Electromagnetic Energy Defined
If you start googling the word energy you'd be amazed at the information that will come back to you. Energy is a generic term that is progressively split into more specific forms depending on the discipline of science that you are working within. If you can get past the notions of "force, work, power, distance, amps, watts, newtons, ergs, etc." that proliferate the literature you are faced with the task of determining how they interrelate within specific formulas that describe the various physical or electromagnetic systems being considered. This blog tries to simplify energy, but concentrates on electromagnetic systems as this is our blog's major theme.
A. ELECTROMAGNETIC ENERGY EXPLAINED - THE PHOTON.
It is a misconception when we say that the Sun sends us "light" or "heat" during the daytime when its brightness beats down upon us. The Sun actually sends us "energy" in the form of a wide range of electromagnetic waves that travel to us at the speed of light and are readily absorbed by the cool surfaces of the Earth. What are the characteristics of this electromagnetic radiation? Consider:
1. Each and every wave is composed of one photon - the smallest particulate of energy possible (it cannot be subdivided to smaller photons). ie. one quantum of electromagnetic energy is called a photon.
2. All photons vibrate because of the inherent energy they possess. The rate of vibration is defined as oscillations / second. This is also called Hertz.
3. The faster they vibrate, the higher their internal energy. Therefore high frequencies indicate high energy "content" and lower frequencies of vibration indicate lower energy "content."
4. Photons are ejected from the Sun's surface and travel to the Earth as electromagnetic waves with a specific frequency which is set by the level of energy the photon composing it possesses. The speed of an electromagnetic wave is always the speed of light:
3 X 10^8 meters / second
5. The range of wavelengths of these electromagnetic waves covers the range from the categories of X rays to radio waves and is called the Solar Spectrum - ranging from (1 X 10^- 15) meters to (100 X 10^-9) meters.
Each photon contains a certain amount of energy. ... Radio waves have photons with low energies, microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and, the most energetic of all, gamma-rays.
Note that energy has "duality" - that is, it can exist in particle form known as a photon OR it can exist in wave form known as an electromagnetic wave. It can only exist as one or the other at any given point in time - it CANNOT exist as both forms at any one point in time.
6. "Heat" waves emitted from the Earth towards the atmosphere as long wave IR radiation cover a wavelength range from 8 micro meters to 15 micro meters. Carbon dioxide will absorb electromagnetic radiation at three wavelengths only - 2.3 um, 4.6 um, and 14.77 um. - mostly outside the "official" IR range.
7. If you know the frequency or wavelength of a chosen electromagnetic wave you can calculate the amount of energy carried by the photon in that wave. This involves a calculation using a non variable number called "Planck's Constant".
8. Planck's Constant is the "energy in joules of one photon at a frequency of 1 hertz). It is equal to:
6.6261 X 10^-34. Joule.seconds
B. CALCULATION OF THE QUANTUM ENERGY of ANY PHOTON.
1. The equation that defines Planck's constant is called the Planck-Einstein relation, and it looks like this:
E = hf = hc / w
E = energy as joules
h = Planck's constant (6.6261 X 10^-34) Joules / second
f = frequency = oscillations / second (hertz)
c = the speed of light (3 X 10^8) meters / second
w = wavelength as meters
hc = 2 X 10^-26 joule.meters
(1055 joules = 1 BTU., 4186 joules = 1 KCal., 1.355 joules = 1 foot lb.)
(1 joule / second = 1 watt)
C. USING FORMULA TO CALCULATE ENERGY OF IR WAVE ABSORBED BY C02
* Using the IR bandwidth of 14.77 um the energy of a single wave can be calculated from the above:
HC (JOULE.METERS) WAVELENGTH (METERS) ENERGY (JOULES)
20 X 10^-26 14.77 uM = 14.77 X 10^-6 1.354 X 10^-20 JOULES
note: this is the energy value quoted in the game changing article listed below (whereby absorption and emission of IR energy by C02 is discussed and the Greenhouse Effect discounted):
This article is summarized and explained in the following blog.
D. TRANSFERRING ENERGY FROM PHOTONS TO MOLECULES.
Vibrational transfer, Compton electron shift, Ramen absorb/scatter, Rayleigh scatter, - these are the four major methods by which energy carried by the photon based electromagnetic wave can be transferred fully or partially to molecules (emphasis on carbon dioxide).
Because photons are the most elemental of energy "particles" it was once thought that they could not be subdivided into smaller pieces and therefore the energy transferred had to be in unit quantities (the amount being displayed by the frequency). It is now known that the energy of a photon / wave can indeed be (sort of) subdivided and this principle (called the Raman effect) is used in the design of some types of Spectrographic analysis equipment.
It is true that photons themselves cannot be physically split into actual fragments. They are indeed the "quantum" of electromagnetic energy. However, remember that a photon is actually an energized "body" that associates itself with unique levels of vibration and this vibration comes with a specific frequency that dictates its numerical energy level (as Joules). By incorporating the variable of frequency into the question, it can be seen that "splitting" of the photon's energy can actually be accomplished.
