Click images for more details



Recent comments
Recent posts
Currently discussing

A few sites I've stumbled across recently....

Powered by Squarespace

Discussion > Simon Abingdon/Jonathan Jones/Radiative transfer


In my view it is really up to mdgnn to perform the experiment as he is the one who claims that text book theory does not apply in this case. Nevertheless, I do see that the claim that the sums are correct could be seen as an appeal to authority. It would certainly be useful to do this experiment to convince the uncommitted one way or the other.

The big problem that stands in the way is that most people will not have access to a decent vacuum pump or a supply of liquid helium to cool the chamber.. I have a proposal to vary the experiment using much more readily available materials and methods. My idea is to turn it into a three disc method where the third disk is cooled to 273.15K (0ºC) and becomes one wall of my original enclosure. Melting ice is a more readily available coolant. The other idea is to stack the discs one above the other with the heated disc uppermost and the cooled third disc at the bottom. In theory this should almost totally prevent heat transfer between the discs by convection without the need for a vacuum at all. This trick is used in some versions of a Lees' method for measuring thermal conductivity in liquid or gas. In these, mainly gas, experiments any radiation between discs is a nuisance that has to be allowed for. We can turn this around and regard the known conduction of the air as the nuisance that has to be allowed for.

We probably need to put the discs inside a thermally conductive tube with the third disc sealing the bottom of the tube to allow insertion into the cooling ice water. We may need to line the inside of the tube with insulating foam to prevent conduction from the edges of the two inside discs and to trap the air inside the disc faces to prevent other convection effects.

Ignoring the conductivity of the air and the thermal resistance of the discs themselves I calculate that the temperature of the middle passive disc will be 292.6K (19.45ºC) and the radiating face of the heated disc will be 308.8K (35.6ºC) using 100W/m2. We will also have to make an allowance for the fact that the radiating faces will not have emissivity/absorptivity equal to that of a true black body but as long as we know the values the text book theory can be used to adjust the prediction. My initial guess is to use discs of 50-100mm in diameter and circa 1-2mm thickness, spaced about 1mm apart.

I think it is important that we get mdgnn to agree that, in principle, this is a valid experiment otherwise it is pointless. I am afraid that I am a bit cynical about this as I have read too many 1000+ threads between orthodox and dissenting posters which never really get to grips with the exact nature of the dispute. As Science of Doom says there are too many words and not enough equations. This experiment should allow for a test of the text book equations.


Apr 24, 2012 at 1:55 PM | Unregistered CommenterJorge

Apr 24, 2012 at 1:55 PM | Jorge

Thank you for that very interesting information.

What material would you select for the discs and the tube?

Whilst it would be good if mdgnn came in on this, I find it incredible that not one (lurking) scientist has popped up here and said that "we do this 2 disc demonstration (as described in the top post of this thread) every year to our students, and here is the worksheet and some sample results".

Perhaps, that no-one has popped up here, is that the "2 disc demonstration as described in the top post of this thread" has not been performed, evah!

I urge any lurking scientist to either, show us your worksheets/results or, tell us that you have set your technical support staff on the case and then keep us informed of progress.

Also, it would be interesting to see if any lurking scientist with access to a laboratory workshop would come here and offer to perform the modified experiment as described by Jorge at 1:55pm today.

What could possibly go wrong?

Thank you.

Apr 24, 2012 at 4:18 PM | Unregistered CommenterBrownedoff

Brownedoff, you are shifting the burden of proof here. It's up to the person arguing for a change in the 'text book equations' to propose and carry out the experiment. But thanks Jorge for doing the proposal part for them - brilliantly.

Apr 24, 2012 at 4:39 PM | Unregistered CommenterRichard Drake

Apr 24, 2012 at 4:39 PM | Richard Drake

I do not care what you think is going on, I am just having an exchange with Jorge about laboratory demonstrations involving discs, heaters and enclosures. Then you pop up with your "opinions", some of which, here and on other threads are, frankly, tedious.

However, as the text book advocates who show up here seem to be too snooty to show their laboratory workings to the peasants, I thought that surely, there must be a seat of learning somewhere, employing a lurking scientist who would be willing to show the peasants, with drawings, photographs, materials lists and logs of instrument readings, that they had performed experiments in their laboratory, either an exact replica of the top post description or that outlined by Jorge above, or even something similar. Note, I am merely looking for material that is already in existance - does it matter who does the work?

