Download HO-13 Naive and Goals 5a Astron

Comparison of Common Student Ideas and Scientific Ideas
about the Sun, Earth, and Moon
for Use in Planning the LSD Grade 5 First-Quarter Science Unit
Planning a science unit is much like planning a trip. To select a route for a trip you certainly need
to know where you want to go. Similarly, when planning a science unit you need to know where
you want your students to be (i.e., what they will know and be able to do) by the end of the unit of
study. Clusters of benchmarks from the Michigan Curriculum Framework (2000) for science, as
specified by our district’s science pacing guides, define the destinations for our quarterly science
units for grades 2 through 5.
But selecting the route for a trip also is dependent on where you start. For example, Interstate 96
is a reasonable route to follow if you want to go from Lansing to Grand Rapids. However, if you
are starting from Traverse City, Interstate 96 isn’t likely to be part of your journey. Similarly, when
planning a science unit, you need to know where your students are when you launch the unit.
Depending on past experiences (both in and out of school), students can begin a new unit of
study from widely different locations. Fortunately, these starting points are not entirely random or
different for every single child. More than three decades of research have indicated that there are
some very common and widely shared naïve beliefs that students bring to their study of many
science topics. By becoming familiar with these naïve conceptions, we can more easily spot them
during pre-assessments and adjust accordingly the route that our unit of study will follow.
Listed below are several issues related to our fifth-grade study of the sun, earth, and moon for
which research (as reported, for example, in the chapter “The Earth in Space” in the book Making
Sense of Secondary Science: Research into Children’s Ideas, edited by Rosalind Driver, et al.,
1994, ISBN: 0-415-097657) has found naïve beliefs that are shared among many students. For
reference and contrast, statements of corresponding scientific conceptions are included as well.
Goal Conceptions or
Understandings
Issue
Earth’s Shape
People on the Earth
Where Is the Earth?
Page 1 of 4
Handout #13
Common Naïve
Conceptions or Beliefs
The earth is simply a flat surface.
The earth is shaped like a flat,
round disk (e.g., like a pizza).
The earth is a sphere; people live
inside the sphere (so they won’t
fall off). [Down is conceived of as
an absolute direction.]
The earth is a sphere; people live
only on the top of the sphere (so
they won’t fall off). [Down is
conceived of as an absolute
direction.]
There are two earths: the one we
live on (which is a flat surface) and
the one in the sky that we can see
as a tiny sphere of light at night
(like any other planet).
[NOTE: For the sake of completeness,
some of these statements involve facts
and understandings that go well
beyond what is expected of students in
our fifth-grade “Astronomy” unit.]
The earth is essentially a large sphere.
People live on the outer land surface of the
spherical earth.
Down is toward the center of the earth.
Gravity pulls all objects near or on the
earth toward the center of the earth.
Earth is the planet on which we live.
Naïve & Goal Conceptions for Sun, Earth, and Moon
2001.08.29 [RTSmith]
Revised 2002.09.01
What Has Gravity?
Animatism
Daytime and
Nighttime
When Is the Moon
Visible?
Size
Page 2 of 4
Handout #13
Only the earth has gravity.
The sun, earth, and moon each have
gravitational fields, with the sun having the
strongest gravitational pull (nearly 28 times
that of earth) and the moon having the
weakest gravitational pull (about 16% of
earth’s) of the three. [Actually, all
“masses” – not just the sun, earth, and
moon – have gravity.]
The sun and/or the moon are
The sun, earth, and moon are all inanimate
animate; they can have and act on objects.
intentions, often treating each
other as companions or as
antagonists.
Daytime and night result from
The sun gives off light in all directions.
active/animate/intentional actions
The side of the earth that faces the sun is
of the sun and/or the moon.
illuminated; this is daytime. The side of
Daytime is when the sun is shining the earth that faces away from the sun is in
a shadow (of the earth itself); this is night
visibly and night happens when
or nighttime. We experience cycles of
other objects (e.g., hills, clouds,
daytime and nighttime because the earth
the moon, night, dark, the
rotates once every 24 hours.
atmosphere) block the sun from
shining.
