3 ms·
It would help, no doubt, even if I cannot estimate how much. OTOH, it would help as well if windows did not filter IR radiation. You know, a greenhouse works b
by pif 12y ago
It would help, no doubt, even if I cannot estimate how much.
OTOH, it would help as well if windows did not filter IR radiation. You know, a greenhouse works because glass is transparent to visible and near IR radiation, but is quite opaque to far IR. Visible light is the peak of the spectrum of solar e.m. radiation and its frequency is proportional to the temperature of the sun photosphere (~6000 K). Visible and near IR radiations traverse the glass, gets absorbed by objects and heat them. Part of this heat will be re-emitted as far IR radiation, with a frequency proportional to room temperature (~300 K), which is 20 times smaller than visible light. This factor 20 is enough for the glass to turn from transparent to opaque. That's why you can have a greenhouse, or simply a car with its windows closed, get hotter than the surrounding atmosphere.
- adrianN 12y agoActually, greenhouses work because they let the sun in but prevent convection from cooling the heated surfaces. The stuff inside would need to get pretty hot to put out enough IR to make much of a difference. https://en.wikipedia.org/wiki/Greenhouse_effect#Real_greenhouses https://en.wikipedia.org/wiki/Greenhouse_effect#Real_greenho...
- pif 12y agoThis doesn't negate what I said. Preventing convection means that hot air stays inside instead of being dispersed. But hot air does emit IR radiation, and if that radiation could escape the air would get fresher.
- adrianN 12y agoIn the wiki link that I posted an experiment is mentioned where they used rock salt instead of glass to build a greenhouse. Rock salt is IR transparent, yet the greenhouse got to nearly the same temperature. Hence IR transparency is mostly irrelevant.
- pif 12y agoThanks for the link, that's interesting. But, please, have a look on this site as well: http://www.drroyspencer.com http://www.drroyspencer.com.