While there were many scientists who contributed to our understanding of gravity, Galileo Galilei is widely credited with being the first to demonstrate and quantify the acceleration due to gravity.

Here's why:

* Observation and Experimentation: Galileo conducted experiments by dropping objects from the Leaning Tower of Pisa (though this is disputed) and rolling balls down inclined planes. He observed that regardless of their mass, objects fell at the same rate, suggesting a constant acceleration.

* Mathematical Formulation: Galileo formulated the concept of acceleration due to gravity (g) and established that it is a constant value near the Earth's surface. He didn't determine the precise value of g, but his work laid the foundation for future scientists.

* Early Attempts at Measurement: It wasn't until the 17th century that physicists like Christiaan Huygens and Isaac Newton began to accurately measure the value of g. Newton's law of universal gravitation further explained the force of gravity.

Therefore, Galileo's contributions are crucial in understanding gravity, even if he didn't determine the exact value of g.