kuz.
Follow

episode · perception

How much of reality can you actually see?

Visible light is one octave out of more than eighty. Your eyes catch a sliver, and your brain paints the rest.

by kuz perception
Thumbnail for How much of reality can you actually see?

The short answer

Almost none of it. The light your eyes detect, roughly 380 to 700 nanometres, is about one octave of an electromagnetic spectrum that spans more than eighty octaves, from radio waves to gamma rays. Infrared pouring off your skin, radio and wifi through the walls, ultraviolet, x-rays and the faint microwave glow of the universe are all here right now and permanently invisible to you. And the thin band you do see is not raw reality either. Your brain flips the inverted retinal image, fills in the blind spot, and predicts what comes next. You have never seen the world. You have seen a fast, useful painting of it, rendered in the dark inside your skull.

Transcript

Look around the room. You feel like you're seeing reality. You're not. You're seeing almost none of it.

Your eyes detect one tiny band of light, about one octave out of more than eighty.

Everything else is here right now, passing through you. Infrared pouring off your skin. Radio and wifi flooding the air. Ultraviolet, x-rays, the faint glow of the universe itself.

You are blind to almost all of it.

And the sliver you do see? Your brain flips it, fills the gaps, and predicts what comes next.

You have never seen the world. You've seen a fast, useful painting of it, rendered in the dark, inside your skull.

So what does reality really look like? You'll never know.

Sources

  1. NASA Science. "Introduction to the Electromagnetic Spectrum" and "Visible Light." The full electromagnetic spectrum runs from long-wavelength radio waves through microwaves, infrared, the narrow visible band, ultraviolet, x-rays and gamma rays. Human vision is confined to wavelengths of roughly 380 to 700 nanometres, a thin slice of the whole. Open source
  2. CIE (International Commission on Illumination), ISO/CIE 11664-1:2019 colorimetry standard, and the CIE definition of visible radiation as optical radiation able to produce a visual sensation, taken as 360-400 nm to 760-830 nm. This bounds the human visible band at approximately 380 to 700 nanometres and frames it as close to a single octave, since 700 nm corresponds to about 430 THz and 380 nm to about 790 THz, almost a frequency doubling. Open source
  3. NASA / Imagine the Universe. "The Cosmic Microwave Background." The CMB is faint microwave radiation left over from the early universe that permeates all of space and passes through everything, including the human body, while remaining entirely invisible to the eye. Open source
  4. Gregory, R. L. (1980). "Perceptions as hypotheses." Philosophical Transactions of the Royal Society of London B, 290(1038), 181-197. DOI: 10.1098/rstb.1980.0090. Established the influential view that perception is not a passive readout of the retinal image but an active, predictive construction, the brain testing hypotheses about the world rather than directly seeing it. Open source
  5. Seth, A. K. (2014). "A predictive processing theory of sensorimotor contingencies: Explaining the puzzle of perceptual presence and its absence in synesthesia." Cognitive Neuroscience, 5(2), 97-118. DOI: 10.1080/17588928.2013.877880. Develops the "controlled hallucination" account in which conscious perception is the brain's best prediction of its sensory causes, reconciled against incoming signals, rather than a transparent window onto reality. Open source

related

other things you've googled.

follow kuz for the next answer.

YouTube

@kuzanswers

TikTok

@kuzanswers

Instagram

@kuzziesa
Follow kuz on YouTube