Marla says that only one person was really responsible for the theory of planetary motion. Do you agree with her? Why or why not?

I do not agree with her. The theory of planetary motion was a group effort between Johannes Kepler and Sir Isaac Newton. I don't feel as if Tycho Brahe had much to do with it seeing as it was really Kepler who figured it all out.

(this is my own answer which worked)

Sample Response: I disagree with her because it took several people hundreds of years to arrive at the current model. Kepler developed his planetary laws on Copernicus's heliocentric model with Brahe's data. Newton based his universal law of gravitation on Kepler's work and Hooke's ideas.