A Rainy Night in Midlands

The other week, Shreya and I figured out how rain works, on a particularly bleak rainy day walking out of Woody's. So there's air with some amount of moisture dissolved in it. That moisture is measured in terms of "relative humidity," i.e., how much of the saturation value of water there currently is. Saturation is dependent on one thing only: vapor pressure of water at a given temperature, such that when the partial pressure of water in the gas phase in the air equals that vapor pressure, the air is saturated.

So that's all fine and good, but how does it explain rain? The answer owes to the psychrometric chart, a hideous monstrosity of curves and grids that can probably tell you the answer to the life, the universe, and everything if you say the magic incantation and find the intersection of any one of about twelve tie lines. One especially useful property (only involving about four lines at a time) is if you cool the air enough, you hit a saturation curve and begin condensing water as you cool further. Everyone knows from their friendly 6 o'clock weatherman that a cold front brings precipitation... and now I know why.

Another interesting property is red dye fading at a rate disproportional to other colors of dye. Emily attempted some relativist INTA explanation that "our society has a limited definition of red compared to other colors." I countered with a (help me, God) physics answer of red being close to the end of the visible spectrum. Of course, violet does not experience the same dye as would be expected from also being at the end of the visible spectrum, so there goes my theory. Eventually we settled on the fact that red is the least abundant of naturally occurring colors, so there is most likely an atmospheric reason that our environment is unkind to redness. Anyone know what this is?

Emily has a point, though. As much as I despise thinking in terms of "society," colors are completely subjective. We've got green and blue next to each other on the spectrum. Those are definitionally different colors. But there are (infinitely many) colors between the two of them. Who decides that "forest green" gets called "green," "sky blue" is "blue," and "turquoise" is somewhere in a chromatic no-man's land, neither green nor blue?

Finally, I bought a copy of the Baghavad Gita from some guy on Skiles who was doing yoga and fundraising for something or another. Theology is a wonderful thing, and it pains me to realize that this book is probably number six or so on my List of Books to Read. Maybe I can make some progress over Christmas?


Currently listening: The Many Moods of Christmas, Robert Shaw