Explanation:

- Option 1: Thomas Alva Edison was a famous inventor, mainly known for the electric bulb and phonograph, and did not work on gravity or falling objects.

- Option 2: Isaac Newton formulated the law of universal gravitation and laws of motion, but he built upon earlier work on free fall.

- ?? Option 3: Galileo Galilei was the first to conclude, through experiments, that in the absence of air (vacuum), all objects fall at the same acceleration, regardless of their masses. He demonstrated this by dropping spheres from the Leaning Tower of Pisa.

- Option 4: Albert Einstein developed the theory of relativity much later and expanded on gravity, but did not first conclude the principle about falling bodies in vacuum.