- Greenhouse gases, predominantly water vapour, do absorb infra red radiation from the earth, radiate the additional energy in all directions, including downwards and so warm the earth.
- So the greenhouse effect does exist.
- This effect must be very small as it has not been detected, despite the enormous effort that has been applied to try and find it.
We read that Vincent here puts forward the idea that the atmosphere by radiating heat energy downwards causes warming of the Earth surface in a process of two-way radiative heat transfer between the atmosphere and surface including "back radiation" from a cold atmosphere to a warm surface. Vincent thus accepts the picture painted by CO2 alarmism based on a "greenhouse effect" and thereby gives it a free ride. Vincent shares this view with many "skeptics".
At the same time as Vincents claims that "the greenhouse effect exists", he informs us that it has not been detected, presumably then because "it must be very small".
All this is unfortunate because the two-way heat transfer including back radiation which Vincent describes, is not true physics but fake physics, as I have argued in extended writing.
Vincent defends his position with a direct attack on my position with the following argument (in bold):
- Radiation energy is converted to heat if it is absorbed by any suitable object.
- The temperature of that object is quite irrelevant.
- The speculation by some that radiation cannot be absorbed by an object whose temperature is bigger than that of the radiant emitter requires the absurd assumption that radiation, is capable of detecting the temperature of distant objects before deciding whether they are fit to receive absorption.
- Such an assumption restores the need for a belief in the existence of an ether.
But is it absurd that an absorber can detect if the temperature of an emitter is bigger than its own temperature? Not at all! That information is encoded in the spectrum of the emission as the high-frequency cut-off described in Wien's displacement law with the cut-off increasing linearly with temperature. The result is that emission from a certain temperature cannot be re-emitted by an absorber at lower temperature and thus must be absorbed and turned into heat causing warming.
A stone put in the sun light, can thus very well detect that the sun light falling upon itself was emitted at a temperature higher than its own, because sun light contains frequencies above the cut-off frequency of the stone. The stone detects this by finding itself being unable to re-emit these frequencies and thus cannot prevent getting heated by the Sun. This is nothing the absorber "decides" to do in Vincent's vocabulary, because atoms have no free will "to decide", but simply something the absorber is unable to do, which involves no "decision" and thus can be physics.
So in conclusion I pose the following question to Vincent (and other "skeptics"): Since the "greenhouse effect" cannot be detected experimentally and your theoretical argument in support of its existence has shown to be incorrect, wouldn't it be more rational to give up arguing that the "greenhouse effect exists" because there is "back radiation", thus giving support to CO2 alarmism?
I have asked Vincent to respond to this post, but it may well be be that Vincent, like some other "skeptics", simply hides (and warms up) after making an attack on a skeptic position of a frequency above his own cut-off.
PS Vincent's claim of existence of a phenomenon that is not detectable, connects to an (unfortunate) aspect of modern physics, as opposed to classical physics, rooted in the Bohr Copenhagen interpretation of quantum mechanics, where the wave function is not viewed to represent real physics independent of human observation, but instead represents human understanding in statistical terms limited to what can be observed by humans. Modern physicists following Bohr are thus allowed to speak about only physics which is observable and then in statistical terms. But this is too narrow, and has opened the possibility of a vast physical landscape beyond observation, which physicists are now eagerly exploring in the extreme forms of string theory and multiversa. The (unfortunate) result is that speaking about phenomena of physics which cannot be detected, which in the view of classical physics is nonsense, has now become mainstream modern physics.
Inlägg
A blackbody consists of enourmous numbers of individually tuned oscillators/receivers, together creating the own blackbody`s spectrum, so there is no possibility for individually receivers to absorb the whole spectrum of another emitting body and so beeing able to "compute" the temp of that body . Therefore your idea is absurd as Vincent G says. The only thing an individual receiver can do is to interact with an incoming e-m wave with the right frequency, whether the wave comes from a warmer or colder body.
