Archimedes of Syracuse said:"Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object." From this quote, we know that buoyancy is a force exerted by a fluid, that opposes an object's weight. According to Archimedes' Principle, the quote can be translated into formula as follows: FB = ρgV  FB refers to buoyancy force, while ρ is density and V is volume of displaced liquid, g is gravitational constant. We know that mass equals density times volume (m=ρ*V), so the formula is making sense according to the quote. From this formula, we can see that the larger the size of the object, the larger the buoyancy. That is why huge ships made with iron can float while a piece of solid iron cube will not float. The huge iron ship has empty space inside, so the volume is much larger. However, a solid iron cube with the same mass of the ship doesn't have empty space inside and so the buoyancy will not be enough to make it float.