|
Post by icefisher on Sept 13, 2009 20:10:02 GMT
And very low is fine. . . .I consider .04% to be relatively very very low. Which is to be our guide? Theory or reality? [/quote] This is the key its also the key difference between an authoritarian socialist society and a free capitalist society. Socialists want to design the perfect world by instructing what others can and cannot do based upon social theory. Capitalists live and die on whether the theory they cook up can sell. Its how you buy in that explains the essential difference between the two. The two social systems pursue very different courses one is a course based on theory the other a course based upon reality. What is it 80% of individual theories (business theories) fail? Its the 20% that succeed that moves us along.
|
|
|
Post by kiwistonewall on Sept 13, 2009 21:26:07 GMT
|
|
|
Post by radiant on Sept 14, 2009 0:09:34 GMT
You seem to be saying that it is pointless to coat dewer flasks with silver mirroring. You are also saying that text books that say nitrogen does not emit IR are wrong so I think if you can find an emission spectrum of Nitrogen it would help clarify this topic. Your first link shows total cloud cover when the earths radiation is reflected back to earth Your second link is theoretical for an atmosphere containing water and mentions black surfaces. Air is transparant of course Your third linked page refers to kirchhoffs law and page 128 of your book says that n2 and 02 with no electric dipole have very sparse absorption lines Kirchhoff's law states that: en.wikipedia.org/wiki/Kirchhoff's_law_of_thermal_radiation At thermal equilibrium, the emissivity of a body (or surface) equals its absorptivity. To be honest i am confused by what you are saying There can be no atmospheric window of no emission of IR back to earth if all of the atmosphere behaves like a black body A black body is black and matt in texture. Talk of black bodies makes no sense in the context of an atmosphere but it might guide you to the temperature of a substance that is emitting strongly at a particular frequency perhaps. For a black body, absorption = Emissivity = 1 So we need to talk of grey bodies And ultimately apart from the greenhouse gases the atmosphere is simply more or less transparent so not even grey applies Answer this question please: If a steel roof is surrounded by hundreds of tonnes of warm air at 24 degrees in calm conditions why can it expect to cool by around 10 degrees less than the air temperature when there is low humidity and the night is clear of clouds? As you will know the roof can only cool when it emits more radiation than it receives from hundreds of tonnes of warm air Why does the roof cool because outerspace is very cold and yet the air is very warm?
|
|
|
Post by kiwistonewall on Sept 15, 2009 22:25:05 GMT
For Radiant: Air is NOT transparent to thermal radiation. It is largely transparent to visible light (even then it wouldn't be blue if it didn't scatter some visible light)
An atmosphere isn't reflective silver, it is a "pure" blackbody if it was optically dense enough (i.e. enough depth). It thus does show a blackbody absorption and emission - simply not at the same intensity as a solid surface. Thus a large fraction of infrared will radiate from the surface to space, but a considerable portion will be absorbed (and reemitted) by all the molecules in the atmosphere.
(Solids are seldom perfect reflectors and absorbers, while gases are close to "perfect" blackbodies in bulk!. Note that the BB effect is a property of bulk matter- due to probability distribution of different molecular speeds - a single gas molecule is not a blackbody!)
The absorption spectrum of discrete polyatomic molecules is made up of very narrow bands. While "intense", these bands make up a small % of the barrier to outgoing thermal heat. The entire blackbody radiation of the earth will heat the atmosphere to a lesser intensity across the entire blackbody spectrum. This is far from insignificant.
Now here is the biggie - since ALL matter emits, (it is a fundamental property of matter after all) then so do normal detectors and instruments used to detect the radiation.
(Accurate work to measure BB is done with cooled detectors to prevent contamination of the spectrum with their own thermal radiation)
Thus, in most cases, background blackbody radiation tends to be "invisible" to normal instruments used to measure the sharp spectra of IR absorbing materials.
