Like all planets and stars, the Earth is approximately spherical in shape. The rotation of the Earth on its axis every 24 hours produces the night-and-day cycle. To people on Earth, this turning of the planet makes it seem as though the sun, moon, planets, and stars are orbiting the Earth once a day. (Benchmark 4B/E2)

    Key idea(s):
    The Earth is approximately spherical in shape. Like the Earth, the sun and planets are spheres.
   
     
    The rotation of the Earth on its axis every 24 hours produces the nighttime/daytime cycle. To people on Earth, this turning of the planet makes it seem as though the sun, moon, planets, and stars are orbiting the Earth once a day.
   

  Clarification Connections Ideas Students Have Diagnostic Questions Phenomena and Activities Representations Assessment Items

Representations

The following representations are designed to clarify the idea that the Earth and planets are spherical in shape. The first five representations help to make clear the spherical shape of the Earth. The sixth through ninth representations clarify the idea that the force of gravity pulls objects toward the Earth. The tenth representation helps to make clear the spherical shape of planets.

  1. Viewing Spheres of Increasing Diameter

Brief Description: A small sphere (perhaps several centimeters in diameter) looks fairly curved even when viewed up close. On the other hand, a larger sphere (more than a meter in diameter) looks less curved. When it is viewed up close, the surface can look fairly flat.

Purpose: The purpose is to clarify the counterintuitive notion that a spherical surface can appear flat when viewed up close. As spheres get larger, their surfaces appear flatter. For example, students could be asked to hold a large inflated balloon next to their cheek and look at the surface with the inner eye while the outer eye is held closed. The surface will look flat (Lightman & Sadler, 1998, p. 25). The students could then be asked to imagine that they are ants on a large sphere (such as a beach ball) and to imagine what the ball would look like from that perspective. If the opportunity is available, students can also be shown firsthand a domed building to give them a sense of how flat the surface of an even larger sphere can appear. Students can contrast the appearance of these differently sized spheres and then imagine how curved or flat a sphere several kilometers (or thousands of kilometers) might appear. The link can then be made to the local flatness of the large spherical Earth. The tremendous size of the Earth makes it difficult to notice its curvature while standing on the ground. These representations may help students reconcile their experiences on the surface of the Earth with the idea of the Earth as a giant sphere (see Ideas Students Have: The Earth is flat, There are two Earths, a flat one that we live on and a spherical one in space, and The Earth is spherical, but people live on a flat surface inside it).

Source: Lightman & Sadler, 1988

  1. Flat Piece of Spherical Melon
Melon

Brief Description: When a small plug is removed from a melon, the surface of the rind side appears flat. When the plug is reinserted into the melon, the surface appears curved.

Purpose: The purpose is to clarify the counterintuitive notion that a spherical surface can appear flat when viewed up close. The link can then be made to the local flatness of the large spherical Earth. This representation may help students reconcile their experiences on the surface of the Earth with the idea of the Earth as a giant sphere (see Ideas Students Have: The Earth is flat, There are two Earths, a flat one that we live on and a spherical one in space, and The Earth is spherical, but people live on a flat surface inside it).

Source: Hayes, B. K., Goodhew, A., Heit, E., & Gillan, J., 2003, p. 271

  1. South-North Oriented Maps and Globes

Click to view a larger, printable version.Brief Description: Maps that have north pointing in some direction other than straight up. (A very useful example may be maps of the Earth that have the southern hemisphere on top and the northern hemisphere on the bottom.)

Purpose: Such maps may help students see that “north” and “up” are not synonymous and so may address naive ideas of an absolute “down” (see Ideas Students Have: There is an absolute “down”). Students will need to know that what we on the Earth call “up” and “down” is not an indication of universal directions but really a case of “toward the Earth” and “away from the Earth.” This involves students knowing the orientation of people and objects in different places on the Earth (e.g., places on opposite sides of the Earth including both the Northern and the Southern hemispheres). People live all over the surface of the Earth without any risk of falling off of it.

  1. Simulated Change of Earth Perspective

Brief Description: A computer simulation can be used to illustrate the change in perspective from seeing the seemingly flat surface of the Earth to seeing the Earth as a sphere from space (e.g., http://www.starrynight.com, http://www.classzone.com).

Purpose: The purpose is to help students reconcile their experiences on the surface of the Earth with the idea of the Earth as a giant sphere (see Ideas Students Have: There are two Earths, a flat one that we live on and a spherical one in space and The Earth is spherical, but people live on a flat surface inside it). In addition, the simulation can help students realize that from the perspective of someone in space looking down at place on the earth, the tops of buildings and houses would be seen rather than the sides of the buildings and houses.

