At any rate that’s what I think you ought to know about the first law. Energy became the central concept of thermodynamics because it has the enormously useful property of being constant in time. How useful? So useful they call it the first law of thermodynamics, and the predictability of the final state of any natural process is grounded in our capacity to write down equations which connect the past and the future. These equations are all in some way derived from the constancy in time of energy. But it is not considered to be the “cause” of anything--gravity and voltages and nuclear forces and so on provide the "how" cause of things. Furthermore, this “law,” or as Feynman says “strange fact,” does not by itself explain why a process does or does not occur. That’s really the second law’s territory, which we’ll get to next time. But understanding entropy, which the second law tells us is the quantity that can only increase, requires this preliminary understanding of energy, the quantity that cannot change. Finally, once we understand the basic ideas of thermo, then we can begin to see how the interaction between that which can’t change and that which can only increase creates these beautiful natural patterns from which we grew.
Fractal pattern indicating self-organization via dissipative flows
Thumbnail image: A forest fire represents a massive transfer of energy from system to surroundings, but the total energy of the universe is unchanged during this process.