Circular Reasoning on Rectilinear Propagation of Electromagnetic Radiation
Posted by Jeff Id on January 26, 2012
I’ve been spending time working on improved sea ice code. Anthony Watts asked for something and Steve McIntyre helped find the right R function to get it going. I want to also overlay SST data as well as flow direction in the videos. Hopefully it will lead us to some statistical analysis.
In the meantime JWL has been discussing backradiation on the previous thread. It is an old argument which doesn’t have a lot of entertainment value for some of us. He has put together a pdf which alleges to prove that backradiation (radiation from cold to hot) is impossible in the climate system and has made the claim that nobody has critiqued his math. I’m going to help him out.
What he does here though is completely circular reasoning. We have two surfaces and a flow between them. f is a variable representing absorption of the medium in between the two surfaces. Surface one emits energy at a power Θ1 which is equal to σT1^4. T is the plate temp and σ is a constant. Now classic physics agrees that emission power is proportional to T^4 so there is no problem with that. Lets look at the assumptions he makes though:
The heat transfer q from i->j is equal to the emission at i minus the emission of j in watts per meter squared. The negative term in equation 1 is the exact magnitude we would expect of back radiation. However, the author is already writing text that the back-radiation is non-physical. How do we know?
We then proceed to the equations at the top of this extensive PDF. Figure 1a includes the emission now from a surface. Joseph has apparently re-written the laws of physics for this as now the emission of the first surface to the second is equal to f(θ1 – θ2) where theta is the flux. I asked how this equation came about and was pointed to equation 1. Equation 1 though doesn’t say anything about the source of the flux, it only says that the sum of the flux is σ(Ti^4-Tj^4). Of course that is not the assumption stated but the math doesn’t know anything about what assumption you state. My question was and still is, how does the surface know to emit less energy when the second surface exists in a different timeframe? If the second surface vanishes instantly, does the first return to emitting a proper amount of radiation?
So then we proceed to the next section of the treatise.
So for system 1 we have in steady state – input = output or f(θ1 – θ2) = f θ2 which with some easy algebra is fθ1 = 2fθ2. In system 2 we have the same thing fθ1 = 2fθ2. They are exactly the same. Now for system 2 Joseph states that plate 2 of model B, having two hand drawn arrows, is emitting twice as much as the first. But wasn’t the original assumption that plate 1 changed its emission based on some spooky knowledge of plate 2? This assumption was based on nothing I can see but it included the plate 1 emission correction which happened to be exactly equal to the emission of plate 2 back to plate 1. He then concludes that B is non-physical based on absolutely NO evidence other than his original (and obviously false) assumption.
The logic is totally circular and the math for both cases is identical.
Joseph hasn’t made the claim that the second plate won’t absorb the photons from the first, he is making the claim that the photons don’t even exit the first surface. As this example of heat is identical to two incandescent lamps, this is physically identical to stating that if you shine a bright light on a dim light the second will dim further.
Many real world examples prove Joseph wrong. Lets assume though that most of us already know this and look at it from a spacetime standpoint – because it is also fun.
Each surface, from its own point of reference, sees the other surface as behind itself in time. The amount each sees the other as behind (X) is equal to the time light takes to travel across the distance between the objects. Imagine that one plate suddenly vanished. The other plate wouldn’t realize it for X seconds and in Josephs world, would stubbornly continue to emit at a reduced level until it became aware of the vanished counterpart. These reduced output photons would pass through the space where the first plate had been for a full 2X the number of seconds. This is because the first plate would become aware that the second had vanished after (X seconds) and then began emitting a greater amount across the same distance (another X seconds)! A sensor behind the second plate would see a reduced output for 2x seconds after the plate disappeared, followed by a sudden jump in brightness of the first plate.
Now imagine the plates were a light-day apart and you had enough time to stick a sensor between the surfaces.
That is unphysical in my book.
So many examples prove radiation does flow from cold to warm. My favorite, presented here before, is one of an uncooled infrared camera looking at an image of ice. Now we know the camera’s sensor is room temp so if radiation does not emit from cold to warm, everything cooler than the camera sensor, should appear midnight black. As this video progresses the color scale shifts so the table – room temp – is significantly warmer than many other objects in the image. Especially the edges of the ice. The manufacturer seems to also believe the camera can measure to minus 20 C. Much to the chagrin of AGW advocates (and Joseph), that would be well below room temp in my room.
Remember, light and IR radiation are the same thing. Your flashlight does not change intensity when you shine it at the sun. Nor does the sun, however the energy from the flashlight will interact with the plasma of the solar surface 8 minutes after you shine it.
After this, I am done with this topic. I won’t mind trying to explain where people go wrong in their thermodynamics, but really this is very much elementary and life is short. I have spent a good deal of time trying to straighten out this form of “skepticism” which unfortunately is flatly not reasonable. However, some are honestly confused and when they read a bunch of math letters piled together with words, they can’t always understand what the author is saying.