What makes Galileo a science hero? For one thing, he moved human knowledge forward against outstanding prejudice and even persecution.
Galileo V. Catholic Church
Back in 1616, when Galileo argued that Copernicus had been right in suggesting the earth moves around the sun, he was met with hostility by the Catholic Church.
They believed the earth stood still while everything else went around it. And the medieval church was powerful enough to punish and even execute people who disagreed with them!
Looking At Jupiter
Galileo, however, used one of the earliest telescopes to look at Jupiter. He noticed that Jupiter has moons going around it. Apparently everything in the cosmos didn't have to go around the earth! Perhaps, Galileo said, it just looks like everything moves around us because we are standing on a planet that itself is in motion.
Every school child now knows Galileo was correct, but his works were banned and he himself was placed under house arrest by the Inquisition in 1633. He was still under arrest when he died ten years later, having been forced to smuggle out his final work.
Father Of Modern Science
Despite all the persecution he faced, Galileo always believed that the universe was not unfathomable but could be understood by rational means. In many ways he became the father of modern science.