Color and Light

White. 

A blank page or canvas. 

So many possibilities. 

– Stephen Sondheim, Sundays in the Park with George

Before I got on the plane to Heathrow, I had reached out to a couple friends and said, “You know, the Northern Lights have been visible even down where we live in Eastern Washington…I wonder if I’ll be able to see them from the plane!” I’ve never seen the aurora borealis before and always wanted to, so I was very excited about the prospect. 

But, before I get into that, a little back story. As an undergraduate and graduate student, I studied classes of solid state materials that produce light when you excite them with a certain amount of energy (think, like, those glow in the dark toys that need to be “charged” with sunlight and then will glow all the brighter in a dark room or anything that’s black light sensitive). These materials are called phosphors (not to be confused with phosphorous). They are used in many modern applications like computer and television screens (displays), fluorescent lighting, sensors, etc. All white light is made up of a combination of red, green, and blue phosphors. It is kind of like learning about red, yellow, and blue as the primary colors – you can mix them together on a palette and they will give you the spectrum of visible colors. This is true, too, of red, green, and blue phosphors, but when you mix them all together, you get white light (as opposed to what I am guessing is a goopy mess…artists? Can confirm?).

You might recognize the prefix “phos” as an indicator of light production – it literally means “light” in Greek. Phosphorescence is the act of our characteristic of glowing when excited with energy (not metaphorical, though I feel like it could be!). In Spanish, fósforo is a match (as in, to start a fire) and, for historically linked reasons, the word for the element phosphorus, which has the element symbol P. It comes from the Greek for “light bearer”, or “one that carries, brings forth light”. I just like that. Poetic. Phosphorous is an important element to chemists because it’s one of the first elements for which we can point to the specific discoverer. 

Hennig Brandt (sometimes translated as Brand) (1630-1710), German merchant and alchemist, is credited with the discovery of phosphorus in 1669. He originally called it ‘icy noctaluca’, which literally means cold, night light. He isolated it from buckets and buckets of his own urine (more on this, undoubtedly, in a future post). He was an alchemist and interested in finding gold – what better place to look than within a golden liquid?!?

Light is energy, which we understand as waves (we’ll stick with that for now, lest we start tumbling down quantum mechanical rabbit holes before we’re ready). Light waves have two components that are perpendicular to each other – one that interacts with an electric field, one with a magnetic field (I like to attempt to show this in class – it looks like a dance trying to make your arms do this!). The entirety of light waves, as far as we know, can be described with the electromagnetic spectrum, which goes from gamma on the high energy (shorter wavelength) side to radio waves on the low energy (longer wavelength) side. The visible portion of this spectrum for human beings is a teeny tiny region (that’s my technical, scientific assessment) right in the middle. Our perceptions of color come from our brain’s evolved interpretation of the different energies/wavelengths of light and how they bend, bounce, and are absorbed by everything. This is achieved through photo- and color-sensitive apparati in our optical arrays called cones (marveling at the evolutionary engineering of the eyeball will also be left to a future post). So, the perception of color, then, is my brain’s way of interpreting the wavelengths of light that I see reflected from an object. “[N]ot mixed on the palette, mixed by the eye” (George Seurat, as imagined by Stephen Sondheim in Sundays in the Park with George).

The aurora borealis, which comes from the Latin “dawn of the north”, is a polar light phenomenon that is seen in the Northern hemisphere due to similar reasons as my phosphors. High energy particles from the sun hit the gases in the atmosphere and excite the electrons up to higher energy states.  When the electrons relax back down, photons of visible light are emitted. As an aside, ‘aurora’ means ‘dawn’ and comes from the same root as gold in Latin, aurum (where we get the chemical symbol, Au). It’s also where Briar Rose (Sleeping Beauty) gets the name Aurora, for her golden tresses. Also poetic.

Anyway, all this to say that the aurora was visible for a couple hours of my flight and I was eye level with it, which was just incredibly magical.  I was the only one with my face and phone camera pressed against the window, so I recognize that I might be the only one who geeks out about such things, but it was a very special start to the trip and made up for not being able to sleep on the plane.