Correct Answer: Option 2 – Galileo Galilei

Explanation:

Before Galileo, the Greek philosopher Aristotle believed that heavier objects fall faster than lighter ones.

Galileo Galilei challenged this idea and showed that, in the absence of air resistance, all objects fall with the same acceleration due to gravity, regardless of their mass.

He concluded that:

• Differences in falling speed are mainly caused by air resistance.
• In a vacuum, all objects fall at the same rate.
• Mass does not affect the acceleration due to gravity.

This principle was later demonstrated during the Apollo 15 Moon mission in 1971, when an astronaut dropped a hammer and a feather simultaneously, and both reached the surface at the same time because there was no air resistance.

Why the other options are incorrect:

Option 1: Albert Einstein
Einstein developed the Theory of General Relativity, which explained gravity in terms of spacetime, but he was not the first to state that all objects fall at the same rate in a vacuum.

Option 3: Thomas Alva Edison
Edison was a famous inventor known for the electric bulb, phonograph, and other inventions, not for studies of gravity.

Option 4: Isaac Newton
Newton formulated the Laws of Motion and the Law of Universal Gravitation, building on Galileo's earlier work.

Therefore, Galileo Galilei was the first scientist to conclude that all objects fall at the same rate in a vacuum.