Eigengrau (German for intrinsic grey) is the term for the colour seen by the human eye in perfect darkness. Also called dark light or brain grey, it is perceived as lighter than black. Even in the absence of light, some action potentials are sent along the optic nerve, causing the sensation of a uniform dark grey colour.
Let’s try to understand as to how humans perceive darkness with a little experiment. Pick a black object in front of you and stare at it for about a second. Now close your eyes for a few seconds and allow them to adjust.
You may need to cover your eyes if you are in a bright room or outside. Now open them quickly and look at that black object. Now it may take you a few tries to fully see it, but you’ll soon notice that the black object appears darker than the black of total darkness.
When our eyes are open, the light-sensitive layers of cells at the back of our eyeballs called the retina are bombarded by packets of light energy called photons.
The photons are a kind of elementary particle. Or, perhaps they are the quantum of the electromagnetic field that includes electromagnetic radiation like the light. They are also the force carrier for the electromagnetic force. The photons have zero rest mass. They always move at the speed of light within a vacuum condition.
The photons represent visuals like a trigger nerve impulses on the retina that pass through the optic nerve to the brain and a visual image is formed on the retina.
When we close our eyes or enter total darkness most people see vague grey field usually composed of changing regions of tiny black and white dots.
This colour is called the Eigengrau, a German word that means intrinsic grey. What we are seeing is visual noise and it is the static of our retina.
Credit : STSTW Media
Picture Credit : Google
