Solubility of CO2 in Water vs. Greenhouse Effect?

[peadar1987]

"Kelvin-Helmholtz mechanism " is merely a fancy term for "expanding and contracting in a cycle". The mechanism can't actually produce any more heat than if the planet simply sat in the center of the cycle at the stable pressure point. Bottom line: the internal pressures within the planet Jupiter are retaining the heat that was created when the planet formed; the planet is cooling (and shrinking!) but it's a multibillion year process.

It's not pressure that retains the heat, it's the thermal mass of Jupiter. Higher pressures only allow the mass to be more concentrated.

Jupiter's expansion and contraction isn't an isentropic process. The conversion between gravitational potential, kinetic, and pressure potential energy is not a perfectly efficient process. Entropy increases, and results in a release of heat, in a process known as hysteresis.

Alrightey, here's a puzzle for you: there's been a lot of talk about how it's a change in pressure that causes a change in temperature. So here's the puzzle: you've got your gas chamber full of gas, and a piston to compress it. You were saying the gas will only heat up if the volume goes down.

So what happens if the volume doesn't go down? You apply pressure to the piston, but the volume doesn't decrease. In real-world physics, for that to happen, something must push back against you when you push on the piston. Normally it's temperature; the gas heats up, which causes it to push harder against the compression. But if that doesn't happen......what else can? What else could possibly produce the force that prevents the compression from occurring?

The volume will go down. If the system is in equilibrium, applying a force to the piston will upset that equilibrium. The system will adjust by decreasing in volume. A decrease in volume results in an increase in pressure. This will also result in a slight temperature increase, which will gradually dissipate to ambient temperature again, so what you will see when you apply force is a sharp displacement of the piston until the increased pressure cancels out the applied force, and then a far slower displacement as the gas cools back to ambient temperature and contracts.

If the volume doesn't go down, there are a few options:

-The piston is sticking due to friction, and there is no change in the state of the gas.

-There is some external force acting on the gas to increase the pressure as you apply your force, e.g. an external heat source

-The system was not at equilibrium in the first place. The forces were unbalanced, the piston was moving, and you just happened to come along and apply a force at the right time in order to restore equilibrium and stop it.

[arkie87]

a change in pressure will tend to cause a change in pressure

Change one of the pressures to temperature?

[AngelLestat]

Are you all still waiting some kind of gratitude or honesty from WedgeAntilles?

Since the begining, he was corrected on co2, energy processes and sources, jupiter potential energy and many other things, apparently he realized that was wrong because he is changing his words now; trying to find some kind of loophole in the coments to not accept the mistake.

[arkie87]

Both of which are ideal cases that can't actually happen.

Isentropic compression: no heat is lost. In real-world thermodynamics, that's impossible. There's no such thing as a perfect insulator; some heat must always be lost to the surroundings.

Isothermal: constant temperature. Yes, in theory V could go down in order to keep T constant. But that process can't happen instantly. It takes time. In the interval, T still goes up. Eventually T will then go back down as the system cools, but that also takes time. In some cases (one of which has a name that starts with the letter J......) the process takes a few billion years.

So, i dont understand what you are arguing then. The discussion was about Venus being hot because it was compressed. There is no Kelvin-Helmholtz mechanism, and there is no reason the atmosphere would have undergone isentropic compression recently.

And arguing that "technically, the process doesnt happen instantly, so that increasing pressure always results in an instantaneous (albeit fleeting) increase in temperature is a pointless point to argue for the sake of being technically right... if that is what you are arguing, then i have no desire to continue this conversation.

Alrightey, here's a puzzle for you: there's been a lot of talk about how it's a change in pressure that causes a change in temperature. So here's the puzzle: you've got your gas chamber full of gas, and a piston to compress it. You were saying the gas will only heat up if the volume goes down.

Actually, what i said that if the volume goes down, either temperature or pressure or both must change to satisfy the ideal gas law. There are three variables (pressure, temperature, and volume), and if you specify a change in one, with the ideal gas law, you still have one degree of freedom (2 equations with three unknowns), so there are infinite solutions. The third equation, which decides which of the infinite solution actually occurs, comes from the process used to get there (isothermal, isentropic, isobaric, isochoric etc...)

So what happens if the volume doesn't go down? You apply pressure to the piston, but the volume doesn't decrease.

This case you are describing is impossible (assuming there is no friction etc... or other monkey business).

In real life,if you apply a force to a piston previously at equilibrium, the gas will not spontaneously heat up in order to maintain at constant volume; it will compress.

