Once again, I wasn't talking about heat, but photons. You're a broken record. Heat and photons aren't the same thing!
You don't seem to get it that the 2nd law is about energy transfers of any sort...not just heat. I repeat ALL ENERGY TRANSFERS ARE GOVERNED BY THE SECOND LAW OF THEROMODYNAMICS. It doesn't matter whether the energy is in the form of IR radiation, photons, microwaves, short wave radiation, water flowing downhill, electricity, pressure in a balloon, BTU's stored in a cord of wood, or TNT. ALL ENERGY TRANSFERS ARE GOVERNED BY THE 2ND LAW OF THERMODYNAMICS. If photons are energy and they are being transferred (moved) then the second law governs that transfer. If you don't understand that, then you don't understand the first thing about physics. Again, here is an explanation of the second law from the most basic source I could find.
How Everything Happens
Energy makes everything happen, and every time something happens, there is an energy change. There are two important natural "
laws of energy" that describe what happens to the energy involved in every change. We call them "laws" because countless observations and thousands of experiments have shown them to always predict what will happen.
Ponder that for a moment - how everything happens.
It means we don't understand much, if we don't understand both the first and second laws of Energy....
Remember that there has to be an energy transfer for something to happen; energy changes form or moves from place to place....
The Rest of the Story...
Alas, my friends, there is always a rub, and when it comes to energy, the rub is described by the Second Law of Thermodynamics. The first law would be quite happy to let us re-use energy over and over. The first law is happy as long as energy is conserved. It's the happy law.
The second law may seem a little less happy to some. It describes the aftermath of every energy change that makes something happen.
The second law says that each time energy gets transferred or transformed, some of it, and eventually all of it, gets less useful. That's the truth. It gets less useful, until finally, it becomes mostly useless (at least as far as its ability to make things happen is concerned).
The Direction Energy Always Goes
The second law tells us which way energy naturally flows when not blocked or "pushed" by other mechanisms. It says energy has an absolute unfailing tendency to go from "more concentrated" to "less concentrated". It sort of "spreads out" and gets "diluted". That's a good way for beginners to think about it.
- Energy flows from a higher temperature to a lower temperature (heat flow).
- Energy flows from a higher pressure to a lower pressure (expansion).
- Energy flows from a higher voltage potential to a lower voltage potential (electric current).
- Energy
flows from a higher gravitational potential to a lower gravitational potential (falling objects).
Marbles and trucks roll downhill.
- Water flows and falls from higher elevation to a lower elevation (downhill).
- And last, but not least, chemical reactions proceed from higher concentrations of
molecular bond energy to lower bond energies.
In each of those cases, we can think of the energy in the higher level as being more concentrated. Energy inevitably moves to a less and less concentrated condition.
Less concentrated = less useful.
For anything to happen, energy has to move or flow or change.
Energy will keep flowing or changing from a higher concentration to a lower concentration until the concentrations are equal (not necessarily more disordered). We call that condition, cleverly enough, equilibrium......
This is the first thing to understand about the 2nd Law. Energy always and inevitably flows from higher concentrations to lower concentrations.
The next thing to understand is that every time energy changes or moves, some of it, or all of it, becomes less useful. That is the unchangeable result of becoming less concentrated.
One thing leads to another - always, always, always - cause and effect.
Energy always, and only, goes from more concentrated to less concentrated. Being less concentrated also means less useful. The cause of everything that happens is a difference in energy concentration. The effect of every energy change is less useful energy.
Get it? Every time energy moves, it moves to a condition in which some of it or all of it becomes less useful. Less Concentrated = Less Useful
I can't find anything more elementary than that for you konradv. It is the rock bottom basic and doesn't simply assume that you know things like heat is just one form of energy and the second law is about all energy exchanges. You can't get around the second law by sneaking energy around in the form of photons and then letting them convert to heat. If you could, then you would have the basis for a perpetual motion machine.
If you believe that the second law isn't about all energy exchange and is just about heat exchange, then do bring some credible source forward that says explicitly that the second law is only concerned with heat exchange and not applicable to any other sort of energy exchange.
