Buoyancy is the upward force on an object immersed in liquid. This affects the object by providing an upward force to reduce the downward force of gravity, or weight.  This makes the object feel lighter.  One way to test buoyancy is to use Archimedes’ Principle. Archimedes’ Principle says that the buoyant force is equal to the weight of displaced water. If the displaced water weighs less than the object, the object will sink, or be negatively buoyant. If the weight of displaced water is equal the weight of the object, it will be neutrally buoyant and neither float or sink. Scuba divers aim to be neutrally buoyant.  If the displaced water weighs more than than the object, then the object will be positively buoyant, and float.

    Archimedes Principle was discovered by a man named Archimedes, and this is how the story goes of his discovery. He was given the task of finding out if a craftsman, who worked for the king, was replacing the king's gold with silver. In the middle of this Archimedes decided he should take a break so went to take a bath. When he entered the bath, he noticed when he submerged his legs, the water rose. He then realized what he had discovered.  He told the king that there was a way to tell if the smith was changing his crown. Knowing that gold has a higher density than silver, he put the king's crown and then a gold crown of the same weight into a pool. The king's crown made more water overflow, showing that it had a greater volume for the same weight. That meant it was less dense than gold, meaning it was silver.  The goldsmith was executed.