It is possible, however, to increase the force at a steady rate while adding heat to the gas to maintain equilibrium. However, applying additional force will not, on its own, increase the temperature to oppose motion while maintaining its original volume. Heat must be added.

In real-world physics, for that to happen, something must push back against you when you push on the piston. Normally it's temperature; the gas heats up, which causes it to push harder against the compression.

Temperature doesnt (directly) generate a force; pressure does. You can have two gasses at different temperature but at the same pressure and the forces will be the same; two gasses at the same temperature will not generate the same force unless they are also at the same pressure.

And as i said above, the temperature cannot increase unless volume is reduced.

But if that doesn't happen......what else can? What else could possibly produce the force that prevents the compression from occurring?

Nothing. If a piston is initially at equilibrium and you apply force to it, it will reduce in volume until the pressure increases enough to oppose your additional applied force. It will not spontaneously heat up without reducing in volume.

If you think this is possible, then there is a serious misunderstanding of the physics here...

Edited August 10, 2015 by arkie87

[arkie87]

If you could find a gas with Cp~=Cv; i.e. gamma = 1, then the gas would not heat up upon compression.

The smallest gamma i could find is for n-heptane with a value of 1.05

Isentropic processes follow: P*V^gamma = constant. If gamma is 1, then P*V=constant, so T cannot change.

To reiterate, the fact that T increases is due to the process that is used to get there; not from the compression itself.

If you had a 1 m3 volume of gas at 300 K and 1 bar pressure, and increased the pressure by a factor of 2 isentropically:

For air: gamma = 1.4, so T would increase to 365.7 K. Because of the increase in temperature, volume would only decrease to 0.6095 m3 (notice the ratio of 365.7/300 = 0.6095/0.5).

For n-heptane: gamma = 1.05, so T would increase to 310.1 K, and V would decrease to 0.5168

For a gas with gamma = 1, T would remain at 300 K and V would decrease to 0.5

Edited August 10, 2015 by arkie87

[arkie87]

The volume will go down. If the system is in equilibrium, applying a force to the piston will upset that equilibrium. The system will adjust by decreasing in volume. A decrease in volume results in an increase in pressure. This will also result in a slight temperature increase, which will gradually dissipate to ambient temperature again, so what you will see when you apply force is a sharp displacement of the piston until the increased pressure cancels out the applied force,

I suppose if the piston had mass, the inertia would allow the piston to over-compress, until the pressure stopped the momentum, which would then lead to expansion, and over-expansion, etc...

Which seems very similar to Kelvin-Helmholtz contraction to me...

and then a far slower displacement as the gas cools back to ambient temperature and contracts.

This is isothermal compression. I dont know enough about Kelvin-Helmholtz contraction, but this sounds an awful lot like it...

If the volume doesn't go down, there are a few options:

-The piston is sticking due to friction, and there is no change in the state of the gas.

-There is some external force acting on the gas to increase the pressure as you apply your force, e.g. an external heat source

-The system was not at equilibrium in the first place. The forces were unbalanced, the piston was moving, and you just happened to come along and apply a force at the right time in order to restore equilibrium and stop it.

If the first or last have anything to do with his response, i quit

[KerikBalm]

"Kelvin-Helmholtz mechanism " is merely a fancy term for "expanding and contracting in a cycle". The mechanism can't actually produce any more heat than if the planet simply sat in the center of the cycle at the stable pressure point. Bottom line: the internal pressures within the planet Jupiter are retaining the heat that was created when the planet formed; the planet is cooling (and shrinking!) but it's a multibillion year process.

*sigh* when things as wrong as this are posted, one must wonder if it is even worth arguing

"expanding and contracting in a cycle"

There is no cycle of expanding and contracting.

It is continual contraction.

"The mechanism can't actually produce any more heat than if the planet simply sat in the center of the cycle at the stable pressure point."

There is no cycle, so this statement is completely non-sensical.

What happens, is that as the planet contracts, the potential energy is converted the thermal energy.

Suppose you have X tons of material Y thousand kilometers from the center. As it contracts, those X tons are now Y-Z thousand kilometers from the center... they have less potential energy.

Where did that energy go?

Heat.

That is the Kelvin-Helmholtz mechanism

"the internal pressures within the planet Jupiter are retaining the heat that was created when the planet formed"

Pressures don't retain heat.

High pressure does not require heat, nor does it cause heat.

Contractions, changes in volume, etc.. like most things where a "change" is involved, do change the energy of the system, and thus the heat of the system.

