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Discussion > Its the Gas Laws what dunnit!

We all accept without doubt that the temperature at the centre of massive gas balls, compressed by gravity to a steady pressure, becomes hot enough to cause nuclear fusion. We also accept it without argument when astronomers tell us that the inner atmosphere of gas giants is hot due to gravity induced constant pressure. So why is it that people cannot accept the fact that gravity induced pressure can ALSO cause a temperature rise in the lower atmosphere of our planet. It's all there in the good old gas laws - If it's good enough for a star and Jupiter it's got to be the same for the Earth.

Jun 28, 2013 at 2:40 AM | Registered CommenterRKS

RKS,

It's not STATIC pressure which causes the heat which enables fusion to take place. It's dynamic pressure caused by gravitational collapse. If the hydrogen wasn't spinning into the centre with a great deal of kinetic energy then there would be no fusion. You're mistaken to think a gas at rest with respect to the gravitational centre would, under pressure, begin to fuse.

See Wikipedia (or any astronomy reference for that matter)
http://en.wikipedia.org/wiki/Stellar_evolution#Birth_of_a_star

Jun 28, 2013 at 8:10 AM | Unregistered CommenterTheBigYinJames

The second part of your argument that we all accept it's pressure which causes gas giants to be hot is also unfounded. A planet like Jupiter is hot for three reasons 1. remnants of the heat generated by gravitational collapse when it was formed. 2. absorbed solar radiation 3. In the case of Jupiter, adiabatic collapse (it's shrinking by 2cm a year, and this releases enough kinetic energy to heat it.

Things get hot under changing pressure, due to work being done on them - i.e. a hand pushing a pump, or gravity pulling something towards itself. They don't stay hot under constant pressure, which would be a violation of Thermodynamics and would make the air in footballs, car tyres and scuba tanks too hot to touch. (e.g. scuba tank at 100 bar should be 100 times hotter?)

Jun 28, 2013 at 9:39 AM | Unregistered CommenterTheBigYinJames

"Jupiter, adiabatic collapse (it's shrinking by 2cm a year,"

However can they measure that? A big ruler? And yet they can't find 2 watts per square meter right here on the surface of the earth, equivalent to finding the light bulb in my front room?

Jun 28, 2013 at 9:46 AM | Unregistered Commenterrhoda

Good question, it's all about Jeans Mass (gravitational collapse of gaseous clouds). I know we should take no-ones word for it, but you're taking it to extremes now :)

Jun 28, 2013 at 10:30 AM | Unregistered CommenterTheBigYinJames

I admit to becommig hugely disillusioned with science in recent years. I cling valliantly to the hope that at least physics is more solidly grounded in mathematics than man of the others. I've almost got to the stage my parents got when we kids were arguing en masse, slapping all three of us because while clearly somebody was right, somebody was wrong they had no way of telling which because we were all shouting. The slaps made us think twice about how important an argument was in the first place.

Jun 28, 2013 at 11:03 AM | Unregistered CommenterTinyCO2

TinyCO2,

I think the problem is that science, having exhausted the main avenues of research has moved onto areas where effects can only be seen by having immensely expensive equipment (e.g. LHC) or by processing data to tease out statistical effects.

While the LHC stuff is exciting, it's very lengthy and stop-start, and the results a bit esoteric.

The stats-based stuff is fraught with false-positives and dependent on data quality and length, and ultimately AGW may prove to be one of these false positives.

Making universities cow-tow to industry and govt for their funding over 20 years won't have helped, either.

Jun 28, 2013 at 11:23 AM | Unregistered CommenterTheBigYinJames

Don't think me rude, TBYJ, but we must try to keep our language clear, and your spelling of kowtow (or kow-tow if you prefer) repeats the error of many other bloggers and commentators, here and elsewhere.

Kow·tow (kou-tou, koutou)
intr.v. kow·towed, kow·tow·ing, kow·tows
1. To kneel and touch the forehead to the ground in expression of deep respect, worship, or submission, as formerly done in China.
2. To show servile deference. See Synonyms at fawn1.
n.
1. The act of kneeling and touching the forehead to the ground.
2. An obsequious act.