SvaraRaderaAs I see it, each of the oscillators of Lasse H are damped because they generate electromagnetic radiation as a result of the dynamic electric dipole moment caused by charge being accelerated in the oscillation process.
RaderaWhen such an oscillator is exposed to an electromagnetic field it will respond in forced damped resonance, where the generated radiation balances the forcing.
In the direction of the forcing a standing wave develops between the forcing and the response. This implies that there is no energy transport into the oscillator or out of the oscillator along this direction.
Therefore I find Claes proposal to be real physics and not just a mathematical construct as the two stream approach definitely seem to be.
It is not entirely correct to say that it is no energy transport into the oscillator. It is, however, no energy transport out of the oscillator in the direction of the forcing.
RaderaTo maintain a stationary response, the energy fed into the oscillator must of course equal the total energy lost through radiation over the sphere surrounding the oscillator. However, in the direction of the forcing the radiation response interferes with parts of the forcing and establishes a standing wave, as stated above. Thus there is no energy transport out of the oscillator in this direction, which means that energy transport by back-radiation cannot be a physical phenomenon.
"As I see it, each of the oscillators of Lasse H are damped because they generate electromagnetic radiation as a result of the dynamic electric dipole moment caused by charge being accelerated in the oscillation process. "
RaderaBut the relevant timescale for the reaction force to be compared with an external force is t=6.26*10^-24s for electrons and yet lower for heavier particles since this time estimates scales as the inverse of the particle mass (from Jackson's Classical Electrodynamics).
So when the external force acts on a timescale larger than t, the force from the radiating oscillator is completely negligible.
In the case of thermal radiation the reaction force is so astronomically dwarfed that it practically doesn't exist since the timescale then is about 10^-14s for room temperature radiation and 10^-16 for stars (The thermal coherence length is of the order of Wiens wavelength so about 10^-5m in room temperature, divided by the speed of light ).
So this doesn't cut it as a feasible mechanism for any damped resonance.
That was for acceleration of a stationary particle.
RaderaBut nothing changes in the case of periodic motion.
The criteria that the radiative effect is unimportant is
(1) E_rad << E_mechanic,
and
(2) E_rad ~ 2*e^2a^2T / (3*c^3) (from Larmors formula).
Oscillatory motion has energy
(3) E_mechanic ~ m d^2/T^2
The acceleration a above is
(4) a~d/T^2
Putting it all together gives that if
(5) 2e^2/(3*m*c^3) << T
the radiation force is unimportant.
Now
(6) t=2*e^2/(3*m*c^3)=6.26*10^-24s
for an electron, and lower for heavier particles.
In a solid the phonon oscillations are typically on the scale of 10THz so that gives about 10 orders of magnitude (a factor 10^10 !!) on the side that radiation effects are unimportant.
Do you still think that Claes model is reasonable in including the radiative reaction force?
The analysis shows that the size of the damping is irrelevant, as long as it is small and positive. That is the beauty of the model as this expresses universality.
RaderaThis shows that your model is always in cutoff mode for all physical materials. It must always accumulate energy no matter the internal state (temperature) and external forcing (incoming radiation).
RaderaThe model can't loose energy by radiation.
The classical treatment is unrealistic, you need quantum mechanics.
Not at all, the damping term models outgoing radiation and the system looses energy through that term. And yes, a classic forced damped resonator model works, and that is a huge advantage since such a model can be comprehended/visualized, while a basic feature of quantum mechanics according to Heisenberg as exposed in a recent post, is that it is not comprehensible/visualizable.
RaderaBut it is shown above that the loss is so extremely small that effectively there is no loss on any reasonable timescale.
RaderaYour model shows a behavior where any kind of radiation heats the material, independent of state.
