Day Length
Seasons
Earth’s revolution around the Sun
Earth spins on
its axis; one
rotation takes
24 hours.
Day time and Night time are caused by the spinning
of the earth on its axis.
The side facing the sun has day time, while the side
away from the sun experiences night time.
Day time hours vary throughout the year due to the
earth’s movement around the sun as it spins on its
axis and the tilt of the earth on its axis.
Equator
Earth’s
movement
around the Sun;
one revolution
takes 365.25
days.
Rotation and
Revolution are
both counterclockwise
Earth’s revolution around the Sun
We have seasons because Earth's axis – the imaginary line that goes
through the Earth and around which the Earth spins — is tilted.
It's tilted about 23.5 degrees relative to our plane of orbit around
the Sun.
As we orbit our Sun, our axis always points to the same fixed
location in space (towards the North Star – Polaris).
The “fixed” tilt means that, during our orbit around our Sun each
year, different parts of Earth receive sunlight for different lengths
of time.
The tilt also means that the angle at which sunlight strikes different
parts of Earth's surface changes through the year.
Indirect sunlight striking the surface at an angle is “spread” across a
wider area compared to direct sunlight striking perpendicular to
Earth's surface.
Areas that receive indirect sunlight receive less energy from our Sun
while areas receiving direct sunlight receive more energy.
All of these factors combine to give Earth its annual cycle of seasons!
Seasons
During winter in the northern hemisphere,
our northern axis continues to point to the North
Star, but, because we have moved in our orbit
around the Sun, our northern hemisphere now
points away from our Sun.
The northern hemisphere experiences shorter
day lengths and colder temperatures of winter
because the Sun's rays strike the surface at a
lower angle.
During fall(autumn)
For part of the Earth’s orbit the northern
half of Earth is tilted toward the Sun.
This is summer in the northern
hemisphere; there are longer periods of
daylight and the Sun's rays strike the
surface more directly, giving us warmer
temperatures.
and spring, some locations on Earth experience milder conditions.
Earth has moved to a position in its orbit where its axis is more or less perpendicular to the incoming rays of
the Sun. Neither hemisphere is receiving direct sunlight.
The durations of daylight and darkness are more equally distributed across all latitudes of the globe.
Seasons of the Southern Hemisphere are opposite of those in the Northern Hemisphere.
When the northern half of Earth is tilted toward the Sun, the southern hemisphere is tilted away. People in the southern hemisphere experience the shorter day
lengths and colder temperatures of winter. When it is winter in the northern half of Earth, the southern hemisphere, tilted toward our Sun, has summer.