summer

What Causes Day Length to Change from Summer to Winter?

today we are going to look at patterns

of day and night to answer the question

why is the length of day change from

summer to winter

let's start with some background

knowledge about the earth the earth is

separated into two halves by an

imaginary line called

the equator the half of Earth that is

between the equator and the North Pole

is called the northern hemisphere while

the half of Earth that is between the

equator and the South Pole is called the

southern hemisphere

there's also another imaginary line that

runs through the earth from the North

Pole to the South Pole and this is

called the Earth's axis the Earth

rotates or spins on this axis and it

makes a full rotation every 24 hours now

let's look and see how the Earth and Sun

relate to each other

what causes day and night

well the half of Earth that is facing

the Sun is illuminated by the sun's

light and in that half it's daytime the

hospital away from the Sun is in

darkness and it is nighttime in that

half now in this diagram the Earth's

axis is straight up and down compared to

the Sun but that's not actually what the

earth looks like if this were true

almost everywhere on Earth would be in

the light for half of this day and in

dark for half of the day meaning that

they would have equal days and nights

all of the time but the earth is not

straight up and down it is tilted at an

angle of 23.3 degrees because of this

the northern hemisphere is pointed

towards the Sun at this time of year in

this picture it's June what do you

notice about the amount of light

compared to the amount of darkness now

in the northern hemisphere

well the northern hemisphere now is

getting a lot more sunlight than it did

when the earth was straight up and down

this means that the days will be longer

than 12 hours it's also a lot less

darkness

in the northern hemisphere meaning the

nice will be shorter than 12 hours in

the northern hemisphere this is our

summer time the northern hemisphere is

not always pointed towards the Sun zone

because the earth also revolves around

the Sun it takes one year or twelve

months to complete one full orbit in

this diagram the earth only completed

half of its orbit so that would only be

six months after June which is December

now in December the northern hemisphere

is now pointing away from the Sun the

side closest to the Sun is in daytime

and the side facing away is nighttime

let's compare the amounts of sunlight in

darkness in the northern hemisphere now

that it's December the amount of

darkness is now much greater than the

amount of sunlight that the northern

hemisphere receives this means that the

days will be shorter during December and

the nights will be longer in the

northern hemisphere this is winter time

now that you know why of the days in

summer time are longer and the days in

winter time are shorter in the northern

hemisphere you could take this a step

farther by researching the following

question how does de length change in

the southern hemisphere or how is de

length difference during fall and spring

thank you for watching and visit WWN gfs

Norcom for more video