To Anonym
RaderaFor lightly damped dynamic systems near or in resonance, the absolute value of the inertia and stiffness forces are irrelevant as a comparison to the absolute value of the excitation forces and/or the generated damping forces. What is relevant is the ratio between the inertia and the stiffness. This ratio determines the natural frequency of the system. When the frequency of the excitation equals or is very close to the resonance frequency, dynamic systems in a real world will respond in (forced) resonant dynamic response no matter how small the amplitude of the excitation force is compared to the magnitude of the inertia and stiffness forces.
To anonym: No, that is not correct. You have not properly understood the model. And listen to what Christopher is saying, because he has understood.
RaderaDid you loose my comments? Or maybe they where to solid for you? ;-)
RaderaI did not loose your comments, but it seems that you have lost the basic physics of lightly damped dynamic systems responding in resonance. This physics is valid both in a classical sense and in the sense that you need to turn to quantum mechanics to explain certain phenomena.
RaderaI did not refer to you loosing any comments of mine, of course, Christopher Hoen-Sorteberg. I'm quite certain that you do not moderate any comments on this blog. I back up the comments locally now so that they don't accidentally disappear in the moderation. I assume that is what happened here.
RaderaI rewrite the comment here, not verbatim though.
You (Christopher Hoen-Sorteberg) wrote
"This ratio determines the natural frequency of the system."
For a real system the natural frequencies are achieved by diagonalizing the dynamical matrix of the system, which gives the normal modes. This represents all accessible states that have the potential to carry and store energy in the system. This gives us dispersion relations over the first Brillouin zone. The thing to notice is that the material isn't an Einstein solid, that is a way to crude approximation for our purpose, so isolated oscillators are rarely present and can safely be ignored to first order at least. You can still see nonpropagating normal modes in the phonon spectra but they are typically isolated near the first Brillouin zone boundary representing Bragg reflection. So almost all the normal modes of the system have group velocities and as soon as any energy is in the system it starts to propagate in the solid. Due to anharmonicity in the system the different normal modes couple and the energy diffuses between normal modes until equilibrating to the Bose-Einstein distribution at temperature T. This is the mechanism of heating within the solid.
That's part one. The reason for introducing this here is to have a common ground to actually discuss what reasonable happens in a real system and how the energy stores in a solid. So if you have any objections to what is written above, now is the time.
The take home message is that isolated resonators, like a Lorentz type of resonator (can be modeled with a simple classical model with of a spring and viscous damping term) is a rarity in solids compared to the bulk and is typically a color center for instance where a charged lattice defect with a trapped loosely bound electron that acts as a rattler localize some of the normal modes.
And further just so we understand each other. You did realize that the radiation mentioned in the estimation above is radiation in response to an accelerated charge? The radiation force mentioned is the "Abraham-Lorentz(Dirac)" force (a constant times the jerk), not the forcing! I think it is perfectly clear from the context but maybe it can be missed. What the estimation shows is that the timescale on which this force is important is lagging at least ten magnitudes to the timescale of the mechanical motion in the solid.
RaderaThis relates to the basic problem with classical electromagnetism that you typically separate an electromagnetic problem into two different classes. Either you separate into a situation where the external field is given and you calculate the response. Or you provide a charge distribution and calculate what field this charge gives. There can be some issues with causality when you try and solve a problem that is of the type mixed (as the one discussed). The estimation shows why and when you can separate your problem into one of the two types mentioned. Here it seems as we can separate the problem into one with external forcing and ignore the response from accelerated charges to at least a factor of one in 10 billion.
I think you are confusing mass oscillation with charge oscillation, where charge oscillation is an electromagnetic phenomenon described by quantum mechanics and not a mechanical phenomenon described by Newtonian mechanics.
RaderaNo. The treatment is purely classical.
RaderaThis is obvious if you understand the derivation.
If it is purely classical, then it is too narrow. Quantum mechanics is the mechanics of electronic oscillation.
RaderaSo, how do you want it to be?
RaderaYou have made a big fuzz that classical mechanics is the rational science, jada jada jada... And now it's not enough??
