How do photons deliver information?

In other words, how do they contribute to our sight? When a photon bounces off an object, is it packaging up information like color, texture, contrast, and that sort of thing, and then delivering that to our retinas? If so, how does it store this information? If not, how do we see anything over than just plain color (wavelength)?

I’m not sure, but I suspect that all that other information like contrast and texture can eventually be boiled down to complex patterns in color and in intensity (which is not a property of a single photon, but of how many photons are reaching our retina in a particular spot.)

Photoreceptors in our eye. Different photoreceptors absorb different things.

All the photon conveys is wavelength (i.e. the color). All the magic happens in the brain and (I think) the optic nerve. Consider a mosaic. Little pieces of monochromatic tile are combined to create a picture that can convey color, contrast, etc. What your eye is picking up is a mosaic made of very small tiles. The brain stitches them together (and turns them right side up).


We don’t see anything besides colour and spatial information, i.e. where the light comes from. Think about a TV screen – it basically emits light in just three colours, red, green and blue; our retina is more or less the inverse. Couple two of them and correlate the differences in perspective, and you got a full three dimensional representation of the world around you.

Everything you see is plain color. Texture and contrast are detected by variations on color due to shading, nearby objects and other local conditions.

Your retinas detect color with cones that react to frequency ranges corresponding to red, green and blue.

Is it fair to say that the images we see are not things in nature, but things in our brains?

I’m not sure that it’s an either/or thing – for one, things in our brains are things in nature, too. I’d probably call it a representation of processed data collected via our eyes; an image in our brain is fundamentally information, and so’s the state of the outside world. Those two sets of information are connected by the process we call ‘seeing’, but they are not the same.

I really like how you hand-wave an assertion over which philosophers have debated since time immemorial

I don’t believe I can be convinced that a thing and a representation of a thing can be said to be the same. I’m reminded of a quote by Arthur Eddington: “There is no essential distinction between scientific measures and the measures of the senses. In either case our acquaintance with the external world comes to us through material channels; the observer’s body may be regarded as part of his laboratory equipment.”

Yeah, I’m kinda smooth like that. :cool:

I don’t think anybody’s tried that, so far?

I was being facetious

You were, at first, but right after, you were wooshed.


A single photon isn’t likely to cause any visual effect at all. When you have lots of photons, those probibilities add up, and you start seeing them.


If you could see it, a single photon would look either red, green, blue, or white, depending on which flavor of cone or rod it hit. When you have lots of identical photons, they can hit multiple receptors, and you can see shades between red, green, and blue, depending on how strongly each receptor is stimulated.


The lens of your eye steers the photons toward a point on the retna which depends on the angle it arrived at. When you have an extended object, the various arival angles result in the formation of an image of the object on the retna.

Texture is a collection of various shapes. see above.

Probability has nothing to do with it. Rod cells can, in fact respond neurochemically to a single photon, however, the resulting signal is not set out to the optic nerve until several photons have stimulated the cell within a certain short time period. Otherwise, our visual processing system would be swamped by noise.

“Ten Philosophical Mistakes” by Mortimer Adler has an interesting chapter on this very subject. He discusses Locke’s and other philosopher’s take on this subject and then says the following:

Very readable and a pretty nice argument that Solipsism is most definitely a mistake. But I’m most certainly not the one to judge his argument’s worth.

I’m pretty sure the only information one photon can deliver is “the photon source is still emitting photons.”

Of course that’s not true. As noted previously, a single photon carries two pieces of fundamental information: a wavelength and a vector.

And BTW many quantum philosophers consider the idea that the universe is brought into existence by our consciousness is a form of teleological solipsism.

I.e. humans became conscious and collapsed the wavefunction of the universe. Pretty neat, huh :slight_smile: