Transcript North Star - 6th Grade Science

Key Concepts:
Earth’s axis of rotation tilts at
23.5° and points to the North Star.
The solar angle is the angle that
light from the sun strikes Earth’s
surface.
Key Vocabulary:
WEATHER AND WATER:
Investigation 3: Seasons and Sun
Approximate Timeline: 10 sessions
Standards Addressed:
S1 C2 PO1, S1 C2 PO5, S1 C3 PO2, S1 C3 PO3, S1 C3 PO4
S4 C3 PO1
Fall (autumnal) equinox
Rotation
Solar Angle
Spring (vernal) equinox
Summer solstice
Beam spreading is the increase in
an area covered by a beam if light
as there’s an increase in the solar
angle.
Learning Goals:
I will be able to graph and analyze sunlight data.
I will be able to model the Earth-Sun relationship while paying
particular attention to the rotation, tilt, and revolution.
Assessments:
Writing Prompt Idea:
Response Sheet: Seasons and Sun
 End of part 2
Mid-Summative Exam 3
 End of investigation
Extra Resources:
http://vortex.plymouth.e
du/sun/sun3.html
Writing Prompt Idea #2:
You are a taxpayer in Arizona. The legislature will be voting to fund a new energy plant. Decide
which energy source will be the best option for Arizona. Write an editorial persuading the legislature
to build this type of energy plant. Choices for energy sources include: wind, dams, fossil fuels,
nuclear, or solar.
Science: S5 C3 PO1
Writing: S3 C4 PO1
You are Copernicus. Write
a letter to fellow scientists
convincing them that you
have the “true” model of
the universe. Explain why
Ptolemy’s model of the
universe with the Earth at
the center is false. Include
diagrams in your letter.
Science: S1 C4 PO1
Writing: S3 C3 PO4; S3
C4 PO1
Winter solstice
LEARNING GOALS
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Investigation 3- Seasons and Sun
Enduring Understanding:
Seasons are related to the amount of solar energy transferred to Earth, and that
amount of energy transferred is affected by latitude, tilt of Earth’s axis, revolution,
and rotation.
Learning Goals:
I will graph monthly day-length data for a single location to look for a pattern.
I will use a globe and light bulb to model daily and seasonal variations in day length.
I will explain how the tilt of Earth’s axis and Earth’s revolution around the sun
produces seasons.
I will discuss seasonal variation in day length as a consequence of axis tilt, rotation,
and revolution.
I will use light sources and surfaces to model beam spreading.
I will explain how beam spreading reduces the intensity of solar radiation.
Seasons and
Sun
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?
What ideas do you have
to explain why daylight
hours change over a
year?
SUN-EARTH MODEL
• How should I set up the model?
• Where should the Sun be and where
should Earth be?
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
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.
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.
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!
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 Starsummer, fall, winter,
spring, day, and night.
NORTH STAR
• That’s why the North
Star has been a
navigation aid to
seafarers and
explorers for
centuries.
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.
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.
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.
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)?
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!
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.
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?
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.
SUN-EARTH SYSTEM
• Turn to this page in
your lab books.
READING:
“Seasons”
page 17
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.
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