The estimation above from Jackson is classical, I thought that was what you were asking for. The reason to bring that estimation into this discussion in the first place is simply because your model in 'Mathematical Physics of Blackbody Radiation' is classical.
The response above to Christopher Hoen-Sorteberg '28 maj 2015 01:24' treats phonons in a solid and that is inherently quantum mechanical. Notice though that it has the element of the adiabatic approximation in it, that approximation is of course assumed to hold.
I base my considerations on a formulation of atomistic physics as Physical Quantum Mechanics exposed in a series of posts, with wave function depending on 3 space dimensions common for an atom with several electrons. This model has the form of a classical wave equation in 3d with the modulus of the wave function representing charge
Raderadistribution without connection to classical mass. This can be viewed as a semi-classical model including quantum effects expressed through a classical wave equation.
In it's present form can you with thid theoty calculate the bandgap of silicon?
RaderaIn principle yes.
RaderaWarming results when emission of incoming waves is impossible because the frequency is above cut-off. Warming thus is an effect of inability and not knowledge, which individual resonators may well show. To not understand an argument does not require any intelligence.
SvaraRaderaYes Claes, the warming of a colder body depends on, as you say, that it can´t resend all the spectrum of the warmer body - there will be a warming net energy - but it can resend all the frequencies of its own spectrum, and that is what is called "back radiation". I am not talking of its ability of heating warmer bodies, I just conclude that it exists. The heating of the earth because of "greenhouse effect" depends on the slowing down of the energy transport from earth to space.
SvaraRaderaIt seems that you now acknowledge that "back radiation" has no role to play for the "greenhouse effect" supposedly heating the globe. Let us then once and for all stop talking about "back radiation" and whether it exists or not whatever it may be.
SvaraRaderaClaes, I think that many of us, reading about your denial of backradiation, have thaught that you really mean that it does not exist in physical meaning - that it is not measurable, which it of course is. That it does not transfer energy to earth is quite another thing. But this denial of the existance of "back radiation" can easily be misunderstood.
SvaraRaderaWell, what we are discussiong is radiative heat transfer in the atmosphere, and when you now say that "back radiation" has nothing to do with that, then that is fine. We can then leave "back radiation" outside the discussion and whether it exists or not is irrelevant. If you believe it exists, and can be measured, then it is like your political or religious views which are irrelevant for the discussion and are not anything we have to or should argue about, right?
SvaraRaderaClaes,
SvaraRaderawhich physical law prevents a individual photon emitted from a colder body being absorbed from the warmer body.
It's frequency is too low to have a heating effect.
SvaraRaderaFrequencies produced by cold objects are produced in *greater* abundance by hot objects. We can therefore direct "analysed" beams of that 'cold' frequency with great intensity upon hot objects and show one way or another if that frequency can be absorbed.
RaderaFrom a "folk lore" point of view if you direct massive wattages of IR of a particular frequency upon an object that is known to be able to emit those frequencies it might be supposed it will become very hot indeed.
We know that low temperature objects produce smaller quantities of an Ir frequency than hot ones do. Therefore a hot object will always produce more energy than a cold one can for that frequency.
We seem to be talking about energy quantity here rather than frequency.
I see you can get commercially available tuneable far infrared lasers for infrared spectroscopy
RaderaI see you can buy high power tuneable Far infrared lasers for spectroscopy or medical use. So you can easily test if narrow bands of low frequency IR are able to heat objects. All you have to do is take the lowest frequency IR produced by a cold object and test if it heats a hotter object that can emit that frequency.
RaderaClaes,
SvaraRaderathis was not my question, because "Absorption" and "heating" are two different processes. I didn't ask about "heating".
So again, which physical law prevents an individual photon emitted by a colder body being absorbed by a warmer body?
What is an "individual photon" and what is the physical process of "being absorbed" and what does that have to do with radiative heat transfer?
