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 -- 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
