|Perpetmo (Image source)|
I am not a physicist, but I believe that the second law of thermodynamics is rather widely accepted among physicists, which leads me to the conclusion that an unintelligible paper published in an obscure journal, which purports to refute the second law, should be regarded with considerable skepticism.
As discussed in an earlier post, such a paper was recently reproduced at Roger Tattersall’s popular Tallbloke’ Talkshop, prompting refutations over at Anthony Watts’ WUWT, first by Willis Eschenbach and, today, by Robert Brown of the Duke University Physics Department.
But Hans Jelbring, author of this remarkable theory, has struck back promptly at the Talkshop with a new derivation of his theory. Unfortunately, the new derivation does not address the inherent absurdity of the conclusion, which seems to be contradicted by any number of simple observations.
Tallbloke, himself, is an advocate of the Jelbring “thermo-gravitational” hypothesis, asserting the Jelbring’ thesis as follows:
… gravity causes there to be a temperature gradient from cold high up, because more of the total energy is locked away as gravitational potential energy compared to warm at the bottom where the near surface air is hotter than the average because less of the total energy is locked away. Again, total energy remains equally distributed throughout the troposphere, as the second law of thermodynamics demands, but because of the difference in gravitational potential energy between molecules at the bottom and top, there is a thermal gradient.
My own off the cuff refutation of this was as follows:
Consider an airless, sunless planet without an internal heat source that passes through a cloud of gas, thereby acquiring an atmosphere.
Initially the planet surface temperature will approximate to the microwave background temperature of 2.75 K. However, as gas accumulates around the planet, the gas is compressed gravitationally, with resultant heating in accordance with the gas laws. The warmth of the atmosphere will heat the planet surface, which will then radiate more energy than it receives from outer space.
Eventually, the thermal energy released in the gravitational compression of the atmosphere will be entirely dissipated, by which time the temperature of the planet surface will have returned to its original value of 2.75 K, though the atmospheric pressure gradient from the surface to outer space remains.
So the gravitational effect on the surface temperature is transient only.
According to this account, the internal temperature of large gas planets must be due either to residual heat acquired during the process of formation, or produced by nuclear reactions, such as as account, in part, for the Earth’s internal heat.
Is this not correct?
Tallbloke, to whom this argument was addressed, made no response. Several others did respond, but with what appeared to be spurious objections, for example, that my argument would be invalid if I made my planet spin, or if I added a sun.Other objections were no more compelling.
In his new derivation of the hypothesis, Jelbring considers:
…two air parcels of equal and suitable mass (a billion molecules) which have to carry an equal amount of total energy regardless of their altitude if an adiabatic condition is assumed.
The proof that follows is mathematical, but the essence of it appears to be that as a parcel of air is raised or lowered in the Earth’s gravitational field its gravitational potential energy is increased or decreased with a corresponding decrease or increase in temperature, thus maintaining total energy constant.
Now the concept of potential energy is not the easiest thing to grasp, and so the Jelbring hypothesis may have some plausibility. But if one considers the various implications, as does the above-cited Robert Brown, one sees that they flatly contradict the second law of thermodynamics, the law that outlaws perpetual motion machines and free energy.
My own attempt at a refutation at the Talkshop, is as follows:
If your packets of air are in rigid, sealed capsules, you can raise them or lower them in a gravitational field as much as you like and they will undergo no change in temperature, even though you have changed their gravitational potential energy.
From this we can infer that the change in gravitational potential energy of air with altitude does not explain the change with altitude in air temperature, which results from the work done as the gas is compressed or expanded with change in barometric pressure with altitude.
Whether that settles the argument for all reasonable people, I leave for reasonable people to decide, but at least my conclusion places me on the same side as the Duke University Physics Department, which I find encouraging.
But in any case, if Hans Jelbring does not want to be affronted by non-physicists continually claiming to have rubbished his theory, he really has no one to blame but himself, since he has failed to put it to the test of the professional physics community by having it published in a reputable physics journal. He has, it is true, published his thesis, but in a sociology journal edited by a retired geography professor, which as I discussed in an earlier post, absolutely does not rate in the eyes of the scientific community.
So what are we to conclude? Seemingly, that popular websites dealing with scientific topics can be swamps of obscurity, nonsense and misinformation. Or is there something sinister at work here? Are we seeing an attempt to discredit the climate warming skeptics by associating them with bogus science, or perhaps part of a general effort to convince the public that the blogsphere as a whole is wasteland to be avoided for the safety and reliability of the mainstream media? But more on that in another post.