On Tue, Jun 24, 2014 at 04:31:00PM -0400, John Mikes wrote: > Russell: > you wrote: > > > *Not really - the peak of the solar spectrum is yellow light. The IR and UV* > *portions are relatively small components, and what little there is is > further absorbed by water vapour and the ozone layer respectively.* > > Is ALL you do mean the SOLAR (!) spectrum we can detect with our > instruments? > Are you sure there is nothing else? Liz mentioned EM spectrum *total*. What > is included in it beyond the above (as part of our unknowables)? > John M >
Nothing. We can measure everything in the EM spectrum from sub 1Hz up to high energy gamma rays. Different instruments are used for different bands, but they all overlap and are cailbrated against each other. I understand that the gamma ray spectrum is unbounded, since any photon with sufficient energy to knock an electron out of an atom (ionising radiation) will be detected by a photomultiplier, regardless of whether it is the photoelectric effect, the Comptom effect or pair production that is involved. The sub 1Hz spectrum really is unimportant, as there is no useful energy in a photon whose wavelength is bigger than the Earth. We also have a well established theory called "blackbody radiation" that gives a distribution of photon energies being emitted from a body at a given temperature. The sun's distribution fits that perfectly, so we have sound theoretical reasons why it is not emitting anything appreciable outside that spectrum. Obviously, the name "blackbody radiator" is a misnomer, as it needn't be black, as in the Sun's case. Another example of a blackbody radiator is the incandescent lightglobe (when turned on!). -- ---------------------------------------------------------------------------- Prof Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders Visiting Professor of Mathematics hpco...@hpcoders.com.au University of New South Wales http://www.hpcoders.com.au Latest project: The Amoeba's Secret (http://www.hpcoders.com.au/AmoebasSecret.html) ---------------------------------------------------------------------------- -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