From Jorge at 1:55pm today:

As Science of Doom says there are too many words and not enough equations. This experiment should allow for a test of the text book equations.

On Apr 12, 2012 at 10:19 AM | Jonathan Jones: (My bold.)

As The BigYinJames says actually doing the experiment would be quite difficult: the situation has been idealised to make the theory simple, which comes at the cost of making the experiment hard! But it could be done reasonably well if needed. Nobody bothers because the two disc result is just a trivial consequence of more fundamental properties (the behaviour of black bodies) which have been checked in great detail.

Perhaps a seat of learning in the UK could give us a quote for "doing the experiment reasonably well", and then any interested peasants here could decide whether to have a whip round if the cost is not an eyewatering sum.

Apr 24, 2012 at 7:06 PM | Unregistered CommenterBrownedoff

Jorge began his last post:

In my view it is really up to mdgnn to perform the experiment as he is the one who claims that text book theory does not apply in this case.

Did you find that opinion tedious as well? The lack of discipline of the Bishop Hill contingent arguing against conventional 'greenhouse' thinking is breathtaking. With the honourable exception of Jorge himself, who I'm very happy to listen to and learn from. This thread isn't your property, Brownedoff. I resented the implication that the burden of proof was on those holding to the textbook views and I said so. And I just have again.

Apr 24, 2012 at 7:24 PM | Unregistered CommenterRichard Drake

Apr 24, 2012 at 7:24 PM | Richard Drake

Did you find that opinion tedious as well?.

No, I respect that opinion because Jorge, having given that opinion, then went on to provide 12 column inches of interesting information and concluded by expressing the view that:

This experiment (i.e. Jorge's) should allow for a test of the text book equations.

I have already mentioned that I would like to see experimental results which are already, presumably, in existence - does it matter who does the work?

I have also asked for a quotation for doing the work, if indeed it is not already in existence, let us see what happens.

I agree this blog is not my property, his Grace can snip me at any time, equally, it is not your property either.

And I just have again.

Like I said, tedious, and now tedious repetition.

Apr 24, 2012 at 7:50 PM | Unregistered CommenterBrownedoff

Brownedoff, I'd love to see an experiment performed as a result of this thread and I think there's a solution at hand. Today mydogsgotnonose spoke about a large number of continental scientists that he claimed agreed with him about very low climate sensitivity to a doubling of CO2. Surely one or more of these academics is in a position to carry out the experiment? It's not just the "interested peasants here" that might be expected to stump up, as you suggested earlier, but those connections of mydogsgotnonose himself that we've got to consider. I look forward to hearing from you'all.

Apr 24, 2012 at 8:31 PM | Unregistered CommenterRichard Drake

Apr 24, 2012 at 8:31 PM | Richard Drake

You seem to be obsessed to the edge of reason with mmgnn; he is ploughing his own furrow and good luck to him.

If the relevant experimental results are in existence now, then why will the snooty academics not just share their working with the peasants? Here, free of charge - irrespective of the machinations of mdgnn.

Surely, UK academics are at least as inquisitive as their continental counterparts.

However, on Apr 12, 2012 at 10:19 AM | Jonathan Jones: (My bold.)

Nobody bothers ..

Maybe that is the problem, nobody, anywhere in the sun dappled groves of academe, is bothered.

By the way, good post, but I think that we should not bother our little heads with continental scientists, we have enough problems engaging with our home grown examples, although I am sure that they exchange e-mails.

Thank you and good night, I am an hour ahead of the UK here.

Apr 24, 2012 at 9:08 PM | Unregistered CommenterBrownedoff

You seem to be obsessed to the edge of reason with mmgnn

I promise you that's not true. Nor with the even tastier mmmgnn. I have been concerned that someone of that approximate acronym has been seeking to disrupt Bishop Hill and, by gaining adherents for his very low sensitivity views, without proper scientific foundation, based on rejection of his probably flawed understanding of back radiation, and for all of which one would certainly need at least one paper to assess, to waste the time of those with better things to do, to lead his followers astray and discredit all sceptics for their lack of judgment.

People may think this idea fanciful but if they do, please note that they have a lower opinion than I do of the importance this blog has gained. Definitely worth attacking in my book, from the perspective of those with vested interests running into billions, but not it seems from yours. And even if mmmgnn and his pseudonymous fanboys are an unfortunate accident I see the outcome as the same, at a time this blog and its host become truly influential, witness the presentation and discussion at St Andrews today.

