Many children are afraid of the dark, and for good reason—human vision can deceive them. As soon as you turn off the lights, silhouettes and rays of light begin to appear in the darkness; In low light conditions, we suddenly become more aware of our bodies and pay attention to objects in our peripheral vision. Portal popsci.com speakWhy.
In fact, the flow of information that we receive and process through our retinas does not always reflect reality. Human vision is a complex system involving both nerves and biochemistry, so it can be fooled.
The simplest way to see the limitations of our visual system in action is through optical illusions. To illustrate in action, close your eyes and use your index finger to gently press the upper edge of the orbital bone. You will see a black circle with light edges and it will move in the opposite direction of your finger.
A trick like this shows that the eye can provide visual information even when that information isn't there—the spot appears bright even when your finger isn't. This occurs due to mechanical deformation of the retina, which causes nerve cells to become active and transmit data to the brain.
This perception of light in the absence of a light source is called phosphene. It usually acts as a response to mechanical pressure or some other form of external stimulus. Sometimes phosphene also occurs in physical trauma: after a blow to the head, it is said that “sparks come from the eyes”, this is exactly what it means.
The fact is that in principle, the eye's retina never stops working, even when there is no light source around. In dim light, rod visual cells, which are very sensitive to light, will be more active. Because they are concentrated mainly at the edge of the retina, a person may pay more attention to peripheral vision. And those random flashes of light and color that we can see in the dark or when we close our eyes are actually called. illusion of a closed eye.
But it's worth taking a closer look at the shadow. Contrary to popular belief, in complete darkness we actually do not see black but a very specific, uniform dark grey, eigengrau – or “inner grey” in German. It was first discovered by physicist Gustav Fechner, who studied the phenomenon in the 1800s using gradually fading stimuli (in this case, light) to understand how they affected human perception.
The reason we cannot see absolute darkness is simple – visual interference. It occurs due to signals from the optic nerve that the brain reads as flashes of light. Although here it is necessary to make a reservation that there are other factors that make it possible for us to see something in the dark. When visual information is lacking, other senses become more active, which is why a person can perceive his or her body better.
