Laws of motion?
"as it would have proved his first law of motion to be correct" - erm no, it wouldn't. It would prove the SECOND law of motion to be correct.
"A body experiencing a force F experiences an acceleration a related to F by F = ma, where m is the mass of the body. Alternatively, force is equal to the time derivative of momentum." - where force is zero (no gravity) then the acceleration should be zero.
The first law of motion is usually expressed as "an object in motion, remains in motion" - inertia, this can't really be proven by having something "not fall" it can be proven by throwing something out of the space station and watching it continue ad infinitum