There's no contraction going on of any relevance on Venus.

Jupiter is hot because it is massive.

None of this has any relevance to global warming.

Venus is hotter than Mercury because of its thick CO2 atmosphere, despite having a much higher albedo.

You can try and distract people from the argument all you want, but I'm calling you out.

All this is an attempt to distract from the real argument which you cannot win, and discredit your opponents with minutiae.

The "greenhouse gas effect" is mechanistically sound, it is easily and repeatedly demonstrated in the lab.

At the planetary scale, one can only make observations, not experiments, but we have observations confirming it.

Venus is hotter than Mercury.

Explain that... you can't just wave your hands and call it an "anomaly"

Pressure does not explain it. Jupiter radiates more heat than it gets from the sun, like any other body that is cooling down. Its massive, it has a lot of potential energy, it takes a long time to cool down.

[arkie87]

*sigh* when things as wrong as this are posted, one must wonder if it is even worth arguing

"expanding and contracting in a cycle"

There is no cycle of expanding and contracting.

It is continual contraction.

"The mechanism can't actually produce any more heat than if the planet simply sat in the center of the cycle at the stable pressure point."

There is no cycle, so this statement is completely non-sensical.

What happens, is that as the planet contracts, the potential energy is converted the thermal energy.

Suppose you have X tons of material Y thousand kilometers from the center. As it contracts, those X tons are now Y-Z thousand kilometers from the center... they have less potential energy.

Where did that energy go?

Heat.

That is the Kelvin-Helmholtz mechanism

"the internal pressures within the planet Jupiter are retaining the heat that was created when the planet formed"

Pressures don't retain heat.

High pressure does not require heat, nor does it cause heat.

Contractions, changes in volume, etc.. like most things where a "change" is involved, do change the energy of the system, and thus the heat of the system.

There's no contraction going on of any relevance on Venus.

Jupiter is hot because it is massive.

None of this has any relevance to global warming.

Venus is hotter than Mercury because of its thick CO2 atmosphere, despite having a much higher albedo.

You can try and distract people from the argument all you want, but I'm calling you out.

All this is an attempt to distract from the real argument which you cannot win, and discredit your opponents with minutiae.

The "greenhouse gas effect" is mechanistically sound, it is easily and repeatedly demonstrated in the lab.

At the planetary scale, one can only make observations, not experiments, but we have observations confirming it.

Venus is hotter than Mercury.

Explain that... you can't just wave your hands and call it an "anomaly"

Pressure does not explain it. Jupiter radiates more heat than it gets from the sun, like any other body that is cooling down. Its massive, it has a lot of potential energy, it takes a long time to cool down.

It is pretty widespread the (false) idea that things are hotter because they are under pressure:

"Since Jupiter is a gas giant, it has no solid surface, so it has no surface temperature. But measurements taken from the top of Jupiter’s clouds indicate a temperature of approximately -145°C. Closer to the center, the planet’s temperature increases due to atmospheric pressure."

from Universe Today

I even remember hearing that as a kid, even though it is wrong.

[GeneralVeers]

Are you all still waiting some kind of gratitude or honesty from WedgeAntilles?

Since the begining, he was corrected on co2, energy processes and sources, jupiter potential energy and many other things, apparently he realized that was wrong because he is changing his words now; trying to find some kind of loophole in the coments to not accept the mistake.

I stated very clearly, and more than once, that I disagreed with your corrections and explanations and counterarguments, and I explained why. And not just yours, either. If you're not going to read them, or if you're going to ignore them or talk past them or whichever it is, I have no reason to bother typing in here. For all practical purposes, just assume I disagreed with you about everything.

then i have no desire to continue this conversation.

That makes two of us. You and I got our wires crossed in a couple of places in the last few posts, but yeah. Not worth bothering about.

I will point out this, though: the arguments this thread have devolved into are the perfect answer to the question you asked in the very first post: what's wrong with the charts you posted on the first page? The biggest problem is that the participants are talking past each other and refusing to listen to each other. Global warming skeptics and alarmists (mostly the alarmists) are dismissing the other side's arguments out of hand, usually with "look, the community has already reached a consensus, and anything to the contrary is not worth considering".

Or did I already cover that when I answered "people are just plain stubborn"?

See ya.

[peadar1987]

Em, there are 8 pages of evidence right here that people who accept AGW are not just refusing to listen. We provided a structured, point-by-point refutation of your arguments, and you are the one who is saying "I just disagree".