Kevin Nolan wrote: > Ivan Anderson wrote: On the matter of FIR - no. Conservation of energy > - the first law of thermodynamics - is not sufficient; there is the > second law to contend with as well. If any (passive) material could > selectively radiate a frequency spectrum different from that of a > surrounding environment at the same temperature as the material, one > could construct a method of extracting heat defying the second law. > This restriction does not apply when the material is held at a > different temperature - emissivity of the material then dictates a > different spectrum from some other material. This may seem > contradictory but it's not - check any good textbook on > thermodynamics.I believe it all gets back to the power of advertizing > hype - if you believe something works, in a sense it does, regardless > of the facts.
I don't know where you get this from. Materials often, in always, emit spectrums that differ from other materials at the same temperature. No material emits a pure "black body" radiation, to obtain such a spectrum requires a box painted black inside with something as close as you can get to black body, with a small hole in it for the radiation to come out. Basically the absorption curve will duplicate the emission curve, so if it emits more of a certain wavelength, it also absorbs more as well. This does not violate any laws of physics. You cannot see this effect in the ir wavelengths, since it is outside the spectrum the eyes see, but you can prove it very easily by heating different materials until they emit in the visible spectrum. Different elements will emit different wavelengths. That is how fireworks give all the different colors. The way fir works is that they have an absorption and emission near the wavelength that the body emits due both to it's composition and higher temperature than the outside. If you are wearing cotton for example, this radiation goes right through your clothes and is lost. Not much comes back because usually one is not surrounded by water which will be emitting at this wavelength preferentially, and because it is cooler, and the amount of ir goes up to the 4th power of temperature if I remember right. However if you have something which will absorb and reemit this wavelength efficiently, it will block the IR leaving the body, and reemit it back to the body, so that part of what is lost will be returned. This no more violates the laws of physics than the use of a reflective surface in a thermos bottle to return heat to either the inside or outside. How much heat is lost through radiation? Apparently quite a bit since a thin plasic film with aluminum evaporated on it to produce a reflective surface is often used as survival gear when hiking to keep warm if you get lost. Marshall -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
