Astro Cast Reflection/ Refraction

So light can do some pretty strange stuff, like pass through objects and bounce off them. It can be broken up and recombined; in fact, everything we see is just the end

result of reflection and refraction of light, so it’s time to understand how it

all works. So this is the part, this is one of the situations…like, I’ve bent the

mind’s of my children when I was explaining to them. You know, the

concept that when they see something that is like green, they’re seeing the

reflected photons that came from the Sun, and they’re like, “What?!” Right?

Furthermore, we’re seeing the refracted photons that have come from the

Sun passing through our atmosphere, and again, it’s super-confusing, so let’s

start with like the journey of a photon, of a photon that leaves the Sun,

travels to Earth, passes through the atmosphere, maybe goes through a

window or two, bounces off something, maybe bounces off something again

and goes into someone’s eyeball. eye that left the Sun originally, or in fact, was originally created because

there’s also a whole lot of absorption and re-emission processes that are

going on. So you start off with something creates a photon, and the original

photon that was created may not be the same photon that reaches your eye,

so you have some sort of an event deep in the core of the Sun gives off

energy, and this bit of energy as it travels through the Sun is going to get

absorbed by an atom, re-emitted in a new direction, absorbed by another

atom, re-emitted in another direction, and this entire process is one of what’s

called “Brownian motion.” It’s the path…the way they always explained it

in physics books, which I think says something about the physics

community is “you know how drunk people walk? That trying to get

somewhere, but they’re sort of going in all directions? That’s the motion of

light as it tries to travel to exit the Sun.” Well, once the light finally breaks

free of the surface of the Sun, then it’s mostly a clean path straight to Earth,

so assuming it doesn’t end up hitting dust, doesn’t end up hitting, well,

Mercury or Venus, or anything else that lies between us and the Sun. when light hits a material that isn’t a vacuum, it’s going to slow down and

this is where something that I consider a bit of the Universe conducting

Black Magic occurs. There’s this property referred to as Snell’s Law that

basically says if you have light at point A and you’re trying to observe light

at point B, the path the light is going to take between those two points, is the

path that causes it to have the shortest journey time. Now, the thing that

makes this kind of Black Magic is if you can imagine that the light is passing

through a series of different materials -- a pocket of hot gas, a pocket of cold

gas, vacuum from the Sun, or vacuum from outer space, and we’re looking

at sunlight, well, as the light passes through each of the materials, its speed

is going to vary, and just as you can imagine driving through a city, and you

have to make these choices. by comparing side by

side a pencil or a straw in a glass of alcohol, in a glass of sugar water, in a

glass of regular water – it’s very small differences, but it’s still just neat that

we can actually play with the path of light.