[NOTE: It may help clarify things if we use
Daytime and night result from the the word “daytime” to refer to that period of
time when the sun is above the horizon
sun revolving around the earth
and use the word “day” to refer to a period
once a day.
Daytime and night result from the of 24 hours. In everyday language we
often use the word “day” to refer to either
earth revolving around the sun
of these time frames, which can be
once a day.
confusing to children.]
Daytime and night result from the
sun moving up and down.
The moon is only or always visible The moon can be visible during the
at night.
daytime or at nighttime, depending on
where it is in its orbit. Considered over the
The moon is only rarely visible
course of a year, the amount of time that
during daytime.
the moon is visible during daytime is
essentially equal to the amount of time it is
visible at nighttime.
The moon, earth, and sun are all
The earth and moon are on the same
relatively similar in size (e.g., the
order of magnitude with respect to size.
sun may be about twice as big as [The moon’s diameter is about 27% of the
the earth and the earth may be
earth’s diameter.]
about twice as big as the moon).
The sun is several orders of magnitude
The sun and moon are the same
larger than the earth. [The sun’s diameter
size (since they each appear to be is roughly 108 times larger than the
the same size when we view them diameter of the earth.]
in the sky). [This belief is
Although the sun is several orders of
supported (if we neglect to
magnitude bigger than the moon, the sun
consider that they are not the
and the moon both appear to be about the
same distance from the earth)
same size when viewed from the earth.
when the moon passes in front of
This is because the sun, while much
the sun during a solar eclipse and bigger, is also much further away from the
essentially appears to match the
earth than is the moon.
size of the sun.]
Sun diameter ≈ 1,382,000 km
Earth diameter ≈ 12,753 km
Moon diameter ≈ 3,474 km
Naïve & Goal Conceptions for Sun, Earth, and Moon
2001.08.29 [RTSmith]
Revised 2002.09.01
Distances
The average distance of the earth from the
sun is slightly less than 150,000,000 km.
Therefore, the average earth-to-sun
distance is equal to approximately 11,730
earth diameters. [The earth is a bit closer
to the sun during winter in the northern
hemisphere and a bit further away from the
sun during summer in the northern
hemisphere.]
The average distance of the moon from
the earth is 384,467 km. Therefore, the
average earth-to-moon distance is equal to
approximately 30 earth diameters.
Distances and
The earth is closer to the sun
The slight change in the distance of the
Seasons
during summer and further away
earth from the sun as the earth orbits the
from the sun during winter. This is sun is an insignificant factor in determining
why it is hotter in summer and
seasonal changes. In fact, the earth is a
colder in winter.
bit closer to the sun during winter in the
northern hemisphere and a bit further
away from the sun during summer in the
northern hemisphere.
Sun/Earth/Moon
The earth is the center of the
The sun is at the center of our solar
Relative Positions and universe. Both the sun and the
system. Nine planets, including the earth,
Motions
moon go around the earth.
plus numerous other objects (e.g.,
asteroids, comets) orbit the sun. The
The moon and the earth each
moon orbits the earth. (Several other
have separate orbits around the
planets also have moons orbiting them.)
sun.
Our solar system is moving within our
[Position and motion are
rotating galaxy (i.e., the Milky Way), and
absolutes.]
our galaxy is also in motion relative to
other galaxies (i.e., the rest of the
universe).
Position and motion are determined
relative to some reference frame.
FYI: Orbital and
The amount of time it takes to make one rotation is called a day,
Rotational Periods
and for the earth that is equal to 24 hours.
The amount of time it takes the earth to orbit the sun is called a year
and is equal to slightly more than 365 days.
The amount of time it takes the moon to orbit the earth is about 27.3
days. However, since the earth is orbiting the sun while the moon is
orbiting the earth, it takes 29.5 days from full moon to full moon,
which is called a lunar cycle. A lunar cycle takes slightly less than
one month.
The moon’s rate of rotation is the same as its rate of revolution;
hence the same side of the moon always faces the earth as it orbits
the earth.
The orbit of the moon is slightly inclined from the plane of the earth’s
orbit about the sun (which is why we don’t have an eclipse with
every new and full moon).
