Changes in Children's Answers to Open Questions about the Earth and Gravity

Table 3

Expected combinations of responses indicating consistent mental models.

Question	Disc/flat Earth	Hollow Earth	Dual Earth	Flattened Earth	Spherical Earth
What is the shape of the Earth?
	The Earth is angular/round/like a circle.	The Earth is round/like a sphere.	The Earth is angular/round/like a circle/like a sphere.	The Earth is round/oval/like a sphere.	The Earth is round/like a sphere.
If you moved in one direction for many days, where would you end up?
	If you moved for many days, you would reach the edge of the Earth/end of the Earth.	Not applicable or if you moved for many days, you would reach the inner side of the sphere	If you moved for many days, you would reach the edge of the Earth or the round Earth in the sky has no edge.	If you moved for many days, you would reach the side of the Earth	If you moved for many days, you would end up back where you started.
Is it possible to fall off the Earth? Where?
	One can fall off from edge/at the end of the Earth.	Not applicable or one cannot fall of the Earth because there is no open edge/we are inside the Earth.	One can fall off from edge/at the end of the Earth.	Not applicable or one can fall off at the side of the Earth.	One cannot fall of the Earth because of gravity
Picture of the Earth with people, clouds, and rain
	A rectangle/circle with people standing everywhere on the surface. People and rain aligned to the edge of the paper. Clouds are above the people/drawn all over.	A circle, people drawn inside, at the bottom of the circle/on a flat surface inside the circle. People and rain aligned to the edge of the paper. Clouds are on top of the circle (inside or outside)/on the upper half of the circle.	Both a circle and a flat line are drawn. People standing on the line, rain and people aligned to the edge of the paper.	An ellipse, people only on the upper part of the ellipse. People and rain, aligned to the edge of the paper	A circle with people everywhere. People and rain at least partially aligned to the circle (towards the centre). Clouds are everywhere on the surface of the circle/around the periphery of the circle.
What does the term round mean, when describing the Earth?
	Disc	Ball	Ball, disc, or both	Ball	Ball

Each child was allowed one acceptable deviation, including a missing or a “do not know” answer (see further [5]). Children, who had at least one unacceptable deviation or more than one acceptable deviation, were classified as inconsistent.