Quantum perception

The physics and biological mechanics of vision are astounding – I find it amazing that we can see at all. A Photon of light is very small (measured by the width of its wavelength). For example, the wavelength of green light is about 500 nanometers, or about two thousandths of a millimeter. That begs the question: why don’t photons just go right though us? Lets look at the problem with an explanation of why photons can pass through glass:

“Particles can pass though objects. For example, right now there are 100 billion solar neutrinos per second passing through every square centimeter of your body. The neutrinos are particles that only have VERY weak interactions with the matter that our bodies are made of so almost all of them pass through without interacting. So, in general, there is no problem with particles passing through matter if they do not interact with the matter – there is lots of space between the nuclei of atoms.

Now light particles, photons, are packets of electromagnetic radiation and the electric fields and magnetic fields can interact with charged particles. Thus photons cannot penetrate through metal because the free electrons that make metals conductors will easily interact with and absorb the photons immediately.

However the electrons in glass are tightly bound to atoms so they are not free to move like the electrons in a metal and therefore they do not absorb the photons. … If the energy of the photon happened to equal the difference between a bound electrons energy level and another unoccupied electron energy level, then the photon would get absorbed by causing the electron to transition between those energy levels.  However, there are no such energy levels available in glass for visible light photons.  On the other hand, ultraviolet photons do get absorbed because there are available energy levels at the energies of those photons.”

– Frank Heile, Physicist

This helps us better understand some of the properties of our eye lens and our retina. But what does happen when a photon strikes the retina and stimulates a rod or cone?

First, it’s important to know that only 1 to 3 percent of photons actually reach a photoreceptor cell – there’s a lot of light that we don’t see and probably the only reason we are able to detect light hinges on:

  1. the number of photons passing into the eye (as many as 10^14 photons per second) and
  2. the massive number of cone and rod cells (120 million rod cells and 6 million cone cells).

When photons “hit” a molecule (on a cone or rod) it raises an electron to a higher level (the molecule absorbs photons in the electrons on the surface, transforming the energy into density vibration). Once stimulated our photoreceptor cells convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell’s membrane potential. The process happens at the atomic level an our photoreceptors are capable of detecting a single photon of light. Astronauts have reported seeing other colors such as yellow and pale green lights that were determined to be cosmic rays (gamma and x rays less than the diameter of an atom).

But some stimuli may be happening at an ever-smaller scale. Physicists now believe that the human eye is capable of detecting quantum effects.[1] To date I know of no direct experiments with humans that prove that conjecture, but there is evidence from experiments with European Robins that does.

It’s long been thought that birds navigate using Earth’s magnetic fields (which is very weak, too weak to detect), Experiments indicated that the robin’s magnetic detection is in the eye – the robin’s chemical compass can see the state of quantum entanglement of photons (which are more likely at magnetic north), the direct observation, by an eye of a quantum state. See: The Secrets of Quantum Physics: Einstein’s Nightmare, Physicist Jim Al-Khalili  [2]

That Darn Cat
There is a line of thought called Biocentrism that posits our perception is creates the universe. This argument is based on a concept expressed in the Schrodinger’s Cat thought experiment.

“A cat imagined as being enclosed in a box with a radioactive source and a poison that will be released when the source (unpredictably) emits radiation, the cat being considered (according to quantum mechanics) to be simultaneously both dead and alive until the box is opened and the cat observed.”

Biocentrism says that the quantum nature of matter sets up a universe where our perception actually creates the universe we experience. But the concept goes further, suggesting that time is an illusion, and that we are living all of our possible decisions/perceptions at the same “moment.”

I’ll revisit this line of thought in the next article, which covers the olfactory system.

Web Application

None known, but isn’t it interesting?

Related Articles

Advertisements

Color

“Mere color, unspoiled by meaning, and unallied with definite form, can speak to the soul in a thousand different ways.”
Oscar Wilde

There are so many things to say about our color perception. For example, the Human eye is capable of seeing between 7 and 10 million colors. Question: why is that massive range of perception so important?

We can define color vision as the ability of our eyes and brain to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit, or transmit. We can point out that the typical human eye is only capable of perceiving light at wavelengths between 390 and 750 nanometers (the “visible” spectrum for Humans), and that our perception of colors is a somewhat subjective process – we all see the same illuminated object or light source a bit differently.

cone_cellWe can delve into the neurological process of three types of cone cells in the retina (up to 7 million) gathering information about visible wavelengths of light that correspond to short-wavelength, medium-wavelength and long-wavelength (red, green, blue). We can even frame the definition of vision as the process of perceiving color:

“‘Vision,’ by common usage, suggest a process; but it is now known that it is built out of many processes, subdivided into at least 32 areas. Before they eye’s input gets to the cortex it goes through two vision systems. One sees motion, and the other color. They largely come together in the primary visual cortex. Nonetheless, the overall visual system continues to stream continues this division into higher areas of the cortex. Vision goes into what a stream that identifies things and into a where stream that locates their positions. And even this description is a gross simplification.” Sagan & Skoyles, Up From Dragons

But the perception of color is much more complex …

What we see as color is, in a sense, an absence of colors. White light from the sun hits an object – let’s say a blue object – and all of the color in the white light (the full spectrum) is absorbed by the object with the exception of blue (and perhaps ultra violet and infrared). The blue is reflected to our eyes. The cones in our retina are stimulated at a specific frequency and sent to our brains for interpretation. We see blue – unless, of course we’re color blind.

