Economists tell us that within the economy there is a lot of substitutability, and they are correct. However, there are a couple of not-so-minor details that they overlook: There is no substitute for energy . It is possible to harness energy from another source, or to make a particular object run more efficiently, but the laws of physics prevent us from substituting something else for energy. Energy is required whenever physical changes are made, such as when an object is moved, or a material is heated, or electricity is produced. Supplemental energy leverages human energy . The reason why the human population is as high as it is today is because pre-humans long ago started learning how to leverage their human energy (available from digesting food) with energy from other sources. Energy from burning biomass was first used over one million years ago. Other types of energy, such as […]