Seasons
What do you KNOW about seasons?
The Big Idea
• Students will understand
how Earth’s tilt on its axis
changes the length of
daylight and creates the
seasons.
Objective 1: Describe the relationship
between the tilt of Earth's axis and its
yearly orbit around the sun.
• Describe the yearly revolution (orbit) of Earth
around the sun.
• Explain that Earth's axis is tilted relative to its
yearly orbit around the sun.
• Investigate the relationship between the amount
of heat absorbed and the angle to the light source.
Objective 2: Explain how the relationship
between the tilt of Earth's axis and its yearly
orbit around the sun produces the seasons.
• Compare Earth’s position in relationship to the sun during
each season.
• Compare the hours of daylight and illustrate the angle that
the sun's rays strikes the surface of Earth during summer, fall,
winter, and spring in the Northern Hemisphere.
• Use collected data to compare patterns relating to seasonal
daylight changes.
• Use a drawing and/or model to explain that changes in the
angle at which light from the sun strikes Earth, and the length
of daylight, determine seasonal differences in the amount of
energy received.
• Use a model to explain why the seasons are reversed in the
Northern and Southern Hemispheres.
Seasons
A regular change in temperature that
repeats itself every year
Words to know:
Axis - imaginary line
around which Earth
spins, causing day
and night, and that
is drawn from the
north geographic
pole through Earth
to the south
geographic pole
http://vortex.plymouth.edu/sun/axis.gif
Words to know:
Rotation - spinning
of Earth on its axis,
which causes day
and night; it takes
24 hours for Earth
to complete one
rotation
http://vortex.plymouth.edu/sun/rot8_an.gif
Words to know:
Revolution - the motion of Earth around
the Sun, which takes about 365 1/4
days, or one year, to complete
http://www.usoe.k12.ut.us
Words to know:
Orbit - curved path followed by Earth as it
moves around the Sun
http://www.vt-2004.org/mt-2003/mt-mercury-orbit.jpg
• http://www.youtube.com/watch?v=DuiQvPLW
ziQ&feature=player_embedded
The Earth’s Tilt
The Earth's axis is tilted by 23.5°
http://www.crh.noaa.gov/fsd/astro/season.htm
As the Earth moves around the
Sun, this axis stays always
pointing in the same direction.
This means that, during part of the
year, the northern part of the
Earth will lean more directly to
the sun, and during other parts of
the year the southern part of the
Earth will.
The Earth during
one full year as
you would see it
if you looked
straight at it from
the Sun.
The part of the
Earth that is
directly facing
the sun
changes with
the time of
the year.
The northern
half faces the
sun for a
while, then
moves south
of the equator,
only to move
back to the
north again.
Seasons - Changing Day Length
When the northern hemisphere is leaning
toward the sun, the rays coming from it
hit this part of the Earth at a larger angle
than on other parts of the world.
This means that the same amount of light
is distributed over a smaller surface, and
so these places receive more heat than
the others.
The southern hemisphere is experiencing
Winter, the northern hemisphere has
Summer.
The energy that hits the Earth by the Sun changes over
the year.
The angle the Sun is above the horizon determines how
much heat and light strike each square meter of
ground.
http://inkido.indiana.edu/a100/celestialsphere5.html
In the winter the Sun's energy is weakened because the
Sun's ray strike the ground rather indirectly as
compared to the summer months when the Sun's
rays strike the ground more directly.
http://inkido.indiana.edu/a100/celestialsphere5.html
This means that the ground receives more
energy (more heat) per square meter in
the summer than in the winter.
More energy is received by the ground
during the summer (high temperatures)
and less energy during the winter (lower
temperatures).
Go to this Website for Instructions on assignment #3
http://www.uen.org/core/science/sciber/sciber6/stand
-2/angle.shtml
Seasons - I'm Spinning and I Can't
Stop!
Activity #4
Please click on the link below
http://www.uen.org/core/science/scibe
r/sciber6/stand-2/revolves.shtml
Activity #5 Worksheet
• Sunrise, Sunset
Activity #6 Worksheet
• Changing Shadows
So, seasons are caused the tilt of
the Earth’s axis
Remember:
• The seasons are the result of this tilt
of the Earth's axis.
• If the tilt of the Earth's axis was 0°
there would be no difference in how
the rays from the sun hit its different
regions, and there would be no
seasons.
The Earth's seasons are not caused by the
differences in the distance from the Sun
throughout the year.
The seasons are the result of the tilt
of the Earth's axis.
I know this is a repeat, but it is important that
you understand this idea. Many Americans,
including Harvard graduates, do not know what
causes seasons!
Review
Look closely at where the Sun is hitting the Earth during each
season:
http://Search.Lycos.com/setup.asp?r=5&src=clear2&query=weather+savvy
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Seasons.shtml
http://www.nmm.ac.uk/uploads/gif/seasons-full.gif
Imagine Earth as it revolves around the sun. The table
below shows Earth at opposite sides of the sun. These
two examples represent Earth's position for summer
and winter.
Example A
Example B
Congratulations we have finished this
Unit
• Make sure you study for the test using the
study guide