Galileo Galilei

Galileo Galilei (1564–1642) is often called the father of modern science, because he insisted on something radical for his time: don't just argue about how nature ought to behave — go and measure it. He rolled balls down ramps, timed pendulums against his own pulse, and let the experiments overrule two thousand years of received wisdom.

Everything falls at the same rate

Aristotle had taught for millennia that heavy things fall faster than light ones. Galileo showed this is simply wrong: ignore air resistance, and a cannonball and a musket ball hit the ground together. That single insight — that gravity accelerates everything equally — underlies the equations of motion and paved the way for Newton's laws. He also turned a new invention, the telescope, to the night sky and found mountains on the Moon, four moons orbiting Jupiter, and the phases of Venus — evidence that Earth is not the centre of everything.

'And yet it moves'

Galileo's evidence that the Earth orbits the Sun put him on a collision course with the Church. In 1633, aged and ill, he was tried by the Inquisition and forced to publicly recant — legend has it that as he rose from his knees he muttered under his breath, "E pur si muove" — "and yet it moves." He spent his last years under house arrest, going blind, still writing the physics that would launch the scientific revolution. In 1992, 350 years later, the Vatican formally admitted he had been right all along.