[From Chinese (Mandarin) kòu tóu, a kowtow : kòu, to knock + tóu, head.]


I take the opportunity to remind those whose spelling is erratic that the correct phrase is "to toe the line" and not "tow the line".

Jun 28, 2013 at 11:40 AM | Unregistered CommenterCassio

Cassio, I will be sure to tow the line on spelling in future and not cow-tow to the spelling zealots. In this way I will be hoisted by my own petard, and have my just desserts - yum!.

Jun 28, 2013 at 11:45 AM | Unregistered CommenterTheBigYinJames

Oh gawd, if I have to spell correctly and not make mistakes you'd shut me up entirely... err don't comment on that ;-)

In my defence, I not only have to manage my own flaws but my computer randomly moves my text cursor about the place and I can start typing anywhere or miss letters out.

Jun 28, 2013 at 12:01 PM | Unregistered CommenterTinyCO2

RKS is not going to be at all happy with what we did with his thread.

Jun 28, 2013 at 1:12 PM | Unregistered CommenterTheBigYinJames

RKS is not going to be at all happy with what we did with his thread.

Jun 28, 2013 at 1:12 PM | TheBigYinJames>>>>>>

when it comes to you and the astronomers I know who's word I'll take on celestial science!

Aren't you the know all who thought he knew better than the scientists who designed and studied the Lunar Diviner instrument?

Give me a break from pseudo scientific bullshit please.

Gas laws tell us kinetic energy in a product of volume and pressure.

Increased kinetic energy in combination with solar or cosmic background radiation increases the temperature of the highly energised gas molecules.

Bugger all to do with work done in a moving body.

Jun 28, 2013 at 3:43 PM | Registered CommenterRKS

RKS, sorry to see you return with the old anger, I was hoping we'd stick to the science.

Where do you think the energy comes from to energise these gas molecules?
Is the earth's gravity a perpetual motion machine?

Jun 28, 2013 at 3:53 PM | Unregistered CommenterTheBigYinJames

RKS, sorry to see you return with the old anger, I was hoping we'd stick to the science.

Where do you think the energy comes from to energise these gas molecules?
Is the earth's gravity a perpetual motion machine?

Jun 28, 2013 at 3:53 PM | TheBigYinJames>>>>>

Are you trying to say that kinetic energy is NOT a product of gas pressure and volume?

Have you actually read the [scientifically undisputed] gas laws and the formula for ascertaining the kinetic energy within the gas?

The gas molecules are energised exactly as predicted by the gas laws - unless of course you think that kinetic energy somehow does NOT energise the gas molecules.

As you deliberately chose to ignore what I said I'll repeat it for you, Solar radiation, or in the case of stars cosmic background radiation, when acting on the energised molecules increases the temperature in proportion the the kinetic energy. Nikolov and Zeller, much much better scientists than you'll ever be with your student level nonsense, have done all the maths for you based on measurement of 8 solar system atmospheric bodies.

Of course I get angry with know all pratts who who try to invent their own version of the laws of nature. As for your description of Jupiter - you made that up in your head, I've never heard any astronomer describe it the way you do. I suggest you stick to programming and leave the real science to the experts.

Jun 28, 2013 at 4:19 PM | Registered CommenterRKS

"Jupiter, adiabatic collapse (it's shrinking by 2cm a year,"

However can they measure that? A big ruler? And yet they can't find 2 watts per square meter right here on the surface of the earth, equivalent to finding the light bulb in my front room?

Jun 28, 2013 at 9:46 AM | rhoda>>>>>

Good point rhoda - it must be documented somewhere along with how they actually arrive at that figure.

Jun 28, 2013 at 4:23 PM | Registered CommenterRKS

The gas molecules are energised exactly as predicted by the gas laws - unless of course you think that kinetic energy somehow does NOT energise the gas molecules.

