The Big Ideas in Earth and Space Science

Earth and Space science include many specific facts, theories, and questions, but among these, scientists and educators have identified a certain small set as the "big ideas" that organize the intellectual domain. The National Science Education Standards (NRC, 1996) is the best and most succinct statement of these ideas. The Benchmarks for Science Literacy (AAAS, 1993) are another. Texbooks, state curriculum frameworks, and local curricula are other attempts to establish frameworks for what should be taught.

In this project, we have attempted to synthesize and distill these statements into a single, compact, and defensible list. We have identified what we consider to be the major ideas in Earth and space science that are worth "uncovering" by middle and high school students. The list of 25 concepts on the following page is the result of this work. It is meant not as a final and authoritative list, but rather as a workable framework for organizing what students should spend time studying.

It is our intention that this list serve as the organizing framework for the teaching resources that we are gathering on this web site and for the units that teachers and staff create as part of this project. We welcome your comments and thoughts.

The Earth System

1. Earth can be conceived as an interacting set of processes and structures composed of the atmosphere, geosphere, hydrosphere, and biosphere.
2. Radiation, conduction, and convection transfer energy through Earth's systems.

The Geosphere

3. The geosphere includes the lithosphere, the mantle, and the dense metallic cores.
4. The surface of Earth has identifiable major features--land masses (continents), oceans, rivers, lakes, mountains, canyons, and glaciers.
5. The movement of Earth's lithospheric plates causes both slow changes in the earth's surface (e.g., formation of mountains and ocean basins) and rapid ones (e.g., volcanic eruptions and earthquakes).
6. Earth's surface is built up and worn down by natural processes, such as rock formation, erosion, and weathering.
7. Physical evidence, such as fossils and radioisotopic dating, provide evidence for the Earth system's evolution and development.

The Atmosphere

8. The atmosphere is a mixture of gases with suspended solids and liquids.
9. Radiant energy from the sun creates temperature differences in water, land, and the atmosphere which drive local, regional, and global patterns of atmospheric circulation.
10. The atmosphere exhibits long-term circulation patterns (climate) and short-term patterns known as weather--storms, hurricanes, and tornadoes.

The Hydrosphere

11. Water cycles through the atmosphere, hydrosphere, geosphere, and biosphere.
12. Circulation patterns in the oceans are driven by density differences and by exchange of momentum with the atmosphere.
13. Liquid water in great abundance makes Earth unique among the planets of the solar system.

The Biosphere

14. Life is pervasive throughout the Earth system--in the atmosphere, the hydrosphere, and the lithosphere.
15. Life appeared early in Earth's history and has been intimately involved in the nature of the Earth--i.e. composition of the atmosphere, weathering, carbon cycle, and rock cycle.
16. The biosphere both shapes and is shaped by the physical environment.
17. Human beings have a unique, large, and growing impact on Earth systems.

Space Science

18. The Earth exists in the solar system, in the Milky Way galaxy, and in the universe, which contains many billions of galaxies.
19. The sun, the Earth, and the other planets were formed in a few hundred million years between four and five billion years ago.
20. The relative position and movements of the earth, moon, and sun account for lunar and solar eclipses, the observed moon phases, tides, and seasons.

The Nature of Earth Science

21. Earth scientists use representations and models, such as contour maps and satellite images to help them understand the Earth.
22. Scientists use quantitative, qualitative, experimental and non-experimental methods of scientific inquiry to understand the Earth.
23. Earth scientists make an assumption of uniformitarianism, that the processes that shaped the Earth in the past are the same processes we observe today.
24. Technological advances, such as seismic sounding and satellite remote sensing, advance Earth science knowledge.
25. As in all scientific disciplines, knowledge in Earth science is subject to revision.