We say that energy isn’t created or destroyed when we see it take other forms. For example, when a car slows down due to road friction, its tires become hot and radiate heat, so kinetic energy is being converted into heat energy. Conversely, a steam engine essentially converts heat energy into kinetic energy. Energy then is seen to take different forms, but with one notable exception.
Lifting an object takes energy that dropping it releases, but where does it go to or come from? There is no heat or radiation, so it is said to have potential energy based on its position in a gravitational field. This balances the energy books, to conserve energy, but where is potential energy stored?
For example, if a rocket blasts off into an earth orbit, where did the liftoff energy go? If it then floats off into space, where is that energy stored when it leaves our solar system? Or if it crashes into a big planet like Jupiter, to release more energy than it took to leave earth, where did the extra energy come from? The current answer, that gravity gives and takes potential energy, is a theory about an unknown mechanism that lets energy be conserved when apparently, it isn’t.
In this model, energy is the transfer of processing that occurs when quantum waves spread. Light then has radiant energy because it spreads, and high frequencies that spread more processing have more energy. Heat energy is also radiant energy, but of a lower frequency. Radiant energy is then conserved because photons are never destroyed, but just restart, as processing can. If every physical event restarts photons in various forms, as light or matter, photons are always conserved.
When light shining on a solar sail makes it move, radiant energy is converted into kinetic energy. If the sail moves because it acquires photons that bias its distribution, kinetic energy is also based on photons. When objects collide in empty space, kinetic energy is conserved because directional photons are exchanged, but their number is constant. Nuclear energy from matter seems different, but if matter arose from light, it is also based on photons.
What then is potential energy? Potential energy is based on gravity, which as Einstein deduced isn’t a force at all, so no energy is involved. When a rocket leaves earth, no photons are lost, and if it crashes on Jupiter, no photons are created, so the conservation of photons avoids the fudge of potential energy.
Current physics conserves matter, charge, momentum, isospin, quark flavor and color, but each law is partial, as matter isn’t conserved in nuclear reactions, and quark flavor isn’t conserved in weak interactions. Energy is then the same, a partial law, because it can’t explain potential energy or the loss of energy due to the expansion of space.
Yet if photons are universally conserved not energy, how does the expansion of space affect this law? The answer is not at all. If our universe began with the creation of light, in what physics calls inflation, which was healed by the expansion of space, the number of photons that exist has stayed constant since then, at a finite number. Expanding space changed the energy of the universe but not the total number of photons in it.
Our universe then conserves only photons, not matter, energy, or anything else, because it arose entirely from light, and nothing but light. What then does the second law mean?