Chapter 6, page 85
Some children develop the dual-earth conception. This conception explains the apparent flatness of
the earth, because we live on the flat ground, not the earth up in the sky. And on the flat ground, things fall
downward. This conception also explains the “round earth” that appears in NASA pictures and that is
embodied in the globe in the classroom. This round earth is the earth up in the sky.
Other children develop the hollow-earth conception. This conception explains the flatness of the
earth by assuming that we live on the flat ground inside the earth. Things fall down as expected on this flat
earth. And the idea that the earth is round is explained by having us live on the inside of the round, hollow
earth. What we see in globes and pictures of the earth is the outside of this sphere.
The flattened-sphere conception is a more advanced conception, because these children have come
to understand something about gravity. These children allow people to live on the bottom of the earth,
because they know that gravity keeps people on the bottom of the earth from falling down off the earth.
However, these children still cannot see how a round earth is compatible with the apparent flatness of the
earth, so they make the earth a flattened sphere, rather than a fully rounded sphere. These children do not
yet understand that a very, very large sphere will appear flat to those on its surface.
Children who adopt the spherical conception have a new understanding of the original facts. They
understand that the earth looks flat because very, very large round things look flat when they are standing
on the surface. And they have a new understanding of what it means for things to fall “down.” Things fall
downward toward the center of the earth, because of gravity. They therefore understand that people and
things on the bottom half of a spherical earth will not fall off the earth.
Why alternative conceptions arise and why they persist. Now let’s summarize what we have
learned from the research on the earth’s shape. First, learners’ alternative conceptions arise because they
do a good job of explaining the facts that they know about. Alternative conceptions are not silly or
misguided; they are the product of very impressive, creative thinking by learners as they actively invent
ideas that can explain what they know. Alternative conceptions arise because learners are actively trying
to make sense of the world (Brewer, in press; Vosniadou & Brewer, 1992; Vosniadou & Brewer, 1994;
Vosniadou & Verschaffel, 2004).
Second, students often resist changing their ideas because the new ideas taught by adults do not
make sense to them. When teachers and parents say that the earth is round and show children a globe,
they cannot understand how people could live on the bottom of the earth or how the earth can look flat.
They may therefore ignore what their teachers say because they cannot make sense of them.
Third, when presented with the correct conceptions, students often develop new alternative
conceptions that combine elements of their previous conceptions with elements of the target
conceptions. When children learn that the earth is spherical, they develop a new idea that incorporates a
round earth but retains elements of a flat earth (as in the dual-earth and hollow-earth conceptions).
The earth’s shape is a topic on which most students do eventually change their ideas after a period
of several years. Most adults do not believe that the earth is flat or hollow. However, on many other topics
(in science and in other disciplines), students’ alternative conceptions may persist into adulthood. For
example, many or most adults retain alternative conceptions about how we see things (Winer, Cottrell,
Gregg, Fournier, & Bica, 2002). Many adults erroneously think that a visual emanation leaves the eyes
when we see things. In fact, we see things when light travels from a light source such as the sun, reflects
off the object we see, and then strikes our retina. Adults also have alternative conceptions about topics
such as the U.S. constitution, such as the conception that the judiciary has the power to make laws (New
Hampshire Bar Association, 2005).
Are Learners’ Alternative Conceptions Coherent?
In the research on the earth’s shape, most children seemed to have coherent conceptions. Learners
have a single conception that they use to think about a topic. A consequence of having a coherent
conception is that when students are asked questions about a topic, they give answers that are all