Gravity is a challenging topic, but can be built from prior knowledge throughout different grades. Unlike many space science concepts, this topic lends itself to hands-on experiments in the classroom. Students have a variety of misconceptions about gravity that will need to be addressed at any age level; for more information about misconceptions about gravity, you may want to read "Learning about Gravity" in the Astronomy Education Review.

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Activities

Grades K-4
Gravity is a complex subject not easily addressed at this age. Students often will confuse weight and mass; students will have an understanding of weight but not of its relationship to gravity. (Science Education Standards)

The students explore gravity and its relationship to weight by weighing themselves on scales modified to represent weights on other worlds, and compare the features of different planets to determine which characteristics cause a planet to have more or less gravity.

Grades 5-8
Students in this age group should understand mass and should be able to apply the mass of the planets to their gravity, with assistance. The older students may be able to calculate the gravitational pull of different planets. Teachers may wish to avoid use of magnetic fields as a model of gravity; a popular misconception is that gravity is related to magnetism. (Science Education Standards)

In this kinesthetic activity, students use their own bodies to create a model of the solar system and the forces the sun and planets exert on each other and on passing objects such as spacecraft.

Students view Web movies of astronauts on the Moon and discuss what they can learn about one's lunar weight; a calculator is provided to get their weight on other planets; a discussion of the causes of weight and gravity is then suggested with different hypotheses.

Students model the gravitational fields of planets on a flexible surface. Children place and move balls of different sizes and densities on a plastic sheet to develop a mental picture of how the mass of an object influences how much affect it has on the surrounding space.

Students measure the effect of gravitational flexing (which keeps Io and Europa's interior warm) by taking the temperature of some flexible rubber balls. They also calculate the force of gravity.

Students discover how the Moon's gravitational pull causes the level of the ocean to rise and fall twice a day along most coastlines through this kinesthetic activity, and consider what the Earth's tides might have been like if there were no Moon.

GRAIL MoonKAM (Moon Knowledge Acquired by Middle school students) allows classrooms to request pictures of the lunar surface from cameras on the twin GRAIL satellites. Students can use the images to study lunar features such as craters, highlands and maria while also learning about future landing sites. All who are part of a school or educational institution are welcome to register now!

Grades 9-14
These grades can apply their understanding of the laws of motion to the force of gravity, and begin to calculate the mass of various planets using the orbits of their moons. (Science Education Standards)

Students use images of Jupiter's Galilean moons to find their orbit periods and orbit radii, and find a "constant" relationship between orbit period and orbit radius to arrive at Kepler's 3rd Law.

Students use the measured properties of the Earth-like planet Kepler 10b such as its size and density, and by solving Newton's formula for gravity, they determine the weight of a 100 kilogram human standing on the planet's surface.

This activity relates an elastic collision to the change in a satellite's or spacecraft's speed and direction resulting from a planetary fly-by, often called a "gravity assist" maneuver. Both hands-on and online interactive methods are used to explore these topics.

The materials relating to gravity, tides, the slowing of the Earth's rotation, and the confirmation of the accuracy of radiometric age dating techniques make an engaging supporting story for high school classes studying radioactivity and age dating of geologic materials.