But all color is perceived in context, as explained in Neuroscientist, Dr. Beau Lotto’s TED Talk,

Dr. Lotto sums our experience up like this, “The light that falls on your eye (sensory information) is meaningless, because it could mean literally anything. … There’s no inherent meaning of information, it’s what we do with that information that matters.”
Dr. Lotto also provides an example of why we evolved to see colors – pure survival. The example he gives in his TED Talk involves seeing a predator in the jungle. But there are alternative hypotheses.

Theoretical neurobiologist Mark Changizi has speculated that the reason Humans see is because it gives us an advantage in sensing emotions or health on the skin of others. Other neuroscientists suggest that our ability to see many shades of green help us differentiate between and choose plants to eat versus avoid poisonous ones.

No matter how we see the world, there always seems to be another view (as followers of biocentrism might say). Here are just a few interesting facts that we know about color:

  • Color Blindness: Men have a higher chance of being color blind than women. 1 out of 12 as opposed to 1 out of 255. The most common type of color blindness is the disability to tell the difference between red and green.
  • Tetrachromats: About 1.36% of the world’s population (only women) have a fourth type of cone cell in their retinas, (resulting in Tetrachromacy) giving them true four-color vision allowing them to see more than 100 million colors.
  • Depression & Color: Research published by Dr. Emanuel Bubl demonstrates that the retinas of depressed patients were less sensitive to contrast – making colors appear duller.
  • Shades of green: Human cones in the eye are more sensitive to green frequencies than any other. Humans are omnivores, so that not only can differentiating between shades of green plant help us find edible plants and avoid poisonous ones.
  • Ultraviolet colors: The Human eye is capable of seeing ultraviolet when the lens is Removed – some people are born with Aphakia – the absence of the lens on the eye. The great impressionist painter Claude Monet developed cataracts in his old age and after struggling to paint (with his colors washed out) he decided to, at age 82, have the lens of his left eye completely removed – the operation allowed him to see familiar colors, but it also let him see, and paint in ultraviolet (colors we cannot see).
monet_waterlilypond_1926

Water Lily Pond by Claude Mone – circa 1926 – includes ultraviolet colors

Web Development Application

Understanding color in for development can be very helpful, underestimating its importance can be crippling, for example, not understanding the limits of users with color blindness. The best bet for avoiding issues is to have a knowledgeable graphic artist on your team.

Related Articles

Shades of Gray

“There’s nothing worse than a sharp image or a fuzz concept.”
Ansel Adams

We perceive light with photoreceptor cells (a specialized type of neuron found in the retina). The best-known rods (for vision in low light) and cones (for detecting color). We think of ourselves as primarily seeing color, but we have 20 times more rods in our eyes than cones. Shades of gray are very important for our survival.

rodRods and cones are narrow cells that are extremely sensitive – they can be triggered by a single photon of light. Rods are distributed differently in the retina (the retina contains about 120 million rod cells and 6 million cone cells), but the chemical process they work by is similar to cone cells – light stimulates the cells, sends signals to the brain, and the brain interprets the signals. At very low light levels you perceive vision using only signals from the rod cells in your eyes.

There’s quite a bit of disagreement on how many shades of gray a human eye can see. Some sources suggest only about 30, others say 450 to 500.

Interestingly, there are no rods at the “center” of the retina (the point directly behind the lens). That’s the location of the fovea (or fovea centralis), which contains only cone cells. The fovea is also the region of the retina capable of producing the highest visual acuity or highest resolution.

Many animals have only rod cells in their eyes: for example, pinnipeds, cetaceans, and some monkeys, and some animals like the tawny owl have tremendous number of rods in their retina. Monochromacy (mono meaning one and chromo color) or “total color blindness” normal in many animals, but a disease state in human vision.

Here a list rod characteristics

  • Used for scotopic vision (vision under low light conditions)
  • Very light sensitive; sensitive to scattered light
  • Loss causes night blindness
  • Low visual acuity
  • Not present in fovea
  • Slow response to light, stimuli added over time
  • Have more pigment than cones, so can detect lower light levels
  • Stacks of membrane-enclosed disks are unattached to cell membrane directly
  • One type of photosensitive pigment
  • Confer achromatic vision – relating to, or denoting lenses that transmit light without separating it into constituent colors.

Blind Spot: There is such a thing as the blind spot. It’s the location where ganglion cell fibers are collected into the optic nerve and leave the eye. No photoreceptors are found at the blind spot, but as always, or mind uses the information it has to construct reality, and we are not ware that we can’t see in that area. See a blind spot illusion:

Web Development Application

Understanding how we perceive shades of gray is very important for designers and graphic artists. See the article below: Shades of Grey in Accessibility

Related Articles