Let me rephrase:

Where does the kinetic energy come from to energise the gas molecules?
What imparts this kinetic energy to the molecules?

Jun 28, 2013 at 4:25 PM | Unregistered CommenterTheBigYinJames

Nikolov and Zeller contend that the temperature of a planet was not dependent on the rate of rotation. It is though. That renders their formula invalid on a fast-rotating planet. IMHO, of course.

Personally I contend that a still atmosphere in the absence of external radiation will be isothermal. But that has not a lot to do with the earth.

Jun 28, 2013 at 4:39 PM | Unregistered CommenterRhoda

Where does the kinetic energy come from to energise the gas molecules?
What imparts this kinetic energy to the molecules?

Jun 28, 2013 at 4:25 PM | TheBigYinJames>>>>>

If you knew the gas laws you wouldn't ask such a stupid student level question.

From the kinetic theory of gases....

Where P = pressure

V = volume

K = kinetic energy

PV = 2/3K

Thus, the product of pressure and volume per mole is proportional to the average (translational) molecular kinetic energy.

If I increase the pressure of a fixed volume of gas I increase it's kinetic energy [ie I impart kinetic energy to the gas molecules], which will remain constant as long as the gas pressure remains constant. The formula says it all!

If you add energy to a body it has been 'energised' - plain English. It makes no difference how a gas is compressed, whether by gravity or some form of pump, the theory, and result, remains the same.

As I said before, radiation acting on energised gas molecules increases the temperature of the gas, the greater the kinetic energy the higher the temperature [N&Z for the maths, they've worked out the constants]. For stars the background cosmic radiation of 2.8K, when acting on the immense pressures within the gas cloud, produces temperatures high enough to initiate fusion.

Jun 28, 2013 at 4:53 PM | Registered CommenterRKS

Nikolov and Zeller contend that the temperature of a planet was not dependent on the rate of rotation. It is though. That renders their formula invalid on a fast-rotating planet. IMHO, of course.

Personally I contend that a still atmosphere in the absence of external radiation will be isothermal. But that has not a lot to do with the earth.

Jun 28, 2013 at 4:39 PM | Rhoda>>>>>

That remains as a matter of personal opinion on this blog rhoda, I've seen powerful arguments to counter this idea on other science based blogs [eg Tallbloke]. The highly experienced NASA scientist who developed the Lunar Diviner probe to measure the temperature of a rotating moon, and who subsequently worked with N&Z when developing their theory, thinks otherwise. Do I go with the opinion of a highly qualified physicist or what seem to be intuitively correct, ie gut feeling? I'm afraid in this case I'll go along with the empirical results made by the physicist who designed the equipment. N&Z's calculations for atmospheric temperature are based on mean insolation - they are completely independent of rotation as the long term mean, 10's - 100's of years or more, is what they base their theory on - please read it in a little more detail of you are unsure about that.

Jun 28, 2013 at 5:14 PM | Registered CommenterRKS

Well, if a planet was rotating infinitely fast the surface temp would be the same all over. If it was stationary, the temp would be half hot and half cold. Because of t^4 the average temp is not the same in both cases. So the rate makes a difference. When we looked at the moon's measured figures they did not match the average the radiation-based figures would have us believe. That story about half a disc-worth of insolation and a whole sphere's worth of outgoing, that turned out to be just not so. We did all the work right here, and rotation makes a difference in real life. It does not average out.

(And I believe the use of averages when discussing climate science is the reason for much misunderstanding. Reject all averages when people are trying to explain something to you. Accept only actuals..)

Jun 28, 2013 at 5:51 PM | Registered Commenterrhoda

We did all the work right here, and rotation makes a difference in real life. It does not average out.

(And I believe the use of averages when discussing climate science is the reason for much misunderstanding. Reject all averages when people are trying to explain something to you. Accept only actuals..)

Jun 28, 2013 at 5:51 PM | rhoda>>>>>

I saw an interesting knock about discussion with LOTS of different personal opinions and that's fine, this is a discussion blog after all and, unlike serious science blogs like Tallbloke, only two or three regulars usually argue it out between themselves.

