Kn 6 Ls 2 The Earth and the Sun

welcome to ckla knowledge six lesson two

the earth and the sun

our purpose for listening today is to

distinguish between the earth's

atmosphere and outer space

we want to be able to identify what

causes day and night

listen carefully to understand the word

rotates

can you say rotates

this is where we are

our solar system is the milky way galaxy

in that solar system is the planet earth

where we live

planet earth has lots of continents

one of them is north america

we live on the continent of north

america

the country we live

on is the united states of america

in the united states of america there

are lots of different states

we live in the state of pennsylvania

our city is eerie

what do we call a scientist who studies

astronomy or space

we call them an astronomer

let's think

what is the first layer of sky

the bubble of air that surrounds the

earth

that's the atmosphere

keep thinking

think of some objects in space we talked

about in the previous lesson

the sun

the moon

and the twinkling stars

what is far away from earth made of gas

and gives us heat

light and energy

that's right it's the sun

listen carefully today to find out how

the earth's rotation causes day and

night

all plants animals and people

rely on the sun for life

the sun's energy

gives life to plants which in turn

provides food for animals and people

the sun's heat keeps the surface of the

earth warm enough for plants and animals

to survive

for people on earth it makes sense to

say that the sun rises in the morning

each morning at dawn the sun appears on

the horizon

in the eastern sky

the horizon is the line in the distance

where it appears that the land meets the

sky

at dawn some people say look the sun is

coming up

the first appearance of the sun above

the eastern horizon is called sunrise

over the course of the day the sun

appears to move across the sky

gradually following its path from east

to west

in the evening the sun sets in the west

ever so slowly it gets lower in the sky

and disappears below the horizon

that's when people say the sun is going

down

this disappearance of the sun below the

western horizon is called sunset

so based on what we can see from where

we live on earth it seems sensible to

say that the sun moves across the sky

each day

rising or moving up in the east and

setting or sinking down in the west

but that's not actually true

it is the daily rotation or spin of the

earth that makes the sun appear to rise

and set each day

earth rotates

or spins on its axis

imagine

the earth's axis as an imaginary pole

sticking through the center of the

planet

from north to south

it takes 24 hours or one day for the

earth to spin

or rotate

all the way around one time this daily

rotation explains why there is always

night and day on earth

as it spins certain parts of earth's

surface face the sun

receiving its heat and light

when it is light on one side of the

earth it is dark on the other side

so if it is daytime where you are right

now

then on the other side of the earth

it is nighttime and the children there

are sound asleep

and when you are nestled in your bed

tonight children on the other side of

the planet will be waking up to a bright

new

day

this spinning or rotation of the earth

however is not the only way

earth moves in space

because earth is a planet it also moves

or revolves around the sun

the word planet means a large object in

space that revolves around a star for

light

earth moves or revolves around the sun

following a constant path

the path earth follows around the sun is

called the earth

orbit

earth follows the same path as it

revolves around or orbits the sun

it takes about

365 days or one year for earth to make

one complete orbit or revolution around

the sun

but how and why does earth orbit the sun

the answer to this question

involves one of the most important

lessons you can learn in the study of

astronomy

in space there are large objects like

the sun

and there are smaller objects like the

earth and moon

all objects in space actually pull on

all other objects but larger objects

pull harder than smaller objects

the force that causes objects to pull on

each other is called gravity

as this polling action happens the force

of the sun's gravity

holds earth in its place

although earth continues to follow its

orbit around the sun the earth does not

wander off into space

the sun's gravity holds the earth in

place

just as the sun pulls on the earth and

other objects out in space

the earth pulls on objects on or near

its surface

because of this your feet stay planted

firmly on the ground

and if you jump up you come back down

if you throw a ball in the air it falls

back down too

this force of gravity holds things on

the ground and holds the planet earth in

orbit around the sun

you cannot tell that the earth is always

moving as you sit in your classroom

it rotates or spins all day and every

day as it travels and it's year-long

course around the sun

these two types of movement

the rotation

and the orbit of the earth create the

days and years that we keep track of on

a calendar

let's think about what we learned

how is an orbit different from a

rotation

how is an orbit different from a

rotation

try these sentence starters i think an

orbit

or

i heard that rotation is

let's share what you learned see you

back here next time