The outer layers of the Sun exhibit “differential rotation.” That
means that at the equator the surface rotates once every 25.4 earth
days while near the poles one rotation can take as much as 36
earth days. This odd behavior is due to the fact that the Sun is not
a solid body like the Earth. The differential rotation extends
considerably down into the interior of the Sun, but the core of the
Sun rotates as a solid body.
Light Sources
The moon is a source of light, just Of the sun, earth, and moon, only the sun
like the sun (although the sun is
emits (or is a source of) light. The side of
much brighter).
the moon that faces the sun reflects light
that strikes it from the sun. We see the
moon primarily by this reflected light.
Page 3 of 4
Handout #13
The distances between the sun,
earth, and moon are on the same
order of magnitude as the sizes of
the three objects. That is to say,
the distance from the earth to the
sun or the earth to the moon is
equal to a few times the earth’s
diameter.
Naïve & Goal Conceptions for Sun, Earth, and Moon
2001.08.29 [RTSmith]
Revised 2002.09.01
The Sun's
Composition and How
the Sun Makes Heat
and Light
Moon Phases
Naming the Type of
Object
FYI: Other Features
or Characteristics
Page 4 of 4
Handout #13
The sun is on fire, made of flame,
burning, producing heat and light
by combustion.
The sun is mostly composed of hydrogen.
The sun releases electromagnetic
radiation (including infrared and visible
light) by the process of nuclear fusion.
The sun is composed of matter that is a
"plasma" (i.e., a very hot, ionized gas,
which scientists consider to be a distinct,
fourth state of matter, different from solids,
liquids, and gases).
Moon phases are actual changes The side of the moon that faces the sun
in the shape of the moon.
reflects light from the sun that strikes it.
We see the moon primarily by this
Moon phases, that is, the
changing shape of the observable reflected light. Depending where the moon
is in its orbit relative to the sun and the
moon from night to night, are
earth when we see it, we see more or less
caused by the earth’s shadow.
of its illuminated surface. As the moon
Moon phases, that is, the
changing shape of the observable completes one orbit (i.e., over the course
of approximately one month), we will see it
moon from night to night, are
increase and then decrease in terms of
caused by clouds.
how much of its surface facing us is
Moon phases, that is, the
illuminated by the sun. This is the
changing shape of the observable recurring pattern of lunar phases (from
moon from night to night, are
new moon to full moon and then back to
caused by the sun’s shadow.
new moon).
Moon phases, that is, the
[The earth also reflects light received from
changing shape of the observable the sun. Some of this reflected light hits
moon from night to night, are
the moon and then is reflected back to
caused by shadows of other
earth. If some of this reflected light strikes
planets.
the portion of the moon facing earth that is
not currently illuminated by the sun, there
may still be sufficient light for us to see this
portion of the moon, albeit very dimly.]
The sun is a planet.
The sun is a star.
The earth is a planet and it orbits the sun.
The moon is a natural satellite of the earth.
Sun's mass ≈ 2x1030 kg (about 330,000 times earth)
Earth's mass ≈ 6x1024 kg
Moon's mass ≈ 7x1022 kg
Sun's density ≈ 1.4 g/cm 3
Earth's density ≈ 5.5 g/cm3
Moon's density ≈ 3.4 g/cm3
Sun's surface temperature ≈ 5,500ºC
Sun's interior temperature ≈ 14,000,000ºC
Earth's average surface temperature ≈ ranges from –89ºC to
+58ºC
Moon's average surface temperature ≈ ranges from –173ºC to
+100ºC
The sun and the earth each have a magnetic field; the moon does
not.
The earth and the moon are essentially “solid”; the sun is an
incandescent ball of plasma. Roughly 70% of the earth’s
surface is covered by liquid water. (There is no liquid water
on the surface of the sun or the moon.)
The earth is surrounded by a relatively thin blanket of air, called
the “atmosphere.” The moon has no atmosphere.
The earth and the moon share some types of surface features, for
example, they both have mountains, plains, and craters
(although the moon has many more easily visible craters).
Naïve & Goal Conceptions for Sun, Earth, and Moon
2001.08.29 [RTSmith]
Revised 2002.09.01