As a visual artist, I as interested in exploring what we see and how we see. We don't see objects, rather we see light reflected off objects. The portion of the light we see is made up of discrete photons with wavelengths within the visible spectrum that are caught by four kinds of photoreceptors arrayed in the back of our retinas. Those receptors emit electric signals that are processed by complex circuitry in layers of the retina and sent to many sites in the brain which create our sense of the real world.
Despite amazing modern day research into their workings, the astounding complexity of our visual and neural networks are largely indeciphered. The best source I have is R. W. Rodieck's "The First Steps in Seeing" 1998, Sinauer Associates, Inc.
We see the mix of photons in the visible spectrum as white light or separately as colors - low energy/long wavelength red, orange, yellow, green, blue to higher energy/shorter wavelength violet. Supposedly we can distinguish between 1 million different colors, although whoever did that research probably lost count after 1,000. We can’t see photons on either side of the visible spectrum, lower energy infrared photons we feel as heat and higher energy ultraviolet photons that give us sunburns. The water in our eyes filter out most of the ultraviolet ones which would damage our retinas.
It seems to me that one starting point of this exploration are the photons that reach our eyes.
The word photon was invented in 1926 and is mashup of the Greek word phos = light. Almost all our photons come from the Sun and have a range of energies inversely proportional to their wavelengths.
Physicists describe photons as part particle and part wave and have derived complex mathematical formulas linking photons with electromagnetism, quantum mechanics, space, time and gravity. Photons travel at the speed of light (redundant description) and have no mass (also redundant; by definition, particles with mass supposedly cannot travel at the speed of light). Photons also have angular momentum [they spin] and they can be separated by interacting with matter, what we call polarization.
My artistic mindset has boiled all this photon stuff into an analogy: Picture the Sun as a giant kettle, spewing out trillions of spinning popcorn kernels called photons. The kernels are all the same size, and travel at the same speed ( duh the speed of light) but they are spinning at different rates and in different orientations. If you have ever played with a child’s top or a gyroscope, you know that the faster they spin the harder it is to move them. So the faster photons spin the more energy they have. I can't find any experimental findings on how fast photons spin, so I am thinking the photon energy/wavelength thing is just a measure of spin speed, longer wavelength photons precessing more than shorter wavelength photons.
Apparently the 20 million photo receptors in each eye catch only a tiny portion of the millions photons that pass into our eye every second. More photons with wavelengths within the range of each of the 4 photoreceptors are captured and the brain integrates the totals to discern color and brightness. Most photons pass right thru and are absorbed by a black layer in the back of the retina and removed as heat by the network of blood capillaries and vessels bringing oxygen and nutrients to the eye.
I think our photoreceptors not only record photon strikes and the wavelength of many of them as a particular color, but can determine their polarity*, which may be involved in our "holographic" ability to discern three dimensionality. More on that subject in a later post.
* Google "Haidinger's brush" and see if you can duplicate Wilhelm Karl von Haidinger's 1844 discovery of our perception polarization of light.