Gravity is Energy

The laws of thermodynamics decree that each quantity of en^rgy has a characteristic quaUty called entropy associated with it. The entropy measures the degree of disorder associated with the energy. Energy must always flow in such a direction that the entropy increases. Thus, we can arrange the different forms of energy in an "order of merit," the highest form being the one with the least disorder or entropy. Energy of a higher form can be degraded into a lower form, but a lower form can never be wholly converted back into a higher form. The direction of energy flow in the universe is determined by one basic fact, that gravitational energy is not only predominant in quantity but also highest in quality. Gravitation carries no entropy and stands first in the order of merit. It is for this reason that a hydroelectric power station, converting the gravitational energy of water to electricity, can have an efficiency close to 100 percent, which no chemical or nuclear power station can approach. In the universe as a whole, the lain theme of energy flow is the gravitational contraction of massive objects, the gravitational energy released in contraction being converted into energy of motion, light, and heat. The flow of water from a reservoir to a turbine situated a little closer to the center of the Earth is in essence a controlled gravitational contraction of the Earth, on a more modest scale than astronomers are accustomed to consider. The universe evolves by the gravitational contraction of objects of all sizes, from clusters of galaxies to planets.