Transfer of complete energy - due to absorption of a complete photon is associated more with the high energy spectrum and the phenomena of fluorescence or laser beams than the lower energy absorption and re-radiation by atmospheric molecules such as carbon dioxide. The Compton effect describes this mechanism where a full photon is absorbed, causing an electron to jump to a higher level orbit followed by a collapse of this briefly energized state as the electron returns to normal orbit - spilling out a new photon wave in the process. - or, escaping the molecule resulting in ionization of the particles.
Transfer of partial energy - is achieved first through a collision of a photon of specific energy / frequency with a molecule (such as carbon dioxide). Depending on the particular molecule, a certain amount of the wave's total energy is transferred causing it to become more energetic through a shifting its conformation from one "microstate" to another. This shifting generally involves increased vibration, stretching of bonds, twisting, rotation or even an electron shift to a much more energetic outer orbit. These higher states are not stable however and don't last long as there is always a "sink" available surrounding high energy molecules that will receive that energy through kinetic transfer or re-radiation. This type of energy shift is known as the Raman Effect.
In this partial energy transfer mechanism what about the original electromagnetic wave? Since it lost some of its energy to the molecule it is obviously not going to vibrate at the same frequency as before. Therefore the transfer of energy causes a frequency shift to a lower energy level (ie. redshift) which will be a longer wavelength than the original. This new is associated with slightly less energy with the longer original wave.
This shift satisfies the demand made by the first law of thermodynamics that energy cannot be created or destroyed. Balance is maintained as the total energy involved in the transfer and in the deflected wave add up to the original energy value. Any shifting of energy out of energized molecules, whether by re-radiation or by kinetic transfers to neighbouring molecules satisfy the second law of thermodynamics as well, in that energy flows from a "hot" state to a "cold" state, not the reverse (ie. no back radiation to the Earth).
FINGERPRINT ABSORPTION BY C02 AND ITS CONNECTION TO GLOBAL WARMING
What is fingerprint absorption? - this refers to the characteristic of some molecules to absorb energy only at very specific wavelenghs, ignoring anything that doesn't meet their "fingerprint". In the case of carbon dioxide the fingerprint wavelenghs are 2.3, 4.7, and 14.66 microns.
Warming by Compton Effect ? - A common assumption is that radiation absorbed by CO2 must be re-emitted by CO2 in exactly the same way it was absorbed, because electrons jump to a higher orbit when absorbing and must fall back to a lower orbit when emitting. However, electrons changing orbit does not apply to global warming. Electron orbit shift only applies to things like fluorescence or lasers (because much higher input energies are required such as x ray or high intensity light).
Some supposed experts insist that CO2 will absorb and instantly re-emit at the same wavelength in the atmosphere. They are wrong, but even if they were right, it would be irrelevant, because instantly re-emitting at the same wavelength is no different from not absorbing at all. No heat is produced that results in atmospheric warming.
There is also the question as to whether IR rays have enough energy to displace energy from a molecule in the form of a new IR ray. The chart below shows the types of molecular reactions to the strengths of the colliding emw waves. IR waves appear to only encourage molecular vibration, not the expelling of a new photon or an electron (ionization) as seen above with the high energy waves such as X rays.
Warming by Raman Effect? - Global warming theory is more about so-called finger print radiation being absorbed because C02 demonstrates this characteristic. However, at low energy IR ranges, finger print radiation (2.3, 4.7, 14.66) is absorbed, not by electron shifts but is manifested as an increased vibration of the whole C02 molecule. This is due to covalent bonds stretching and bending during vibrations, where no electrons shift orbits as with higher energy Compton absorption situations.
This is the basis of arguments using the Raman Effect as a basis for "incomplete" energy transfers, not the Compton effect concerning complete electron shifts and full energy re-radiations. If the lower energy as heat is indeed re-emitted by transforming into radiation, it is emitted as variable wavelengths (ie. blackbody radiation) dependent on the various temperatures of the C02 molecules emitting it.
Warming by molecular contact - although C02 is said to have capability to absorb and re-emit IR energy, it is more likely it warms up or cools off excess heat by making contact with the 100 or so water molecules surrounding it or the 2500 nitrogen and oxygen molecules also surrounding it. This kinetic transfer of energy does not involve creating any new photon based electromagnetic waves by the C02 molecules (so no back radiation occurs) and it happens fast so the whole system is dynamic, not static. This form of energy transfer is termed Collisional De-excitation.
A Workable Model for Global Warming - Using these mechanisms here's how the dynamic probably works. The long wave IR emitted from the surface of the earth 1s black body radiation (all wavelengths), which has a wide bandwidth. Water absorbs almost 80% of it leaving about 20% that it was unable to absorb. CO2 absorbs within this range in a fingerprint set of frequencies (2.3, 4.7, 14.66), which represents 8% of that total available black body radiation not absorbed by water.
