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Thomas11y00

A photon is absorbed and then emitted after some time.

Never just reflected.

Thomas11y-30

I wander who dared to down-vote this. It's a physics fact. Less known, what's the reason I wrote it on this occasion.

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-6

The sun reflected off things

by polymathwannabe

22nd Nov 2013

1 min read

-6

An insight I had a while ago:

When I'm out in the daylight, and I see a tree, what I actually see is not the tree itself. What I see is the sun reflected off the tree. Likewise with rocks, grass and birds: it's always the sun I'm seeing reflected off them. This is possible because the sun emits all visible colors (or rather, our eyes evolved to perceive almost all EM frequencies that almost all solid matter deflects). I'm not seeing the things. I'm seeing the light. We live surrounded by the sun.

Is this too obvious? Inconsequential? Redundant?

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[-]dougclow11y160

If that's an interesting insight for you, you might get a kick out of realising that trees come from out of the air.

[-]NancyLebovitz11y110

For a different mind-blowing angle, a tree is the combined trajectory of its buds.

(From Theodore Stugeon's "The Education of Drusilla Strange", but I think it's fairly sound if you ignore persistent wind, random damage, and some thickening.)

[-]polymathwannabe11y70

Mind officially blown.

Will file along with "honey is bee barf."

[-]fubarobfusco11y110

"honey is bee barf."

Now there's an ADBOC if ever I heard one.

[-]Adele_L11y130

I don't think this is what "see" means. Even if the light came from the sun originally, you still are primarily receiving and processing information about the tree.

[-]ThrustVectoring11y40

Well, what you see is causally entangled both by how the tree is and what the lighting of the tree is. I mean, you'd see something different if it's night out, so it's really transmitting information about both.

That said, what you notice yourself seeing isn't photons - it's what the visual processing center of your brain thinks is out there. It's why optical illusions work, it's why hallucinations happen, and it's why sleight of hand works.

[-]Brillyant11y00

Can you explain sleight of hand in more detail? What is happening? And why does it work?

[-]hyporational11y30

I don't think sleight of hand fits in that bunch too well. It hasn't got that much to do with vision per se, but rather attention. You consciously process much less than you think. Those tiny resources are directed by your attention. If your attention doesn't fix on the right object, you're screwed. This effect applies to all sensory modalities, I think.

Here's a pickpocket giving a TED talk on attention.

[-]ThrustVectoring11y00

http://www.youtube.com/watch?v=oXGr76CfoCs

I can't, but here's a good example

[-]byrnema11y30

I think you missed the point of this post. You are invoking definitions, when this post is just a sharing an interesting experience/observation. It's appropriate for a Less Wrong Discussion post because it's noticing (and enjoying) another way that the map is different from the territory --In this case, in a way that pretty much involves most of our daily experience.

[-]Mitchell_Porter11y20

Also, all the substances around you are held together by electromagnetism.

[-]NancyLebovitz11y20

It's kind of obvious from one angle, but it's an important step from another angle. Knowledge doesn't just happen, there's always a transfer process.

[-]hyporational11y20

Does this belief pay rent to you?

People have believed crazier) things about vision.

[-]JoshuaZ11y50

Emission theory only seems crazy because you know all the evidence against it. As a hypothesis for the amount of data that someone had 2000 years ago, it wasn't obviously wrong. Moreover, we know now that in fact some other sensory systems work very similarly to the emission theory of eyesight (e.g. bats using echolocation).

[-]hyporational11y20

Emission theory only seems crazy because you know all the evidence against it.

I think that applies to most beliefs that are called crazy, inferential distance works the other way too. Then again, some people simply fail to update no matter how much evidence they have.

Moreover, we know now that in fact some other sensory systems work very similarly to the emission theory of eyesight (e.g. bats using echolocation).

That's a good point, and I hadn't made this connection before, although I've done some reading on bats.

[-]A1987dM11y00

People have believed crazier things about vision.

I still alieve that one.

[-]polymathwannabe11y00

It might make for a good poem.

[-]byrnema11y10

I had a similar 'epiphany' a year ago, so I know exactly what you mean. In my case, I thought of it as sun or any light source, and in terms of the electromagnetic waves. We are in this ocean of electromagnetic waves and with a little bit of effort (like flipping one's perspective in a optical illusion image) I can reinterpret everything I see as 'just' spherically symmetric waves emitting from sources that are caught and trapped by molecules in my eye (and then interpreted by my brain as others are pointing out in the comments so far).

[-]byrnema11y00

To elaborate, what was most interesting about the perspective was that I realized that while I wasn't directly interacting with the objects, we were causally entangled (and thus interacting indirectly) via these electromagnetic waves. The perspective paid rent, in some sense, in that now I had a much better understanding of light scattering in general (and different kinds of mirages specifically) and I found it amazing that this kind of interference doesn't happen more often. We are literally in a bath of these EM waves (the ones that I can see) and they are just bouncing around until they hit something. The thing that they hit -- all the things that I see -- catches them and destroys them (collapses the wave), so that what I actually see is a new EM wave that the thing emits a moment later.

[-]Viliam_Bur11y00

All photons are fundamentally the same. So, we live surrounded by the photon.

Except at night.

[-]Lumifer11y00

You do see a tree via sunlight reflected off it. Most (but not all) of the information in what is in your mind's eye comes from the tree and only a little bit comes from sunlight. Alternatively, you can think of photons as a way to deliver information about the tree to your brain.

Light is necessary for you to see the tree but is not sufficient.

[-]Thomas11y00

A photon is absorbed and then emitted after some time.

Never just reflected.

[-]Thomas11y-30

I wander who dared to down-vote this. It's a physics fact. Less known, what's the reason I wrote it on this occasion.

[-]arundelo11y60

If you meant that to truly understand reflection you need to understand that a photon is absorbed then a photon is emitted, that's true. (Or at least I'll take your word for it; I'm a physics amateur.)

If you meant that there's no such thing as reflection, that's false. Reflection is what we call photon absorption and re-emission. (With certain other conditions, like a very short time period, re-emission at the same frequency, and re-emission in a different direction.)

(I didn't downvote it.)

[-]Thomas11y00

If you meant that there's no such thing as reflection, that's false

I've said "just reflection". I was referring to original poster intention and wanted to show him that photons on his retina probably originate from the tree he is looking. Or from the air in the middle. Or from his eye itself.

Absorbed and emitted many times. A rare photon we detect, is from the Sun.

[-]arundelo11y40

When I first read the great great grandparent I almost wrote a response along the lines of the grandparent, because it triggered a pet peeve of mine where people use science and equivocation to say that commonplace knowledge is wrong. (Example: "Your table is not really solid; it's mostly empty space." No, solid is what we call things like tables that act a certain way at a certain size scale.) But looking at it again, especially in the light of the parent, I see it as exactly in the spirit of the OP (which, despite its use of an unusual sense of "see" along the lines of my pet peeve, got more downvotes than I think it deserved).

[-]Thomas11y-20

got more downvotes than I think it deserved

I've just corrected that a bit.

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