Whose principle explains why a ship floats and an object seems lighter in water?

Archimedes, the Greek mathematician and engineer of Syracuse, is credited with this classic principle of buoyancy. It explains why ships made of steel can float if they displace enough water, and why objects feel lighter when submerged. The principle is a cornerstone of fluid mechanics and is named after Archimedes, who lived in the 3rd century BCE. It is used in ship design, hydrometers, submarines, and density measurements.