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Post by socold on Feb 25, 2009 2:31:13 GMT
what does O2 emit if it doesnt emit IR? If O2 was warm surely it radiates?
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Post by donmartin on Feb 25, 2009 7:45:10 GMT
I could be quite wrong, but I am unaware of any atomic theory which suggests that energy is "emitted" from an atom or molecule, unless alpha or beta decay is considered energy "emission" in the context you suggest. Or "absorbed" for that matter. Further, reference to emission or absorption bands may belie a misunderstanding of the Zeeman effect. And I simply do not accept the concept that a photon is emitted upon a "quantum leap". That is supported by neither empirical evidence nor a priori analysis.
I would say that "warm" is not a condition obtained by "energy released" or radiated from an atomic structure.
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Post by steve on Feb 25, 2009 10:53:53 GMT
Apologies, but I'm a hedgehog - slow and siple. "Trap", "hold", "absorb"? Is there a theory within the Dalton model wherein it is convincingly concluded that an atom or molecule traps, holds, or absorbs anything. Do photons attach to neutrons and become "pheutrons"? And the wave theory of atomic structure doesn't assist because were an atom as conceived in the wave theory to "absorb" energy, then its atomic structure would change thus creating a different element - and no one has hypothesized that yet in relation to GHG. And, again, is it not correct that temperature is a measurement of atomic velocity only, and not heat, which is a function of the aggregate number of atoms or molecules (n) within a defined space, which on Earth is a function of gravity and the dipolar magnetic field? Just asking. I, personally, didn't use the word "trap". It misconstrues the process. After all a good absorber is a good emitter - a good "trapper" is a good "releaser". If a CO2 molecule absorbs a photon the energy causes the molecule to vibrate. Vibration can only happen in certain ways. The energy difference between the common modes of vibration is the energy of the photons it is keen to emit and absorb. The vibrational energy can also be lossed or gained in a collision with other molecules. As it can be transferred as kinetic energy to other molecules, and as any absorption of IR by the CO2 molecules is quickly "averaged out" or thermalised, the absorption of the IR is reflected by a change in the temperature of the gas as a whole. I'm sure in the quantum mechanical world it's more complex than that.
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Post by kiwistonewall on Feb 25, 2009 11:14:04 GMT
Apologies, but I'm a hedgehog - slow and siple. "Trap", "hold", "absorb"? Is there a theory within the Dalton model wherein it is convincingly concluded that an atom or molecule traps, holds, or absorbs anything. Do photons attach to neutrons and become "pheutrons"? And the wave theory of atomic structure doesn't assist because were an atom as conceived in the wave theory to "absorb" energy, then its atomic structure would change thus creating a different element - and no one has hypothesized that yet in relation to GHG. And, again, is it not correct that temperature is a measurement of atomic velocity only, and not heat, which is a function of the aggregate number of atoms or molecules (n) within a defined space, which on Earth is a function of gravity and the dipolar magnetic field? Just asking. Hi Don, some teaching. You seem to be confused with radio activity - that is with high energy gamma photos, not low energy IR radiation. Thus speakest the Physical Chemist: (Air Temperature is the average kinetic energy (KE) of a large group of molecules. Individual molecules may be moving faster or slower. The KE isn't just linear velocity, but includes rotational and vibrational energy. When a photon of the correct energy is absorbed by a molecule, the photon vanishes, and its energy is added to the molecule. For CO2, (a tri-atomic molecule) there are more complex motions possible than with simple diatomic O 2 & N 2. Hence, Oxygen & Nitrogen do not absorb the IR energies that CO 2 does. Quantum mechanics means that each vibrational state is associated with a particular energy absorption. This is all well known & well understood from real experiments. The 'excited' CO 2 rapidly re-emits the photon as the vibration returns to the lower state. The new photon can go in any direction. This is why a little less that 50% of the energy in the IR band gets send back in the general direction of Earth. The half life for the transition is well known, and very short, so there is no real heating effect. The effect is a scattering, not an absorption. Note that molecules do not act like black bodies that emit a spectrum of IR radiation (the spectrum depends on the temperature). Rather, molecules that are heated will tend to emit discrete IR radiation at particular band widths. If the atmosphere itself is heated, CO2 will emit IR radiation without first receiving a photon, as the molecule will gain the needed energy from random collisions if the temperature rises. So warm air will radiate more IR than it receives from Earth - a reason why the air doesn't warm up. There is no "trapping" - only scattering. One complication is particulates and aerosols of an amorphous nature. These will absorb IR of a wider range of energies and also emit black body radiation. They also interfere with visible light from the sun. But, as a whole, there is no mechanism whereby energy can be created by the greenhouse effect, and no mechanism where anything more than a little less than 50% of the IR energy in the relevant bands can ever be returned to the Earth. The geometry of the Sphere means that it is always less than 50%. Desert air is dry, and only CO2 is there to warm the air - and desert nights are COLD. When clouds form at night, the IR radiation at night is strongly reflected by the water vapour. If there was an accelerating GH effect from CO 2, then night time temperatures would be rising (and that is official IPCC doctrine.) It simply isn't happening, not in Australia where in the middle of the (reportedly) worse heatwave, we have record night time low temperatures, and the mean minimums are below the long term means. i.e. the GH effect is NOT increasing. cheers
