Hey all,
Sorry if this is a bit rambly, I've been up for almost 24 hours and the lack of sleep is catching up to me. I hope it's able to demonstrate what I've got bouncing around up in my head. If there are any questions, feel free to ask.
I had a brief discussion with Evgeni on the youtube episode Lights concerning spectroscopy. The general conclusion was that there is no physical phenomenon which would be able to lengthen bands of light after the light has been sent through a prism as we see Navani do with various Lights. I've put a bit more thought into it and wanted to propose what could be the Cosmere explanation for what is happening here.
The fact that certain bands of light are physically lengthening out and other bands seem to be contracting has the interesting implication that at least the three dimensions of space are being distorted here. This has the implication that typed investiture naturally distorts physical reality in natural ways we perhaps haven't seen yet. I wish I could examine this using reference frames and taking exact measurements, but unfortunately that isn't quite possible and I'm not quite up to the task right now. However, it appears the spatial dilation and contractions only occur when invested light is passed through a prism, and while the magnitude of the distortion appears to not be insignificantly large (at least enough to be noticed), the total distortion would likely not appear too terribly abnormal on it's own to an outside observer.
The only way I can really justify this within the Cosmere, and I think some of this is fairly canon already, would be to suggest thinking about investiture as a field which exists everywhere and is in everything, but isn't necessarily effecting anything at any given point, not unlike the electromagnetic field or the gravitational field. Then investing something would be putting energy into the investiture field in such a way that it is able to effect things physically. At this point, the investiture would appear to be typed. You might think of this as being like a proton with a positive charge or an electron with a negative charge but instead there are sixteen kinds of "charges" and they all interact with each other differently.
Regardless of how the investiture is stored within gems or what gems the investiture is stored in, it does appear that there is a baseline investiture to energy conversion rate where the energy is given off as light (and frankly, if the above is true, then given that the light appears to distort space, it's giving off some small amount of investiture too). Though at this point I imagine that regardless of the gem it's in, the investiture to energy conversion rate is so insignificant as to be negligible in the very long term. Either that, or investiture contained in more perfect containers would glow much less brightly than in significantly cracked containers, but I would bet there is a baseline conversion rate regardless, I'll have to think more about long range order vs short range order and see if there are any non-obvious implications to the interactions gems have with investiture, but that'll have to come in a future post.
Additionally, it appears that typed investiture is naturally more present within or around certain natural phenomena. Given equal quantities of Stormlight and Voidlight, I would guess the total amount of investiture present would be equal. And given that Voidlight massively distorts the purple band vs Stormlight only moderately effecting the blue band, it likely also means that Stormlight has an overall more balanced effect on many physical phenomena vs Voidlight which appears to be quite concentrated in how it's used. Though that is mostly an unprovable idea, it might just be that we see an exaggerated effect for Voidlight only within the light itself, whereas it could be that within more mundane parts of reality, it may have a more balanced effect than Stormlight.
I am curious how the light from the Well of Ascension would have broken into colors and also whether or not the presence of Ruin within the Well (or his conscience or... however he was contained) would have affect the light as it is being passed through a prism. And also, if you shine light at the god metals, and then pass the reflecting light through a prism, does it break down differently and could you reflect light off of say, Raisium and then Tanavastium, and have the resulting light break into the bands formed by Warlight?
tl,dr: Given that the bands of light grow and shrink based on which form of investiture is passed through a prism, no gem can perfectly contain the investiture placed within it forever. Also light is weird and so are metals.