  1. Flat Map vs. Globe Earth

Brief Description: Observe non-stop travel routes and times between different cities around the Earth (such as New York, Tokyo, Buenos Aries, London, Cairo, Sydney, Cape Town, and New Delhi). For example, when flying from New York to Tokyo, does it make sense to stop for fuel in Hawaii or Alaska? What will take a shorter flying time, from New York to Moscow or from New York to Rio de Janeiro?

Purpose: The purpose is to show that non-stop travel times between different cities are more consistent with a spherical than a flat model of the Earth (see Ideas Students Have: There are two Earths, a flat one that we live on and a spherical one in space). Ask students to determine which representation is more useful for understanding the travel times. Have students compare the distances on a flat map vs. a globe using tape measures. While this representation implies a spherical shape of the Earth, it does not rule out a disk shape.

  1. Drawings of People All Over the Earth

Click to view a larger, printable version.Brief Description: Drawings of people at different positions on the Earth. (Limitation: In order to make the orientation of people on the Earth clearly visible, the figure is not to scale.)

Purpose: The purpose of this representation is to clarify the idea that the Earth pulls any object toward it no matter where it is on the Earth. Some students may think that people cannot be in the Southern Hemisphere because they would fall off (see Ideas Students Have: There is an absolute “down”). This representation addresses the connection between the key ideas about the spherical shape of the Earth and gravity, accounting for why people do not fall off the Earth.

  1. Drawings of Objects Falling to Earth

Click to view a larger, printable version.Brief Description: Drawings of people at different positions on the Earth dropping objects. (Limitation: In order to make the orientation of people on the Earth clearly visible, the figure is not to scale.)

Purpose: The purpose of this representation is to clarify the idea that the Earth pulls any object toward it no matter where it is on the Earth. Some students may think that objects fall off the Earth from certain places on Earth (see Ideas Students Have: There is an absolute “down”). This representation addresses the connection between the key ideas about the spherical shape of the Earth and gravity, accounting for why objects do not fall off the Earth.

  1. Water in Bottles at Different Places on Earth

Click to view a larger, printable version.Click to view a larger, printable version.Brief Description: Drawings of empty and filled water bottles at different positions on the Earth.

Purpose: The purpose of this representation is to clarify the idea that the Earth pulls any object toward it no matter where it is on the Earth. Some students may think that objects fall off the Earth from certain places on Earth (see Ideas Students Have: There is an absolute “down”). This representation addresses the connection between the key ideas about the spherical shape of the Earth and gravity, accounting for why objects do not fall off the Earth.

  1. Rocks Dropped in Holes in the Earth

Click to view a larger, printable version.Click to view a larger, printable version.Brief Description: Drawings of a child dropping a ball next to holes dug halfway through the Earth.

Purpose: The purpose of this representation is to clarify the idea that the Earth pulls any object toward it no matter where it is on the Earth. Some students may think that objects fall in a universal “down” direction (see Ideas Students Have: There is an absolute “down”). This representation addresses the connection between the key ideas about the spherical shape of the Earth and gravity, accounting for why objects fall toward the surface of the Earth and not in a universal “down” direction. [Note: At this grade range, students are not expected to understand the more sophisticated idea that gravity is directed toward the center of the Earth.]

  1. Spheres as Planets

Brief Description: Spheres to represent the planets in the solar system.

Purpose: The purpose is to help reinforce the idea that the planets all have a similar spherical shape, even if they are different sizes.

References

Learning Research

American Association for the Advancement of Science. (1989). Science for All Americans. New York: Oxford University Press.

American Association for the Advancement of Science. (1993). Benchmarks for Science Literacy. New York: Oxford University Press.

American Association for the Advancement of Science. (2001). Atlas for Science Literacy. Washington, DC: AAAS.

Baxter, J. (1989). Children’s understanding of familiar astronomical events. International Journal of Science Education, 11, 502-513.

Driver, R., Squires, A., Rushworth, P., & Wood-Robinson, V. (1994a). Making sense of secondary science: Research into children’s ideas. London: Routledge.

Driver, R., Squires, A., Rushworth, P., & Wood-Robinson, V. (1994b). Making sense of secondary science: Support materials for teachers. London: Routledge.

Ehrlen, K. (2002, June). The problem of pictures when studying children’s conceptions of the earth. Paper presented at the meeting of EARLI SIG symposium on conceptual change, Turku, Finland.

Hayes, B. K., Goodhew, A., Heit, E., & Gillan, J. (2003). The role of diverse instruction in conceptual change. Journal of Experimental Child Psychology, 86, 253-276.

Kikas, E. (1998). The impact of teaching on students’ definitions and explanations of astronomical phenomena. Learning and Instruction, 8(5), 439-454.

