Ane here is a interesting column by Cecil on naming colors
Passing lightly over the fact that salt is not a rock, but a mineral, there’s actually another one that we ingest: water, for that, too is a mineral.
I also learned about color around grade 7–from a Time Life book. It wasn’t taught to me in school so if I hadn’t read the book on my own I wouldn’t have known.
Ay caray… thank you.
<totally:offTopic>Well you should consider it. Plasma is just ionized gas. However, electromagnetic radiation can come from, say, electron-positron annihilation. I don’t know that single leptons are considered chemicals, but I think chemical doesn’t really have a rigorous definition anyway.</totally:offTopic>
I’m a chemist so perhaps I take a traditional view on the subject. If you want to get technical, perhaps plasma is just another phase of matter. I don’t beleive there are any compounds that exist inside a plasma so the chemistry at this phase is entirely different.
My point was that at these high energies, color has a different mechanism from normal everyday absorption/reflection.
Actually this just reminded me of another mechanism for color, refraction. I think that most birds feathers are not colored by pigment, but by small structures in the feather that refracts light. I think a physicist will have to explain that but I has to do with the size of the wavelength and the size of the microstructures in the feathers. Also diffraction is another one I’m not very well equipped to describe.
As to how things made out of colorless objects can have color, consider this analogy. I have a bunch of grains of sand. It’s river sand, so all of the individual grains are rounded off. If I look at an individual grain of sand under the microscope, it’ll look smooth, like a very small pebble. But now suppose that I take all of my sand, and I glue it to a piece of paper. Even though the individual grains of sand don’t have any roughness, the piece of sandpaper is rough. Roughness is not a property of the individual things which make up the sandpaper; it’s a property of how they’re arranged and bound together. In a similar way, color is a property of how atoms are arranged and bound together.
Whoops, this wasn’t there when I posted:
Refraction is another method of producing colors (for instance, in rainbows). But bird feathers (and blue eyes, and oil slicks on puddles, too, for that matter) don’t use that, either. Those are all a result of diffraction, another method yet of producing colors. But this is probably getting a bit far afield of what’s necessary to answer the OP’s question.
Um, why? (am curious - this would be such a cool fact to know). I thought it was a gas, cool enough, and under enough pressure to be fluid. But then ‘rocks’ would become gaseous, if hot enough… OK, now my head is spinning…
And now that you have straightened my understanding out, I beleive I can explain both reasonably well. Still, I’d differ such discussions to physicists wherever possible.
Not leptons, certainly. But a baryon can be a chemical. A single proton is a hydrogen ion.
How about brightly colored iridescent beetles? I heard they are made with a molecule that, because of its size, diffracts a given color. I would love to know the Straight Dope on this phenomenon.
Look guys. I’m a chemist. If I don’t think its a chemical, then its not a chemical. That’s how the definition works. I am the decider!
No, it is not.
I don’t know beetles, but “iridescent” usually describes things which get their color from diffractive effects. And the particular wavelength(s) diffracted by a structure do depend on its size. So you’re probably correct.
I hate to contradict my good friend, the redoubtable Q.E.D., but I don’t understand why you use the term “arbitrary” or why you would claim that color, as opposed to any other sensory experience, exists only in the brain. The physical effects that create the experience we call color exist out in the world and our brains create an analog of them that allow us to perceive the world more or less as it is. It make as much sense to call those various wavelengths of light “color” as it does to call certain chemicals that drift through the air “the scent of roses.”
Actually color perception is quite complicated. For example pink is not a spectral color that corresponds to any wavelength. As far as the human eye is concerned, most colors can be generated by a combination of three colors (magenta, green, blue for TV’s). The color we see does not relate well to the spectrum at all.
All sensory experiences exist only in the brain. I didn’t bring them up because this thread is about, y’know, color. Color is arbitrary; there is no natural reason why light between about 620 and 700 or so nanometers should appear red to us, but it obviously does. There is, however, no sharp dividing line between the different colors other than the mechanisms of our own perception; it’s a continuous spectrum. Evolution basically assigned colors to various bands of wavelengths more or less randomly. That’s the definition of arbitrary.
To get technical, rainbows really are a diffraction phenomenon. You can’t really understand things like supernumerary rainbows unless you use the wave nature of light. Thomas Young, who championed the wave theory of light, proposed this, but it was George Biddell Airy who first showed it mathematically. For a very good intro, see R.A. R. Tricker’s Introduction to Meteorological Optics. For quick treatments without the math, see Minnaert’s The Nature of Light and Color in the Open Air, or Greenler’s book. The effect goes beyond supernumeraries – the size of the raindrop (relative to the wavelength of light) determines the relative widths of the colors in the main rainbow itself, and Minnaert gives a neat chart that lets you determine the size of the drops making the rainbow, based upon the relaive widths of the colors. That wouldn’t be possible if rainbows were purely a refractive phenomenon – in that case, every rainbow would look the same.
Although this discussion may ultimately deserve its own thread, I’ll continue since we’re still more or less on the same topic
What does this mean? What kind of reason do you want for the correlation of a physical stimulus to our perception of it? What is the reason that a certain sound should appear to be that of a bell or zither or a baby crying, other than that the source of the stimulus creates the reaction in our brains that we call that particular sound? How is this not the same for color?
We say that a blanket is soft or a piece of glass is smooth. Are you also going to say that there is no such thing as “soft” or “smooth,” that they are just arbitrary constructs of our sensory apparatus? If so, then you seem to be asserting that there’s no connection between our sensory experience and the real world. If not, then what’s the problem with calling anything between 620 and 700 nanometers “red”?
Sorry, I’m just not getting this at all.
One might also ask why blue and red make purple. Spectraly that makes no sense since purple is shorter in wavelength than either of them. The fact is our perception of color is only partly related to the spectrum of what we observe.