The Buoyant Force, supposedly first observed by Archimedes, is the upward force exerted upon a solid in a fluid, and can be expressed as a ratio of densities between the fluid and solid. Density, as you may know, is defined as the mass divided by the volume, or D = m/v. Every solid has a mass and a volume, and therefore the density can be calculated. A solid will float in a fluid if its density is less than that of the fluid; it will conversely sink if its density is more than that of the fluid. Floating implies that the solid displaces a weight of fluid greater than itself; sinking implies it displaces a weight of fluid lesser than itself. Strictly speaking, the weight of an object is not the same as the mass; mass is a singular property expressed in kilograms or pounds; weight is actually a measure of a mass under the force of gravity, given by the formula w = mg, where w is the weight, m is the mass, and g is the force of gravity.