Any C02 absorption most likely is Raman style absorption rather than high energy dependent Compton style. As the long wave IR is absorbed it is instantly converted into heat. The heat is then distributed over all molecules in the atmosphere through collisional de-excitation and limited re-radiation, which means heat goes over primarily to water (up to 4%), 78% nitrogen and 21% oxygen. This physically warms all of the (moist) air and this happens close to ground level primarily as the IR energy doesn't get very far from the Earth's surface before it contacts the waiting C02 and H20 atmospheric molecules.
Warm air can then be blamed for heat transfer into oceans, ice, ground mass or for disturbing the atmosphere through creating abnormal weather situations. Warm air indeed does take part in these mechanisms but its primary role is to reach the upper atmosphere in order to dump its heat load into outer space through re-radiation into this 3 A degree absolute infinite sink.
It is important to not lose focus on the role of water vapour when immersing oneself in the elegance of C02 fingerprint absorption theories. There are about 30 times as many water vapor molecules in the air as CO2 molecules, and water vapour has a more effective fingerprint spectrum which is about three times wider than that of CO2. This means water vapor will swamp whatever CO2 does. It is obviously not being honest to say CO2 does twenty percent of the heating, when there is a hundred times as much effect by water vapor doing the same thing.
The amount of delay before all molecules eventually re-emit their heat to outer space determines how much heat is held within the atmosphere. No one knows how much time delay there is to reach the edge of space, so no one knows how much heat the atmosphere should hold in the processes of sending it into space. These are areas where theories and models gain credibility, not because they are necessarily correct, but rather because there isn't enough real science to accurately dispute their claims.
The best approach to evaluating all claims is to apply the laws of thermodynamics to their mechanisms and overlay it all with the law of common sense.
CONCEPT OF BACK RADIATION
Often, the whole concept of how greenhouse gasses create global warming is described in terms of such radiation being redirected to the surface of the earth.
The concept of redirected radiation is absurd. The wavelengths in question saturate, meaning they get totally absorbed. They can't travel far enough to get to the surface of the earth, unless they are emitted from air which is very close to the earth's surface. Such radiation certainly can't get from the top of the troposphere to the surface of the earth. If greenhouse gasses are absorbing radiation on its way up, they are going to absorb it on its way down.
All matter absorbs and emits black body radiation. This includes the 99% major molecules of the atmosphere, up to 4% water present as vapour or suspended liquid as well as the .04% CO2 in the atmosphere. If the earth was actually giving off significant black body radiation, it would be absorbed by this whole atmosphere, not just the greenhouse gasses, which only absorb a small percent of the wavelengths as fingerprint radiation.
The reason why CO2 absorbs fingerprint radiation but emits almost none, is because all molecules absorb a lot of radiation and emit very little. This is why black asphalt heats in the sun. It absorbs most of the radiation and emits almost none. Radiation leaves almost entirely as black body radiation, because vibration of whole molecules, which creates black body radiation, is vastly greater than vibration within molecules, which creates fingerprint radiation.
Saturation makes the entire subject of what greenhouse gasses do irrelevant.
THE CONCEPT OF EMISSIVITY AND ATMOSPHERIC WARMING
The fingerprint type of IR absorption is due to stretching and bending of internal bonds. Nitrogen does not do that. But all matter absorbs and emits IR in proportion to its temperature. This is called "black body" radiation. Physicists say all matter has the same characteristics in absorbing and emitting black body radiation, except that the quantitative proportions vary, mostly due to reflection.
For nonreflective substances, such as wood and concrete, the percent IR absorbed or emitted (called emissivity or absorptivity) is around 90% of a perfect black body. Metals are good reflectors of IR, so they have an emissivity of around 50%. This means they emit or absorb about 50% of the infrared radiation which contacts them. Kirchhoff's law says emissivity equals absorptivity, which means everything absorbs and emits black body radiation in the same way.
There is a curve for black body radiation, and it applies to all matter. The curve slides toward higher frequencies for higher temperatures. At earth temperatures (around 300 degrees Kelvin) the black body curve (or Planks curve) peaks at a wavelength of about 10µM. The sides of the curve taper off at about 1µM and 30µM. Visible light is 0.4 to 0.8µM, which is just above the curve for cold black body radiation, but hot objects will radiate into the visible range, which is of course how an incandescent light bulb works. Carbon dioxide has fingerprint peaks at 2.7, 4.3 and 15µM, which are all within the black body radiation curve.
In some quantity, everything in the air including nitrogen and oxygen absorbs and emits black body radiation at frequencies which overlap the frequencies absorbed by CO2. In fact, the only reason why there is IR in the air is because the surface of the earth emits black body radiation in proportion to its temperature. The air then does the same thing at some level.
The question then is, in what quantity is the atmosphere absorbing and emitting black body radiation. The emissivity of nitrogen and oxygen gasses should be close to 100%, since they do not reflect IR significantly.
But the larger question is how does the total quantity of atmospheric black body absorption compare to the fingerprint absorption of CO2. Actual measurements and numbers do not seem to exist, So promoters use computer models and pull numbers out of the hat which say increases in CO2 levels will create a global temperature increase).