Buoyancy is the ability of an object to float in a fluid, such as water or air. It occurs when the upward force exerted by the fluid is greater than the downward force of gravity acting on the object. This upward force is known as the buoyant force, and it depends on the volume of fluid displaced by the object. The principle of buoyancy was discovered by the ancient Greek scientist Archimedes. According to Archimedes' principle, an object submerged in a fluid experiences a buoyant force equal to the weight of the fluid it displaces. This principle explains why some objects float while others sink.