I had (the idea) that…
Comment on Open thread by Rob Ellison
↧
↧
Comment on Open thread by Peter Lang
It certainly spread up – up to 100 km/h. the rates did change each time they raised and lowered the water level.
Much of what i wrote is not on the wen sites. I worked on the Revelstoke hydro project in BC Canada. A major part of the project was the stabilisation of a landslide up stream from the dam. The land slide is 2 km x 2 km in plan area and 300 m thick. It’s one great rock mass. It’s moved very slowly about 300 m down-slope towards the Columbia river since the retreat of the ice sheets. It’s moving slowly. The dam would flood the toe of the slide by about 100 m. It’s similar to Vajont in may ways. Much instrumentation was installed into it, tunnels dug into it and and modelling don on it. I was responsible for the on site geotechnical investigation work and then continued during construction of the stabilisation program. The stabilisation involved draining it by digging tunnels right through to the slide plain and drilling many kilometers of drain holes from the tunnels.
I posted this short video of the spillway in flood a while ago.
↧
Comment on Gravito-thermal discussion thread by Pekka Pirilä
Jim,
You continue to use a totally false argument
Spontaneously transitioning from an isentropic state to an isothermal one decreases entropy.
Transition towards isothermal does not decrease entropy, it increases entropy. That’s true by the most basic formulas of thermodynamics that involve entropy. That’s also part of the proof that a perpetum mobile of the second kind is impossible. All these formulas include temperature, not potential temperature, and that’s not by omission, but because that’s correct even under gravity.
Molecular diffusion takes place everywhere. It leads towards isothermal also under gravity. Eddy diffusion is a form of collective movement of gas that involves small parcels of gas, not individual molecules. Part of the molecular diffusion and related heat conduction occurs between parcels of gas that are considered in derivations that you seem to be familiar with, but it’s left out of the derivation, because its influence is negligible in most cases. In the phenomena that P-N and I have been discussing everything else is absent or so weak that heat conduction dominates in heat transfer. Therefore our conclusions are totally different from those obtained assuming that this effect is negligible. Those derivation are correct for the applications, where they are normally used, but they cannot tell anything on the mechanisms we have been discussing.
The Secod law tells that the total entropy of a closed system cannot decrease. That law does not tell that the entropy must increase until it has reached its maximal value. Formulas of thermodynamics that ignore diffusive processes allow for a non-maximal value of entropy to persist for ever, but including the diffusive phenomena of heat conduction and viscosity leads to the additional result that the total entropy of a isolates volume of gas will increase towards the maximum and is strictly constant only at that maximum. The state of the maximal entropy is isothermal,it’s not one of constant potential temperature.
↧
Comment on Super Pollutants Act of 2014 by rmdobservations
@Barnes I disagree. There are some real issues that cross state lines. That’s the necessity of this being at the federal level. Also workers and local populations who cannot move elsewhere need to be protected. Local government cannot be relied upon. The companies who are targetted have had decades to deal with their pollution (during good economic times) and their lack of improvement on their own only demonstrates that they need to be regulated.
I agree that good bills are very hard to find. (for example, I can agree with the necessity of Affordable care for all but think the bill itself is a gargantuan mess). This bill looks like a narrow focus bill which addresses a few small problems.
I believe that the mix of pollution and climate change is a mistake. CO2 is not a pollutant. I am en environmentalist but I believe the EPA has made a mistake by doing so and made matters worse. Calling these molecules “climate pollutants” is playing with words. I wonder how this phrase was chosen.
↧
Comment on Gravito-thermal discussion thread by Vaughan Pratt
<i>It would be nice if you could talk some sense into Jim D also!</i>
If Jim D can produce a force that would drive the isothermal column towards a better equilibrium I would be fascinated to see it. If not then his argument is all hot air from top to bottom.
