In physics, buoyancy 's the upward force that keeps things afloat. The net upward buoyancy force's equal to the magnitude of the weight of fluid displaced by the body. This force enables the object to float or at least seem lighter. Archimedes' principle It's named after Archimedes of Syracuse, who first discovered this law. According to Archimedes' principle, "Any object, wholly or partly immersed in a fluid,'s buoyed up by a force equal to the weight of the fluid displaced by the object." A… (More on Buoyancy)