3. Seasons
• What are our seasons like?
• What are seasons like in
other parts of the world?
• What do you think causes
the seasons?
4. Vocabulary
• Axis: the angle between an object's
rotational axis, and a line perpendicular to
its orbital plane.
• Tilt: moving into a sloping position
• Seasons: Each of the four divisions of the
year (spring, summer, autumn, and winter)
marked by particular weather patterns and
daylight hours, resulting from the earth's
changing position with regard to the sun
5. Vocabulary
• Summer Solstice: marks the onset of
summer, at the time of the longest day,
about June 21 in the northern hemisphere
and December 22 in the southern
hemisphere
• Winter Solstice: marks the onset of
winter, at the time of the shortest day,
about December 22 in the northern
hemisphere and June 21 in the southern
hemisphere
6. Vocabulary
• Equinox: occurs twice a year, when the tilt
of the Earth's axis is inclined neither away
from nor towards the Sun, the center of
the Sun being in the same plane as the
Earth's equator
• Examples of Equinoxes: Spring and
Autumn Equinox
7.
8. Earth’s rotation
• The Earth rotates on its axis
(imaginary vertical line
around which Earth spins)
every 23 hours & 56
minutes.
• One day on Earth is one
rotation of the Earth.
• Day on Earth is when our
side of the Earth faces the
sun.
• Night on Earth is when the
side of Earth we are on
faces away from the sun.
9. Earth’s revolution
• It takes the Earth
365 days (or
rotations) to travel
or revolve around
the Earth once.
• This is called a
year.
10. Why do we have seasons?
• The Earth’s orbit
around the sun is
NOT a perfect circle.
It is an ellipse.
• Seasons are not
caused by how close
the Earth is to the
sun.
• In fact, the Earth is
closest to the sun
around January 3 and Ellipse
farthest away from
the sun around July 4.
11. Why do we have seasons?
• Seasons are the result of the
tilt of the Earth's axis.
• Earth’s axis is tilted 23.5°.
• This tilting is why we have
SEASONS like fall, winter,
spring, summer.
• The number of daylight
hours is greater for the
hemisphere, or half of Earth,
that is tilted toward the Sun.
12. Why do we have seasons?
• Summer is warmer than winter (in each
hemisphere) because the Sun's rays hit the
Earth at a more direct angle during summer than
during winter
14. Why do we have seasons?
• Also the days are much longer than the
nights during the summer.
• During the winter, the Sun's rays hit the
Earth at an extreme angle, and the days are
very short. These effects are due to the tilt
of the Earth's axis.
16. Solstices
• Solstices occur twice a year, when the tilt of the Earth's
axis is oriented directly towards or away from the Sun,
causing the Sun to appear to reach its northernmost and
southernmost extremes.
• Winter solstice is the shortest day of the year. In the
Northern Hemisphere. It occurs on December 21 and
marks the beginning of winter.
• The Summer Solstice is the longest day of the year. It
occurs on June 21 and marks the beginning of summer.
17. SOLSTICE
• During the winter the
Northern Hemisphere day
lasts fewer than 12 hours
and the Southern
Hemisphere day lasts more
than 12 hours.
• During the winter solstice,
the North Pole has a 24-hour
night and the South Pole has
a 24-hour day.
• Sunlight strikes the earth
most directly at the Tropic of
Capricorn.
18.
19. Equinoxes
• A day lasts 12 hours and
a night lasts 12 hours at
all latitudes.
• Equinox literally means
"equal night".
• Sunlight strikes the earth
most directly at the
equator.
• This occurs twice a year.
20. Equinox
• The vernal (spring)
equinox occurs March
21.
• The autumnal (fall)
equinox occurs
September 21.
22. The Earth's seasons are not
caused by the differences in the
distance from the Sun throughout
the year.
23. 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!
26. Dramatization of Earth’s
Seasons
• I need two volunteers.
• One will hold the “Earth”.
• One will hold the “Sun”.
• Earth should be tilted at what degrees?
• The Earth should rotate around the sun in
what shape?
27. Dramatization of Earth’s
Seasons
• Tell the Earth to stop when it is at summer.
• Tell the Earth to stop when it is at winter.
• At which point is the Earth having the
longest day?
• At which point is the Earth having the
shortest days?
28. Review Questions
• What causes the seasons?
• At what angle is Earth tilted on its axis?
• Is the Northern Hemisphere pointed
toward the sun or away from the sun
during summer?
• Which season do we have the longest
days?