SvaraRaderaThe individual photon is a single quantization of the photon field as an excited quantum oscillator in that field with a certain momentum, angular momentum and energy. These are experimentally verified in the sense as currently the only feasible theoretical model that can explain a huge set of different experiments that started to be done since the 1980. Photon antibunching for instance that definitely rule out any kind of semiclassical theory where the electromagnetic field is a classical field and the matter quantum mechanical.
SvaraRaderaIf you are true in your question about individual photons you should read up on these experiments.
Absorption is the process where a single photon in the photon field is anhilihated by transfering its momentum, angular momentum and energy to another system.
This is what radiative "heat transfer" is on a more fundamental level from the current theoretical view. "Heat transfer" is put in quotes because this models works both on systems without temperature that are not thermodynamically well defined and systems that are in the thermodynamic limit.
What is the heating effect of the process you are describing?
SvaraRaderaPlease give your definition of heating.
SvaraRaderaHeating is a process in which the temperature, or internal energy in thermodynamical terms, increases.
SvaraRaderaOk, then you assume that you are in the thermodynamic limit so that a temperature exists at all. That is a way to restrictive condition and forces the systems relaxation times to be short compared to the relevant timescale.
SvaraRaderaA fundamental description doesn't explicitly treat heating as you think about it unless you go to the thermodynamic limit.
Maybe this is the source for your great confusion.
Thermodynamics isn't really that intuitive for you to use in case of radiative energy transport, obviously.
Temperature is a measure of internal energy as the energy of electronic oscillators acting according to quantum mechanics.
SvaraRaderaIs there a temperature without an equilibrium?
SvaraRadera"Temperature is a measure of internal energy as the energy of electronic oscillators"
SvaraRaderaThis looks really weird. The vast majority of the electrons are in the ground state. It is the ions that carries the bulk of the energy through lattice vibrations. Or do you disagree?
Unless it is a metal then of course, but then the excited electrons don't oscillate, they carry energy in the vicinity of the fermi-level.
I agree that atom-infrarred electromagnetic forcing mainly involve electrons in outer shells.
SvaraRaderaSo you disagree. Why can't you just say that instead of playing on vague fucking innuendos impossible for interpretation. That's the worst kind of science imaginable. Feynman said it quite clear in his lectures that's been called The Character of Physical Law (you can find them on youtube)
SvaraRaderaAnother thing I must point out is that you cannot prove a vague theory wrong. If the guess that you make is poorly expressed and rather vague, and the method that you use for figuring out the consequences is a little vague - you are not sure, and you say, ‘I think everything’s right because it’s all due to so and so, and such and such[,] do this and that more or less, and I can sort of explain how this works …’, then you see that this theory is good, because it cannot be proved wrong! Also if the process of computing the consequences is indefinite, then with a little skill any experimental results can be made to look like the expected consequences
The really sad thing is that we will probably never see if your theory has any merit.
Time will tell. Maybe you are right, or maybe you are wrong. I don't think that Feynman means that it is meaningless to try a new approach to an old problem which never was satisfactorily resolved. In any case I am pursuing a theory that is computable and if something is computable then it can be tested against observation. Too much of current physics including multidimensional wave functions, and even worse string theory and multiverse, is uncomputable and then testing is impossible and then only lofty theoretical arguments remain, and that is what Feyman does not like. If you don't like what I am saying, why don't you use your energy on something else than trying to stop my investigation by dirty words which add nothing of interest.
SvaraRaderaDear Claes,
SvaraRaderaAs I have pointed out to you before, you have a problem with your 'stone-in-the-sunshine' example. You claim that the stone has no oscillators correspondning to the high temperature oscillators characteristic for the sun. Therefore the stone must absorb. The empirical truth, however, is that the stone also reflects a fair fraction of the incoming radiation. You then have the problem to explain how this reflection is created by the object! In the absence of oscillators - it is impossible.
C-G. Ribing
No C-G: Reflection does not require any oscillator; it is sufficient that the stone is completely rigid, which is a fair assumption concerning a stone.
SvaraRadera