This isn't conjecture or opinion. Thermal emission of all matter is a fundamental property related to Temperature.
|
|
|
Post by radiant on Sept 16, 2009 2:58:28 GMT
For Radiant: Air is NOT transparent to thermal radiation. It is largely transparent to visible light (even then it wouldn't be blue if it didn't scatter some visible light) An atmosphere isn't reflective silver, it is a "pure" blackbody if it was optically dense enough (i.e. enough depth). It thus does show a blackbody absorption and emission - simply not at the same intensity as a solid surface. Thus a large fraction of infrared will radiate from the surface to space, but a considerable portion will be absorbed (and reemitted) by all the molecules in the atmosphere. (Solids are seldom perfect reflectors and absorbers, while gases are close to "perfect" blackbodies in bulk!. Note that the BB effect is a property of bulk matter- due to probability distribution of different molecular speeds - a single gas molecule is not a blackbody!) The absorption spectrum of discrete polyatomic molecules is made up of very narrow bands. While "intense", these bands make up a small % of the barrier to outgoing thermal heat. The entire blackbody radiation of the earth will heat the atmosphere to a lesser intensity across the entire blackbody spectrum. This is far from insignificant. Now here is the biggie - since ALL matter emits, (it is a fundamental property of matter after all) then so do normal detectors and instruments used to detect the radiation. (Accurate work to measure BB is done with cooled detectors to prevent contamination of the spectrum with their own thermal radiation) Thus, in most cases, background blackbody radiation tends to be "invisible" to normal instruments used to measure the sharp spectra of IR absorbing materials. This isn't conjecture or opinion. Thermal emission of all matter is a fundamental property related to Temperature. If the atmosphere was so dense you could not see the stars or see mount taranaki from the beach at kapiti what you are saying would be applicable to this conversation perhaps Meanwhile it is almost irrelevant that a gas is not quite totally absolutely transparant. Obviously we are talking about relative differences here. You have to get to grips with some simple physics. Atoms and molecules have relative emissivities regardless of your opinions about all matter in the universe I am talking about the relative differences in the ability of atmospheric gases to emit radiation A number of authorities have said that nitrogen and oxygen are such poor emitters of ir radiation they can be considered to not emitt in the IR Wood 1909 said that air is a poor radiator. Do you recognise that a gas has an absorption and emission spectra that can be measured by human beings or not? If aluminium foil from the supermarket only emitts 0.04% of IR radiation of a black body why do you think there is some physical law that a gas so transparant that a person with exceptionally good eyesight can see a moon of jupiter cannot match this or better it?
|
|
|
Post by kiwistonewall on Sept 16, 2009 3:08:19 GMT
Radiant, what indeed are YOU talking about? ALL matter emits thermal radiation. Seeing (visible light) ISNT thermal.
The air is NOT transparent to infrared (thermal heat), nor is it totally opaque.
The whole blackbody radiation from the Earth is partially trapped at ALL frequencies. This is why ALL planets with atmospheres show a greenhouse effect (with or without so-called greenhouse gases)
Because the greenhouse gases absorb only at discrete peaks, the power (Area under the frequency curve) is proportionally smaller, while since all gases absorb at a lesser intensity over all frequencies, the power is proportionally higher.
Have you studied Physics/Physical Chemisty at University level? (Not trying to be arrogant here, but you are failing to understand the fundamental physics of matter and the interaction with EMR.)
