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
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