sun

ap

pea

rs t

o ri

se; t

hen

th

e Su

n a

pp

ears

to s

et. T

his

cyc

le h

as h

app

ened

at

leas

t as

lon

g as

hu

man

s h

ave

been

on

Ear

th. I

t w

ill

mos

t li

kely

con

tin

ue

for

mil

lion

s of

yea

rs.

Bec

ause

Ear

th i

s ti

lted

, th

e le

ngt

h o

f

day

an

d n

igh

t fo

r an

y on

e pl

ace

on E

arth

chan

ges

as t

he

year

pas

ses.

Th

is t

able

sh

ows

how

hou

rs o

f d

ayli

ght

chan

ge a

t d

iffe

ren

t

lati

tude

s du

rin

g th

e ye

ar. W

hen

it’s

su

mm

er

in t

he

Nor

ther

n H

emis

pher

e, t

he

Nor

th P

ole

tilt

s to

war

d t

he

Sun

. Du

rin

g th

is t

ime

at t

he

Nor

th P

ole,

th

e Su

n n

ever

set

s. A

bove

th

e

Arc

tic

Cir

cle

(66.

5° n

orth

), d

ayli

ght

can

last

up t

o 24

hou

rs o

f th

e d

ay i

n t

he

sum

mer

.

Dar

knes

s ca

n la

st u

p t

o 24

hou

rs o

f th

e d

ay

duri

ng

the

win

ter.

Thin

k Q

uest

ion

sG

o ba

ck t

o yo

ur

not

eboo

k en

try

abou

t

the

reas

ons

for

the

seas

ons

that

you

mad

e at

th

e be

gin

nin

g of

th

is a

rtic

le.

Wh

at d

o yo

u n

eed

to

add?

Wh

at d

o

you

nee

d t

o ch

ange

?

Len

gth

of

Dayli

gh

t in

th

e N

ort

hern

Hem

isp

here

Lati

tud

eSu

mm

er

sols

tice

Win

ter

sols

tice

Eq

uin

oxes

0° N

12 h

r.12

hr.

12 h

r.

10°

N12

hr.

35 m

in.

11 h

r. 25

min

.12

hr.

20°

N13

hr.

12 m

in.

10 h

r. 48

min

.12

hr.

30°

N13

hr.

56 m

in.

10 h

r. 4

min

.12

hr.

40°

N14

hr.

52 m

in.

9 h

r. 8

min

.12

hr.

50°

N16

hr.

18 m

in.

7 h

r. 42

min

.12

hr.

60°

N18

hr.

27 m

in.

5 h

r. 33

min

.12

hr.

70°

N24

hr.

0 h

r.12

hr.

80°

N24

hr.

0 h

r.12

hr.

90°

N24

hr.

0 h

r.12

hr.

Inve

stig

atio

n 3

: Se

ason

s 1

3