Here's the solution: this person unknown should publish his paper for all to review, he should not interrupt threads with off-topic claims, he should desist from making claims that he cannot substantiate (like the ridiculous "rapidly evolving consensus from objective scientists is that real CO2 climate sensitivity cannot be more than ~0.3 - 0.4 K" interrupting the Goldacre thread yesterday) and he should give straight answers when challenged, rather than trying to change the subject and move on.

As I say, these behaviours combined in one pseudonymous package may be an unfortunate accident but we do well to consider the alternative. Trolls come in various forms, as The Air Vent and others have learned to their cost in recent days.

Apr 25, 2012 at 9:19 AM | Unregistered CommenterRichard Drake

Apr 25, 2012 at 9:19 AM | Richard Drake

Ah yes, I seem to have invented a new nom de plume if anyone wishes to adopt it: mymoggygotnonose. Sorry, a senior moment not picked up in preview, particularly with one eye on the action in Barcelona.

Look, I get it that you have a point of view about the activities of you know who and what he should do next.

However, in the first few posts on this thread it was said that the introduction of a two sided disc into the enclosure containing a heated one sided disc caused that one sided disc to achieve a higher temperature as a result. In addition, it was said that the introduction of further two sided discs would result in an ever higher temperature of the one sided disc at each step. It has been stated up-thread that, to double the temperature of the single sided disc, 16 two sided discs would be required.

It was also said these equations are widely used in the real world, in which case there must surely be in existence by now, a written report with log sheets, photographs, drawings, material lists etc. documenting a laboratory demonstration of the temperature increasing phenomenon at the one sided disc, as described up-thread. Nobody yet has owned up to possessing such a report.

Possibly because nobody has yet come up with a citation for such a laboratory demonstration, it can be seen on this thread that at least three contributors have tentatively suggested that a laboratory demonstration of this phenomenon might be a good thing.

I have gone further along that path and requested a quotation for such a laboratory demonstration because it has been stated on this thread that "it (i.e. the laboratory demonstration) could be done reasonably well if needed".

Apr 25, 2012 at 2:28 PM | Unregistered CommenterBrownedoff

Richard, the Goldacre thread which mdgnn interrupted so egregiously is about slamming his cock in a door, and is not really helping the reputation of this blog. Which depends on the reputation of the Bish himself, not his worst commenter. Now, mydog may be irritating, and may be bringing little new to his argument, but he does little harm. He may even be right, or rightish.

Oh, and the thought experiment? Nobody is going to test it. Nobody has done this particular test, and if any experiment were done, the same parties would take the same sides about the result no matter what. They'd crit the terms, the conditions, the failure to achieve perfect black body emissivity or whatever. It would not resolve anything. and even if it did, it would prove nothing, not one diddy little bit, about what happens in the real world in the atmosphere.

Apr 25, 2012 at 3:52 PM | Unregistered CommenterRhoda

Thankyou for that breath of frfesh air.
I was very interested in this discussion to start with and I'm grateful to Simon and Jonathan for starting it. I have learned something but not what I was hoping for.
The perfect black body and its behaviour with discs is fine but can somebody stretch that to the point of telling me what happens in a scenario where the original equipment for the experiment is in place but instead of disc 1 being the heat source, the heat source is independent and in order to heat disc 1 the radiation has to pass through disc 2.
That seems to me more closely to represent the situation that we actually experience. No?

Apr 25, 2012 at 5:08 PM | Registered CommenterMike Jackson

Rhoda: I disagree that the person unknown is harmless or that his ideas are harmless, until they've been laid out in a published paper and properly reviewed. But I agree that this month he became more harmless, because of the precision of Jones, Abingdon, Harvey and co here, and because of a person whose real name I am too modest to mention. After his latest claim of "rapidly evolving consensus from objective scientists that real CO2 climate sensitivity cannot be more than ~0.3 - 0.4 K" could not be backed up with a single published paper, and other such moments, his credibility is indeed reduced. But that required a challenge to which his answers were far from direct, leading to more distraction. Not harmless and not benign, in my book, but becoming less harmful as more people (and the anchor for 'more' has to be those using real names or longstanding pseudoni of integrity, to save us from the sockpuppet effect) realise that he's not worth the mind share.