Kikas, E. (2000). The influence of teaching on students’ explanations and illustrations of the day/night cycle and seasonal changes. European Journal of Psychology of Education, XV(3), 281-295.

Lightman, A., & Sadler, P. (1988). The Earth is round? Who are you kidding? Science and Children, 25, 24-26.

Mali, G., & Howe, A. (1979). Development of the Earth and gravity concepts among Nepali children. Science Education, 63(5), 685-691.

National Council for the Social Studies. (1994). Expectations of excellence: Curriculum standards for social studies. Washington, DC: Author.

National Council of Teachers of Mathematics. (2000). Principles and standards for school mathematics. Reston, VA: Author.

National Research Council. (1996). National science education standards. Washington, DC: National Academy Press.

Nussbaum, J. (1985). The Earth as a cosmic body. In R. Driver, E. Guesne, & A. Tiberghien (Eds.), Children’s ideas in science. Milton Keynes: Open University Press.

Nussbaum, J., & Novak, J. D. (1976). An assessment of children’s concepts of the Earth utilizing structured interviews. Science Education, 60(4), 535-550.

Nussbaum, J., & Sharoni-Dagan, N. (1983). Changes in second grade children’s preconceptions about the Earth as a cosmic body resulting from a short series of audio-tutorial lessons. Science Education, 67(1), 99-114.

Nobes, G., Martin, A. E., & Panagiotaki, G. (in press). The development of scientific knowledge of the earth. British Journal of Developmental Psychology.

Nobes, G., Moore, D. G., Martin, A. E., Clifford, B. R., Butterworth, G., Panagiotaki, G., & Siegal, M. (2003). Children’s understanding of the earth in a multicultural community: Mental models or fragments of knowledge? Developmental Science, 6(1), 72-85.

Osborne, J., Wadsworth, P., Black, P., & Meadows, J. (1994). SPACE research report: The Earth in space. Liverpool: Liverpool University Press.

Roald, I., & Mikalsen, O. (2001). Configuration and dynamics of the Earth-Sun-Moon system: An investigation into conceptions of deaf and hearing pupils. International Journal of Science Education, 23(4), 423-440.

Sharp, J. G. (1996). Children’s astronomical beliefs: A preliminary study of Year 6 children in south-west England. International Journal of Science Education, 18(6), 685-712.

Skopeliti, I., Ikospentaki, I., & Vosniadou, S. (2002, June). The influence of external representations on children’s models of the Earth. Paper presented at the meeting of EARLI SIG symposium on conceptual change, Turku, Finland.

Sneider, C. I., & Ohadi, M. M. (1998). Unraveling students’ misconceptions about the Earth’s shape and gravity. Science Education, 82, 265-284.

Sneider, C., & Pulos, S. (1983). Children’s cosmographies: Understanding the Earth’s shape and gravity. Science Education, 67(2), 205-221.

Vosniadou, S. (1991). Conceptual development in astronomy. In S. M. Glynn, R. H. Yeany, & B. K. Britton (Eds.), The psychology of learning science. New Jersey: Lawrence Erlbaum.

Vosniadou, S., & Brewer, W. F. (1994). Mental models of the day/night cycle. Cognitive Science, 18, 123-183.

Curriculum and Trade Materials

Grossman, M. C., Shapiro, I. I., & Ward, R. B. (2000). Exploring the Earth in motion: Daylight, sun and shadow patterns. ARIES: Astronomy-based physical science. Watertown, MA: Charlesbridge Publishing.

Earth, moon, and stars, teacher’s guide, Grades 5-9. (1986). Berkeley, CA: Lawrence Hall of Science, University of California.

Fraknoi, A. (Ed.). (1995). The universe at your fingertips: An astronomy activity and resource notebook. San Francisco, CA: Astronomical Society of the Pacific.

Fraknoi, A., & Schatz, D. (2000). More…universe at your fingertips: Astronomy activities & resources. San Francisco, CA: Astronomical Society of the Pacific.

http://gisdata.usgs.net/Website/Seamless/viewer.php

http://rsd.gsfc.nasa.gov/rsd/images/Linda.html

http://www.classzone.com/books/earth_science/terc/content/investigations/esu101/esu101page02.cfm

http://www.eclipticenterprises.com/gallery_rocketcam.php

http://www.powersof10.com

http://www.starrynight.com

http://www.terraserver.com

http://visibleearth.nasa.gov/advsearch.html

Lauber, P. (1990). How we learned the Earth is round. New York: HarperCollins.

Nuffield primary science, Science processes and concept exploration: The Earth in space, ages 5-7, Teachers’ guide. (1993). London: Collins Educational.

Nuffield primary science, Science processes and concept exploration: The Earth in space, ages 7-12, Teachers’ guide. (1993). London: Collins Educational.