↧
↧
Comment on Gravito-thermal discussion thread by David Springer
Pierre-Normand | December 9, 2014 at 3:28 am |
“David, I can’t follow your argument”
Well that’s nothing new. Centripetal force is mostly in the context of gravity and orbiting satellites which is why CaptDallas first mentioned escape velocity. Centripetal force caused by tension in a string or electromagnetism in a particle accelerator has no time dilation effect. This was proven beyond doubt in a experiment expressly meant to test it under electromagnetic centripetal force of 10^17 gees in a particle accelerator. Muon decay time was uneffected by trillions of artificial gravities but was effected as predicted by the velocity of the the particles. It’s not a complicated experiment if you can’t follow it you either don’t want to follow it or you’re incapable of following it neither of which is a flattering reason for the failure.
.
↧
Comment on Gravito-thermal discussion thread by Pekka Pirilä
The lower limit of conditional stability is not always 6°C/km, which is only a typical value. The actual limit is given by the moist adiabatic lapse rate for the actual local moisture level.
A conditionally stable atmosphere is stable against small deviations from its state, but not against very large ones.
↧
Comment on Gravito-thermal discussion thread by Pierre-Normand
Vaughan Pratt wrote: “If not then his argument is all hot air from top to bottom.”
I think it’s Gibbs free energy from the bottom up, but he doesn’t see it yet.
↧
Comment on Super Pollutants Act of 2014 by oppti
US can lead us into another focusarea-away from CO2 as leading greenhousgas. It will help the developing countries to deal with a real problem. Global dimming. Air in China is not healthy.
↧
↧
Comment on Gravito-thermal discussion thread by Vaughan Pratt
@PP: Vertical position in gravitational filed is a degree of freedom with energy proportional to the first power of the variable, while the power is 2 for kinetic energy
Where presumably the variables in question are respectively z-position (height) and translation (i.e. velocity, for which KE partitions conveniently by axis).
My sense is that the point you’re making obscurely about cp and cv is made clearly in Toth’s article as cited above. Is there a prior treatment of the point? If so it would be very interesting to see. If not, and if you have an alternative to Toth’s way of making the point, it would be great to see it so that people could compare it to Toth’s account.
There is nothing on this in the Wikipedia article on the virial theorem. Conversely I’m thus far unable to see anything in Toth’s account of cp and cv that makes any connection with what you wrote: “The average potential energy of each molecule is twice as large as the average energy of the each translational degrees of freedom.” Please clarify.
↧
Comment on Gravito-thermal discussion thread by Pierre-Normand
David, the text that you yourself quoted explains your mistake.
“The time dilation in a gravitational field does not depend on the local strength of the field, but rather “how deep you are inside” one. If the gravitational field is nearly uniform, so that it is almost as strong way up high as it is near the ground, then there will still be gravitational redshift of light climbing up against gravity.
My source here is the fine book “Gravitation”, by Misner, Thorne and Wheeler — the specific case you mention is discussed on p. 1055.”
Unfortunately, I misplaced my copy of MT&W, big and heavy as it is. It must still be in a box. I’ll try to dig it up.
Consider a rocket accelerated at constant g in deep space. A clock on the bottom of the rocket would lag with respect to a clock on top, right? This can be inferred from the principle of equivalence when you accept gravitational red-shift (or conversely when you accept special relativistic time dilation, you can infer gravitational red-shift and time dilation).
Now there is nothing very special about centripetal acceleration (apart from Coriolis forces). Suppose the acceleration vector of the rocket very slowly and uniformly rotates in a plane. Then the rocket will be moving in a circular trajectory, always pointing in the direction of the centripetal acceleration, towards the center of the circular trajectory. This is just another way to realize a centrifuge on a very large scale. The bottom clock is still going to lag at the same rate with respect to the top one. Just because the direction of the acceleration slowly changes ought not to change that.
↧
Comment on Gravito-thermal discussion thread by Pierre-Normand
Vaughan Pratt quoted Pekka: ““The average potential energy of each molecule is twice as large as the average energy of the each translational degrees of freedom.” Please clarify.”
