Open Thread: Purple

First off, while most open threads a pretty much totally open, and recommends are for recommending anything.  That's not the case here, if you want to talk about Mad Max: Feminist Road use the thread that exists specifically for that purpose.

Originally I was going to do pollination but it occurred to me that a giant picture of a bee could be a bad idea, especially since I know at least one person who is allergic reads here.

So purple.  Some people say purple is a made up color.  That's obviously untrue, there's all kinds of purple.  Light purple, dark purple, pinkish purple, bluish purple, royal purple, purple cow.  Many types of purple.

What the people are talking about is that purple is not on the visual spectrum (which you can see via rainbows) but is on the color wheel.  The difference between the two is simple  The spectrum is a spectrum.  It's a line.  It doesn't loop around.  You may have heard ROYGBIV, named after the Famous Roy G. Biv, inventor of the eyeball.  That's a tangent though, the important thing is the visual spectrum: Red Orange Yellow Green Blue Indigo Violet (but blue-violet, not purple-violet.)

It seems like the color wheel, but while the wheel connects the two ends via purple, the spectrum keeps on going in both directions: infra red and ultra violet.  So where does the purple come from?

It comes from this:

The colors we can see occupy a three dimensional space (called a color space) and there are various ways to define it and such.  That's not important.  What is important is that you can't really draw it on a piece of paper.  So no color wheel if you stick with all possible colors.  But if you fix lightness (say halfway between washed out to pure white or dimmed to pure black) then they fit on a plane in a single closed shape, completely possible to draw and topologically equivalent to a circle,  and that's where we get the color wheel.  In the middle (ish) is completely desaturated gray, on the outer rim are colors that are totally saturated.  Most of that outer rim is the visual spectrum. Red to Orange to Yellow to Green to Blue to Indigo to Violet.  But since they don't connect, there's another part of the rim.  That part, the part that closes the loop, the fully saturated color that is not on the spectrum, is purple.

Purple isn't made up.  It's just the only color that attains full saturation without falling on the spectrum.  (Mind you if we had different eyes there would be a different visual spectrum and the connector would be somewhere else thus current purple wouldn't be full saturation.)

Anyway, that's today's discussion of color and flowers.  Now time for open thread.

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Saturday Recommendations!  What have you been reading/writing/listening to/playing/watching lately?  Shamelessly self-promote or boost the signal on something you think we should know about - the weekend’s ahead, give us something new to explore!

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And, like on all threads: please remember to use the "post new comment" feature rather than the "reply" feature, even when directly replying to someone else!