I also think you're too negative about the decisiveness of real experiments in what you write here. But as Jonathan began with mind-experiment only I won't say more about that. Everyone, not least a professor of physics working on quantum computation, knows that the earth's atmosphere, plus oceans, plus biosphere, is a rather different thing. "The best model of the universe is the universe itself" and, despite being a strict subset, the climate system seems to me to exhibit the same property for most purposes.

Apr 26, 2012 at 5:51 AM | Unregistered CommenterRichard Drake

Apr 25, 2012 at 3:52 PM | Rhoda

Oh, and the thought experiment? Nobody is going to test it. Nobody has done this particular test, .......

What a shame.

Surely this phenomenon is so interesting that it should have a dedicated demonstration room at the Science Museum, South Kensington, London, SW7 2DD.

I imagine that the entrance to the room would be flanked by life-sized statues of Jožef Stefan and Ludwig Boltzmann and the room would be fitted out with an exact replica of the Faraday Lecture Theatre at the Royal Institution.

There would be demonstrations daily at 10am, noon, 2pm and 4pm. There would be a modest entrance charge (adults £6.00, children and OAPs £2.50).

The demonstrator (a Brian Cox look-alike?), who would have been cleared by a CRB check, would introduce an animated presentation displayed on massive plasma screens of Wallace explaining to Grommet what is to follow.

Wallace would describe the first stage where only one 2 sided disc is involved and then describe the follow up where eventually sixteen 2 sided discs are in action to show the reducing effectiveness of adding more discs in order to achieve a doubling of the initial temperature rise.

The apparatus would be mounted on a ludicrous plinth whose appearance is based on the one used in this clip.

I imagine that initially the sixteen two sided discs would be covered in Rex rabbit fur shrouds and there would be a system whereby the shrouds would be removed one by one by pulling on brightly coloured levers.

These levers would be operated by a series of cute children who would be invited down from their seats to stand with the demonstrator (hence CRB check) to do this job.

The apparatus would be fully instrumented for input power and the temperatures of the discs and this real time information would be displayed as moving images on the massive plasma screens.

A running commentary would be provided in the form of a voice-over performed by Rory Bremner giving his impression of Sir David Attenborough.

Background music would be provided by an endless tape playing whatever was top of the BBC singles chart that week.

Surely this event would be so popular that advance booking arrangements would have to be introduced.

Apr 26, 2012 at 8:13 AM | Unregistered CommenterBrownedoff

"Nobody has done this particular test, and if any experiment were done, the same parties would take the same sides about the result no matter what. They'd crit the terms, the conditions, the failure to achieve perfect black body emissivity or whatever. It would not resolve anything. and even if it did, it would prove nothing, not one diddy little bit, about what happens in the real world in the atmosphere."

That is a bit depressing don`t you think. There I was, happily thumbing through my well worn copy of Kaye and Laby looking at thermal conductivities of copper, air and the like when I read your post. What makes me sad is that you are probably right.

I should make clear that I have no special knowledge of heat transfer in general or radiation in particular. During most of my working life I styled myself as a jobbing electronics engineer, knocking up circuits to help other people make measurements that they thought would be of some value. In those days components could be seen by the naked eye and came with wires attached that could be joined together to make a circuit. The main practical problem was trying to bring four wires, a soldering iron and a bit of solder into the same space at the same time with only two hands! The procedure was always the same. First do a quick sketch followed by a few simple sums to choose component values. Join up the wires and the power supply, then connect up things like signal generators to the input and a scope to the output and then scratch your head when the observed patterns weren't quite what you were expecting. It was a very quick design build test redesign cycle. I think this experience is why I am so much in favour of experiment as the final arbiter.

Prior to the global warming scare nobody was complaining about the theoretical toolkit that had been put together to handle heat transfer by radiation, especially between solid surfaces. Practical meaurements on real surfaces were made years ago and all the geometric complications were well known. My problem is that there are now claims that the very foundations of radiation physics are wrong, mainly in an attempt to show that carbon dioxide can´t possibly ever affect the temperature of the surface of the earth.

My concern here is not about the huge complexity in the sun/surface/atmosphere/space problem but the attack on something as simple as the heat transfer between a few solid surfaces. The disc experiment may have been done a long time ago, but it is not a particularly interesting configuration for many practical purposes. It would be of interest to the designers of heat exchangers who use finned tubes that could radiate to each other instead of into the room. It is only now that radiating shells or atmospheres are so contentious that even the radiation between two discs is being challenged.