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Post by kiwistonewall on Feb 25, 2009 11:25:12 GMT
Apologies, but I'm a hedgehog - slow and siple. "Trap", "hold", "absorb"? Is there a theory within the Dalton model wherein it is convincingly concluded that an atom or molecule traps, holds, or absorbs anything. Do photons attach to neutrons and become "pheutrons"? And the wave theory of atomic structure doesn't assist because were an atom as conceived in the wave theory to "absorb" energy, then its atomic structure would change thus creating a different element - and no one has hypothesized that yet in relation to GHG. And, again, is it not correct that temperature is a measurement of atomic velocity only, and not heat, which is a function of the aggregate number of atoms or molecules (n) within a defined space, which on Earth is a function of gravity and the dipolar magnetic field? Just asking. I, personally, didn't use the word "trap". It misconstrues the process. After all a good absorber is a good emitter - a good "trapper" is a good "releaser". If a CO2 molecule absorbs a photon the energy causes the molecule to vibrate. Vibration can only happen in certain ways. The energy difference between the common modes of vibration is the energy of the photons it is keen to emit and absorb. The vibrational energy can also be lossed or gained in a collision with other molecules. As it can be transferred as kinetic energy to other molecules, and as any absorption of IR by the CO2 molecules is quickly "averaged out" or thermalised, the absorption of the IR is reflected by a change in the temperature of the gas as a whole. I'm sure in the quantum mechanical world it's more complex than that. The energy absorbed by the CO2 cannot be passed on to Oxygen or Nitrogen easily, and can only be added to the direct linear motion. This energy is then very likely to be absorbed by another CO2 molecule and re-emitted. The warming effect of the IR absorption process is totally negligible, unless you are an AGW believer. All Physical Chemists would understand the process as effectively immediate scattering. The GH effect is the return, by scattering, of IR energy back to the Earth. Only particulates (smoke, dust, aerosols & water droplets) possess the absorption properties to "trap" IR radiation, but they act as an extension of the Earth's surface. The whole theory of layers of the atmosphere heated by the Greenhouse effect is (a) not part of the GH effect itself as originally conceived, (b) is theoretically nonsense, (c) experimentally not observed and (d) only invented to prop up the failed run away Greenhouse effect - the runaway forcing. No Physical Chemist (to my knowledge) accepts this nonsense. If one does, can someone please post the links, as I'd love to read their work. cheers
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Post by steve on Feb 25, 2009 11:41:25 GMT
I could be quite wrong, but I am unaware of any atomic theory which suggests that energy is "emitted" from an atom or molecule, unless alpha or beta decay is considered energy "emission" in the context you suggest. Or "absorbed" for that matter. Further, reference to emission or absorption bands may belie a misunderstanding of the Zeeman effect. And I simply do not accept the concept that a photon is emitted upon a "quantum leap". That is supported by neither empirical evidence nor a priori analysis. I would say that "warm" is not a condition obtained by "energy released" or radiated from an atomic structure. Where does all the light and heat come from then?
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Post by steve on Feb 25, 2009 12:02:10 GMT
what does O2 emit if it doesnt emit IR? If O2 was warm surely it radiates? O2 oxygen emits in the microwave region, but not very much. 60GHz is what is monitored by satellites to determine atmospheric temperatures. This is off well beyond the far right of the emission spectrum of the earth such as this (it's 5000 microns), so not that much energy is emitted by O2. Given that ozone is a greenhouse gas, I'm guessing the peak in the "Oxygen and Ozone" spectrum is from the ozone, not O2.
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Post by steve on Feb 25, 2009 12:14:14 GMT
The 'excited' CO 2 rapidly re-emits the photon as the vibration returns to the lower state. The new photon can go in any direction. This is why a little less that 50% of the energy in the IR band gets send back in the general direction of Earth. The half life for the transition is well known, and very short, so there is no real heating effect. The effect is a scattering, not an absorption. Kiwistonewall, I agree with much of the top third of what you said. This bit I don't agree with. At typical atmospheric temperature and pressure, the rates of collision are far far higher than the rate of reemission of energy by a greenhouse gas molecule. ie. an excited molecule will far more likely collide with another molecule before it emits a photon. This means that IR energy absorbed by greenhouse gases is thermalised - the energy is shared out with the non-absorbers (ie. N2, O2, Argon) through collisions, so warming the atmosphere as a whole.
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Post by donmartin on Feb 25, 2009 17:55:22 GMT
As an inveterate hedgehog I will think on this for a little while and get back. But I will ask a question: Is the concept of "collisions" of atoms or molecules related to the Pauli Exclusion Principle and Brownian motion? And are these theories relevant to the thread and discussion?