You seem to imply that the scientists designing and measuring the Lunar Diviner instrument, in the many years of developing it, somehow did not do their collective homework and 'forgot' to allow for the fact that the moon was rotating. I regard that as highly improbable as NASA must have experts in celestial mechanics by the hundreds. For my part I will defer to NASA and take the Diviner results and interpretation as factual and how this applies to bare Earth without an atmosphere ie before the so called greenhouse effect of an atmosphere is applied. Once an atmosphere is applied it rapidly becomes mixed throughout the planet, largely due to coriolis effects, and mean long term insolation becomes an accurate measure of net energy input to the system. Because the atmosphere stores and redistributes heat it is neither boiling on the sunlit side or way below freezing at night.

Jun 28, 2013 at 6:22 PM | Registered CommenterRKS

"You seem to imply that the scientists designing and measuring the Lunar Diviner instrument, in the many years of developing it, somehow did not do their collective homework and 'forgot' to allow for the fact that the moon was rotating."

I used their results. I don't know what their opinion was, I used the measurements they came up with, including a temperature average which does not match the disc vs sphere calculated number. Because of rotation speed. The moon being slow enough to pretty much stand in for a non-rotating planet. The earth rotates fast enough to equalise temps quite a lot, although not quite enough to be equivalent to the infinitely fast rotation case. The rotation makes a difference. It can't be discounted in the case of a thin atmosphere earth. Although I do believe a non-GHG atmosphere would still help to retain heat. I just think earth has too many special case factors to be subject tto the N&Z formula. You just can't make the sort of inter-planetary comparisons they make with such abandon. Rotation and water make enough difference on their own, never mind GHGs, and none of them are in the N&Z formula. There is no validity at all in comparing some figure of what earth's average temp 'ought to be' with what it is when measured with thermometers and fed through a dodgy algorithm to average it. Yet we see people put it up as an argument all the time.

Jun 28, 2013 at 6:49 PM | Registered Commenterrhoda

RKS,

Charming as your insults are, let's stick to the science.

If I increase the pressure of a fixed volume of gas I increase it's kinetic energy [ie I impart kinetic energy to the gas molecules], which will remain constant as long as the gas pressure remains constant. The formula says it all!

We're getting close.

You have a sealed box, with a gas at a certain temperature and pressure.
You have increased the pressure and thus increased its kinetic energy, very good.
No disagreements here, all according to the laws of physics.

How exactly have you increased the pressure? You've turned on an electric pump, or pushed in a manual pump, or otherwise collapsed the box using energy. You haven't increased that pressure and temperature for free. The only way of increasing the pressure inside the box (apart from adding more molecules) is to compress it into a smaller volume, which involves the expenditure of energy. You have to push the molecules (which want to expand through entropy) into a smaller space, this means spending energy.

It's this energy which heats the gas. It doesn't come from the 'pressure'. Both the increase in pressure and the increase temperature is coming from the work you did compressing the gas. This is what the Ideal Gas equation is telling us - that pressure and temperature are flip sides of the same coin - they are effects of energy, a way we measure energy, but not a source of energy itself.

Temperature is a measure of 'kinetic energy per volume of space'. Pressure is a force produced when the molecules bash that kinetic energy against the sides of the box. The ideal gas laws tell us temperature and pressure are aspects of the same thing, not that one is the driver of the other.

But also remember that the Ideal Gas law is ideal because it ignores other ways that the gas in the box can change temperature. The box is assumed to be completely insulated. In the real world, you would compress your gas and observe the temperature and pressure go up and you could conclude that the gas laws are wonderful, so you would go out for a drink at the pub.

You'd tell your friends that you converted the energy in your arm into temperature in a gas, and they would adore you as a god.

The next day you would come back, and you would be startled to see that the temperature had fallen, in fact almost right back to where it was before you compressed the gas. You check the pressure reading - that has fallen too. You check for leaks, but there are none. What on earth has happened?