I am not at all surprised that this experiment has not been done nor am I surprised that someone like Prof. Jones would regard this as a trivial application of well known physics. You are quite right that some will want to say the experiment was flawed in some way and will carry on as before but if the result is replicable and clearly inconsistent with the theory, the cat really will be among the pigeons.


Apr 26, 2012 at 2:25 PM | Unregistered CommenterJorge

Brownedoff, I see you haven't been to the Science Museum in a while.

There's barely any science left there, instead replaced with strips of plastic hanging from the ceiling and flashing lights, and loads of interactive displays which appear to consist of wooden jigsaw puzzles with most of the pieces missing, or bioxes where you put your hand in and try to guess what the resin cast or a Once Real thing is in there.

Dumbing down isn't the phrase for it. The place isn't even on the dumb/clever scale.

Apr 26, 2012 at 2:32 PM | Unregistered CommenterTheBigYinJames

Apr 26, 2012 at 2:32 PM | TheBigYinJames

You are correct that I have no recent direct experience of the Science Museum.

I am not sure, but it may be that my sister took me there when we were visting London for the 1951 Festival of Britain.

London is not my favourite place for leisure activities; even when I was working in London for 5 years in the late 80s, every sinew was strained at knocking off time to get on the train to get out of the bl**dy place.

However, I have read various stories in blogs about its demise, that is why I tried to "fun" things up a little in my imaginary version of an exhibit at the Science Museum.

It has been said at least twice that the experiment is trivial, and yet there are comments on this thread which indicate that there are others who wish they could, however tentatively, get sight of a write-up.

So, as nobody will own up to having possession of a written report and nobody will submit a quotation for this trivial experiment and as it is unlkely that the Science Museum in its present state will put on a display, I might as well give up on this particular "disc" subject.

However, does anybody have a link to an existing write up of any interesting heat transfer demonstration which provides equally mind boggling results, i.e. has the "appearance" of getting something for nothing?

Thank you.

Apr 26, 2012 at 5:16 PM | Unregistered CommenterBrownedoff

OK, I admit to knowing practically nothing about reaitive physics. I couldn't even picture the disk experiment. I am aware of the propensity of such thought experiments to generate hundreds of blog comments, each one opposed to all the others. That's why I go on about measurements. The one with the square metre of surface. Does it heat faster in the daytime when the sun is on it? Does it lose heat slower at night? Does the failure to radiate as much as expected due to back-radiation (see, I know this is not illegal under the 2nd law) lead to more heat exchange via conduction, convection and evaporation? Does this mean a little heat is retained, or merely that it gets to min temp a little later, or maybe I should say gets not quite so far along the asymptote? Note, I don't want the theory. I want the measurements. Has anybody ever done that? Does the met office ever check its assumptions for models against that sort of data? It's the kind of thing I would do, if trying to convince a reluctant world to spend a lot of money. I can't see the warmists doing it, they are just models all the way down, dodgy proxies all the way back and scares all the way forward. I want to see better. Asking too much? Asking too often?

Apr 26, 2012 at 7:13 PM | Unregistered CommenterRhoda

Apr 12, 2012 at 9:32 AM simon abingdon

For a long time, when MDGNN was on about how the physics of greenhouse effect was erroneous "ask any chemical engineer/physicist" (if I r member his words correctly - not sure I do exactly), I asked for a reference to a textbook that would explain what he was saying - but I never seemed to get a clear answer.

The website Scienceofdoom makes a policy of not debating with people who want to discuss how the physics of the 20th century was fundamentally incorrect/photons don't exist and so on.

S.o.d. has a page on the claims that some people make that the normal understanding of radiative heat transfer is incorrect - you may have seen it - amazing-things-we-find-in-textbooks.

Apr 26, 2012 at 10:40 PM | Registered CommenterMartin A

I will post this to WUWT...maybe the US audience can help out - and Anthony W is not incli9ned to defend the likes of mdgnn

Apr 26, 2012 at 11:52 PM | Unregistered Commenterdiogenes

Apr 26, 2012 at 7:13 PM | Rhoda

I spent several years recently in the middle east and lived in an apartment block which was clad with marble slabs.

Our top floor dwelling (lowest rent in the block) had a terrace with low perimeter walls which were topped with marble slabs fully exposed to the sun.

At the height of one summer day, my wife fried an egg on the top of the wall in about the same time it would have taken in a frying pan. The weather section in the local English language paper said that the daily maximum temperature at that time was 49 deg C.

