Galileo Galilei (not active but influential)

Galileo Galilei was a pioneering Italian scientist and astronomer from the 17th century who significantly influenced our understanding of the universe. He improved telescopes, allowing him to observe planets, moons, and stars more clearly, leading to evidence that supported the heliocentric model—Earth and other planets orbit the Sun—challenging long-held beliefs. His experiments on motion and mechanics laid the groundwork for modern physics. Although not active today, his ideas and discoveries fundamentally changed science, shifting it from relying solely on philosophy and religion to empirical evidence and experimentation. Galileo's work remains a cornerstone of scientific thought.