Galileo Galilei (1564-1642)

Though Galileo didn't invent the telescope, he built superior versions and directed them skyward - revealing observations that challenged millennia of astronomical assumptions.

Jupiter's moons proved not everything orbited Earth. Venus's phases confirmed heliocentric models. The Moon's cratered surface contradicted Aristotelian perfection. His 1610 Sidereus Nuncius transformed scientific understanding permanently. Beyond astronomy, his motion experiments established that falling objects accelerate uniformly regardless of mass, contradicting Aristotle's physics. The Inquisition convicted him of heresy in 1633 for defending Copernican theory. House arrest didn't stop his work. He died in 1642 - the year Newton was born - having dismantled the geocentric cosmos through systematic observation.