Listings Question About Ping

[les]

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