Copernicus argued that Earth revolved around the sun, not the other way around. Newton introduced the idea of gravity and formulated crucial laws of physics. Lavoisier made important contributions to chemistry, particularly around the discovery of oxygen. Einstein is perhaps most famous for his theory of relativity, which linked space and time. Kuhn lists these well-known scientists together to emphasize his point that scientific progress isn’t linear—instead, it’s a constant cycle of revolutions, all of which are important.