You check the IR cameras you sneakily installed to watch the experiment. The box was glowing hot after the experiment, and as the night went on, it cooled. Energy was escaping through radiative heat from the surface of the box. Overnight, a great deal of the extra kinetic energy was transferred from the gas molecules to the box molecules, which were only too happy to radiate it at IR wavelengths out into the room.

Back on the earth. Atmospheric air under pressure near the surface does not have any work done on it - gravity has already collapsed it as far as it can. The air isn't any hotter than the mountains it surrounds. Any extra kinetic energy that being compressed might have given it has long ago dissipated in radiative heat, just like the cold pressurised air in your morning box. Gravity can only give it more kinetic energy if it has lost potential energy, i.e. it has fallen in a gravitational field. It CANNOT continue to heat the air against radiative loss indefinitely, that's not how potential energy works.

A static pressure cannot induce a static temperature. A change in pressure can induce a change in temperature, but that temperature will subsequently fall as it radiates away, and only by further compression could be heated again.

Something for you to ponder between thinking up new insults.

Regards.

Jun 28, 2013 at 6:59 PM | Unregistered CommenterTheBigYinJames

A static pressure cannot induce a static temperature. A change in pressure can induce a change in temperature, but that temperature will subsequently fall as it radiates away, and only by further compression could be heated again.

Something for you to ponder between thinking up new insults.

Regards.

Jun 28, 2013 at 6:59 PM | TheBigYinJames>>>>>

I'm sorry if you find me rude but I find your condescending and quite frankly hubristic posts almost insufferable. Adopt a different tone when dealing with others and you might get a different reaction. I might add that this thread and it's title, because of past experience, were aimed at you and the fact you were the first to post provided me with a small degree of satisfaction.

How many more times do I have to repeat what is clearly written on the page but ignored by you in every one of your posts. I did not say temperature rise was a result of pressure alone, and please don't try to rewrite the gas laws - they apply to planets perfectly well

The rise in temperature is caused by external radiation acting on energised gas molecules!!! N&Z have produced mathematical constants, based on empirical measurement of 8 atmospheric solar system bodies, by which the temperature rise can be calculated for different combinations of kinetic energy and insolation. If you disagree with what I regard as your scientific betters that's fine by me, but perhaps you might explain why an irradiated pressurised gas would not increase in temperature and why, if the pressure of this irradiated gas was increased, resulting in a net increase in it's kinetic energy, why the temperature of this now more highly energised irradiated gas would not also increase. Just to be absolutely clear I am referring to an irradiated gas.

Your arguments have all been dealt with a dozen or more times over on the Tallbloke blog. Why not look at the threads there, not only regarding N&Z and their many answers to questions posed, but regarding the effects of the gas laws on atmospheres in general. Look at the arguments in the posts and perhaps then decide what is and isn't possible. By the way, I looked up the Wiki entry on Jupiter and the 2cm per year contraction and adiabatic contraction were both referred to as covered by the Kelvin Helmholz Mechanism, a theory dating from the 19th century, although I assume the 2cm figure was derived mathematically.

Jun 28, 2013 at 8:03 PM | Registered CommenterRKS

First, scientists can be wrong. Whenever two disagree, at least one is wrong. it is no use bringing argument from authority into it. Rotation makes a difference. I don't know how much, but when some person of whatever qualifications comes up with a formula which omits rotation, I suspect he is mistaken.

Eschenbach thinks N&Z are curve-fitting with their chosen parameters. He may be right.

TBYJ gives a clear explanation of what the ideal gas law says. I am not clear at all as to how it works in the absence of 'work done' but I reckon a non-insolated atmosphere will all go to the same temperature and on a sunlit planet the surface will heat the gas, inducing convection. But when there are GHGs and three-state H2O, and rotation and tilt, those things dominate what happens to the sunlight.

Jun 28, 2013 at 9:10 PM | Unregistered CommenterRhoda