In many religious traditions (not only Christian ones) it is customary to depict significant figures with radiance around their heads.
This radiance, or halo, is a kind of "insignia" and symbolically indicates some of the special qualities of its "bearer".
To my surprise, I have not yet come across a convincing explanation of how and why this symbol arose. Wikipedia writes in the article "The origin of the halo" that
“… the opinions of scientists differ: some believe that this iconographic symbol of divinity originates from the meniscus (μηνίσκος) - a round metal circle placed horizontally, with which the Greeks covered statues exposed in the open air to protect them from bad weather and from bird impurities; others look for the origin of the halo in shields, which were usually hung on the backs of people who were awarded triumph; still others think that the halo originally appeared as a very pertinent attribute in the images of deities who were heavenly bodies, and only then became the property of not only all Olympians in general, but also those mortals who are taken or worthy to go to heaven. Most likely, the halo owes its origin to the folk belief of the Greeks, who imagined that the body of the gods, when they appear in human form,emit from themselves a dazzling shine and is surrounded by a shining cloud …"
Meanwhile, everything is quite simple. Nimbus as a phenomenon is explained by natural science reasons, and it is quite possible to conduct experiments with repeated results.
Three sources and three components ©
We need the following facts, known from the physiology of vision.
Promotional video:
1. The eyeball in the wakefulness mode continuously, about 5 times per second, makes chaotic micromovements, and the direction of sight 5 times per second changes by an amount of the order of a degree or slightly less. These movements are called microsaccades. A person is not aware of them and is not able to "turn off" them. Moreover, any ways to slow down, "turn off" microsaccades (for example, with medication) lead to inhibition and disconnection of consciousness.
2. If you fix the eyeball and keep the picture visible to the eye motionless, then the retinal light-sensitive receptors "fade", the "afterimage" is imprinted on the retina, and the brightness and contrast in the perceived picture decrease rather quickly. Up to the point that in a few tens of seconds the eye stops seeing. It is very easy to regain "lost" vision: it is enough to change the picture, or to shift the direction of gaze, or just to blink. If, however, a small detail changes in a motionless picture, then this particular detail turns out to be the most (or only) visible.
3. In the center of the fundus there is an area of maximum visual acuity, the so-called. "yellow spot". When a person looks at an object with interest, the direction of gaze makes rather large jumps - so that the significant points of the object are projected onto the macula. Such races are called macrosaccades. They may well be arbitrary. The nature of macrosaccades is related to where attention is directed.
Listener in a trance
Let's imagine a situation. There is a Speaker who says something meaningful. The background behind it is light, bright. For example, a white, brightly lit wall or sky. The Speaker's head is inactive. Distance to spectators / listeners - several meters (tens of meters).
If all attention is directed to audio information, then vision becomes less active, the state of the Listener may approach the trance state, and the macro-saccades may stop at this time (unnecessarily). The Listener's gaze is intent - so as not to miss anything! - and almost motionlessly directed at the figure (silhouette) of the Speaker. At the same time, this silhouette is imprinted on the listener's retina for a long time, imprinted by means of fading of receptors. Where a bright background is projected, the sensitivity is reduced, where a dark silhouette is projected, there the sensitivity is high.
Let us now take into account the phenomenon of microsaccades. As we remember, these are chaotic involuntary micromovements of the eyeball about 5 times per second. If the direction of gaze is slightly shifted, for example to the right, then a bright "highlighted" half-contour will be visible to the right of the dark silhouette of the Orator. It occurs due to the fact that a bright light background in this place fell on non-discolored receptors that retain high sensitivity. If then the gaze moves to the left or up, then the left border or the upper one turns out to be "highlighted", respectively.
As a result, our Listener-In-Trance observes the figure of the Orator surrounded by a light shimmering halo along the outline. If the Listener suddenly switches his attention from the audio information to the halo, then the trance will surely end, the macrosaccades will resume, and the halo will be outside the Orator's figure and quickly "dissolve" - disappear. On the other hand, if the audio information did not let go of the listener's attention, then at the end of the "session" he will surely retain in his memory that very actually observed radiance of the contours - a halo.
From particular to general
Despite the micro- and macro-saccades, despite the “blind spot” and uneven sensitivity on the retina, the picture we perceive does not “jump”, it looks solid and geometrically stable. It turns out that on the way from the retina to the image perceived by the consciousness, visual information undergoes rather deep processing, including "synchronous compensation of saccades", stitching of fragments, brightness leveling, and three-dimensional perception.
It seems that we see not just a "stream of frames" from the retina. For the normal perception of visual information, it is necessary that the mind chooses a certain semantic model of the observed picture. And each next "frame" from the retina updates and clarifies the fragments of this model, as a schoolchild puts details on a contour map. And we perceive this model, proposed by consciousness and updated by means of vision.
Evgeny Chekulaev