|
|
|
Post by radiant on Sept 16, 2009 3:47:47 GMT
Radiant, what indeed are YOU talking about? ALL matter emits thermal radiation. Seeing (visible light) ISNT thermal. The air is NOT transparent to infrared (thermal heat), nor is it totally opaque. The whole blackbody radiation from the Earth is partially trapped at ALL frequencies. This is why ALL planets with atmospheres show a greenhouse effect (with or without so-called greenhouse gases) Because the greenhouse gases absorb only at discrete peaks, the power (Area under the frequency curve) is proportionally smaller, while since all gases absorb at a lesser intensity over all frequencies, the power is proportionally higher. Have you studied Physics/Physical Chemisty at University level? (Not trying to be arrogant here, but you are failing to understand the fundamental physics of matter and the interaction with EMR.) You seem to think that thermal radiation which is infra red radiation is some unique property of matter when it is simply one part of the electromagnetic spectrum that can be released by a substance in the form of what we think of as being photons. www.physics.uoguelph.ca/applets/Intro_physics/kisalev/java/atomphoton/index.htmlen.wikipedia.org/wiki/Emission_(electromagnetic_radiation)So this subject is about how substances can become excited and how they can then release photons of a particular EMR we call infra red radiation which in turn is divided into short wave IR radiation or long wave IR radiation. Solar infrared radiation is not considered to be majorly absorbed by the atmosphere - it is high energy high frequency ir radiation that mostly passes thru or gets reflected outwards The materials of the earth being warm but not hot, emit low frequency or long wave ir radiation depending upon the properties of the various atoms and molecules at the surface The area of concern for low temperature atmospheric gases is the long wave ir band of the electromagnetic spectrum. Once again i feel the need to point out to you that we are talking about relative differences here rather than absolutes. The air is not transparant but we are talking about relative differences betweens atoms and molecules in that atmosphere. Surely you can see that? The atmospheric gases are majorly warmed by convection by contact with the earths surface. A smaller amount of heat is absorbed via greenhouse gases of which water is overwhelmingly the major gas. You seem for some reason interested that nitrogen absorbs over the entire band at some % which you think is sufficiently high that it merits the claim nitrogen significantly emitts IR radiation. Where is the evidence for this theory? C02 absorption is measured while being diluted by nitrogen gas for example. And how about we focus on science please rather than your theory about my ignorance and lack of education in this matter because i think you are wrong. So far your science has been to claim the atmosphere emits black body radiation by producing a study with total cloud cover. I think we both know that total cloud cover is one way the earth is not warmed by the sun since it reflects the energy to space Obviously if you are under total cloud cover you are going to detect the energy reflected from the earth. The following part of your reply is where you seem to be going wrong yourself: The whole blackbody radiation from the Earth is partially trapped at ALL frequencies. This is why ALL planets with atmospheres show a greenhouse effect (with or without so-called greenhouse gases)
Because the greenhouse gases absorb only at discrete peaks, the power (Area under the frequency curve) is proportionally smaller, while since all gases absorb at a lesser intensity over all frequencies, the power is proportionally higher.With no greenhouse gases the atmosphere would be warmed by convection and could only be cooled by contact with the cool earth or the very small amount of emitted atmospheric radiation. Since hot gases rise the upper atmosphere would be relatively warm and have no way to cool unless this gas returned absolutely to the lowest point of the atmosphere and found the earth was cooler than the gas.
|
|
|
Post by kiwistonewall on Sept 16, 2009 7:12:59 GMT
Radiant. I have an honours degree in Physical Chemistry. I specialized in molecular absorption. Please don't try and explain what you don't understand.
I quoted text books & you think I am wrong? I only talked about the fundamental properties of matter & made no comments on HOW the atmosphere works.
I DO understand what is happening at the molecular level. I can also safely say that no one truly understands how the atmosphere works, and I make no attempt to do so. Every model so far has been a total failure.
