On Sun, 2011-12-25 at 17:12 +0000, Marko Vojinovic wrote: > Wow, look, another OT thread to contribute to! :-D > > On Sunday 25 December 2011 23:35:15 Tim wrote: > > Tim: > > >> We're mostly sensitive to green, then red, then blue. > > > > Joe Zeff: > > > Not quite, AIUI. The wavelength the human eye is most sensitive to is > > > in the "greenish yellow" range, much more yellow than green. > > > > Well, as far as coloured sight goes, the primary colours are red, green, > > and blue. That is, the sensors in our eyes are attuned to those > > colours, with a small spread either side of them. > > [me loading extension_Biochemistry... done] > > Um, no, the "red" receptors in the eye are actually peaked at green-yellow, > not red. Let me quote a piece from > > http://en.wikipedia.org/wiki/Color_vision#Physiology_of_color_perception > > <quote> > For example, while the L cones have been referred to simply as red receptors, > microspectrophotometry has shown that their peak sensitivity is in the > greenish-yellow region of the spectrum. Similarly, the S- and M-cones do not > directly correspond to blue and green, although they are often depicted as > such. It is important to note that the RGB color model is merely a convenient > means for representing color, and is not directly based on the types of cones > in the human eye. > </quote> > > You can find more details on http://en.wikipedia.org/wiki/Photopsin , and the > picture at > > http://en.wikipedia.org/wiki/File:Cone-fundamentals-with-srgb-spectrum.svg > > shows clearly which part of the spectrum is covered by S, M and L > photoreceptors, and how well it is covered. > > At least as far as humans are concerned. ;-) > > > From the point of the receptors, it is green > > that we see the most. If one were to draw a rainbow across a page as a > > graph of the sensitivity of our eyesight, there's a peak around the > > green, that slopes off either way, with the blue side sloping off faster > > than the red side. > > That would be http://en.wikipedia.org/wiki/File:Eyesensitivity.png . > > > > Considering that the Sun is a yellow dwarf, it's much more likely for us > > > to find the wavelengths near and/or at its peak output to be easiest to > > > see rather than something off to one side. > > > > It's not actually yellow. > > [me loading extension_Astrophysics... done] > > True, it's white, not yellow. The sunlight only appears to be yellow on Earth > because of the atmospheric refraction. > > Otherwise, the Sun emits pretty much the same amount of (visible part of) > light of each color, summing up to white. The peak frequency is mostly > somewhere near blue, actually. > > The picture > > http://en.wikipedia.org/wiki/File:Solar_Spectrum.png > > can give you a good idea of EM emmision spectrum of the Sun that reaches Earth > (the upper atmosphere and the ground surface). The vast majority is actually > in infrared, but the most intensive part is the visible light. > > > If you were going to argue the line of us > > being sensitive to the colour of the sun, actually it's far more logical > > that we're least sensitive to the strongest colours about. > > [me loading extension_Darwinian_Evolution... done] > > Why would that be? As per the spectrum picture above, the most intensive > radiation from the Sun is in the part of the spectrum that is visible to us. > I'd say that this is just good adaptation of humans to the environment --- the > most efficient way to collect information about our surroundings comes by > observing the most intensive radiation available --- which turns out to be the > "visible" part of the Sun's spectrum. > > And then there is the biochemistry part --- in order to actually observe some > part of the Sun's spectrum, biological organisms need biomolecules which are > chemically sensitive to those wavelengths only. The number and types of such > biomolecules may be quite constrained by laws of chemistry and biology (IIRC > there are at most 12 of them to be found in a single animal), having nothing > in particular to do with available sunlight itself. That's why most animal > species can detect the visible light, some can see ultraviolet, but very few > (if any) can see infrared. This is a consequence of the fact that there are > basically no molecules which are specifically sensitive to infrared spectrum, > despite the abundant amount of it provided by the Sun. For more info, see: > > http://en.wikipedia.org/wiki/Color_vision#In_animals > http://en.wikipedia.org/wiki/Evolution_of_color_vision > > > And for our next off-topic, do we have someone who'd like to discuss the > > theory of relativity for us? ;-) Makes a change from discussing why > > Gnome and Windows suck. > > [me loading extension_Relativity... skipping: already hard-coded] > > In any discussion related to theory of relativity it always helps to have an > expert around --- so you can consider yourself lucky. ;-) Since this part of > the thread is already completely OT, feel free to ask whatever you like about > relativity, I'll try to respond as long as I don't become too busy with real > life stuff... :-) > > HTH, :-) > Marko > > Hi, Marko, This is a great offer. I have a smattering of knowledge about some things, and complete blanks about most in physics. One of the recent things I became aware of is something called ballistic transport of electrons in carbon nano-tubes. I read somewhere (and don't remember where) that electrons in carbon nano-tubes appear to exceed the speed of light. I have made really precise measurement of various electrical things, such as 500femto farad capacitors, and currents into hundreds of picoamps, along with time measurements resolved into the attosecond range, so I realize that there is a lot of capability out there, but how is it that the speed of an electron through a carbon nanotube can be measured repeatedly at speeds greater than light speed? I have a few ideas, but I haven't read any articles on how the actual physical measurement was made. Regards, Les H -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
