dark, shiny, matte, clear: light v. stuff

I want to know how much we understand about transparency, opacity and reflectivity.

I mean, there might be a block of glass I cannot even budge that almost perfectly passes light/images, as opposed to a cloud of smoke that blocks all light but I could move right through with easy (albeit, probably using an oxygen mask).

What I understand:

There is a quip, that if you look at our atoms, we are mostly empty space. This is evidently a misrepresentation of reality. I would guess that most of what controls stuff are the electrical fields that spread out around stuff’s atoms to establish its material properties. The so-called empty space between our atoms is not really empty at all, it is full of charge, and that geek who thinks he can pound the desk till his hand passes through it has no understanding of the electron pressure that keeps white dwarfs from collapsing.

So, the pervasive electrical fields might explain why we are opaque, but what about glass? Light passes through glass almost perfectly (or with tailored distortion), yet, as I understand it, glass is amorphous (lacks crystal regularity). How is it that photons can traverse random electrical fields and come straight out the other side? Surely not all of them are being absorbed and re-emitted perfectly? Do they experience some sort of electromagnetic drag in passage but not actually encounter electrons? And how can the aforementioned smoke cloud have such a strong electrical presence that it captures nearly all of them?

Also, why does it seem like most transparent solids and liquids tend to have surfaces that reflect light as well as they pass it?

Electrons are what interact with light. There is an excellent presentation without much dumbing-down in QED: The Strange Theory of Light and Matter by Feynman.

Maybe you should read this:


And then come back if you have more questions.

Everything reflects light to some degree. That’s how we see things that aren’t producing their own light, by the light that they reflect. What you’re noticing about glass and water and such is not just that they’re reflecting, but that they’re reflecting in such a way that they produce images. Which is mostly just because they’re really smooth. That’s why agitated water and frosted glass don’t produce clear images, because they’re not smooth.