If we, as humanity, are concerned about our environment and the survival of the human life form as we know it, the sources of energy we use need to be controlled. Immediately the discussion becomes cloudy because of the myriad of definitions that can enter and influence the conversation. But we all know what energy is. We are tired and need an energy bar. The faster we move, the more kinetic energy we have. Last month’s utility bill says we used 8,000 kilowatt hours of electricity.
There is really a significant difference between science and engineering, between physicists and engineers. I should include all of the types, but please forgive me. I am an engineer. In physics, energy equals mass times the speed of light squared and the amount of mass and energy in the universe is constant. Energy is something that must be transferred to an object to do work on it or heat it up. The International System of Units, abbreviated SI, unit of energy is the joule, the amount of work in moving an object one meter against a force of one newton. Having “clarified” what energy is, everything is “simplified.”
As humans, we use and waste energy every day, even when we are asleep. Using the physics definition, however, it is a bit difficult to measure. So we have adjectives that modify the word energy to create “types” of energy that are measurable. These might include mechanical, electric, magnetic (better titled electromagnetic), gravitational, chemical, ionic, nuclear, elastic, wave, radiant, rest and thermal. And energy is central to biology, chemistry, earth sciences, and cosmology. If everything in creation is mass and energy, obviously it is everywhere. The role of information is a separate topic.
Go back to physics for a moment. In the universe there are only two force fields: gravitational and electromagnetic. These fields interact with matter to do work. For example, the gravity, a weak force field, of a given object will apply a force on another object. The earth has gravity that accelerates a dropped object thereby changing its velocity, thus giving it kinetic energy defined as one half the mass times the velocity squared. Gravity determines our weight on the scale, a measure of mass. It’s not energy yet but could be if we fall. I cannot really explain gravity, but I know it by observation.
In contrast, electromagnetic force fields are strong fields that can perform work on an object or heat it up. Or, the energy can be stored. For instance, the sun emits energy in packets called photons – light. When it arrives on earth it partially does work, with some of it being rejected and some of it being stored. As an example, the light energy interacts with plants, where it is stored in chemical bonds ready to be transferred to humans and other animals when consumed. Or it might be released as heat when it is burned.
Over many, many years part of the energy arriving from the sun has been stored in what we call fossil fuels. The term is confusing because fossils are generally thought of as preserved remains, impressions, or a trace of something once alive. In describing oil, coal, and natural gas as fossil fuels we acknowledge that they were created by something that chemically stored the arriving energy and then transformed it some way into the substances we call fossil fuels. The electromagnetic energy was stored in a chemical bond – work was done. When we “burn” these fuels, we break the bond while creating other chemicals (CO2?) and the energy is reused.
So here on earth we have a store of available energy, we receive new energy constantly from the sun and, as a planet, we emit energy. If the stored energy is released as opposed to stored and the sum of received energy plus stored energy is greater than the work performed and the energy released to outer space, we heat up and our entropy (the measure of disorder) increases.
There is another form of stored energy available on earth called nuclear. The nucleus of an atom is held together by energy. Much like breaking a chemical bond but much more difficult, if you break the right atom, energy is released (called fusion). Likewise, if you can create the right atom from smaller atoms, you can release energy (fusion).
Electricity deals with the movement of electrons. It can be potential (or stored) energy or it can be kinetic energy. And if it is used correctly, it can perform work necessary for human survival, growth, and evolution. But it deals with electromagnetic forces, the stuff that is necessary to do work and heat other stuff. As humans we can be likened on average to 80 watt light bulbs in the energy we emit continuously. But we cannot plug ourselves into an electric socket. And we need other energy to perform the needed activities to acquire the two kilowatt-hours we burn up each day. Force, energy, work, heat, efficiency, and sources….