|
|
|
Post by radiant on Sept 16, 2009 7:51:13 GMT
Radiant. I have an honours degree in Physical Chemistry. I specialized in molecular absorption. Please don't try and explain what you don't understand. I quoted text books & you think I am wrong? I only talked about the fundamental properties of matter & made no comments on HOW the atmosphere works. I DO understand what is happening at the molecular level. I can also safely say that no one truly understands how the atmosphere works, and I make no attempt to do so. Every model so far has been a total failure. I have an ordinary degree in Applied Analytical chemistry with particular emphasis on analytical techniques so i suppose that makes you the smart guy on the block with your superior intelligence How about focusing on the science and cutting the crap. What you are talking about does not make sense to me so far. For the record i also quoted text books including your own text books!!!!! Why quote a study that shows atmospheric radiation when there is total cloud cover! What is your reasoning for putting that forwards??? And instead of reacting as if you know better how about you go thru my last post line by line and refute what i say or agree with it until we find why we dont agree? That to my way of thinking is the none Al Gore approach to Science. If i am wrong then i am wrong. But why am i wrong? I need more than your opinion and irrelevant links to text books Heat radiation is just a radiation like the colour green or xrays Why is long wave infra red radiation so 'special'? What makes it so different to red or short wave infra red? And i am not talking here about the atmosphere i am talking about the observation that nitrogen oxygen and the rare gases do not emit IR radiation at ordinary temperatures You have referenced black bodies which are idealised theoretical objects en.wikipedia.org/wiki/Black_bodyI have tried to steer you towards grey bodies and emissivity. I have also used your reference to phrases such as: An atmosphere isn't reflective silver, it is a "pure" blackbody To get you to see there is a difference between a theoretical concept which is useful and what actually happens when 99% of our atmosphere is heated to ordinary temperatures
|
|
|
Post by kiwistonewall on Sept 16, 2009 10:54:48 GMT
Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics arxiv.org/abs/0707.1161All matter emits radiation based on its temperature. You must have skipped those lectures. I am not in the least interested in debating with you. I was just pointing out the common ignorance about radiation & correcting the assertion that O2 & N2 do not absorb & emit thermal radiation.
|
|
|
Post by radiant on Sept 16, 2009 12:16:38 GMT
All matter emits radiation based on its temperature. You must have skipped those lectures. An idealised black body emits radiation based on its temperature. Real substances emit radiation according to their atomic structure and surface properties And I note now that you keep talking about the air. I am talking about 99% of the air that does not include water co2 etc. And why are you supplying a link to falsification of C02 warming? I think now we are talking about cross purposes. Your link appears to address the same kinds of issues that woods (1909) did when he constructed a greenhouse with NaCl 'glass' that does not trap longwave radiation.
|
|
|
Post by socold on Sept 16, 2009 20:31:20 GMT
Citing Garblick and Tosscheuschner should invoke a climate equivalent of Godwin's law
|
|
|
Post by magellan on Sept 17, 2009 1:44:34 GMT
|
|
|
Post by radiant on Sept 17, 2009 8:19:28 GMT
Citing Garblick and Tosscheuschner should invoke a climate equivalent of Godwin's law I note the following response to the Gerlich and Tscheuschner paper seems wrong. arxiv.org/abs/0802.4324:A recently advanced argument against the atmospheric greenhouse effect is refuted. A planet without an infrared absorbing atmosphere is mathematically constrained to have an average temperature less than or equal to the effective radiating temperature. Observed parameters for Earth prove that without infrared absorption by the atmosphere, the average temperature of Earth's surface would be at least 33 K lower than what is observed. As i have explained above a none absorbing atmosphere will be a none emitting atmosphere that will take the earths surface heat to the upper atmosphere until equilibrium is established and there will be no obvious mechanism to return heat to the surface for cooling. Additionally the earth has a hot core that is cooled by radiation to outerspace. Hot or warm winds could easily keep the surface of the earth higher than people believe because it is only the very absolute top of the earths molecular solid surface that is radiating heat to space while the rest is being warmed slightly from below. If by day the earth heats to a few hundred degrees and by night it cools to a few hundred degrees what actually is the temperature of the earth just below the surface which experiences the average of this warm cold cycle and experiences the warming from below? Permafrost must have taken a period of more minus than plus for a number of years to freeze so far down. In a warm cold cycle that is not going to happen i would guess. You would just get an average of hot and cold with warming from below Meanwhile the oceans exist and so the whole dynamic of a none water based planet are rediculously unreal. If water was not evaporating from the oceans they would be warmer than if not. When water evaporates the heat is transported into the atmosphere. Some mechanism is required to cool the atmosphere for life to be possible and what would happen at the surface is not clear to me. I have to wonder if people have thought this topic thru properly before building their models of earth
|
|
|
Post by kiwistonewall on Sept 17, 2009 11:20:40 GMT
|
|