Thermodynamics is the study of energy and its relationship to other forms of energy in a system. There are at least three laws of thermodynamics. The first law states that the total amount of energy in a system remains constant. The second law deals with heat flow, where heat cannot flow into a system that has a higher degree of heat unless it is acted upon by another force or system. This law also deals with entropy, where there is an increase of useless energy in a system as heat distribution becomes even in a system, and no useable energy can be obtained. In other words, things run down. The third law states that a system cannot be reduced to absolute zero, the lowest possible temperature where atomic movement ceases.