Who was the first person to prove that trajectory is a curve, and not a straight line?

The first person to demonstrate that the trajectory of a projectile is a curve, rather than a straight line, was Galileo. He conducted various experiments and mathematical analyses in the early 17th century, leading him to conclude that projectiles follow a parabolic path. This was a significant advancement in understanding motion, ultimately laying the groundwork for classical mechanics. His studies on the motion of objects, specifically how they are influenced by gravity and other forces, effectively reshaped contemporary views on ballistics.

Galileo's work was foundational for later scientists, notably Isaac Newton, who expanded on his principles. The other figures listed contributed to various aspects of physics and mathematics, but it was Galileo's investigations into projectile motion that established the understanding of curved trajectories in relation to gravitational forces.