Thanks all
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Post by steve on Feb 25, 2009 18:10:06 GMT
As an inveterate hedgehog I will think on this for a little while and get back. But I will ask a question: Is the concept of "collisions" of atoms or molecules related to the Pauli Exclusion Principle and Brownian motion? And are these theories relevant to the thread and discussion? Thanks all Brownian motion is a demonstration of small particles being buffeted by the random collisions from molecules in a fluid (air or liquid). Not sure that the Pauli Exclusion Principle really applies, except that the electrons in an atom are governed by it - without it, the universe would turn into goo, and the discussion would be moot.
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Post by donmartin on Feb 26, 2009 2:10:09 GMT
And that goo would be a black hole - and the issue would be less than moot
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Post by kiwistonewall on Feb 26, 2009 10:49:01 GMT
The 'excited' CO 2 rapidly re-emits the photon as the vibration returns to the lower state. The new photon can go in any direction. This is why a little less that 50% of the energy in the IR band gets send back in the general direction of Earth. The half life for the transition is well known, and very short, so there is no real heating effect. The effect is a scattering, not an absorption. Kiwistonewall, I agree with much of the top third of what you said. This bit I don't agree with. At typical atmospheric temperature and pressure, the rates of collision are far far higher than the rate of reemission of energy by a greenhouse gas molecule. ie. an excited molecule will far more likely collide with another molecule before it emits a photon. This means that IR energy absorbed by greenhouse gases is thermalised - the energy is shared out with the non-absorbers (ie. N2, O2, Argon) through collisions, so warming the atmosphere as a whole. Read this for good background: Start around page 56. books.google.com.au/books?id=Q12AaljGQvYC&pg=PA59&lpg=PA59&dq=collisions+of+excited+CO2+molecules&source=bl&ots=v7welE0IUK&sig=mhUlZSm78i_ChyChGcruBfIUPdI&hl=en&ei=lm6mSZL8K5qqtQPgsOD3Dw&sa=X&oi=book_result&resnum=2&ct=result#PPP1,M1 The energy isn't thermalised significantly except in the minds of the AGW proponents. If the atmosphere warms up, that will excite more CO2 by collisions so that more IR is emitted than absorbed! The main cause of thermalisation of the atmosphere is incoming solar radiation (the IR portion gets absorbed by CO2 in the outer atmosphere and doesn't reach the surface directly.)
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Post by steve on Feb 26, 2009 13:39:18 GMT
Unfortunately, the relevant pages aren't available in the preview. The questions to answer are what is the mean time to reradiating a photon, and what is the mean time between collisions. The latter is much much less than the former, IIRC. If you have a reference that says otherwise I'll have to go and dig out my calculations again to see where I or your reference went wrong. These two sentences don't go together. If the energy isn't thermalised then essentially the atmosphere temperature is independent of what is going on with the CO2 (the CO2 won't have a temperature in this scenario as it is not in thermal equilibrium, but it'll have an average energy that is related to the IR flux). If the atmosphere is cool such that the molecules are on average less energetic than the CO2, then mostly it is the CO2 transferring energy to the atmosphere. If it is more energetic than the CO2 then, yes, the atmosphere will lose energy to the CO2. What I am stating though is that they're in approx equilibrium. By "thermalisation" I'm talking about the redistribution of IR energy absorbed by the greenhouse gases. Since you don't believe it isn't effectively distributed, this doesn't scan.
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Post by kiwistonewall on Feb 27, 2009 0:21:32 GMT
Steve, you fail to understand both equilibrium & the quantum nature of energy.
The CO2 molecules have the same average kinetic energy as the rest of the atmosphere.
The issue is what happens when an IR photon arrives.
The four equations were listed in that post, but I'll give them here:
1. CO2 + photon = CO2* 2. CO2* = CO2 + photon
and: (where M = another molecule, M* is a fast moving molecule)
3. CO2 + M* = CO2* + M 4. CO2* + M = CO2 + M*
When a photon imparts the energy for the excitation to occur, then these four equations will continue until the photon has exited the system.
Note that if that quanta of energy is transferred to another molecule, it retains the exact energy needed to excite the next CO2 molecule.
There is negligible temperature rise - the process is one of scattering, not thermal heating of the atmosphere.
Were the atmosphere to warm, then the reactions 3 followed by 2 become more likely, cooling the atmosphere.
The temperature cannot rise by increasing the CO2 concentration. The only thing driving this are the photons which ultimately come from the sun. NOTHING drives this except photons, as long as there is enough CO2 for saturation - and that book stated there were many extinction layers (100% absorption) in the atmosphere.
This was always recognized until recent years when the IPCC had to come up with something to prop up a failed idea.
The danger comes if we remove CO2 from the atmosphere. All we need know is someone to come up with a neat idea to remove all the CO2- destroy all life on the planet & reduce us to an ice ball. Surely they wouldn't be that stupid - like dumping iron dust all over the oceans - would they? ;D
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Post by donmartin on Feb 27, 2009 0:48:02 GMT
K'l: This may sound ridiculous, but when you refer to CO2 concentration, does this not bring into consideration Avogadro's law to the extent that the greater the concentration of CO2 in a given volume, the lower the temperature of the CO2?
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