Written by Joseph E. Postma
Anthony Watts has performed an experiment in follow-up to Roy Spencer’s challenge to the Slayers/Principia Scientific International to “put up or shut up”, to which we replied that we had already put up, and in which we proved that Dr. Spencer’s understanding of the offered challenge was somewhat lacking. Curt Wilson has also done a follow-up experiment for WUWT.
Unfortunately, our successful answer to the original challenge was ignored and a new line of questioning was instead pursued by Watts et al. Sometimes this is called changing reference frames. The distraction comes from a diagram we used to present a general physical principle of thermodynamics, such that radiant emission from a source cannot act as an additional source, for the source. This means that the source cannot become brighter, which in radiative emission terms of the Stefan-Boltzmann Law means hotter, from its own radiation. If such a thing could happen, then an object’s own radiation could act as a source or cause of temperature increase for the object, which is of course plainly in violation of thermodynamics.
The diagram which has presented the hapless convenience for Watts et al. to reframe the rebuttal to their challenge, is reproduced below:
Figure 1: (Image courtesy of Alan Siddons.)
This diagram (Figure 1) was included in the context of a previous diagram, as shown here:
Figure 2: (Image courtesy of Alan Siddons.)
The point of the discussion surrounding these diagrams was in terms of an elucidation of the underlying physical principles which govern the fundamental thermodynamic behaviour. Unfortunately, the underlying physical principles of thermodynamics, such that a source of light cannot make itself shine brighter (i.e. become hotter) with its own light, or that two equal sources of light cannot make each other brighter (hotter at the source), can be ignored at the expense of mischaracterizing an experiment to test them. It would have been just as well if Watts et al. would have chosen to create an experiment based on Figure 2, because the brightness results would have been much more obvious. However, Figure 1 and Figure 2 do allow for significant misperception if the underlying principles are not understood, or ignored. This is something we didn’t consider would occur, and it is an important lesson for science communicators.
Regarding the underlying theoretical principles of what such an experiments requires to be understood and in regards to the greenhouse effect, Mr. Watts replied at his site: “And yet, in the diagram proposed in the essay by Postma, such fine details were not mentioned nor required. Demanding them now post facto doesn’t fly.”
Unfortunately, expecting the “fine details” to be appreciated is something we expected a-priori. That was our mistake. Unfortunately, it is the onus of the experimentalist to be competent and responsible for their complete understanding of what it is they’ll be intending to measure, and to quantify it. If all of the details aren’t sorted out, such as what the underlying physical principles are, as opposed to a simple literal interpretation of words without context and misidentifying original causes, then any such discussion by the experimentalist of the empirical results cannot be expected to be meaningful. It has always been a tricky business.
The underlying physical principles we had expected to be understood can be expressed in terms of the general equivalence of concepts between three major areas of physics: force mechanics, electrical mechanics, and thermal mechanics. It is sometimes helpful for a student to consider that a problem in one domain can be qualitatively solved equivalently in another domain, for example: voltage is like temperature is like force; current is like heat flow is like acceleration; and electrical resistance is like thermal mass is like material mass.
In terms of an energy analysis, force, voltage, and temperature all represent the potential to induce action if there is a non-zero differential in them. That is, a force differential causes acceleration, modulated by a physical parameter; a voltage differential causes current, modulated by a physical parameter; and a temperature differential causes heat flow, modulated by a physical parameter. In all cases the nature of the action is similar: the acceleration caused by the force does not increase the force; the current caused by the voltage does not increase the voltage; and the heat flow caused by a temperature differential does not increase the temperature. In all cases, if one wishes to modify the action, they must either modify the differential, or modify the relevant physical parameters. We will see ahead the importance of these facts.
In an electrical circuit, dissipation of energy is performed by the resistor. The energy dissipation takes the form of heat in the resistor, and if the physical parameters of the resistor and the circuit are appropriate, the resistor can become hot enough to emit visible light. Typically, light bulb filaments run at 3300K and produce emission close to a blackbody. It is important to comprehend that the source of the thermal emission/heat generation in the resistor is caused by the current running through it, and the current is caused by the voltage applied to the circuit. If the filament emits similar to a blackbody, then its radiant output flux density can be related to the Stefan-Boltzmann equation. The radiant emission has as its source, then, the current going through the circuit, which is caused by the voltage applied to the circuit. If you want to increase the temperature of the source of light/heat so that you can produce more light/heat, and the source of those is the filament, then you have to increase the current going through the filament, and this is done by increasing the voltage across the circuit. It cannot be done by giving the filament the light or heat it produces back to itself, as the light is dissipated energy, not source energy for the circuit or filament. The filament’s dissipated energy cannot be used to increase the voltage across the circuit, and hence cannot be used to increase the brightness/temperature of the source.
Both of the WUWT experiments make the mistake of considering that the frosted glass of the bulb is the source of light and heat. PSI acknowledges that such a confusion is possible if you look naively at the diagrams and see what looks like a frosted bulb and simple-mindedly assume that the frosted glass itself is the source of the energy, and assume a bland interpretation of the words describing the scenario.
The frosted glass is a source of light in as much as it scatters the incoming spectrum, and it is a source of heat in as much as its absorbs the incoming spectrum. Obviously, the actual source of light and heat is the filament inside the bulb producing the spectrum at a typical temperature of 3300K, and the source of energy for the filament is the voltage applied to the circuit. The frosted glass is a passive semitransparent screen in front of the actual source. The frosted glass bulb itself, once heated, can be a source of heat for something cooler than it, such as a finger or hand, but it is not the source of energy.
We did not expect that the underlying physical principles would be disregarded, or plainly not understood, nor scientifically quantified. This experiment could be repeated to check for a brightness increase of the frosted glass when another bulb is brought nearby; this might actually occur, but the reason would be that the frosted glass has a high albedo and some additional light would simply be reflected back. Again, this would not actually get down to the underlying physical thermodynamic principle involved nor of what is claimed with the greenhouse effect, because the true source wouldn’t actually increase in temperature. Mr. Watts has insisted that we do not consider such fundamentals of theory and its quantification and instead focus only on the surface appearances of his experiment; doing such a thing obviously presents the opportunity for obfuscation, and we can wonder if this is intended, or simply not comprehended.