Gravity and Motion in Space
By Lori Altenbaumer, 7th/8th Math & Science
Last week, our 7th grade scientists stepped into the shoes of astronomers as they investigated one of the biggest questions in space science: How does gravity affect the motion of the solar system?
Using a marble, softball, and a simple piece of fabric, students modeled the delicate balance of forces that keep Earth and the other planets moving in orbit around the sun.
In the experiment, the marble represented Earth and the larger softball represented the sun. Students first pushed the marble across a flat surface, watching how inertia caused it to travel in a straight line unless acted upon by another force. Then, by introducing a piece of fabric stretched with the “sun” in the center, they were able to see how the marble’s path bent toward the sun - an excellent hands-on model of gravity’s pull.
Through trial and error, students experimented with different pushes and starting points for their “Earth”. They observed how:
Inertia alone would send the marble moving endlessly in a straight line.
Gravity alone would cause Earth to be pulled directly into the sun.
When gravity and inertia worked together, the marble curved around the sun, just like Earth does in its orbit.
Students were even able to achieve a stable “orbit”, discovering firsthand that it takes just the right balance of speed, direction, and force to mimic Earth’s year-long journey around the sun.
The lab made abstract concepts come alive, helping students visualize how the invisible forces of gravity and inertia interact to shape the predictable motions of our solar system. This hands-on investigation not only deepened their understanding of space science but also reminded us all of the incredible precision of the universe we live in.