Local rumour had it that the Met Office there was not allowed to declare temperatures higher than 50 deg C because the local labour laws granted workers time off with pay if that temperature was exceeded. I recall many occasions at work standing in front of the site thermometer registering 50 deg C feeling nose hair gently toast with each breath.

In the late summer evenings those marble slabs were quite cool and very pleasant to lean against, but not capable of cooking eggs.

Is this a proxy for your one metre square plot?

Apr 27, 2012 at 10:47 AM | Unregistered CommenterBrownedoff

Brownedoff. Kuwait? I heard a rumour about that law when I was there. Yes, the idea of your roof marble, and say a square metre of ice in Queen Maud land all having their heat flows averaged to produce the trenberth budget seems flaky to me, if they can't even measure one example. Although I suppose space observation of the IR budget would do to compare against that average. If we could just possibly measure something rather than theorising I'd be happier. Do we measure the 3.7 watts thing? No, I don't think so. Do we even measure the back radiation in meaningful terms? I doubt it.

Apr 27, 2012 at 11:23 AM | Unregistered CommenterRhoda

I do wish people would stop trying to apply quantum mechanics to the macro Einstein/Newtonian world of Earth's climate.

At least not until some genius comes up with the Quantum Theory of Gravity.

As a mind exercise - What percentage of surface radiation would be re-emitted by CO2as 'back radiation' by an atmospheric concentration for CO2 of 0.039%, if we assumed that the emissivity of CO2 was over 1000 times greater at a figure of 1 [black body].

An awful lot less than the 40% quoted by the IPCC, and definitely only the tiniest fraction of a deg K.

May 1, 2012 at 12:55 AM | Unregistered CommenterRKS

Having proposed a new version of the disc experiment I felt I should try to check the validity of some of the assumptions. As I don't have any "feel" for the quantities the calculations rather surprised me.

The first surprise was just how small 100W/m2 is when applied to a 10 cm diameter disc. It turns out to be 785 mW so the heater could be run from a battery of quite reasonable size. What had worried me the most was the temperature difference between the faces of the discs because of the finite thermal conductivity. In fact for a copper disc, 1mm thick at 100W/m2, it is minute at 250 * 10-6 ºC.

As still air is known to be a superb insulator I had not expected much heat to transfer between the discs by conduction through the air. I was quite wrong to think this and the reality is that it almost completely drowns the heat transferred by radiation. I had calculated that there would be about 20ºC between the faces of the passive disc and the cooled disc by radiation alone. In fact conduction, with an air gap of 1mm, would reduce this to 4ºC without any radiation and the two combined would give about 3.3ºC. Much the same problem occurs betwen the faces of the heated and passive discs which were supposed to have a 16ºC difference by radiation alone. The reality is that this difference will also be close to 3.3ºC and will not prove much.

This needs some comment from our friend mdgnn as he maintained that without the conduction the temp difference between these two discs would be zero. It would seem odd that supplying an additional parallel path for the heat flow could actually raise the temperature drop.

It rather looks like a vacuum is needed after all to prevent the air conduction. Looking into this provided another surprise. The pressure needs to be around 1*10-3 mbar to have much effect. Not the sort of vacuum we could achieve with a reversed bicycle pump! The other thing I learnt is that in this reduced pressure regime the conductivity of the air is itself a function of the disc spacing. The smaller the gap the more the conductivity decreases so increasing the gap achieves nothing in the actual heat conducted.

I don't suppose this is very interesting to many readers but as it is tucked away on a small specialist corner of the blog it seemed appropriate to share what I had discovered.


May 1, 2012 at 2:24 PM | Unregistered CommenterJorge

May 1, 2012 at 2:24 PM | Jorge

Thank you for your further thoughts on the discs business.

In the meantime, I have been re-reading the first two pages or so of the thread and I came across something which had not clicked first time through:

Apr 13, 2012 at 9:58 AM | TheBigYinJames

The internal heater is providing the extra work.

If only the "thought experiment" had carried on to the point where the "demonstration" was complete, the heater was switched off and then what happened next was explained.

Presumably (I hope I have got this right), in time, both discs would eventually have equal temperatures of zero K?

I am going to stop now, because I am starting to wonder which disc gets to zero K first!

May 1, 2012 at 3:29 PM | Unregistered CommenterBrownedoff