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The night hag or old hag is the name given to a supernatural creature, commonly associated with the phenomenon of sleep paralysis. It is a phenomenon in which the sleeper feels the presence of a supernatural, malevolent being which immobilizes the person as if sitting on their chest or the foot of their bed. The word "night-mare" or "nightmare ...
Closed-eye hallucinations and closed-eye visualizations ( CEV) are hallucinations that occur when one's eyes are closed or when one is in a darkened room. They should not be confused with phosphenes, perceived light and shapes when pressure is applied to the eye's retina, or some other non-visual external cause stimulates the eye.
Exploding head syndrome ( EHS) is an abnormal sensory perception during sleep in which a person experiences auditory hallucinations that are loud and of short duration when falling asleep or waking up. [ 2][ 4] The noise may be frightening, typically occurs only occasionally, and is not a serious health concern. [ 2]
Blue light, a type of high-energy light, is part of the visible light spectrum. High-energy visible light (HEV light) is short-wave light in the violet/blue band from 400 to 450 nm in the visible spectrum, which has a number of purported negative biological effects, namely on circadian rhythm and retinal health (blue-light hazard), which can lead to age-related macular degeneration.
The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon . Natural light sources in a night sky include moonlight, starlight, and airglow, depending on location and timing. Aurorae light up the skies above the ...
Chromostereopsis. Blue–red contrast demonstrating depth perception effects. 3 Layers of depths "Rivers, Valleys & Mountains". Chromostereopsis is a visual illusion whereby the impression of depth is conveyed in two-dimensional color images, usually of red–blue or red–green colors, but can also be perceived with red–grey or blue–grey ...
“A lot of times, blue feels the need to talk on behalf of people that can’t,” says Hill. “You’ll find blues are naturally advocating [for others] even though they sometimes don't like to ...
Color vision. Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different frequencies independently of light intensity. Color perception is a part of the larger visual system and is mediated by a complex process between neurons that begins with differential stimulation of different ...