Exploring an idea 
Abstract it!
Good mathematicians do it a lot.
Theoretical physicists often make a point of it.
Solipsism, egocentrism, enthocentrism, anthropocentrism....   These are pretty good descriptions of attitudes of a human being maturing from infancy toward...

What is "color"?
And what is colorblindness?

a few other critters
only humans
a stretch for us
beyond comprehension
We see what we see.
We imagine what we might see.
We see patterns in how we might arrange colors, and so we assign names.
We discover patterns within the patterns: we see abstractions
We might somehow sense that there is much we do not see.  It is very, very much.
We see a world of color.
3 Munsell parameters:
Hue - Sat. - Lum.

3 families of screen-dots:
Red - Green - Blue
3 CIE parameters:
X - Y - Z
CIE diagram
(a nomograph)

depiction of the protanope's 2-D projection from the 3-D of normal human color.

Birds and insects see color we have (almost) no way to think about.

It seems to everyone that what we see is just what's there.
In about 1685, Isaac Newton discovered realms of vision beyond human vision.


Since Newton, science has discovered much, much more that lies beyond human perception.
(Many other animals have known about some of this for millions of years.)

Light is a bit like waves on water.
Those water waves are a few feet apart.

Light wave lengths are measured in millionths of a millimeter.

Far violet:
400 millionths 
  Far red:
700 millionths
 ULTRAVIOLET                                                                  INFRARED

Our eyes are blind to the rest:


Then, just what is color?
It's Mother Nature's attempt to give us perception of wave-length distribution of light!
at least of that tiny bit of the spectrum that we can see.

The light that gets to our eyes is almost never of just one wavelength.
It's a whole range of wavelengths, with more of some and less of others.

This is a graph of the wave-length distribution of light that might be reaching our eyes just after sunset.
That spike in the yellow is a bit of light from a sodium-vapor street light.
The sharp cutoff in the ultraviolet is due to a number of atmospheric effects;
for example, Rayleigh scattering (the scattering of light that makes the sky blue and
the sunsets red) and chemical  absorption, especially by that of ozone...(cont.)

Of course, we see none of this.
Because our eyes aren't spectroscopes.

Mother Nature didn't do a very good job when she designed our color vision.
Our color vision is a good first step, though (birds did better).  Here's how it works:

At the back of our eyes (on the retina) are three different kinds
of bright-light sensors, very, very small and very, very many.

Each kind of these "cones" samples a bit of the spectrum.
One kind is most sensitive to light of about 450 millionths of a meter.

One kind is most sensitive tol ight of about 550 millionths of a meter.
One kind is most sensitive to light of about 580 millionths of a meter.
(But it also has ehanced sensitivity to light of about 430.)


So when some light enters our eyes, those three kinds of cones take
a first step toward constructing that graph.  A complete graph needs
a point for every wavelength that we can see.  Our cones give us just
three points.  Those three points are not points on the graph, but are
only raw material for our brains to work with to inform us of a little bit
of the information that would be given us if our eyes were spectroscopes.

The mathematics level of abstraction
can help us ask and answer questions where our vision fails us.

What about

totally colorblind
All three cones functioning
Blue and green cones functioning.
Blue cones only functioning
Colors order in three dimensions Colors order in two dimensions Colors order in one dimension.
Color blindness can be of many other kinds.
For example; deuteranopia is blue and red cones functioning.

When normal human color vision sees this . . .  ...protanopic vision sees this and blue-cone only vision sees this.

What does a bird (with 4, 5, or 6, components of color vision) see?
We have no way of seeing that with our eyes.

What does a bee (with polarization vision) see?
We have (almost) no way of seeing that with our eyes.

our solipsisms,
our egocentrism,
our enthocentrism,
our anthropocentrism,
(or whatever)

we tend to be blind to so much of our world.
and so
even our more erudite teachers
might miss the meanings

RETURN to From Perception to Magic