See also this post for the same conclusion, and derivation, about this 2 to 1 ratio.
http://judithcurry.com/2014/12/01/gravito-thermal-discussion-thread/#comment-653483
↧
Comment on Gravito-thermal discussion thread by Pierre-Normand
For convenience:
The virial theorem and planetary atmospheres, Viktor T. Toth
↧
↧
Comment on Gravito-thermal discussion thread by Rob Ellison
‘Speaking of equilibrium means that the net fluxes of all properties determining the state of a system are locally balanced. Normally in a gas we associate this with constant pressure, density and temperature. But in a system, which is influenced by volume forces such as gravitation, the equilibrium state may well exhibit gradients of the state variables. Mass flow equilibrium in these systems is obtained by the balance between
the gravitational force and the counteracting pressure gradient, which is related to the density gradient by some equation of state. But if there is a density gradient in such a balanced system, there must be also a temperature gradient, balancing the Dufour effect, to obtain zero net energy flux. Below we will derive the equilibrium conditions for a system, which is fully relaxed with respect to
flux of mass, momentum and energy, within the scope of a simplified kinetic model.’ http://cds.cern.ch/record/631177/files/0307532.pdf
↧
Comment on Gravito-thermal discussion thread by Bryan
But an isothermal column has no lapse rate whatsoever – surely!
↧
Comment on Gravito-thermal discussion thread by Pekka Pirilä
Vaughan,
I don’t remember, where I learned about Virial theorem the previous time, but that reminded me on the connection between the power law that occurs in the energy component and the contribution of the related degree of freedom to the specific heat. That connection is presented in several places in the Wikipedia article. The related derivation for power-law forces can be found there. (What’s written on gravitating systems does not apply to this case as that’s applicable to planetary systems etc.)
The difference between Cp and Cv can be obtained from many different approaches, but pondering for a while starts to reveal that all those are really consistent, and must be consistent.
The easiest way of deriving the effect I mentioned is to calculate the energy per particle of monoatomic non-interacting molecules that bounce from warm surface in homogenous gravitational field. By bouncing from a warm surface I mean that their three velocity components just above the surface are distributed according to the Maxwell-Boltzmann distribution. The average kinetic energy of every orbit from the vertical velocity is 1/3 of the initial kinetic energy, and the average potential energy is 2/3. That applies to every flight from the surface back to the surface, and thus also to the average of all flights. Still the average vertical kinetic energy of particles is the same at every altitude (sounds paradoxical, but is true, as the barometric density profile makes it possible).
For interacting molecules that do not vary altitude like that the effect of pressure replaces the above derivation, but the result must be equal in strength for consistency.
↧
Comment on Gravito-thermal discussion thread by Pierre-Normand
That’s interesting.
↧
↧
Comment on Open thread by Rob Johnson-Taylor
UK’s Channel 4 program (apx 1hr in length)
The Great Global Warming Swindle
But perhaps you have all seen it
↧
Comment on Gravito-thermal discussion thread by Pekka Pirilä
Bryan,
Right. All lapse smaller than the moist adiabatic lapse rate are stable, including the zero lapse rate (isothermal) and all lapse rates of the opposite sign that result from heating the upper atmosphere. The Earth stratosphere is an example of that.
↧
Comment on Gravito-thermal discussion thread by Joe Born
Pierre-Normand: “This, together with the condition of ergodicity, justifies the probabilistic interpretation of canonical and microcanonical ensembles.”
Yet, I had gotten that far; what I had accepted without digging deeper, however was ergodicity; it was intuitively appealing and seemed non-controversial.
Anyway, I greatly appreciate the discussion. Not being a scientist, I was introduced to the equilibrium-temperature-profile question a few years ago at Science of Doom, but the discussion was ultimately unsatisfying because, although the disputants threw around the names of various scientific laws known to them, it really involved nothing more than plausibility arguments. When I later encountered Velasco et al. and Roman et al. at Tallbloke’s Talkshop, I saw papers that struck me as coming within shouting distance of rigorous, but they were intimidating. So I attempted to provoke scientist to discuss them at Watts Up with That when Mr. Eschenbach and Dr. Brown gave their laughable attempts at proofs, but I was taken aback at the poor quality of the discussion from the several scientists there. (Although some exhibited a better grasp of the physics than Dr. Brown has ever betrayed, they seemed unable to apply the physics logically.) And I have engaged Dr. Brown since then, too.
In short, I’ve had a number of blogosphere discussions of the topic. This has been the high-water mark.
↧
More Pages to Explore .....
