Science 7 Quarter 4 Lesson on Equinoxes and Soltices

1. LEARNING GOALS
• I will be able to graph and
analyze sunlight data.
• I will discuss seasonal variation in
day length as a consequence of
axis tilt, rotation, and revolution.

3. GRAPH QUESTIONS
• What does the graph reveal about the
amount of daylight over a year in
Berkley?
– Days get longer from January to June,
shorter from June to December
• When do people in Berkley have their
longest day? Shortest?
– Longest= June, Shortest= December
• When do people in Berkley have
about 12 hours of daylight?
– March and September

4. GRAPH QUESTIONS
• How many hours of daylight do
people in Berkley have on their
longest day? On their shortest
day?
–Longest= 14+, Shortest= 9+
• In what season do people in
Berkley have their longest day?
Their shortest day?
–Longest= Summer, Shortest= Winter

5. GLOBAL DAYLIGHT
• When one location on Earth has 14
hours of daylight, is all the rest of the
world having 14 hours of daylight as
well?
• Is the longest day of the year the
same length all over the world?
• Are the longest days always in the
summer? Are the shortest days
always in the winter?

6. READING:
“Wendy and Her
Worldwide Weather
Watchers”
page 12

7. Wendy and Her Worldwide Weather
Watchers
****ANSWER ALL QUESTIONS IN COMPLETE SENTENCES. USE THE QUESTION TO
ANSWER THE QUESTION.
1. Which locations have the greatest number of hours of daylight on June 21? The fewest
hours of daylight?
Greatest=________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
Fewest=_________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
2. Which locations have the longest hours of daylight on December 21? The shortest hours of
daylight?
Longest=_________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
Shortest=________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
3. Alpena, Michigan, is located 45 degrees north of the equator. How much daylight do you
estimate they have on June 21? On December 21?
June 21=_________________________________________________________________
December 21=_____________________________________________________________
4. Boulder, Colorado, has a latitude of 40 degrees North. Wellington, New Zealand, has a
latitude of 41 degrees South. Which city has the longest amount of daylight on June 21? How
do you know?
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________

8. Seasons and
Sun

9. GLOBAL DAYLIGHT
• When one location on Earth has 14
hours of daylight, is all the rest of the
world having 14 hours of daylight as
well?
• Is the longest day of the year the
same length all over the world?
• Is the longest day of the year the
same day all over the world?
• Are the longest days always in the
summer? Are the shortest days
always in the winter?

10. What ideas do you have
to explain why daylight
hours change over a
year?

11. SUN-EARTH MODEL
• How should I set up the model?
• Where should the Sun be and where
should Earth be?

12. REVOLVE
• The movement of one object
around another.
• Earth revolves around the sun.
• How long does it take for Earth
to make one revolution around
the Sun?
–1 year or 365 days

13. AXIS
• Earth has a North
Pole and a South
Pole. These are the
north and south ends
of an imaginary axle,
called an axis, on
which Earth rotates.

14. ROTATION
• Earth turns like a top,
and this turning motion
is called rotation.
• Earth does not spin
straight up and down,
but is tipped over at a
significant angle of 23.5
degrees.

15. LET’S THINK…
• How long does it take for Earth to
rotate (turn around once) on its
axis?
–1 day, or 24 hours
• How do we know where it is day and
where it is night on these globes?
–The side illuminated by the Sun is day,
the dark side is night.
• How much of the globe is in daylight
at any given time?
–The globe is always exactly half light,
and half dark. ALWAYS!

16. NORTH STAR
• There is a star in the night
sky called Polaris, or the
North Star. It is
positioned directly over
Earth’s North Pole.
Earth’s North Pole always
points to the North Star-
summer, fall, winter,
spring, day, and night.

17. NORTH STAR
• That’s why the North
Star has been a
navigation aid to
seafarers and
explorers for
centuries.

18. NORTH STAR
• In our Sun-Earth system,
we need a North Star.
You will have to visualize
the North Star through
this wall and way, way off
in the distance. The
North Pole of our model
Earth will always point at
the North Star as it
revolves around our
model Sun.

19. KEY QUESTION
• Why do hours of daylight
differ depending on time of
year and location on Earth?
• Use our model to help us
figure it out.

20. KEY QUESTION
• Position Earth and the Sun on
the same plane.
• Keep Earth’s North Pole pointed
at the North Star at all times.
• Place Earth at various positions
around the Sun.
• Rotate Earth on its axis at each
position, and observe the time in
the light and the time out of the
light.

21. DEMONSTRATION!
For each stop, think about
these questions.
• Which region of Earth is getting the
greatest number of hours of
daylight now?
• Which is experiencing the most
hours of darkness?
• When Earth is at this point in its
revolution, what season is it in the
Northern Hemisphere (our town)?

22. SUMMARY
• Is there a part of Earth that
experiences only daylight or only
darkness?
–Yes, above the Arctic Circle and
below the Antarctic Circle
• Is there ever a time when the day and
night are equal everywhere on Earth?
–Yes
• How many times does this happen
during a revolution?
–Twice!

23. EQUINOX
• There are 2 days during the year that
day and night hours are equal.
These days are called equinoxes.
Equinox comes from Latin, meaning
“equal night”. One equinox, the
spring or vernal equinox, occurs
around March 21.
• When do you think the other equinox
occurs?
–Around September 21, in the fall. This
equinox is the fall or autumnal equinox.

24. SOLSTICE
• When is the longest
day of the year in the
Northern Hemisphere?
• Which way is the North
Pole tilted, toward the
Sun or away from the
Sun?

25. SOLSTICE
• The longest day of the
year is the summer
solstice. Solstice means
“Sun stands still”.
• When is the shortest day
of the year in the Northern
Hemisphere?
• The shortest day of the
year is the winter solstice.

26. WORD BANK
• Rotation- Earth turning around
on its axis. One rotation=24
hours.
• Revolution- One object moving
around another. One Earth
revolution around the Sun=365 ¼
days.
• Axis- Imaginary line from North to
South pole on which Earth
rotates. Tilted at 23.5 degrees.

27. WORD BANK
• Polaris (North Star)- Star directly
over Earth’s North Pole. Always
points North.
• Equinox- Day and night hours are
equal.
–Spring Equinox=March 21
–Fall Equinox=September 21
• Summer Solstice- Longest day of
the year. June 21
• Winter Solstice- Shortest day of the
year. December 21

28. READING:
“Seasons”